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Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
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3
Energy for Transportation

BACKGROUND

The Current Mix of Energy Sources for Transportation

According to the U.S. Energy Information Agency, approximately 28% of all energy used in the United States is currently in the transportation sector (NAS/NAE/NRC 2009d). Of that used, approximately 96% is in the form of petroleum, 2.6% is natural gas, and less than 1% is biomass, electricity, or other fuels. Overall, transportation is responsible for approximately 70% of all U.S. petroleum consumption.

In its recent report, the National Research Council (NRC) Committee on America’s Energy Future reports that, as of 2003, the transportation sector used approximately 28.4 quadrillion British thermal units (quads) of energy, of which more than 75% was expended in highway transportation, 17% in nonhighway transportation (for example, air, rail, and pipeline), and 8% in other off-highway use (for example, agriculture and construction) (NAS/NAE/NRC 2009d).1 Figure 3-1 from its report illustrates that, of the highway sector, cars account for 43% of highway energy use (approximately, 34% of all transportation energy use), light trucks for 32% (approximately 26% of the total), and medium and heavy trucks for 24% (approximately 19% of the total).

Of the fuels consumed, AEF reports that gasoline accounted for approximately 62% of the energy used (measured in British thermal units)

1

The Transportation Energy Data Book (Davis et al. 2009) indicates that highway transportation expended 80% of the energy used by the entire transportation sector in 2007.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×
FIGURE 3-1 U.S. transportation energy consumption by mode and vehicle in 2003. SOURCE: U.S. Department of Energy’s Transportation Energy Data Book (Bodek 2006) in NAS/NAE/NRC (2009d). Reprinted with permission; copyright 2006, Massachusetts Institute of Technology.

FIGURE 3-1 U.S. transportation energy consumption by mode and vehicle in 2003. SOURCE: U.S. Department of Energy’s Transportation Energy Data Book (Bodek 2006) in NAS/NAE/NRC (2009d). Reprinted with permission; copyright 2006, Massachusetts Institute of Technology.

(EIA 2006b), and diesel (primarily in medium- and heavy-duty vehicles) accounted for approximately 17% of energy used.

Regulation of Transportation Air Quality Emissions

The past four decades have seen a substantial national effort to regulate the emissions from transportation, starting with light-duty vehicles in the 1970s, and moving to heavy-duty on-road vehicle, and most recently to a range of other transportation sources, including construction and agricultural equipment, locomotives, boats, and ships (NRC 2004c). These efforts have been driven in part by even stricter standards adopted by California, which have in turn been adopted by a number of states. The result has been substantial reductions in emissions and ambient levels of a number of pollutants, even as vehicle miles have increased. For example, there have been substantial reductions of ambient levels of carbon monoxide (CO), in most cases to levels below2 the current National Ambient Air Quality Standards (NRC 2003b).

2

As of July 31, 2009, Clark County, Nevada is the only U.S. county in nonattainment for carbon monoxide (see EPA 2009f).

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

Starting in the late 1980s in the states and in 1990 on the national level, a number of rules have been aimed at changing the formulation of fuels to reduce a variety of emissions (for example, benzene and other volatile organic compounds [VOCs]) and to facilitate the introduction of new emission-control technologies (for example, ultra-low-sulfur diesel fuel) (NRC 2004c). Substantial requirements have also been enacted this decade that require enhanced use of biofuels (more details provided later in chapter).

Improving Vehicle Efficiency

In addition to regulation to reduce emissions in the transportation sector, the United States has seen substantial efforts, beginning in the 1970s and renewed recently, to improve vehicle efficiency (NRC 2002c). The recent AEF efficiency panel report (NAS/NAE/NRC 2009d) assessed the opportunities for reducing energy consumption in the transportation sector through advances in efficiency.

That report notes that energy usage in transportation has grown rapidly in the United States over the past decades except for brief pauses during economic recessions in 1974, 1979-1982, 1990-1991, and 2001. The present economic decline, along with the 2008 spike in petroleum prices, is also likely to slow the demand for transportation fuels. Globally, the major drivers for energy efficiency are the price of fuel (influenced by taxes), regulations, personal choice, and the personal environmental values movement. In Europe, where high fuel and vehicle taxes raise owner costs and where diesel fuel is taxed less than gasoline, new-vehicle fuel economy is approaching 40 miles per gallon (mpg). In 1999, Japan instituted a fuel economy program to encourage vehicle efficiency per mile traveled, and its present new-vehicle fuel economy is similar to Europe’s. In 2006, Japan revised its fuel economy standard to 47 mpg by 2015 (Ann et al. 2007).

In the United States, technological efficiency improvements are available at fairly modest costs. With present market structures, vehicle drive-train efficiency has been improving at a rate of about 1% per year. However, rather than reducing their fuel expenses as a result of these improvements, most U.S. consumers have opted to purchase larger vehicles with more acceleration and accessories that consume even more energy. So in spite of technological improvements in the efficiency of vehicle components, the fuel demand has continued to rise, and the U.S. light-duty vehicle fleet now has an average new-vehicle fuel efficiency of about 25 mpg.

Recently, California adopted so-called GHG emission standards that would require substantial reductions in GHG emissions, primarily through enhancements in fuel economy, by 2016; 13 additional states indicated that they would adopt the standards once the U.S. Environmental Protection

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

Agency (EPA) approved a waiver of the Clean Air Act to allow the standards to move forward. Although EPA had originally rejected California’s application for a waiver, in January 2009 EPA began a formal process to reconsider the waiver, and in May 2009, after detailed discussions among California, EPA, and auto makers, President Obama announced an approval of the waiver and a new unified approach to both federal corporate average fuel efficiency (CAFE) and GHG emissions standards that will result in a national standard comparable to the California standards. This action is expected to result in the achievement of the former 35.5 miles per gallon CAFE goal by 2016, several years sooner than originally envisioned.

A wide variety of technologies are available to improve fuel economy, in particular those to improve drive-train efficiency, vehicle aerodynamics, rolling resistance, and weight reduction (NRC 2008b). Many of these will be widely deployed by 2020, but further gains will be possible. Diesel engines and hybrid electric vehicles (HEVs), such as the Toyota Prius, are currently available and can reduce fuel consumption by more than 25% relative to today’s gasoline vehicles. A shift to these technologies, coupled with other improvements, could result in a new-vehicle fleet with substantially improved fuel efficiency.

APPROACH TO ANALYZING EFFECTS AND EXTERNALITIES OF TRANSPORTATION ENERGY USE

Rationale for the Selection of Vehicle Fuels and Technologies

In considering its task, the committee recognized that it could not estimate quantitative externalities for every possible energy use in the transportation sphere. Therefore, the committee attempted to place transportation energy uses in order of importance on the basis of two key factors: (1) the degree to which a current transportation energy use is a significant part of energy use, and (2) the degree to which an emerging fuel and technology is likely to become a significant part of transportation energy use in the future. In applying these criteria and assessing the degree to which the data would support quantitative analysis, the committee focused on two key areas:

  • A quantitative analysis of current and 2030 energy use, emissions, and externalities for highway transportation for both petroleum-based fuels and conventional biofuels (for example, corn ethanol) using the GREET (Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation) model for primary analysis tied to the APEEP (Air Pollution Emission Experiments and Policy) model to estimate physical effects and monetary damages. This analysis applies to more than 75% of all current U.S. energy use in the transportation sector.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×
  • A qualitative and quantitative synthesis of what is currently known on several other key fuels and technologies, including emerging biofuels (for example, corn stover and grasses); hybrid, plug-in hybrid, and electric vehicles; and other fuels (natural gas and hydrogen fuel cells).

Transportation Life-Cycle Analysis

Our goal is to develop and apply an LCA framework that can provide more detailed quantitative assessments of the comparative health and environmental benefits, risks, and costs of existing fossil fuels (petroleum), as well as future mixes of transportation technologies and fuels. To meet this goal, we build on state-of-the-art life-cycle-impact-assessment (LCIA) methods that have been developed for evaluating and allocating the health, resource, and environmental impacts of industrial, agricultural, and energy technology systems (Guinée and Heijungs 1993; Horvath et al. 1995; Hoffstetter 1998; IAEA 1999; Hertwich et al. 2001; Bare et al. 2002; EC 2008). This effort and its resulting framework provide quantitative estimates of impacts that can be considered “external” in the context of Chapter 1.

One can take either a top-down or bottom-up approach when allocating health and environmental costs to transportation technologies. The top-down approach considers morbidity and mortality statistics for a specific population, such as the inhabitants of a country or of a large urban region, and attempts to allocate these impacts to a specific source, such as transportation emissions or power-plant emissions. The bottom-up approach provides a list of hazard sources (such as pollutant releases) and tracks these hazards from the source to exposure and damage. Top-down assessments for air pollution have been carried out for many regions, making it possible to provide a disease-burden estimate for air pollution. However, allocation to specific energy systems cannot be resolved because the top-down approach lacks the spatial and temporal resolution needed to track impacts to specific technologies. In contrast, the impact pathway assessment used in the ExternE study (EC 2003, p. 3) and the more recent analysis by Hill et al. (2009) of air-emission impacts from transportation fuels both used a bottom-up approach in which environmental benefits and costs are estimated by following the pathway from source emissions through pollutant-level changes in air, soil and water to health and environmental impacts.

The life cycle of effects associated with using energy for transportation includes upstream effects, such as extracting and processing the fuels, building the infrastructure needed to use transportation systems (for example, roads), building the infrastructure needed to deliver energy for vehicles (for example, pipelines and tankers), and manufacturing the vehicles. The life

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

cycle of effects also includes the use of energy in vehicles, such as effects associated with emissions from vehicle tailpipes.

With respect to the categories of interest in this study, the committee summarized some of the key pathways by which energy sources for transportation lead to impacts. In general, most of the emissions occur as a result of burning fossil fuels in the life cycle of transportation fuels. Such energy use occurs across the supply chain, including fuel use for drilling oil wells or farming biomass fields, to transporting feedstocks and fuels to and from refineries, the refining process, transporting fuel to and from consumers, and the use of the fuels by consumers.

The movement of feedstocks and fuels in the supply chain of transportation fuels is different from that of electricity. Petroleum and petroleum products (for example, gasoline or diesel fuel) are generally transported by pipeline or truck; whereas coal, the primary energy source for electricity, is predominantly transported by rail. A significant share of the petroleum used to make fuels is from foreign sources (where it is extracted and delivered to the U.S. market via ocean tanker).

Various studies have been conducted of externalities of energy use in transportation. Before the phrase “life cycle” became popular, studies of this scope in the energy domain were referred to as “fuel-cycle” studies. The term fuel cycle was intended to represent the entire cycle of effects associated with using fuels. Today, such studies are often called “well-to-wheel” analyses because their scope goes from the oil well to powering the wheels of the car. In general, these terms all refer to the holistic study of impacts from extraction through combustion of the fuel for transportation. Other scopes exist too, for example, “well to tank,” which involves all steps needed to get a fuel to the vehicle, but not using the fuel.

Prior studies around the world have assessed the relative contribution of environmental burdens from producing and using fuels for transportation (for example, Delucchi 1993, MacLean and Lave 2003a,b, Ogden et al. 2004, Brinkman et al. 2005, EC-JRC 2008, Ruether et al. 2005). Different from the study of environmental burdens related to electricity, those studies presented a mixed view of the relative importance of upstream-emissions versus in-use vehicle emissions. In prior studies, for petroleum-based fuels, the largest amount of emissions generally occurred when burning fossil fuels in vehicles while driving them, and upstream emissions were relatively modest (although they did not, in general, include vehicle manufacturing in those upstream effects).

Scope of the Analysis

Because this study is about externalities associated with energy production, distribution, and use, this chapter considers the externalities from

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

transportation technologies that use different forms of energy and fuels. The externalities of transportation per se are not within the scope of the study. Thus, the committee generally does not consider vehicle safety issues and traffic accidents, damage to road pavement from heavy trucks, or traffic congestion. These are not related to energy options. We consider them only to the extent that there are significant damages from the transport of fuels. For instance, Chapter 2 considers rail accidents associated with the transport of coal, but not all rail accidents. Similarly, our study considers oil tanker accidents, but not all transportation accidents.

The committee’s goal was to estimate the external damages, in dollars per additional mile traveled, of different types of vehicle-fuel technologies, both current (2005) and future (2030). To do this properly, the committee recognized that it would be necessary to keep track of each type of pollutant and its source location and other factors that would vary spatially and over time. We also wanted to track the life-cycle stage of the damage and the end point category (for example, mortality and morbidity).

To obtain the estimates of emissions per vehicle miles traveled (VMT) by vehicle-fuel technology and life-cycle stage, the committee relied primarily on the GREET model. Sponsored by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE), Argonne National Laboratory developed a full-life-cycle model called GREET. It allows researchers and analysts to evaluate various vehicle and fuel combinations on a full fuel-cycle and vehicle-cycle basis. The GREET model and analyses using the model have been published in a large number of peer-reviewed journals. The model has been widely used by Argonne, and other organizations have used GREET for their evaluation of advanced vehicle technologies and new transportation fuels. GREET users include government agencies, the auto industry, the energy industry, research institutions, universities, and public interest groups. GREET users are in North America, Europe, and Asia.3

GREET includes more than 100 fuel production pathways and more than 70 vehicle and fuel systems. Fuels include conventional and oil-sands-based petroleum fuel, natural gas, coal-based liquid fuels; biofuels derived from soybeans, corn, sugarcane, and cellulosic biomass; and grid-independent hybrids, grid-dependent hybrids, and all electric and hydrogen fuel cells. Unfortunately, although GREET covers light-duty autos and two types of light-duty trucks,4 it does not contain information on heavy-duty

3

A comparison of GREET 1.8b and Mobile6.2 emission factors for gasoline vehicles reveals that the latter are generally higher. See Appendix F for details.

4

Class 1 trucks are under 6,000 lb gross vehicle weight rating (GVWR) and less than 3,750 lb loaded vehicle weight (LVW); class 2 trucks have the same GVWR and greater than 3,750 LV W.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

trucks, which represent almost the entire U.S. fleet diesel fuel consumption, which is sizable compared with the consumption of all transportation fuels. Accordingly, the committee made separate estimates of direct emissions from heavy-duty trucks based on EPA’s Mobile6.2 model and then used GREET to calculate the upstream emissions for the given fuel cycle. The committee decided in the interest of time, given their relatively smaller overall contribution, to omit rail, sea, and air transport and off-road vehicles from consideration in the modeling analysis of emissions from transportation energy use (that is, less than 25% of total transportation energy use).

Table 3-1 provides the complete list of vehicle-fuel technologies that the committee modeled with GREET5 and the heavy-duty vehicles modeled by the committee outside of GREET.

To address technology improvements over time, GREET simulates fuel-production pathways and vehicle systems over a period from 1990 to 2020 in 5-year intervals. The results for any given year reflect GREET’s estimates from 5 years before, so as to reflect the average fleet on the road in the year being analyzed. Thus, the committee, which was interested in external damages for 2005 (the base year for our analysis), used the 2000 GREET results for 2005. For its 2030 estimates, the committee used the 2020 results (that is, those vehicles on the road in 2020) with one major adjustment, replacing the default vehicle fuel efficiency for light-duty autos in GREET with the 35.5 mpg, which will be required by 2016 under the recently announced new efficiency and GHG emission standards. For heavy-duty diesels (HDDs), the committee captured emission improvements expected as dirtier trucks are retired from 2021 to 2030 and are replaced by HDDs meeting the 2007 and 2010 tailpipe standards. This approach will probably overestimate emissions in those years if emissions continue to fall with efficiency improvements (as GREET assumes until 2020).

For a given vehicle and fuel system, GREET separately calculates the following:

  • Consumption of total energy (energy in nonrenewable and renewable sources), fossil fuels (petroleum, natural gas, and coal together), petroleum, coal, and natural gas.

  • Emissions of carbon dioxide (CO2)-equivalent GHGs—primarily CO2, methane (CH4), and nitrous oxide (N2O). (The committee recognizes the potential importance of other climate-change agents, such as black carbon and ozone. Although our estimates of damages unrelated to climate change included particulate matter and ozone, it was not feasible to obtain climate-change-related estimates through GREET.)

5

The committee used Version 1.8b for estimating fuel-related emissions and Version 2.7a for estimating vehicle manufacturing emissions.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-1 Vehicle-Fuel Technologies in the Committee’s Analysis

Light-Duty Autos and Class 1 and 2 Trucks

Heavy-Duty Vehicles

RFG SI autos (conventional oil)

HDGV2B

RFG SI autos (tar sands)

HDGV3

CG SI autos (conventional oil)

HDDV2B

CG SI autos (tar sands)

HDDV3

RFG SIDI autos (conventional oil)

HDDV4

RFG SIDI autos (tar sands)

HDDV5

CNG

HDDV6

E85—dry corn

HDDV7

E85—wet corn

HDDV8A

E85—herbaceous

HDDV8B

E85—corn stover

 

E10—dry corn

 

E10—wet corn

 

E10—herbaceous

 

E10—corn stover

 

Electric

 

Hydrogen (gaseous)

 

Grid-independent SI HEV

 

Grid-dependent SI HEV

 

Diesel (low sulfur)

 

Diesel (Fischer Tropsch)

 

Diesel (soy BD20)

 

NOTES: The modeling analysis included 33 vehicle-fuel technologies (23 light-duty vehicle fuels and 10 heavy-duty vehicle fuels). BD20 = 20% biodiesel blend; CG = conventional gas; CNG = compressed natural gas; E10 = 10% ethanol blend; E85 = 85% ethanol blend; HEV = hybrid electric vehicle; HDDV = heavy-duty diesel vehicle; RFG = reformulate gasoline; SI = spark ignition; SIDI = spark ignition, direct injection.

  • Emissions of six substances that form criteria air pollutants: VOCs, CO, nitrogen oxides (NOx), particulate matter smaller than 10 microns (PM10), particulate matter smaller than 2.5 microns (PM2.5), and sulfur oxides (SOx).

GREET represents “well-to-wheel” life-cycle emissions in four stages: feedstock, fuel, vehicle manufacturing, and operations. For gasoline vehicles, these stages translate to the following:

  • Feedstock: Extraction of oil and its transportation to the refinery.

  • Fuel: Refining of the oil and its transportation to the pump.

  • Vehicle: All emissions associated with production of the vehicle, which accounts for all life-cycle stages because it involves energy use.

  • Operations: Tailpipe and evaporative emissions.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

For other types of vehicles, the stages are analogous. For grid-dependent hybrids, a more complicated example, several energy types are involved. First is the gasoline life cycle for that portion of driving that uses gasoline. Second is the electricity life cycle. In this case, the feedstock emissions are those involving such activities as extraction of coal and natural gas that are weighted to reflect a default mix of electricity-generating technologies. (The committee used a national electricity-generation mix of fuel types taken from the national energy modeling system (NEMS) model for estimating 2030 electricity emissions.) The fuel emissions are those from the power sector’s smokestacks. Emission estimates for vehicle manufacturing are adjusted to reflect the differences between energy and materials requirements for hybrids vs. conventional vehicles, say, regarding battery manufacturing.

The GREET model is fully assumption-driven but comes with a series of default values representing various assumptions. The committee set these values primarily at their default values but tested alternative values when it appeared warranted. See Appendix D for details on settings chosen by the committee.

The level of spatial detail in GREET is limited to whether the emissions are from urban or rural use. This choice appears to be primarily related to considerations of how direct grams per mile emissions from vehicles are dependent on vehicle speeds, which, in turn, are different in an urban vs. rural setting. To estimate damages, however, particularly by air pollutants, a finer degree of spatial detail is necessary.

The committee’s strategy was to define U.S. counties in the 48 contiguous states as either urban or rural and then assign urban or rural emission factors to counties. This approach probably works well for direct vehicle emissions, since every county has vehicle emissions. However, decisions had to be made on where to locate sources of upstream emissions, such as refineries for petroleum and ethanol.

In general, such sources (except for emissions from electricity produced for electric vehicles and grid-dependent vehicles) were assumed to be located in every county, although some adjustments were made for oil refineries, ethanol production, and vehicle manufacturing). The committee located refineries by petroleum administration for defense districts (PADD), calculated damages per unit emissions by PADD from the APEEP model, assigned counties to PADDs, and from there assigned the PADD-specific unit damages to each county. Clearly, these assumptions simplify a complex situation where fuels can be imported as well as domestically produced. But the purpose of the analysis is to examine damages from sources in the United States. Thus, one should interpret the GREET results as what the damages would be if the county featured all the stages of the life cycle, for example, a refinery (see Appendix D for details).

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

Once GREET produces estimates of the emissions per mile associated with various vehicles and fuel types, this information (with the exception of emissions associated with vehicle operation and electricity production for electric vehicles and grid-dependent hybrids) was paired with results from the APEEP model, which provides estimates of the physical health and other non-GHG effects and monetary damages per ton of emissions that form criteria air pollutants.6 For electric and grid-dependent hybrid vehicles, a similar approach was used to estimate damages for the feedstock and vehicle manufacturing components of the life cycle; however, the allocation of electric-utility-related damages to the operations and electricity production components of the life cycle were better approximated by applying a GREET-generated kWh/VMT and applying that to the estimated average national damages per kWh from the electricity analysis presented in Chapter 2 (details of this approach can be found in Appendix D).

Damages are estimated for mortality, morbidity and “other,” which includes recreational damages related to visibility and crop damage related to ozone. These estimates are delivered for individual U.S. counties and for four stack heights, including tall stacks (appropriate for modeling source-receptor relationships [SRRs] associated with electric utility emissions), medium stacks (appropriate for modeling SRRs for industrial emissions), low stacks (appropriate for modeling SRRs for commercial emissions), and ground level (appropriate for modeling mobile-source SRRs). Thus, one can think of there being four matrices of physical and dollar per ton estimates, one matrix for each stack height, with each matrix covering counties and effects and damages. Because we have life-cycle emissions information, emissions per mile estimates at various stages of the life cycle were paired with the appropriate stack-height estimates.

Presentation of Results

Results are provided by light-duty autos, two classes of light-duty trucks and eight classes of heavy-duty diesel trucks, covering 2005 and 2030, for all the vehicle-fuel technologies, all the pollutants, and all the life-cycle stages, as well as for alternative assumptions about the value of statistical life (VSL). All damages are expressed in dollar (2007 USD) per VMT terms, unless specified otherwise. With damages estimated at the county level for the 48 contiguous U.S. states, a distribution of damages over all counties was obtained. Thus, for all life-cycle stages, the 5th and 95th percentile range and median county damages are presented for each

6

A more detailed description of the APEEP model is given in Chapter 2 and Appendix D. In estimating monetary damages, APEEP uses a value of a statistical life of $6 million/year (in 2007 dollars), as discussed further in Chapter 2.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

pollutant, type of effect, year (2005 and 2030), and vehicle-fuel technology combination. For the operation stage, damage estimates are averaged over all the counties, both unweighted and weighted by population. The latter is more realistic as more-populated counties are doing more damage.

The committee also made estimates of these health and other non-GHG damages on a per gallon basis, although interpretation of these estimates is complicated by the fact that those fuel and technology combinations with higher inherent fuel efficiency would appear to have markedly higher damages per gallon than those with lower efficiency solely because of the higher number of miles driven per gallon. Also, GHG-related life-cycle emissions per mile are presented in this chapter, but damages are not discussed here (that occurs in Chapter 5). Information on energy use per mile was also calculated.

Finally, the committee did attempt to estimate aggregate annual damages for light-duty vehicles and heavy-duty vehicles in 2005—by multiplying per mile damages for each of the fuel and technology combinations in use in 2005 by the best estimates available of total VMT. Estimates for light-duty vehicles are somewhat conservative because, given the limitations on separating VMT among light-duty autos and light-duty trucks, we estimated aggregate damages using the per VMT damages we estimated for autos only. Similar estimates could not be made for 2030 given the substantial uncertainty in what fuels and what technology market shares will be at that time.

PRODUCTION AND USE OF PETROLEUM-BASED FUELS

Current Status and Brief History of Petroleum

Crude oil, a nonrenewable energy source, comprises the largest fraction of energy consumed in the United States (Figures 1-3 and 1-4 in Chapter 1). In 2007, the United States consumed 7.5 billion barrels of crude oil and petroleum products, of which nearly 70% was used by the transportation sector. U.S. consumption declined briefly in 1973 because of the Arab OPEC oil embargo (Figure 3-2). In response to the embargo, the U.S. government created the Strategic Petroleum Reserve (SPR). As of 2007, the SPR holds 697 million barrels of crude oil. Once the Arab OPEC embargo was lifted, U.S. consumption dramatically increased until rising oil prices in early 1980s caused a steep decline in consumption. Since the mid-1980s, U.S. oil consumption has steadily risen. In 2007, motor gasoline consumption reached a record high of 9.29 million barrels per day (390 million gallons/day).

Since the mid-20th century, U.S oil consumption has exceeded domestic oil production, thus nearly 60% of crude oil and petroleum products are

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×
FIGURE 3-2 Overview of petroleum consumption, production, and imports from 1949 to 2007. SOURCE: EIA 2008a, p. 124, Figure 5.1.

FIGURE 3-2 Overview of petroleum consumption, production, and imports from 1949 to 2007. SOURCE: EIA 2008a, p. 124, Figure 5.1.

imported. In 2007, 71% of net crude-oil imports came from five countries: Nigeria (11%), Venezuela (12%), Mexico (14%), Saudi Arabia (15%), and Canada (19%). Domestic and imported crude oil are transported to U.S. refineries primarily by pipeline, barge, and ocean tankers (EIA 2008d).

The United States currently has 150 operable oil refineries capable of processing 17.6 million barrels of crude oil per day. Refineries are located in urban and rural areas across the United States. A map of current refineries is provided in Figure 3-3.

Approximately one barrel of crude oil produces 44 gallons of finished petroleum products, including jet fuel, diesel, and gasoline (Figure 3-4). More than 40% of crude oil is refined to finished motor gasoline (Figure 3-5).

U.S. Vehicle Fleet

The U.S. Department of Transportation maintains an online report entitled “National Transportation Statistics.” The report is updated quarterly and includes data beginning in 1960. Table 3-2 provides a summary of the most recent transportation statistics.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×
FIGURE 3-3 Location of U.S. oil refineries. Texas and Alaska each account for large shares of U.S. crude-oil production, but the federal offshore areas in the Gulf of Mexico and California produce roughly a one-fourth share of the U.S. total, which surpasses the individual shares of Texas and Alaska. SOURCE: EIA 2009g.

FIGURE 3-3 Location of U.S. oil refineries. Texas and Alaska each account for large shares of U.S. crude-oil production, but the federal offshore areas in the Gulf of Mexico and California produce roughly a one-fourth share of the U.S. total, which surpasses the individual shares of Texas and Alaska. SOURCE: EIA 2009g.

Technology and Fuel Pathways

Hydrocarbon fuels (gasoline, diesel fuel, and their potential substitutes) have a complex web of production and transport processes that include resource extraction, transport, refining storage, transfers, and combustion. Therefore, to understand externalities, one has to develop a map of the life

FIGURE 3-4 Products made from one barrel of crude oil (gallons). One barrel of crude oil is approximately equal to 45 gallons. SOURCE: EIA 2009h

FIGURE 3-4 Products made from one barrel of crude oil (gallons). One barrel of crude oil is approximately equal to 45 gallons. SOURCE: EIA 2009h

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×
FIGURE 3-5 U.S. refinery and blender net production of refined petroleum products in 2007 (total = 6.57 billion barrels). SOURCE: EIA 2008d.

FIGURE 3-5 U.S. refinery and blender net production of refined petroleum products in 2007 (total = 6.57 billion barrels). SOURCE: EIA 2008d.

cycle of fuel. Different populations are affected at different stages of the life cycle. Despite the complexity, there are a few components of the fuel life cycle that tend to dominate with respect to overall health and environmental damage associated with the full life cycle of a transportation fuel. Figure 3-6 illustrates how the committee conceived the different stages of the fuel life cycle in several key phases: extraction and transport of petroleum feedstock; production and transport of refined product; transport, retail storage, and distribution; fuel use; and waste generation and management to carry out a life-cycle impact assessment. The potential effects of each of these phases are described briefly below.

In general, each phase of the cycle can contribute to deleterious effects from components of the hydrocarbon mixture itself; from activities and materials associated with a particular phase in the fuel cycle (for example, road development for oil production); and from generated wastes or by-products that pollute air, water, and soil or that contribute to climate-change effects.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-2 Number of U.S. Aircraft, Vehicles, Vessels, and Other Conveyances

 

1960

1990

2000

2006

Air

 

 

 

 

Air carriera

2,135

6,083

8,055

U

General aviationb (active fleet)

76,549

198,000

217,533

221,943

Highway, total (registered vehicles)

74,431,800

193,057,376

225,821,241

250,851,833

Passenger car

61,671,390

133,700,496

133,621,420

135,399,945

Motorcycle

574,032

4,259,462

4,346,068

6,686,147

Other 2-axle 4-tire vehicle

N

48,274,555

79,084,979

99,124,775

Truck, single-unit 2-axle 6-tire or more

N

4,486,981

5,926,030

6,649,337

Truck, combinationc

11,914,249

1,708,895

2,096,619

2,169,670

Bus

272,129

626,987

746,125

821,959

Transitd

 

 

 

 

Motor bus

49,600

58,714

75,013

(P) 83,080

Light rail cars

2,856

910

1,327

(P) 1,801

Heavy rail cars

9,010

10,567

10,311

(P) 11,052

Trolley bus

3,826

610

652

(P) 609

Commuter rail cars and locomotives

N

4,982

5,498

(P) 6,403

Demand response

N

16,471

33,080

(P) 43,509

Othere

N

1,197

5,208

(P) 8,741

Rail

 

 

 

 

Class I, freight cars

1,658,292

658,902

560,154

475,415

Class I, locomotive

29,031

18,835

20,028

23,732

Nonclass I, freight cars

32,104

103,527

132,448

120,688

Car companies and shippers freight cars

275,090

449,832

688,194

750,404

Amtrak, passenger train car

N

1,863

1,894

1,191

Amtrak, locomotive

N

318

378

319

Water

 

 

 

 

Nonself-propelled vesselsf

16,777

31,209

33,152

32,211

Self-propelled vesselsg

6,543

8,236

8,202

8,898

Oceangoing steam and motor ships (1,000 gross tons and over)h

2,914

635

461

286

Recreational boatsi

2,450,484

10,996,253

12,782,143

12,746,126

NOTE: N = data do not exist; R = data are revised; U = data are not available.

aAir carrier aircraft are those carrying passengers or cargo for hire under 14 CFR 121 and 14 CFR 135. Beginning in 1990, the number of aircraft is the monthly average of the number of aircraft reported in use for the last 3 months of the year.

b1991-1994 are data revised to reflect changes in adjustment for nonresponse bias with 1996 telephone survey factors; 1995-1997 data may not be comparable to 1994 and earlier years because of changes in methodology. Includes air taxi aircraft.

cIn 1960, this category includes all trucks and other 2-axle 4-tire vehicles.

dPrior to 1984, transit excludes most rural and smaller systems funded via Sections 18 and

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

16(b)(2), Urban Mass Transportation Act of 1964, as amended. Also prior to 1984, includes total vehicles owned and leased.

eOther includes aerial tramway, automated guideway transit, cablecar, ferry boat, inclined plane, monorail, and vanpool.

fNonself-propelled vessels include dry-cargo barges, tank barges, and railroad-car floats.

gSelf-propelled vessels include dry-cargo and passenger, offshore supply vessels, railroad-car ferries, tankers, and towboats.

hBeginning in 2006, vessels are reported if they are greater than 10,000 deadweight tons, and prior to 2006, boats of greater than 1000 deadweight tons were reported.

iRecreational vessels include those required to be numbered in accordance with Chapter 123 of Title 46 U.S.C.

SOURCE: BTS 2009, Table 1-11.

This section describes pollutant releases and other stressors that can lead to effects described above. It does not attempt to quantify effects and does not attempt to assess the efficacy of the various approaches used to manage risks of those effects.

FIGURE 3-6 Conceptual stages of fuel life cycle. SOURCE: Adapted from Energy Biosciences Institute, University of California.

FIGURE 3-6 Conceptual stages of fuel life cycle. SOURCE: Adapted from Energy Biosciences Institute, University of California.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

Each phase of the petroleum cycle involves the use of electricity. Because Chapter 2 discusses life-cycle effects associated with electricity production, they are not included here.

Extracting Crude Oil

Conventional Oil Reserve The major oil producing areas in the United States are in the Gulf of Mexico region (onshore and offshore), California, and Alaska. As of 2007, there were about 500,000 active oil wells in the United States (onshore and offshore) (EIA 2008a, p. 127, Table 5.2). Much of U.S. extraction activities take place near sensitive coastal and estuarine habits.

When a potential oil reservoir is discovered, exploratory drilling is conducted to confirm the presence of oil. For onshore drilling, the land is cleared and leveled to construct a drill platform and install ancillary equipment. Depending on the location, roads, air strips, and buildings may also be constructed. Offshore, floating barges, semi-submersible vessels, or specially designed floating oil rigs are used to support exploratory drilling (API 2009). Inland water and wetland drilling and transportation can have significant effects on wetlands and estuarine habitats, requiring additional techniques to reduce disruption of those ecologic habitats.

Land is excavated to form a reserve pit where wastes from drilling are placed. Drilling wastes from offshore operations can cause a rapid build-up of a debris layer on the ocean floor that can degrade benthic communities. Drilling wastes may contain trace amounts of mercury, cadmium, arsenic, and hydrocarbons.

Drilling operations also produce combustion-related emissions, such as exhaust from diesel engines and turbines that power the drilling equipment. Hydrogen sulfide may be released.

When the presence of oil is confirmed, oil wells are constructed to extract the crude oil. Initially, oil may rise by “natural lift.” Over time, mechanical pumps or injection methods, using steam, for example, are needed to bring the oil to the surface. Storage tanks, pipelines, and processing plants are also built.

Crude oil is prepared for shipment to storage facilities and then to off-site refineries. Natural gas can be separated from the oil at the well site and processed for sale, or the gas can be flared as a waste (usually at onshore operations), releasing CO, NOx, and possibly sulfur dioxide (SO2) if the gas is sour. Triethylene glycol is commonly used as a desiccant to remove water from the gas.

Wastewater generated at the production facility may contain organic compounds (for example, benzene and naphthalene), inorganics (for example, lead and arsenic), and radionuclides. VOCs may be emitted via

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

leaks from the production process equipment. Emissions also occur from combustion of fuel to operate machinery.

Oil spills may come from storage tanks, during transfers, or from pipes, valves, joints, or gauges. For onshore spills, concern is for surface-water contamination via runoff and for seepage into groundwater. Effects of offshore spills can vary substantially, depending on factors such as coastal proximity and degree of turbulence. Accidents known as well blowouts can result in large releases of contaminated water, oil, methane, or other fluids. The mixture can be spread in a wide area around the rig, possibly leaching through the soil to a freshwater aquifer or running off into nearby surface waters. The blowout may also result in a well fire.


Nonconventional Oil Reserve: Oil Sand Oil sands (also called tar sands or bituminous sands) contain a viscous oil referred to as bitumen that serves as a nonconventional source of synthetic crude oil. Oil sands can be extracted by surface mining using methods similar to those used for coal. The sands are transported to an extraction plant, where bitumen is separated from the sands using hot water and agitation. Once separated, the bitumen is upgraded to synthetic crude oil, which can then be refined into fuels. Approximately 2 tons of tar sands generates one barrel of synthetic crude oil In situ extraction is generally used for deep oil-sand deposits. Heat is applied underground, and bitumen is pumped to the surface for subsequent refining.

Currently, there is no production of synthetic crude oil from tar sands in the United States. The largest commercial oils sands industry is located in Alberta, Canada. Oil sands contribute more than 40% of total crude-oil production in Canada. Approximately 20% of crude oil imported into the United States is from Canada.

Impacts of oil-sand extraction and processing generally arise from degradation of ecological habitats, water and consumption, and waste (tailings) disposal. Canada’s National Energy Board reports surface and in situ mining operations require 2-4.5 barrels of water to produce one barrel of synthetic crude oil (NEB 2006). Tar-sand extraction and upgrading also requires a high level of energy input. Natural gas is used to heat steam and generate electricity required for in situ recovery, as well as to upgrade bitumen. The government of Alberta reports that oil-sand production is responsible for 5% of Canada’s GHG emissions (Alberta 2008).


Nonconventional Oil Reserve: Oil Shale Oil shale is a sedimentary rock that contains kerogen, a solid bituminous material that can be processed to create synthetic crude oil. The United States contains the world’s largest deposit of oil shale. The Green River Formation of Colorado, Utah, and Wyoming contains an estimated 800 billion barrels of recoverable oil (BLM 2008). Although technological methods exist to extract crude oil from oil

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

shale, commercial extraction and processing is not economically or environmentally viable in the United States.

Potential impacts from oil-shale extraction arise from changes in land use, habitat disturbance, mining waste production, water consumption, and energy consumption. Oil-shale development is expected to consume between two and five barrels of water per barrel of oil produced (Bartis et al. 2005).

From among this wide range of potential impacts at different stages of resource extraction, the committee was constrained—by the limitations of the GREET model and the scarcity of available national databases on many ecosystem impacts and other impacts—to quantify only those impacts that result directly or indirectly from energy use and the air-quality emissions produced during these operations.

Refining Crude Oil

Refineries separate conventional and synthetic crude oil into different petroleum products that can be used as fuels, lubricants, chemical feedstocks, and other oil-based products. Fuels make up the vast majority of the output (see Figure 3-5). Pollutants generated during crude-oil refining typically include VOCs, CO, SOx, NOx, particulates, ammonia (NH3), hydrogen sulfide (H2S), metals, spent acids, and numerous toxic organic compounds. Emissions occur throughout refineries and arise from the thousands of potential sources, such as valves, pumps, tanks, pressure relief valves, and flanges. Emissions also originate from the loading and unloading of materials (such as VOCs released during charging of tanks and loading of barges), as well as from wastewater-treatment processes (such as aeration and holding ponds).

Relatively large volumes of wastewater are generated by the petroleum refining industry, including contaminated surface water runoff and process water. Accidental releases of liquid hydrocarbons have the potential to contaminate large volumes of groundwater and surface water, possibly posing a substantial risk to human health and the environment.

Storage tanks are used throughout the refining process to store crude oil, intermediate products, finished products, and other materials. The tanks are a considerable source of VOC emissions. Hazardous and nonhazardous wastes are generated from many of the refining processes, petroleum handling operations, as well as wastewater treatment.

Transporting and Distributing Crude Oil and Refined Products

Oil imported to the United States from outside North America is transported predominantly by ocean tanker. Imports from Canada flow through several pipelines that connect with the U.S. pipeline infrastructure

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

in Illinois, Oklahoma, Wyoming, and Washington. Crude oil is transported from production operations to refineries by tankers, barges, rail tank cars, tank trucks, and pipelines. Refined petroleum products are conveyed to fuel marketing terminals and petrochemical industries by these same modes. From the fuel marketing terminals, the fuels are delivered by tank trucks to service stations, other commercial facilities, and local bulk storage plants. The final destination for gasoline is usually a motor-vehicle gasoline tank.

The United States has an extensive oil pipeline network used to transport oil from wells and ocean tankers to refineries. There are about 30,000-40,000 gathering pipelines and 55,0000 trunk pipelines to transport oil in the United States (API/AOPL 2007). Pipelines also carry refined petroleum products from oil refineries to bulk terminal storage sites. There is an estimated 95,000 miles of pipelines carrying refined petroleum products (API/AOPL 2007). Airports often have dedicated pipelines to carry fuel directly to them (API/AOPL 2007).

Transport and distribution of oil is a source of air pollution. Each of the transport and distribution activities is a potential source of evaporation loss. Transport of crude oil and refined petroleum products also present risks of oil leaks, spills, and large scale accidents (for example, the 1989 Exxon Valdez oil spill). Environmental releases of crude oil or refined petroleum products can pollute terrestrial and aquatic habitats as well as drinking water. The NRC report Oil in the Sea III: Inputs, Fates, and Effects (NRC 2003c) assessed data gathered between 1990 and 1999 and estimated that 9,100 tons of petroleum are released in North American waters as a result of transportation of crude oil and refined products. Pipeline leaks and other accidents related to petroleum fuel are discussed in Chapter 6.

Storing Refined Products

Crude oil and refined petroleum products are stored in large volumes throughout the fuel cycle. In 2008, more than 338 million barrels of crude oil and refined products were held in storage at refineries. Bulk terminal storage facilities held more than 320 million barrels of refined petroleum products, including distillate fuel oils (diesel fuel), gasoline, and aviation fuels. Finished gasoline and diesel fuel are also stored in underground storage tanks (USTs) at gasoline stations. EPA regulates more than 623,000 USTs at approximately 235,000 locations (EPA 2009g).

The primary concern surrounding storage tanks is the potential for leaks, spills, and explosions. Similar to pipelines, crude oil and refined petroleum products leaking from storage tanks can accumulate into soils and seep into surface and groundwater, contaminating terrestrial and aquatic habitats as well as drinking-water resources. Since 1988, there have been

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

about 479,800 confirmed releases from USTs and about 377,000 completed clean-ups (EPA 2008b). Storage tanks are also a source of evaporative emissions.

Using Fuel for Light-Duty and Heavy-Duty Transportation

The category of on-road or highway mobile sources includes vehicles used on roads for transportation of passengers or freight. On-road vehicles are further divided in such categories as light-duty vehicles, light-duty trucks, heavy-duty vehicles, and motorcycles. The vehicles may be fueled with gasoline, diesel fuel, or alternative fuels, such as alcohol or natural gas. Nonroad sources include vehicles, aircraft, marine vessels, and locomotives, and other vehicles and equipment used for construction, agriculture, and recreation.

Cars, trucks, and buses consumed about 80% of the transportation energy used in the United States in 2007. Portions used by other transport modes are air (9%), water (5.2%), pipeline (3%), and rail (2.4%) (Davis et al. 2009).

NAS/NAE/NRC (2009d) indicates that incremental improvements in vehicle technology could reduce the fuel consumption of gasoline internal-combustion-engine vehicles by up to 35% over the next 25 years. Diesel-fueled trucks are expected to continue dominating the freight transportation sector for at least the next 25 years. The report estimates 10-20% reductions in fuel use by heavy-duty and medium-duty vehicles by 2020, resulting mostly from technological and design improvements. Advances in jet engine and aircraft technology have the potential to improve the efficiency of new aircraft (for passenger and freight) by up to 35% over the next two decades. The AEF report indicates that it is feasible to reduce energy consumption in marine shipping by 20-30% by 2020 through a combination of technological innovations (such as improved hull design) and systems improvements (such as speed reduction). Technological improvements could reduce CO2 emissions by 5-30% in new vessels and 4-20% in existing ones.

Combustion of petroleum-based fuels by motor vehicles results in exhaust emissions that include VOCs, NOx, particulate matter, CO, and CO2. Evaporative emissions from the onboard reservoir of unburned fuel can occur while the vehicle is in use or when the engine is turned off.

Vehicle emissions include a class of pollutants referred to as air toxics. These include known carcinogens, such as benzene, and probable human carcinogens, such as formaldehyde and diesel particulate matter. EPA estimates that mobile sources of air toxics account for about half of all cancers attributed to outdoor sources of air toxics. Some toxic compounds occur naturally in petroleum and become more concentrated when petroleum is

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

refined. Others are not present in fuel but are formed as by-products in the vehicle exhaust or formed from reactions of vehicle emissions in the atmosphere.

Lead emissions occur from piston-engine aircraft that use a commonly available aviation gas 100LL (100 octane low lead). Lead is added to 100LL in the form of tetraethyl lead to improve engine performance. Lead is not added to jet fuel that is used in commercial aircraft, military aircraft, or other turbine-engine-powered aircraft (EPA 2008c).

Modeled Estimates of Life-Cycle Emissions and Damages from Petroleum Use in Light-Duty and Heavy-Duty Highway Transportation

The committee selected VMT as the primary unit for characterizing external damages for highway transportation. Rather than a gallon of fuel, which is difficult to compare because of large variations in energy content, or a joule of delivered energy, which depends strongly on vehicle efficiency, the VMT best characterizes the type of service associated with transportation vehicles. The use of VMT as the functional unit for comparison makes it possible to address the life-cycle impacts of fuel and vehicle technology combinations, which was a key goal for comparing current and future damages for transportation options. There is also the option of using person-VMT, but this option requires assumptions about vehicle passenger loads that confuse the goal.

Modeling damages from the life-cycle emissions attributable to petroleum requires characterization of emission factors for both the life cycle of the fuel and the production and operation of the vehicle. Both GHG emissions expressed as CO2-equivalent and local air-pollution emissions are included. For air-pollution emissions, not only the magnitude of the emissions (per VMT) but also the geographic distribution of the emissions is important. The committee modeled the monetized damages associated with pollutant emissions using the APEEP model. For GHG emissions, for which damages do not depend on the geographic location of release, only the life-cycle CO2-equivalent emissions for the petroleum and vehicle life cycle are reported. Damages for CO2-equivalent emissions are discussed in Chapter 5.

Emissions Characterization

Emissions characterization included life-cycle emissions for light-duty gasoline- and diesel-fueled vehicles and for heavy-duty diesel vehicles for 2005 and 2030 fuel and vehicle technology combinations. Life-cycle emissions for gasoline- and diesel-fueled light-duty vehicles are obtained primarily from GREET (Argonne National Laboratory 2009) and include emissions of GHGs, VOCs, NOx, SOx direct PM2.5, secondarily formed

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

PM2.5 (from VOCs, NOx, and SOx emissions) and secondarily formed ozone (from VOC and NOx emissions). The committee carried out its own analysis to obtain (1) life-cycle NH3 emissions related to PM2.5 formation for 2005 and 2030, (2) emissions from gasoline- and diesel-fueled heavy-duty vehicles for 2005 and 2030 (which are not covered in GREET), and (3) estimated emissions for those substances covered in GREET for the year 2030 based on using the most current 2020 data in GREET, further updated to incorporate the expect 35.5 mpg required fuel efficiency after 2016 (see discussion in Scope of the Analysis above and in Appendix D on how this analysis was accomplished). For each pollutant-vehicle mix, emissions per VMT include emissions from (1) feedstock production, (2) fuel production, (3) vehicle operation, and (4) vehicle production (except heavy-duty vehicles). To assess health and other monetized damages, emissions from vehicle operation are allocated to U.S. counties based on the estimated fraction of aggregate U.S. VMT that occur within that county. Emissions for other stages are allocated to regions based on the geographic distribution of the economic activity associated with each specific life stage, for example, the distribution for refineries.

Results

Table 3-3 contains a summary of the results from the GREET-APEEP modeling effort related to gasoline and diesel fuels in light-duty autos. Calculations were also carried out for light-duty trucks, but these did not vary significantly from the results for light-duty autos. Each row of Table 3-3 contains the range- and population-adjusted mean for health damages in 2005 and 2030 reported on a VMT basis. There is also a column showing the health costs per gasoline gallon equivalent (gge). It can be seen from this table that year 2005 health impacts do not vary significantly among the fuel-vehicle technology options. Only compression ignition, direct injection using Fischer-Tropsch diesel shows a significant difference from other options, largely due to the more-intense energy use needed to process that type of fuel. (In its analysis, the committee considered only the use of methane for the production of Fischer-Tropsch diesel fuel.) Although damages from 2005 to 2030 would be expected to increase due to population growth, the increase is largely offset in these analyses by the substantial increase in fuel economy to 35.5 mpg by 2016.

Table 3-4 provides a summary of the modeling results from the GREET-APEEP modeling effort related to gasoline and diesel fuels in heavy-duty vehicles. Each row of Table 3-4 lists the range- and population-adjusted mean for health and other non-GHG damages on a VMT basis in 2005 and 2030. A column shows the health and other non-GHG damages per gasoline gallon equivalent for light-duty vehicles. Within the heavy-duty class, larger vehicles have a greater impact per VMT, as is expected. A

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-3 Health and Other Non-GHG Damages from a Series of Gasoline and Diesel Fuels Used in Light-Duty Automobilesa

 

2005

2030

5th and 95th Percentile Rangeb (Cents/VMT)

Population-adjusted Mean (Cents/VMT)

Population-adjusted Mean (Cents/gge)c

5th and 95th Percentile Rangeb (Cents/VMT)

Population-adjusted Mean (Cents/VMT)

Conventional gasoline (SI, petroleum)

0.34-5.07

1.34

29.02

0.43-4.87

1.35

Conventional gasoline (SI, tar sands)

0.35-5.36

1.35

29.26

0.45-4.99

1.36

Reformulated gasoline (SI, petroleum)

0.35-5.12

1.38

29.83

0.45-4.87

1.35

Reformulated gasoline (SI, tar sands)

0.35-5.40

1.39

30.07

0.45-4.99

1.36

Reformulated gasoline (SIDI, petroleum)

0.33-4.89

1.32

32.68

0.45-4.96

1.37

Reformulated gasoline (SIDI, tar sands)

0.33-5.14

1.33

32.92

0.45-5.09

1.38

CIDI using low-sulfur diesel

0.30-7.57

1.49

38.65

0.40-4.22

1.19

CIDI using Fischer-Tropsch diesel

0.41-7.77

1.80

46.65

0.58-5.48

1.61

aCosts are in 2007 USD.

bFrom the distribution of results for all counties in the 48 contiguous states in the United States.

cCents/gallon of gasoline equivalent, calculated by multiplying average miles per gallon by per VMT damages. This calculation will therefore show highest damages for the most fuel-efficient vehicles. Costs are in 2007 USD.

ABBREVIATIONS: GHG = greenhouse gas; VMT = vehicle miles traveled; gge = gasoline gallon equivalent; SI = spark ignition; SIDI = spark ignition, direct injection; CIDI = compression ignition, direct injection.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-4 Health and Other Damages Not Related to Climate Change from a Series of Gasoline and Diesel Fuels Used in Heavy-Duty Vehiclesa

 

2005

2030

5th and 95th Percentile Rangeb (Cents/VMT)

Population-adjusted Mean (Cents/VMT)

Population-adjusted Mean (Cents/gge)

5th and 95th Percentile Range (Cents/VMT)

Population-adjusted Mean (Cents/VMT)

HDGV2B

Heavy-duty gasoline vehicles class 2B

1.01-31.89

6.14

61.39

0.36-11.43

1.87

HDGV3

Heavy-duty gasoline vehicles class 3

1.15-38.82

7.23

66.47

0.41-13.86

2.41

HDDV2B

Heavy-duty diesel vehicles class 2B

0.46-18.79

3.23

41.34

0.24-8.63

1.23

HDDV3

Heavy-duty diesel vehicles class 3

0.51-20.76

3.58

41.50

0.27-9.87

1.39

HDDV4

Heavy-duty diesel vehicles class 4

0.20-22.83

3.90

39.40

0.29-10.26

1.53

HDDV5

Heavy-duty diesel vehicles class 5

0.68-31.87

5.29

51.87

0.33-13.47

1.76

HDDV6

Heavy-duty diesel vehicles class 6

0.88-38.38

6.49

56.48

0.38-15.92

1.97

HDDV7

Heavy-duty diesel vehicles class 7

1.08-47.53

8.01

60.08

0.45-15.92

2.39

HDDV8A

Heavy-duty diesel vehicles class 8A

−0.50-56.61

9.47

61.52

0.47-16.77

2.53

HDDV8B

Heavy-duty diesel vehicles class 8B

−2.20-62.65

10.41

64.53

0.49-16.94

2.63

aCosts are in 2007 USD.

bFrom the distribution of results for all counties in the 48 contiguous states in the United States.

ABBREVIATIONS: VMT = vehicle miles traveled; gge = gasoline gallon equivalent.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

significant decrease in impacts is also seen from 2005 to 2030 in spite of rising populations. The decrease is attributable to lower particulate matter and SO2 emissions from heavy-duty vehicles in 2030 relative to 2005. Negative cost estimates represent conditions for which NOx emissions from vehicles would contribute to a decrease in ambient ozone concentration, when particulate matter emissions are reduced. For the pollutants considered and for these few cases, the negative results reflect benefits within this analytical framework.

Table 3-5 shows how emissions of CO2-equivalent vary among different fuel types, among different vehicle types, and between the years 2005 and 2030 on a VMT basis. Although there is a significant difference between CO2-equivalent emissions from light-duty vehicles and those from heavy-duty vehicles, there is not a significant difference among light-duty

TABLE 3-5 Carbon Dioxide Equivalent (CO2-eq) Emissions of GHGs from a Series of Gasoline and Diesel Fuels

Fuel and Vehicle Combination

CO2-eq 2005 g/VMT

CO2-eq 2030 g/VMT

RFG SI autos (conventional oil)

552

365

RFG SI autos (tar sands)

599

399

CG SI autos (conventional oil)

564

365

CG SI autos (tar sands)

611

399

RFG SIDI autos (conventional oil)

487

366

RFG SIDI autos (tar sands)

527

399

Diesel (low sulfur)

476

372

Diesel (Fischer Tropsch)

537

401

HDGV2B heavy-duty gasoline vehicles class 2B

1,095

1,080

HDGV3 heavy-duty gasoline vehicles class 3

1,187

1,165

HDDV2B heavy-duty diesel vehicles class 2B

969

957

HDDV3 heavy-duty diesel vehicles class 3

1,071

1,064

HDDV4 heavy-duty diesel vehicles class 4

1,224

1,216

HDDV5 heavy-duty diesel vehicles class 5

1,262

1,255

HDDV6 heavy-duty diesel vehicles class 6

1,433

1,424

HDDV7 heavy-duty diesel vehicles class 7

1,650

1,647

HDDV8A heavy-duty diesel vehicles class 8A

1,903

1,882

HDDV8B heavy-duty diesel vehicles class 8B

2,007

1,969

NOTE: 2030 estimates assume 35.5 mpg for all light-duty vehicles.

ABBREVIATIONS: GHGs = greenhouse gases; VMT = vehicle miles traveled; RFG = reformulated gasoline; SI = spark ignition; SIDI = spark ignition, direct injection; CG = conventional gas.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
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vehicles in CO2-equivalent emissions, with the exception that the vehicles fueled with petroleum derived from oil shale had notably higher life-cycle emissions.

Regarding GHG emissions, there is no significant reduction in CO2-equivalent releases per VMT between 2005 and 2030.

PRODUCTION AND USE OF BIOFUELS

History and Current Status

It has long been known that alcohols, which are produced from the fermentation of sugars, can be used as a fuel in internal combustion engines. Serious and recent interest in the production of biofuels for transportation was spurred by the oil embargo and petroleum supply disruptions that occurred in the 1970s. This interest in producing biofuels from biomass was of interest because biomass could be grown domestically and could serve as a possible substitution for petroleum. Also, if the crops growing the biomass feedstock were managed properly, it could serve as a renewable fuel—that is, each year, or on some appropriate crops rotation bases, fuels could be continually produced. In recent years, the potential benefit of biofuels to reduce the amount of GHGs per unit energy content of fuel compared with petroleum and other fossil-fuel-based sources of transportation fuels has become another important factor in developing production and vehicle technologies for the use of biofuels.

Ethanol produced from corn is currently the largest and most economically viable biofuel being produced in the United States (biodiesel from soy is the second largest). Ethanol’s production has grown over the years stimulated by federal subsidies and rose to a level of about 8 billion gallons per year in 2008. Corn is the primary feedstock in the United States and is converted to ethanol through dry-milling or wet-milling production processes (NRC 2008c). One bushel of corn produces about 2.8 gallons of ethanol. In Brazil, sugar cane is the primary crop used, and an extensive ethanol industry has evolved, producing about 4.5 billion gallons per year to fuel vehicles that can use mixtures of gasoline and ethanol.

Regulations and Technologies Current and Anticipated in 2030

The Energy Independence and Security Act (EISA) of 2007 stipulates that 36 billion gallons per year of biofuels should be produced and used by 2022, with 21 billion gallons per year produced from cellulose-based technologies beyond an expected corn-based ethanol target for 2015 of 15 billion gallons per year. Both the legislation and energy analysts see cellulosic-based biofuels as the most important long-term feedstock for

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
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producing ethanol, with the underlying assumption that in the long term, breakthroughs and bioengineering of organisms might lead to processes that convert cellulose through more advanced production technologies to produce other fuels, such as gasoline, biobutanol, or possibly hydrogen. Whether these targets stipulated in EISA will be realized depend on how quickly the technology for production of biofuels evolves, the cost of such fuels, federal policies, and the economics of the fuel market.

Biofuel Supply

The Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts (NAS/NAE/NRC 2009c) report from the America’s Energy Future (AEF) study provides summaries of the likely technologies and growth in the use of coal and biomass liquid transportation fuels until 2020. They identify the primary technologies for converting cellulosic feedstocks (biochemical and thermochemical), discussing many of the technological challenges associated with each.

Table 3-6 lists the main feedstocks that the AEF panel discussed, the time frame in which these feedstocks are expected to be technologically and economically viable, the region of the United States in which they are most likely to be of significant magnitude and a qualitative list of the externalities that may be associated with the production of these feedstocks.

Of the feedstocks identified in Table 3-6, only corn-grain ethanol is in production at a scale that can be viewed as significant and technologically mature. Thus, only reasonable speculations can be made about the other feedstocks and their market location and associated set and magnitude of externalities. Overall, the recently completed analysis of the prospects for these sources by the AEF study estimated that approximately 420 million tons of a variety of such fuels could be produced using technologies available today, and 550 million tons could be produced using technologies expected by 2020 (NAS/NAE/NRC 2009c, Table S-1). It is difficult to accurately project what that will mean in terms of actual fuel produced; indeed, the rapidity with which the corn ethanol market has grown and the volatility of prices mean that neither the technology nor the set of externalities generated by its presence are particularly well understood or appraised.

Given the uncertainties associated with these feedstocks, the committee has identified three that are among the most likely to be relied upon and for which some data are available from which we can produce educated guesses concerning the likely externalities associated with them. The feedstock we focus on for further analysis include the following: corn grain, corn stover, and a perennial grass to produce transportation fuels. These feedstocks represent the current technology (corn grain), a likely mid-term technology (corn stover) and a likely long-term, so-called “second generation” technology (perennial grasses).

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
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TABLE 3-6 Feedstocks Identified in AEF Report and Partial List of Their Externalities

Feedstock

Time Frame

Likely Location

Potential Externalities

Corn, grain

Current

Corn Belt

Water quality (nutrients, sediment, pesticides), wildlife habitat, GHG

Corn stover

a

Corn Belt

Soil erosion and water quality, carbon sequestration in soils, GHG

Traditional hay crops (alfalfa and clover)

a

Pacific Northwest, Great Plains

Wildlife habitat

Perennial grasses

a

Existing CRP land (spread throughout the U.S.), marginal lands, existing crop land

Water quantity, water quality (nutrients, sediment, pesticides), wildlife habitat, GHG

Switchgrass

Miscanthus

Diverse mixes

Woody biomass (hybrid polar and willow, forest industry residues, fuel treatment residues, forest product residues, and urban wood residues)

a

a

Forest fires

Animal manure

a

a

Water quality (positive externality if diverted from excess agricultural application or storage spills)

Waste paper and paperboard

a

a

 

Municipal solid wastes

a

a

 

aAn analysis of the potential for these fuels can be found in NAS/NAE/NRC 2009c.

Another biofuel under consideration and in some use is the so-called biodiesel, that is, fuels derived from biomass that can replace diesel fuels for use in diesel engines. Typically, biodiesel refers to fuels produced from crops that contain oils, such as soy beans, which can be converted quite efficiently with well-known processes into diesel fuel. The NRC (2008c) estimates that because of limitations on soy bean production, only about 1.5 billion gal-

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

lons per year of soy-based diesel fuel could be produced without significant impacts on the food and agricultural markets. Demand for biodiesel greater than that would probably have to be satisfied with imports. Other investigators are pursuing research and development on the production of biodiesel through the growth of algae in algal farms, but there is disagreement on how far from commercial readiness this technology might be. Its potential role probably lies in the 2020-2035 time frame and beyond.

Fuel Cycle and Externalities

The upstream production externalities of feedstock effects will be location-specific because different feedstocks will be economically viable in different locations (for example, corn stover and switchgrass in the Corn Belt region, miscanthus in warm climates, and trees and forestry in the southeast). In addition, the externalities associated with any given feedstock are also likely to vary by specific field and watershed within a region (such as depending on climate, land-use history, soils, slope of the land, and proximity to water bodies) and can be attenuated by farming practices (such as the use of conservation tillage, nutrient management of both fertilizer and manure applications, and placement of buffers or wetlands).

Finally, transportation of feedstocks to processing facilities is expected to remain expensive even after technological improvements so that numerous, small processing facilities located throughout the region is a likely configuration of the industry. Therefore, externalities associated with production and transportation of the feedstock and liquid fuels will be both site-specific and widespread (the AEF reports that “hundreds of conversion plants, and associated fuel transportation and delivery infrastructure” (NAS/NAE/NRC 2009c, p. 5) will be needed. The AEF report also calls for watershed-specific studies to address the suite of externalities and technological challenges associated with alternative feedstocks.

In characterizing the externalities associated with liquid transportation fuels from biomass, the externalities generated at each of the following stages need to be considered:

  1. Production of the feedstock (farm or forest externalities).

  2. Transportation of the feedstock to the processing facility.

  3. Processing of the feedstock into liquid fuels.

  4. Transportation of the fuel to distribution endpoints.

  5. Downstream effects of using the fuel.

There may be different external effects and different magnitudes of externalities along each of those steps associated with each type of feedstock. A complete externality accounting would need to include those occurring at

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

each step. The externalities listed in Table 3-6 are those associated primarily with the first step, the production of the feedstock.

The technology associated with transforming alternative feedstocks into fuel is developing for the cellulosic feedstocks and include biochemical and thermochemical conversion processes. In both cases, a large quantity of water is required for processing that, in water-constrained areas, will probably constitute an externality (measured in terms of increased water scarcity via quicker drawdown of reservoirs and increased pumping costs). Water and air emissions will probably be externalities as well.

The Sources of Externalities in Production of Feedstocks

The three feedstocks that the committee targeted for analysis all require land for their growth and production. Eventually, all three feedstocks as well as a mixture of others may be used to produce biofuels and may compete with each other for land and profitability or may be located in different regions of the country. Briefly, the externalities investigated and the way in which feedstock can generate the externality are described next.


GHG Emissions The production and harvesting of corn generates GHG emissions in a number of ways, including the use of fuel for tillage, planting, applying inputs (nutrients and pesticides), harvesting, and shipping of the product. By tilling the soil in preparation for planting, carbon that is stored in soil is released into the atmosphere. Farmers that practice conservation tillage (one of many forms of reduced or no tillage) generally increase the carbon stored in the soil (carbon is sequestered), but this tillage practice is not profitable for all farmers and depends on the characteristics of the land, climate, and crop grown. Currently, regardless of tillage practice, corn stover is left to decompose and rebuild carbon and other nutrients in the soil.

If corn stover were to be used for ethanol production, it would be removed from the soil and therefore not left to decompose and rebuild the soil. Agronomists and others debate about how much stover can be removed to maintain soil productivity, but there is no reason to believe that soil carbon storage does not decline immediately as stover is removed (although the magnitude could be quite small). Thus, on any given field, biofuel production using stover can be expected to have the same GHG emission consequences associated with planting and harvesting corn as just described, with additional losses of carbon sequestration. There may be additional fuel usage needs for the stover to be harvested, and almost certainly there will be high fuel needs for the transportation of stover from the field to the processing facility.

Switchgrass or other perennial grass will not need annual planting or

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
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tilling once established, and, hence, should have lower fuel usage and corresponding GHG emissions than corn production. The degree to which switchgrass or other perennial will be fertilized is unclear. Large-scale commercial production of switchgrass is not currently viable, so the amount of inputs that farmers will use to maximize their profitability of growing this crop is unclear. Heggenstaller et al. (2009) provides estimates of fertilization that maximizes profitability.

A number of studies have looked at the life-cycle emissions of GHGs associated with ethanol produced from various feedstocks. Delucchi (2006) provides such an analysis and a review of earlier analyses. Estimates by NAS/NAE/NRC (2009c) of well-to-wheels CO2-equivalent emissions in tonnes per barrel gasoline equivalent7 are the following: for petroleum-based gasoline, 0.40; for corn ethanol, 0.22; for biochemical cellulosic ethanol, −0.02; for thermochemical coal and biomass conversion, 0.5, and with carbon capture and storage (CCS), −0.19; and for thermochemical biomass conversion, −0.12, and with CCS, −0.95. Thus, there could b significant GHG benefits for biomass fuels as well as a reduced dependence on imports, although the projections by NAS/NAE/NRC (2009c) indicated that biofuels could replace only a proportion of what is consumed in the transportation sector. The impacts on reducing CO2 emissions could be significant, especially if CCS technology is developed between now and 2020, becomes ready for commercial deployment, and can be coupled to some of the technologies, such as gasification-based systems.

The committee used estimates from GREET to generate estimates of the GHG emissions from alternative feedstocks.


Water Quality and Soil Erosion Corn is a heavily fertilized crop with large water demands. The major water-quality issues related to corn production include the runoff of nitrogen, phosphorus, and sediment. The amount of nutrients and sediment that leave a field can vary greatly depending on the slope of the land, climate (particularly heavy rains), field tiling, cropping history, soil type, tillage practice, and a variety of other factors. Thus, to undertake a careful analysis of the water-quality consequences of corn production, one must know where the additional corn that would be used for feedstocks would be produced as well as such information as how the field is managed and whether any conservation practices are in place. To further complicate the issue, the amount of pollutant that enters a waterway and how far it moves within a waterway depend on a variety of geologic and hydrologic factors.

Additional corn to produce biofuels can come from producing more corn on land that is already in corn production. This can occur by the use

7

One tonne is equal to 2,200 pounds.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
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of more inputs or by changing rotation practices, for example, by moving from a 2-year corn–soybean rotation to the continuous planting of corn. Although continuous corn planting has lower yields than rotated corn, if price differentials are high enough, it will be profitable for farmers to grow corn more often in their rotations. The second way that additional corn can be produced is to grow it on land that was previously not in agricultural production or that was used for a lower valued crop. A major potential source of such land is land that has been placed in the Conservation Reserve Program (CRP), a federal program that pays farmers to have idle land. About 5% of agricultural land nationwide is enrolled in the CRP; this land tends to be of lower value and higher environmental sensitivity than average. The water-quality effects of additional corn production will depend on how and where the additional corn is generated; that in turn will depend on the profitability of corn production for biofuel usage. There is evidence that the higher corn prices experienced in the past 2 years or so has resulted in increased conversion of CRP to working land (Secchi et al. 2009).

If corn stover is used to produce biofuels, the same set of water-quality externalities described above will apply, but will be magnified for two reasons. First, when stover is left on the land, it acts to reduce soil erosion and helps to retain nutrients on the land (especially phosphorus). Second, when stover can be sold for biofuels, the overall profitability of corn production will rise (because the ears can still be sold for biofuels or feed), thus making corn more profitable and increased production more likely.

The water-quality effects associated with perennial grasses will also depend on the location in which they are grown, but their perennial nature and lower input use (although again without evidence of how these crops will be commercially grown, this is difficult to gauge) should translate into lower water-quality impacts than corn-production impacts.


Wildlife Habitat and Biodiversity The effect on wildlife and biodiversity from using more land for corn or perennial grass production will depend on how the land was used prior to production (for example, whether a different row crop was planted, left idle in CRP, or used as pasture). Perennial grasses are more likely than corn to be suitable habitat for more wildlife, but may be less suitable than the land use prior to biofuels production.

A number of other externalities related to biofuels production and industry expansion should be noted. First, a significant expansion of the industry will require a major increase in production facilities that will generate externalities associated with the building and maintaining of these facilities. Depending upon the technology used to convert feedstocks to ethanol, there may be solid waste or other pollution externalities associated with the ongoing production of ethanol in these facilities. There also are potentially significant concerns about water consumption and ethanol

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
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production. For an extensive discussion, see the recent National Research Council report Water Implications of Biofuels Production in the United States (NRC 2008d).

Indirect Land Use and Externalities

The role of “indirect land use”—changes occurring indirectly as a result of biofuels policy in the United States and the effect of such changes on GHGs—has been a major source of discussion since a paper by Searchinger and colleagues was published in Science in 2008. The argument put forth by Searchinger et al.(2008) is that when demand for corn or farmland in general increases, crop prices increase, making it profitable for farmers to increase their acreage. If this increased acreage comes from plowing up land that has not been in agricultural production and is particularly environmentally sensitive (for example, rainforests in Brazil and pristine ecosystems in the United States), GHG emissions could increase (for example, burning rainforests would release large amounts of carbon) and have other detrimental environmental concerns. The loss of Brazillian rainforests due to these market pressures is particularly cogent, but the issue of increased GHG emissions applies to a variety of land-use changes as long as the land that is brought into production to grow biofuel feedstocks results in lower carbon storage.

Under the requirements of EISA, EPA recently released its revised Renewable Fuels Standards (RFS2). As mandated, EPA performed its life-cycle computation of GHG contributions of corn ethanol, two types of biodiesel, and three cellulosic ethanol feedstocks (sugarcane, switchgrass, and corn stover) using indirect land-use effects as a component of the GHG contribution. In recognition of the uncertainty associated with measuring indirect land-use effects, EPA presented its emission estimates both with and without the indirect effects (see EPA [2009h] for a summary of its life-cycle analysis). The effect of indirect land uses can be quite large; in some cases, EPA’s analysis suggests that significant positive gains in GHG of a fuel relative to gasoline could be largely offset by indirect land use changes. The state of California has also adopted the approach of including indirect land-use effects in its fuel standards.

The committee’s task in this report is to identify and monetize the externalities associated with energy production and consumption. We discussed whether these externalities should include both the direct and the indirect land-use effects and chose to report only the direct land-use effects (as captured in GREET). In doing so, we by no means dismiss the potential importance of indirect land-use effects in policy design, but we do not wish to treat externalities associated with the production of biofuels any differently than the externalities associated with the production of other fuels.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

Why did we come to this choice? First, there is an important distinction between the externalities associated with the direct use of land to grow crops for biofuels and the externalities associated with the indirect effects. The indirect effects are induced by price changes and are associated with the production of a second product. To avoid double counting, it is important that the externalities associated with the indirect effects be associated with the second product and not have both assigned to the first product.

For example, when a crop is planted and grown to produce a gallon of ethanol, there are externalities (such as GHGs and changes in water quality) associated with its production; these externalities of course are appropriately counted against the production of that gallon of ethanol. These externalities include the direct land-use effects. In contrast, the indirect effects occur from a market response due to some price changes. When the price of a biofuel crop increases due to a policy that promotes biofuels, farmers elsewhere will find it profitable to plant that crop, which will then be used to produce a second product (perhaps another gallon of biofuels or a food product). This “indirect effect” will generate externalities, but these externalities should be associated with the second product, not the first.

In the specific context of the biofuels land-use debate, the lost carbon and ecosystem services from indirect land-use changes are appropriately viewed as an externality from growing crops elsewhere, say Brazil, not from production of biofuels in the United States. Or if these indirect land uses occur within the United States, they would already be counted as the direct land-use effects of growing biofuels for carbon in that second location. Thus, when estimating the externalities associated with U.S. biofuel production, analysts shouuld include the externalities associated with direct land-use changes to produce the feedstocks, but not the market-induced indirect effects.

The second reason we do not attempt to incorporate indirect land-use effects is that if we were to do so, for consistency we would need to include all market-induced changes in externalities that could be linked to any other energy source. For example, an increase in the price of electricity generated by an expanded electric-vehicle requirement could result in more people using wood-burning stoves in lieu of electric heaters, more usage of gas-powered lawn mowers, and earlier turning out of lights in the evening. The first two changes would increase the negative externalities of smog, GHGs, and noise, whereas the third would reduce light pollution. The accounting of the indirect-effects argument would be to add all of the effects of these externalities on to electric vehicles. These are just a few of the externalities that could be induced by price changes.

The fact that there are two separate externalities associated with production at two locations is not merely an academic distinction; it is critical to keep them separate to avoid double counting and therefore to inform

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
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policy making appropriately, as the second set of externalities may be policy irrelevant. For example, if GHGs worldwide were subject to a tax, then it would be appropriate to tax agricultural crops in the United States based on their GHG emissions and to tax agricultural crops grown elsewhere separately based on their emissions. In this case, it would be inefficient to tax U.S. agricultural crops for the sum of their own emissions plus those associated with land-use changes elsewhere—this would be double counting. Ideally, the U.S. policy would correct the market distortion for the production of externalities for crops grown in the United States, and other governments would do the same. On the other hand, if policy makers in the United States wish to set policy recognizing that GHGs are not optimally regulated elsewhere, then it may be appropriate to tax or regulate U.S. biofuel crops based on more than the direct externalities, taking into account some or all of the indirect externalities induced by market prices. In economics, this would be called policy design in a second-best setting. In this policy design, it generally would not be appropriate to add the damages from the indirect externalities to the direct externalities to form a basis for a tax. For purposes of this report, we do not attempt to explicitly inform decision making in a second-best setting, despite the presence of many distortionary tax elements in the U.S. economy (such as labor taxes and imperfect competitive sectors).

The committee’s goal throughout this report is to define and estimate the externalities associated with the production of energy sources. By providing estimates of the direct effects of land use (as reported in GREET), we are providing an estimate of externalities that are consistent with those presented elsewhere. We recognize the important issue of indirect land uses, but we do not evaluate or incorporate them in our analysis.

Land-Use Externalities from Biofuels: A Case Study of the Boone River Watershed

Given the relatively recent broad interest in biofuels, studies that assess the magnitude and value of externalities related to direct land-use changes and soil carbon provide incomplete coverage of the issues, particularly at the local landscape level where these effects may vary considerably across locations. A number of studies provide information on components of the externalities related to water quality. For example, Donner and Kucharik (2008), Simpson et al. (2008), and Secchi et al. (2009) examine the consequences of expanded corn production to produce ethanol and the amount of nitrogen and phosphorus entering the Gulf of Mexico, therefore potentially contributing to the recurrent hypoxic zone there. Other work addresses the consequences of higher corn prices on conservation reserve lands, and concerns have been expressed about the loss of habitat and lo-

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

cal water quality. Much is still unknown about the set of externalities that a particular region or watershed might be expected to experience with expanded ethanol production.

To demonstrate one approach for estimating some of the externalities that are location-specific, the committee used an existing set of data and models for the Boone River watershed in central Iowa to perform a case study. The estimates for the externalities described here relate to water quality (nutrients and sediment). We stress that this exercise is meant to shed light on the process and approach needed to estimate these externalities associated with ethanol production rather than to provide firm estimates. Further, the estimates are unlikely to be transferable to other regions where biofuels may be produced and to other feedstocks grown for biofuel production.

To evaluate the water quality and carbon sequestration externalities associated with biofuels production in the Boone watershed, we analyzed three possible feedstocks: corn grain, corn stover, and switchgrass. To do so, we used a biophysical model, EPIC, to estimate the nitrogen, phosphorus, and erosion changes associated with different agricultural land uses and management at the field scale, then aggregated these to the watershed level. The EPIC model (Williams 1990, 1995; Williams et al. 1984, 1996, 2008) was designed with this purpose in mind, specifically to estimate the impacts of different cropping and management systems on a variety of environmental indicators, including soil erosion, nutrient losses, and soil carbon levels. EPIC is a field-scale model that functions on a daily time step and can simulate a wide range of crop rotations, tillage systems, and other management practices. More detailed discussion on modeling analysis is provided in Appendix E.

EPIC Results

Table 3-7 provides estimates of the average amounts of erosion, nitrogen, and phosphorus, and the amount of soil carbon sequestered for the baseline and for each of the scenarios. Recall that carbon sequestration is a positive externality where the nutrients (nitrogen and phosphorus) and sediment are negative externalities. It is also important to recall that EPIC is an “edge-of-field” model in that it predicts the amount of nutrients and sediment removed from each field under each scenario, but this does not necessarily mean that the pollutants will enter the waterways. (A fate-and-transport model that incorporates the hydrology of the region would be needed to estimate the waterway loadings.) For conciseness and ease of interpretation, several of the environmental indicators generated by EPIC have been combined. Specifically, the column entitled “Erosion” represents the sum of water and wind erosion predicted by EPIC. Likewise, “Nitro-

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
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TABLE 3-7 Water Quality and Externalities Estimated for Ethanol Scenariosa

 

Erosion (tons/acre)b

Nitrogen (kg/acre)c

Phosphorus (kg/acre)d

Baseline

0.31

20.11

0.29

Corn stover: 50%

0.44

19.62

0.35

Corn stover: 80%

0.69

21.09

0.48

Corn stover: 100%

1.23

24.53

0.72

Corn, continuous planting

0.45

30.68

0.29

Corn stover, continuous planting: 50%

0.78

29.12

0.43

Corn stover, continuous planting: 80%

1.16

30.46

0.61

Corn stover, continuous planting: 100%

1.55

32.19

0.79

Switchgrass: 25%

0.23

26.11

0.24

Switchgrass: 50%

0.16

31.93

0.18

Switchgrass: 75%

0.08

37.93

0.13

Switchgrass: 100%

0.01

43.79

0.08

aAll values are annual averages.

bErosion reports the sum of wind and water erosion.

cNitrogen reports the sum of nitrogen loss with sediment, nitrate loss with runoff, and nitrate leached.

dPhosphorus reports the sum of the loss with sediment and runoff (labile phosphorus).

gen” represents the sum of soluble N loss, N leaching, and N loss via sediment. Although the pathways by which N leaves the field differ in each of those cases, most of the N losses that ultimately escape the crop fields and drainage ways will enter surface water because of the subsurface tile drains that capture the majority of leached N, so the aggregated N amounts are reasonable representations of the overall system losses. Finally, the numbers in the “Phosphorus” column represent the sum of sediment-bound and soluble phosphorus that is transported in surface runoff.

As expected, the water-quality externalities increase relative to the baseline when continuous corn planting becomes the predominant cropping system. This result reflects the fact that corn has high input requirements and is relatively “leaky.”

In each of the first three stover scenarios, it is assumed that the baseline crop rotation is maintained but that some or all of the above-ground biomass is harvested for biomass to be used in ethanol production. Because the removal of stover (biomass) will generally increase erosion, three levels of removal are simulated for comparison: 50%, 80%, and 100%. As can be seen, model results predict that the average erosion per acre will increase from just under 1/3 ton/acre in the baseline to .45 tons/acre under a 50% removal, and well over 1 ton under 100% removal. The changes in nitrogen export are much less dramatic, which is expected, but larger for

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

phosphorus. This result is expected, given that the majority of nitrogen is transported in the soluble phase while the phosphorus moves mainly with sediment.

Because stover removal could also occur under continuous corn planting, the committee evaluated the same three scenarios under continuous corn planting. The combination of continuous corn planting and stover removal at any of the three rates has fairly dramatic effects on the magnitude of both rates of erosion and phosphorus loss with the rate of nitrogen loss being lower.

The final four scenarios all relate to switchgrass produced as a feedstock. In this case, we evaluated four alternative levels of switchgrass planting in the watershed: 25%, 50%, 75%, and 100% of the acreage converted to the switchgrass production. The substitution of this perennial has notable effects on the erosion rates as well as on nutrient loss.

It is worth reiterating that the edge-of-field sediment loss indicators reported here cannot capture the complex watershed scale and in-stream sediment movement dynamics that have been reported in previous studies, such as Trimble (1999) and Simon and Rinaldi et al. (2006). Similar caution is stressed for the edge-of-field nutrient indicators.


Ethanol Production and Monetization Each of the scenarios presented are associated with different amounts of potential ethanol production. In Table 3-8, the committee presents estimates of the amount of ethanol that the feedstocks grown in the Boone watershed could produce so that the magnitude of the externalities reported can be compared with the fuel production with which they are associated. The first column of the table provides estimates of the total amount of ethanol that the identified scenario could produce, including the baseline. In each case, the predicted yield of corn grain is assumed to be convertible to ethanol at a rate of 105 gallons/metric ton. The predicted stover removed for biomass in the stover scenarios is assumed to be converted to ethanol at a rate of 100 gallons/metric ton. This is the same rate used for the switchgrass scenarios. These are the same values assumed in the GREET model transportation runs used in the rest of this report and are chosen for internal consistency.

The second column of the table shows the incremental amount of ethanol the scenario is predicted to produce above and beyond the production in the baseline. When the land use is changed to produce additional ethanol, it creates additional externalities. By computing the additional ethanol produced, those incremental externalities (a cost to society) can be compared with the incremental ethanol (a gain).

To demonstrate the monetization of land-use externalities, we focused on the erosion estimates reported in Table 3-7. We chose to monetize erosion only for several reasons. First, more information about the costs of

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-8 Estimated Ethanol Production from Feedstocks in the Boone River Watershed

Scenarios

Potential,a,b Including Baseline Corn (gal/year)

Potentialc Increment Over Baseline (gal/year)

Baseline

112

Corn stover: 50%

167

55

Corn stover: 80%

196

85

Corn stover: 100%

214

103

Corn, continuous planting

217

105

Corn stover, continuous planting: 50%

325

213

Corn stover, continuous planting: 80%

384

272

Corn stover, continuous planting: 100%

421

309

Switchgrass: 25%

150

39

Switchgrass: 50%

187

75

Switchgrass: 75%

226

115

Switchgrass: 100%

264

152

aThese values assume that 105 gallons of ethanol can be produced per dry metric tonne of grain and 100 gallons/metric tonne of stover or switchgrass (GREET default values). Values in this column represent all the corn in the baseline that is used to produce ethanol as well as the addition of stover, corn, or switchgrass assumed in the scenario.

bMultiply the number of ethanol gallons by 0.6575 to convert to the gasoline gallon equivalent. That is the conversion factor used in the GREET model.

cValues in this column represent the additional ethanol produced by the scenario beyond the baseline: 0.6575.

erosion is available relative to the damages from nitrogen and phosphorus. Further, phosphorus and sediment tend to move together; therefore, the estimates of damages from erosion are already likely to include some of the costs associated with phosphorus. Likewise, the water-quality damages from all three (nitrogen, phosphorus, and erosion and sediment) are likely to be interrelated, and if separate values were added together for all three, we would risk double counting.

In a recent report, Hansen and Ribaudo (2008) provided a summary of studies that have valued erosion damages (or benefits from erosion reduction) from agricultural sources for numerous categories. They provided dollar per ton estimates of erosion reductions by 8-digit watershed code (the Boone River watershed represents HUC 07100005) for the following categories: sedimentation in reservoirs, navigation, water-based recreation, irrigation ditches, road drainage, municipal water treatment, flood damages, marine and freshwater fisheries, marine recreational fishing, municipal and industrial water use, and steam power plants. Estimates appropriate for the Boone River watershed indicate that the value of a 1-ton reduction in erosion is $4.43 (2007 USD). Hansen and Ribaudo noted that these values

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

omit some potentially important categories of benefits, including effects on wetlands, endangered species, coastal recreation, and existence values, and they suggested that the numbers be viewed best as a lower bound.

Table 3-9 uses this value to monetize the erosion reductions on a per acre basis, and, in the final column, on a per gallon of ethanol basis. The scenarios that remove stover for ethanol production have fairly high costs when aggregated to the watershed level, particularly when stover removal is combined with continuous planting of corn. However, even in those cases, the costs on a per gallon of ethanol basis are quite small, averaging less than 1 cent per gallon in all cases except for 100% stover removal. It is worth bearing in mind that these results represent the externality costs associated with erosion only and are probably underestimated. We also note the need for enhanced capabilities for simulation of N2O and other GHG emissions in EPIC; such capabilities are now being tested and will be included in future releases of EPIC (Izaurralde et al. 2006). Nonetheless, the health-effect damages considered elsewhere in this report are significantly greater.

The scenarios that introduce switchgrass into the landscape yield gains in erosion—that is, total erosion is reduced relative to the baseline cropping pattern and, therefore, the costs are negative (a benefit). At a watershed level, the value of the benefits seems relatively large, while on a per gallon basis, these gains are again quite small.

TABLE 3-9 Monetized Land-Use Damages of the Boone River Case Studya

 

Erosion Loss/Acre

$/Acre

$/Watershed

Damages $/gal Ethanol

Damages $/gge

Corn stover: 50%

0.13

$0.49

$261,427

$0.005

$0.003

Corn stover: 80%

0.38

$1.41

$752,857

$0.009

$0.006

Corn stover: 100%

0.93

$3.43

$1,828,204

$0.018

$0.012

Corn, continuous planting

0.14

$0.52

$278,084

$0.003

$0.002

Corn stover, continuous planting: 50%

0.47

$1.74

$929,355

$0.004

$0.003

Corn stover, continuous planting: 80%

0.86

$3.17

$1,690,837

$0.006

$0.004

Corn stover, continuous planting: 100%

1.25

$4.61

$2,459,075

$0.008

$0.005

Switchgrass: 25%

−0.08

−$0.28

−$149,076

−$0.004

−$0.003

Switchgrass: 50%

−0.14

−$0.53

−$284,211

−$0.004

−$0.003

Switchgrass: 75%

−0.23

−$0.83

−$444,829

−$0.004

−$0.003

Switchgrass: 100%

−0.30

−$1.09

−$581,777

−$0.004

−$0.003

aErosion monetized at $3.70 (2000 dollars). See Hansen and Ribaudo (2008), Appendix 1.

ABBREVIATION: gge = gasoline gallon equivalent.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

Modeled Estimates of Life-Cycle Emissions, and Damages from Biofuel Use in Light-Duty Vehcle Highway Transportation

Table 3-10 contains a brief summary of the modeling results from the GREET-APEEP modeling effort related to biofuels. The first row of the table contains the range and population-adjusted mean for conventional gasoline vehicles for 2005 and 2030, reported on a VMT basis. The remaining rows contain the same information for the three feedstocks (dry corn, herbaceous crops, and corn stover) used in production of E10 and E85, respectively.

The estimates do not differ significantly across the feedstock types, nor do the ethanol blends differ significantly from conventional gasoline. Given that only dry corn as a feedstock is truly a proven technology, the small differences in either the range across counties or the population-adjusted

TABLE 3-10 Comparison of Health and Other Non-GHG Damages from Conventional Gasoline to Three Ethanol Feedstocksa

 

2005

2030

5th and 95th Percentile Rangeb (Cents/VMT)

Population-adjusted Mean (Cents/VMT)

Population-adjusted Mean (Cents/gge)c

5th and 95th Percentile Rangeb (Cents/VMT)

Population-adjusted Mean (Cents/VMT)

Conventional Gasoline

0.34-5.07

1.34

29.20

0.45-4.87

1.35

E10 (dry corn)

0.35-5.26

1.35

29.18

0.44-4.87

1.32

E10 (herbaceous)

0.33-5.06

1.30

28.09

0.43-4.66

1.30

E10 (corn stover)

0.33-5.08

1.30

28.10

0.43-4.71

1.30

E85 (dry corn)

0.57-7.31

1.52

32.90

0.56-5.84

1.39

E85 (herbaceous)

0.40-5.45

1.20

25.89

0.47-4.06

1.22

E85 (corn stover)

0.39-5.78

1.21

26.13

0.47-4.63

1.22

aCosts are in 2007 USD.

bFrom the distribution of results for all counties in the 48 contiguous states in the United States.

cCents/gge, calculated by multiplying average miles per gallon by per VMT damages. This calculation will show highest damages for the most fuel-efficient vehicles. Costs are in 2007 USD.

ABBREVIATIONS: GHG = greenhouse gas; VMT = vehicle miles traveled; gge = gasoline gallon equivalent.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

mean should not be given much attention. Even the somewhat higher estimate for dry corn E85 of 1.52 cents is likely to contain enough error that it should not be viewed as distinctly different from the other feedstocks of conventional gasoline.

Several factors contribute to the aggregate damage estimates being similar for ethanol blends and gasoline in Table 3-10. The GREET model calculated similar estimates of vehicles emissions for all fuels shown in the table; thus, the operational component of the aggregate damages are the same. Because the E10 fuel is only 10% ethanol and 90% gasoline, similar damage estimates were obtained across the entire life cycles for E10 and gasoline. The damage costs for E85 (herbaceous and corn stover) are the lowest for any of the vehicle-fuel life cycles when looking at the population-adjusted means. A main reason is higher vehicle-fuel damages attributable to the feedstock and fuel components of the other vehicle-fuel life cycles.

To aid in comparisons with other studies and policy uses, we converted the costs/VMT into an equivalent costs per gallon. The mean-adjusted population costs computed in cents/gge are reported for the 2005 results in Table 3-10. These units are the same as those that Hill et al. (2009) used to summarize their findings. A comparison of the results in the table for 2005 with theirs is instructive. Hill et al. (2009) also use the GREET model to estimate the health effects associated with conventional gasoline and various forms of ethanol. They report estimates of health costs from gasoline averaging $0.34/gallon. They contrast this estimate with estimates of ethanol ranging from $0.16 for ethanol produced from prairie grasses to $0.93 for ethanol produced from corn by using coal as the process heat. As can be see via comparison with the results in Table 3-10, their estimates are generally higher and somewhat more discouraging for corn ethanol than our estimates.

One difference is that their results correspond to 2010 rather than our 2005 baseline. More important, the results that we report include emissions from feedstock production, fuel production, vehicle operation, and vehicle production. In contrast, Hill et al. (2009) focused only on fuel production and use and did not consider vehicle production.

ELECTRIC VEHICLES

History and Current Status

The late 1990s saw the emergence—in large measure in response to so-called zero-emission vehicle requirements of the California Air Resources Board (CARB)—of both a small number of all-electric vehicles and the first gasoline hybrid vehicles. Although the all-electric vehicles did not continue in production, gasoline hybrid vehicles have continued to develop and spread in the marketplace, more recently because of higher gasoline

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

prices and substantial tax incentives. Currently, such vehicles constitute approximately 1-2% of the U.S. light-duty vehicle fleet. Recently, there has been increased interest in developing different versions of “plug-in” hybrid electric vehicles (PHEVs) (which some are calling “extended-range electric vehicles”), although, other than after-market conversions, there are few such vehicles on the market.

There are two primary advantages that are usually cited for PHEVs. First, they will use electricity to power a portion of a vehicle’s energy requirements and thus avoid some fraction of petroleum that would otherwise be consumed. This vehicle would presumably lead to reductions in petroleum imports. Second, although there would be some impact on emissions from electric power plants, vehicle emissions would be reduced especially in metropolitan and urban areas.

Regulations and Technologies: Current and Anticipated in 2030

Although there are no formal national requirements for increased use of such vehicles (in the manner of the Renewable Fuel Standards that require increased use of biofuels), there are a number of regulatory and incentive programs that have the potential to affect the use of such vehicles. These programs have been put in place to address multiple objectives, including energy efficiency, reduced dependence on imported petroleum, and reduced GHG emissions. They include the following:

  • Continued regulation by CARB (and other states) requiring some number of so-called partial zero-emission vehicles (PZEV) as well as the pending CARB regulations for GHG emissions (which many other states have proposed to adopt as well).

  • Substantial tax credits for purchase of such vehicles, which, although they have been exhausted for some manufacturers (for example, Toyota), are still available for others (and could be revised and extended).

  • Substantial government-supported research and development of advanced battery technologies.

NAS/NAE/NRC 2009d estimates that gasoline and plug-in hybrids are likely to play an important role in the 2035 time frame that the committee is considering. (15-40% and 7-15%, respectively; see Table 3-11). Strictly speaking, the gasoline hybrids are more of a fuel-efficiency improvement than a new technology, placing new demands on the electricity grid. However, several important parts of the pathway described below concerning batteries are also relevant to this technology, especially if it expands dramatically.

On the basis of the AEF analysis, a significant market penetration of

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-11 Plausible Light-Duty-Vehicle Market Shares of Advanced Vehicles by 2020 and 2035

Propulsion System

Plausible LDV Market Share by

2020

2035

Turbocharged gasoline SI

10-15%

25-35%

Diesels

8-12%

15-30%

Gasoline hybrid vehicles

10-14%

15-40%

Plug-in hybrid vehicles

1-3%

7-15%

Hydrogen fuel-cell vehicles

0-1%

3-6%

Battery electric vehicles

0-2%

3-10%

ABBREVIATIONS: LDV = light-duty vehicle; SI = spark ignition.

SOURCE: NAS/NAE/NRC 2009d.

either fuel-cell or full-electric-battery vehicles is unlikely within the 2030 time frame.

Technology and Fuel Pathways

Facilities involved with manufacture and assembly of motor vehicles are located throughout the United States, but many are clustered in the Great Lakes states, California, and Texas. Manufacturing and assembling the thousands of different parts that make up motor vehicles include the following processes: raw material recovery and extraction, material processing and fabrication, vehicle component production, finishing or electroplating metal surfaces, painting the vehicle body, vehicle assembly, and vehicle disposal and recycling. These processes are energy- and material-intensive, involving components made of metal (for example, steel, aluminum, or copper), glass, rubber, plastics, and fluids. Energy is required to transport the raw and processed materials along each process step. Some of the material production and transport takes place outside the United States.

Waste streams are generated by manufacturing and assembly facilities as a result of fuel combustion, materials used in processes that are not shipped out in product streams, and chemical reactions occurring within specific processes. Air pollutants include particulate matter, VOCs, SO2, NOx, and CO. GHG emissions are also produced. In addition, various manufacturing processes generate sludge or wastewater that contains toxic metals (for example, cadmium, lead, and chromium), oils, acids, and solvents.

The fuel cycle and potential effects pathways for electric vehicles are similar to other vehicles in a few respects (for example, manufacture of the vehicle) but substantially different in nearly all other respects. Major com-

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

ponents of those pathways (for example, see Axsen et al. 2008; Samaras and Meisterling 2008) are the following:

  • Natural Resource Extraction. The expanded use of electric batteries is likely to increase demand significantly for certain metals that come from relatively limited sites (some in unstable regions). The metals include lithium (major stocks in the Congo and Russia) and cobalt (major stocks in Bolivia). This use may pose national security costs (although they might not be an externality per se). It also would involve significant increases in worker exposure and emissions associated with transport.

  • Displacement of Imported Oil. Increased use of hybrids could reduce dependence on imported petroleum. For example, a study by the Pacific Northwest National Laboratory (PNNL) (Kintner-Meyer et al. 2007) made aggressive projections for the introduction of PHEVs and estimated that “a shift from gasoline to PHEVs could reduce the gasoline consumption by 6.5 MMBpd, which is equivalent to 52% of the U.S. petroleum imports” (Kintner-Meyer et al. 2007).

  • Battery Manufacture. This poses issues of worker exposure to metals as well as a potential for both conventional and GHG emissions from the manufacturing process. Table 3-12 provides estimates of the use of energy for the manufacture of batteries and other vehicle-related technologies.

  • Electric Power Grid Implications. The PNNL study of the current capabilities of the electric power system in the United States analyzed 12

TABLE 3-12 Energy Use During Vehicle Manufacturing and Disposal of Light-Duty Vehicles

Propulsion System

Energy (gigaJoules/Vehicle)a

Current gasoline

97-125

Current diesel

99-128

Current gasoline hybrid

114-144

2035 gasoline

115-159

2035 diesel

117-152

2035 plug-in hybrid vehicle (PHEV)

138-175

2035 battery electric vehicle (BEV)b

2035 hydrogen fuel-cell vehicle (FCV)

158-203

aRounded estimates are presented. Lower values in each range are for cars; upper values are for light-duty trucks

bGREET 2.7 does not have the capability to estimate the BEV vehicle cycle impact accurately. The future versions of this model may include this capability.

SOURCE: Bandivadekar et al. 2008.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

regions and estimated how many PHEV-33 vehicles could be supported and what impact they might have, for example, on emissions (summarized in Kintner-Meyer et al. 2007). This study was not a dynamic analysis, and there was no estimate of the market penetration of such vehicles. In some ways, it was a maximum estimate of what could be. Their conclusions were the following:

The existing electricity infrastructure as a national resource has sufficient available capacity to fuel 84% of the nation’s cars, pickup trucks, and SUVs (198 million) or 73% of the light-duty fleet (about 217 million vehicles) for a daily drive of 33 miles on average.

Several other grid-related impacts are likely to emerge when adding significant new load for charging PHEVs. Higher system loading could impact the overall system reliability as the entire infrastructure is utilized near its maximum capability for long periods. “Smart” PHEV charging systems that recognize grid emergencies could mitigate the extent and severity of grid emergencies. Near maximum utilization of the nation’s power plants is likely to affect wholesale electricity markets. The mix of future power-plant types and technologies may change as a result of the flatter load-duration curve, which favors more base-load power plants and intermittent renewable energy resources.

  • Vehicle Use. The use of these vehicles is likely to involve three major externalities:

    Conventional pollutant and GHG emissions. Potential reductions in urban emissions and exposures (a positive externality) from the use of HEVs and PHEVs and the potential increases in emissions from grid electricity are expected. NAS/NAE/NRC (2009d) (and other analyses reported below) estimated that the gradual expansion of the use of these technologies will result in emissions being representative of the average grid emissions (rather than the peak), although its assessment noted the probable unequal geographic distribution of these emissions.

    Safety. Safety has been raised as a concern with a number of the battery formulations. This concern includes possible malfunction (with inappropriate chemical reactions, heat, and fire) and, probably most relevant for vehicles, potential exposures and impacts in vehicle accidents. Given the wide range of potential mixtures and significant uncertainty about which of these might become most prevalent, it is difficult to quantify these externalities at this time.

    Battery recycling and disposal. With substantially increased use of batteries containing unusual metals, a key question will be where battery recycling and disposal will take place. In the United States and under U.S. regulatory requirements, improper emissions and worker

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

exposures will probably be minimized (although at a minimum, there is a need for a review of current requirements to ensure their adequacy). If any significant portion of this activity takes place in the developing world, however, past experience suggests that there could be significant exposures of workers and even populations.

Estimates of Effects and Monetized Damages for Electric Light-Duty Highway Vehicles

The analysis of damages attributable to the operation of different electric technologies is highly dependent on the assumptions made about the energy mix and emissions from the electric utility system. The damage estimates for operation of hybrid and electric vehicles show significant lower damages than those for vehicles fueled by conventional gasoline (even when accounting for the uncertainty in the analysis). The difference is greatest when comparing damages resulting from the operation of electric vehicles to those resulting from the operation of vehicles fueled by conventional gasoline. Even damages resulting from the operation of grid-independent hybrid electric vehicles (which also consume gasoline) are approximately 20% lower compared with damages resulting from the operation of vehicles fueled solely by conventional gasoline.

However, emissions from electricity generation are included in the full life-cycle damages of the grid-dependent vehicles, specifically the emissions from the power plants as well as emissions from activities to produce the fossil fuels used in these plants. As shown in Table 3-13, when the damages attributable to other parts of the life cycle were included, especially the emissions from the feedstock and the fuel (emissions from electricity production), the aggregate damages for the grid-dependent and all-electric vehicles became comparable to, or somewhat higher than, those from gasoline.

Projections of the Annual Energy Outlook of the U.S. Energy Information Administration were used in this analysis and in Chapter 2 to estimate the electricity damages. Although very large decreases in emissions from fossil-fueled plants were projected for 2030 compared with current emissions (on a per kilowatt-hour basis), electricity from coal- and natural-gasfired power plants would still account for 66% of total generation. This percentage is only a slight decrease from the 70% in 2005. Thus, although the committed estimates that the damages associated with electricity generated for use by the vehicle will decrease, the total life-cycle damages of the electric-vehicle technology are still estimated to be slightly greater than those of the conventional gasoline vehicle [by 1.49-1.35 = 0.14 cents/VMT (see Table 3-13)].

One or two important transformations would be needed for the (non-climate-change-related) life-cycle damages of electric vehicles to be equal

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-13 Comparison of Health and Other Non-GHG Damage Estimates for Hybrid- and Electric-Vehicle Types with Conventional Gasoline, 2005 and 2030a

 

2005

2030

5th and 95th Percentile Range Aggregate Damagesb (Cents/VMT)

Population-adjusted Mean Aggregate Damages (Cents/VMT)

Population-adjusted Mean Operations Only (Cents/VMT)

5th and 95th Percentile Range Aggregate Damagesb (Cents/VMT)

Population-adjusted Mean Aggregate Damages (Cents/VMT)

Conventional gasoline

0.34-5.07

1.34

0.38

0.45-4.87

1.35

Grid-independent HEV

0.31-4.12

1.22

0.31

0.49-5.57

1.50

Grid-dependent HEV

0.27-8.90

1.46

0.22

0.45-9.20

1.62

Electric

0.20-15.0

1.72

0.05

0.35-12.2

1.49

aCosts are in 2007 USD.

bFrom the distribution of results for all counties in the 48 contiguous states in the United States.

ABBREVIATIONS: GHG = greenhouse gas; VMT = vehicle miles traveled; HEV = hybrid electric vehicle.

to or less than those of conventional vehicles. One of the transformations needed would be a dramatic shift to much greater nonfossil-fuel electricity generation—from renewable energy sources as well as nuclear power plants (for example, see Samaras and Meisterling, 2008). Instead of fossil fuels accounting for 66% of total generation in 2030, they would need to be lowered to about 37%. This estimated decrease is based on the assumption that no improvement in manufacturing efficiency will occur (see below) and that the fuel component of the damages would decrease by the 0.14 cents/VMT difference between gasoline and electric vehicles.

The other technological transformation would have to be a great improvement in energy efficiency in vehicle manufacture. As noted in Table 3-12, energy use in manufacturing a plug-in hybrid vehicle is about 13-23% greater than that for a gasoline vehicle in 2035, and both are greater than energy use to manufacture current gasoline hybrid and gasoline vehicles. Damages from the emissions associated with vehicle manufacture account for a large percentage of the overall life-cycle damages. Thus, even with the large decreases in emissions from generating electricity at fossil-fueled plants, the large damages from the vehicle-manufacture component mean that life-cycle damages for electric vehicles would probably be somewhat greater than those for conventional vehicles, unless there is significant

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

reduction in energy use in manufacturing batteries and other electric vehicle components.

The aggregate damages also reflect approximately 20% higher energy use and emissions from the manufacture of the vehicles, based on higher estimated energy inputs in GREET for battery manufacture.

NATURAL GAS

Current Status

Natural gas vehicles (NGVs) are very similar to gasoline vehicles; the major difference is in fuel storage. Light-duty NGVs, and some heavyduty vehicles like urban transit buses, use compressed natural gas (CNG). Heavy-duty vehicles can also use liquefied natural gas (LNG), which is denser but must be maintained below −260°F in very well insulated tanks (NGV America 2009; DOE 2009b).

In 2008, there were more than 150,000 NGVs in the United States. The main markets for NGVs are new transit buses and corporate fleet cars that are used mainly for short trips. That demand is due mainly to EPA’s Clean-Fuel Fleet Program. NGVs are more expensive than hybrid vehicles or gasoline vehicles. For example, the Honda Civic GX NGV has an MSRP of $24,590 compared with $22,600 for the hybrid sedan, and $15,010 for the regular sedan (Rock 2008).

About 1,500 NGV fueling stations are in the United States as of 2008; a substantial portion is part of private company facilities and is not available to the general public. Natural gas is sold in units of gasoline gallon equivalent. One gasoline gallon equivalent represents the same energy content (124,800 British thermal units) as a gallon of gasoline. Natural gas for CNG is obtained directly from a distribution line. Stations require large, high-pressure compressors and storage tanks to fill a vehicle quickly. Alternatively, a small compressor can work overnight. Natural gas for LNG can also be taken from a gas pipeline and then liquefied on-site, but it also can be transported in liquid form to a refueling facility via tanker truck.

Technology Development and Barriers

The main benefit of CNG has been its relatively low price (about 80% that of gasoline on a gasoline-gallon-equivalent basis). Also, transport and distribution can rely on an existing infrastructure for both industrial and household use (Yborra 2006). According to the AEF report (NAS/NAE/NRC 2009c), if natural gas were to be used for transportation instead of for electricity production, North American natural gas reserves could supply about 20-25% of transportation fuel needs by 2020 but only with

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

investment in distribution infrastructure. To supply more would require importing natural gas and LNG to meet that increased demand. (Chapter 6 discusses hazards related to infrastructure for distribution of LNG in the United States.)

The AEF report indicates that the main challenges to increased use of NGVs include an insufficient number of refueling stations and inconvenient on-board CNG tanks that take up most of the trunk space. Another key disadvantage is a limited range. The average range of a gasoline or diesel vehicle is 400 miles, and the range of an NGV is only 100 to 150 miles, depending on the NG compression. The AEF report suggests that the most important barrier for NGVs could be a public perception that using CNG as a fuel would involve carrying a dangerous “explosive” on board a vehicle and that self-service refueling with a high-pressure gas would be too risky to offer to the general public.

Fuel-Cycle Effects and Externalities

Natural gas has several significant advantages as a fuel for vehicles when compared with gasoline or diesel. Dedicated NGVs have the least exhaust emissions of CO, nonmethane VOCs, NOx, and CO2. NGVs emit unburned methane (which has a higher climate forcing potential than CO2), but this might be compensated for by the substantial reduction in CO2 emissions.

The choice of fuel pathway for CNG can have a large impact on GHG emissions over the fuel life cycle. If non-North American natural gas is imported as LNG via ocean tanker and then regasified and compressed to produce CNG, for example, CNG reduces life-cycle GHG emissions by only 5% compared with gasoline. If domestic gas is used, life-cycle GHG emissions are reduced by 15%. If gas that otherwise would be flared or landfill gas is used as the feedstock, net GHG emissions can be negative.

Modeled Estimates of Damages from Light-Duty CNG Vehicles

Table 3-14 contains a summary of the modeling results from the GREET-APEEP modeling effort related to natural gas light-duty autos and trucks (with a row for reformulated gasoline autos for comparison purposes). Each row of Table 3-14 contains the range and population-adjusted mean for health damages on a VMT basis in 2005 and 2030. There is also a column showing the health costs per gasoline gallon equivalent. Because of population growth, other things being equal, damages would tend to increase from 2005 to 2030. So, decreases in damages mean that for a variety of reasons, emissions per VMT are diminishing over time faster than the population is growing.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-14 Health and Other Non-GHG Damages from CNG Light-Duty Autos and Trucks (Values Reported in Cents/VMT)a

 

2005

2030

5th and 95th Percentile Rangeb (Cents/VMT)

Population-adjusted Mean (Cents/VMT)

Population-adjusted Mean (Cents/gge)c

5th and 95th Percentile Rangeb (Cents/VMT)

Population-adjusted Mean (Cents/VMT)

Conventional gasoline SI autos

0.35-5.12

1.32

29.83

0.45-4.87

1.35

CNG autos

0.30-4.54

1.20

23.35

0.38-4.41

1.16

aCosts are in 2007 USD.

bFrom the distribution of results for all counties in the 48 contiguous states in the United States.

cCents/gge, calculated by multiplying average miles per gallon by per VMT damages. Therefore the highest damages are shown for the most fuel-efficient vehicles.

ABBREVIATIONS: GHG = greenhouse gas; CNG = compressed natural gas; VMT = vehicle miles traveled; gge, gasoline gallon equivalent; SI = spark ignition.

In fact, damages for CNG autos are 1.2 cents per VMT or about 23 cents/gge. Emissions for trucks are much larger, reaching 28 cents a gallon for LDT2 in 2005. Emissions per VMT are increasing over time for all CNG vehicle types except for LDT2, where the population-adjusted means are 12% lower in 2030 than 2005. CNG autos outperform gasoline autos, with only 87% of the damages in both 2005 and 2030, implying that the emissions per VMT of CNG autos over the life cycle are that much lower than emissions of gasoline autos. On a per gasoline-gallon-equivalent basis, CNG autos do even better, with only 78% of the damages of gasoline vehicles.

By life-cycle stage, the difference in damages from CHG vehicles compared with gasoline vehicles is accounted for by lower operations emissions (particularly of NOx and VOCs) and lower emissions from the fuel stage for CNG, offset only somewhat by higher feedstock emissions (with identical emissions from the vehicle manufacturing stage).

Table 3-15 shows how the CO2-equivalent emissions vary for CNG autos and reformulated-gasoline autos for the years 2005 and 2030 on a VMT basis. As can be seen, CO2-equivalent emissions for CNG autos are about 89% of those for gasoline vehicles in 2005 but this advantage is greater in 2030, CNG emissions being only 79% of gasoline vehicle emissions in 2030. As expected, methane emissions for CNG vehicles are greater than those for gasoline, but CO2 emissions are much lower, yielding a net decrease in CO2-equivalent emissions for CNG vehicles.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-15 Carbon Dioxide Equivalent (CO2-eq) Emissions of GHGs from CNG Autos and Light-Duty Trucks Compared with Reformulated Gasoline Vehicles (Grams/VMT)

Fuel-Vehicle Combination

CO2-eq 2005 gal/VMT

CO2-eq 2030 gal/VMT

RFG SI autos (conventional oil)

552

365

CNG autos

492

280

NOTE: Costs are in 2007 USD.

ABBREVIATIONS: VMT = vehicle miles traveled; RFG = reformulated gasoline; SI = spark ignition; CNG = compressed natural gas.

One caveat with these estimates is that they take, as given, GREET default assumptions with respect to LNG imports. If LNG imports grow by more than assumed between 2005 and 2030, much, if not all, the gains from CNG vehicles relative to gasoline vehicles (at least from the perspective of GHG emissions) will be eroded.

HYDROGEN FUEL-CELL VEHICLES

Current Status

According to the AEF report (NAS/NAE/NRC 2009c), hydrogen fuel-cell vehicles (HFCVs) can yield large and sustained reductions in U.S. oil consumption and GHG emissions, but several decades will be needed to realize these potential long-term benefits. The NRC report Transitions to Alternative Transportation Technologies—A Focus on Hydrogen (NRC 2008c) estimates that the maximum practical number of HFCVs that could be operating in 2020 would be approximately 2 million in a fleet of 280 million light-duty vehicles. The number of HFCVs could grow rapidly to about 25 million by 2030 and account for more than 80% of new vehicles entering the fleet by 2050. These estimates assume that technical goals are met, consumers readily accept HFCVs, and policy instruments are in place to facilitate the introduction of hydrogen fuel and HFCVs through the market transition period.

Modeled Estimates of Damages from Hydrogen Fuel-Cell Vehicles

Table 3-16 contains a summary of the modeling results from the GREET-APEEP modeling effort related to hydrogen fuel-cell autos relative to gasoline light-duty autos. GREET covers two technologies for fuel cells—one that assumes the vehicle uses hydrogen gas directly and another

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-16 Health and Other Non-GHG Damages from Hydrogen Fuel-Cell Autos Compared with Reformulated Gasoline Autosa

 

2005

2030

5th and 95th Percentile Rangeb (Cents/VMT)

Population-adjusted Mean (Cents/VMT)

Population-adjusted Mean (Cents/gge)c

5th and 95th Percentile Rangeb (Cents/VMT)

Population-adjusted Mean (Cents/VMT)

Conventional gasoline SI autos

0.35-5.12

1.32

29.83

0.45-4.87

1.35

Hydrogen (gaseous) autos

0.38-4.17

1.34

66.68

0.61-5.61

1.64

aCosts are in 2007 USD.

bFrom the distribution of results for all counties in the 48 contiguous states in the United States.

cCents/gge, calculated by multiplying average miles per gallon per VMT damages. Therefore the highest damages are shown for the most fuel-efficient vehicles.

ABBREVIATIONS: GHG = greenhouse gas; VMT = vehicle miles traveled; gge = gasoline gallon equivalent; SI = spark ignition.

that assumes the vehicle carries a liquid fuel on the vehicle that is converted to hydrogen gas in a reformer. Because of the substantial uncertainties associated with the likely types and amounts of energy use for liquid hydrogen fuel, only results for hydrogen gas are included here. Each row of Table 3-16 contains the range and population-adjusted mean for health damages on a VMT basis in 2005 and 2030. There is also a column showing the health costs per gasoline gallon equivalent.

Table 3-16 shows that estimated damages for hydrogen (gaseous) and reformulated gasoline are similar in 2005. Yet, there are large differences in emissions over the life cycle. Hydrogen fuel cells have far larger emissions from the fuel stage and the vehicle-manufacturing stage than gasoline vehicles, which is about fully offset by lower emissions in the operation stage and to a lesser extent in the feedstock stage. By 2030, however, reformulated gasoline is less damaging than hydrogen (gaseous) owing to a bigger increase in emissions per VMT in the vehicle-manufacturing stage. Note that it is misleading to compare damages on a per gallon-gasoline-equivalent basis since hydrogen fuel cells use such a different means of propulsion and get such apparently “high” mileage per damage unit.

Table 3-17 shows how the CO2-equivalent emissions vary among the different fuel vehicle types and between the years 2005 and 2030 on a VMT basis. As shown, the hydrogen (gaseous) vehicle fuel significantly

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-17 Carbon Dioxide Equivalent (CO2-eq) Emissions of GHGs from Hydrogen Fuel-Cell Autos Compared with Reformulated Gasoline Autos

Fuel-Vehicle Combination

CO2-eq 2005 gal/VMT

CO2-eq 2030 gal/VMT

RFG SI autos (conventional oil)

552

365

Hydrogen (gaseous) autos

341

294

NOTE: Costs are in 2007 USD.

ABBREVIATIONS: GHGs = greenhouse gases; RFG = reformulated gasoline; SI = spark ignition.

outperforms gasoline vehicles for CO2-equivalent, with only about 60% of the latter’s emissions.

SUMMARY AND CONCLUSIONS

The committee has presented here a detailed summary of the wide range of potential emissions and damages from the use of energy in transportation. Our discussion and analysis focus on the components of transportation energy use—for light- and heavy-duty on-road transportation—that account for the great majority of annual transportation energy use. Other transportation energy uses—for example, for nonroad vehicles, aircraft, locomotives, and ships—are not inconsequential, but they account for a smaller portion of transportation energy use and were beyond the scope of this analysis.

Results of the Analysis: Health and Other Damages

Given these limitations, our analysis does provide some useful insight into the relative levels of damages from different fuel and technology mixes. Overall, we estimate that the aggregate national damages to health and other non-GWP effects would have been approximately $36.4 billion per year for the light-duty vehicle fleet in 2005; the addition of medium-duty and heavy-duty trucks and buses raises the aggregate estimate to approximately $56 billion. These estimates are probably conservative, as they do not fully account for the contribution of light-duty trucks to the aggregate damages and of course should be viewed with caution, given the significant uncertainties described above in any such analysis.

Health and Other Non-GWP Damages on a per VMT Basis

Although the uncertainties in the analysis preclude precise ranking of different technologies, Table 3-18 illustrates that on a cents per VMT basis

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-18 Relative Categories of Damages 2005 and 2030 for Major Categories of Light-Duty Fuels and Technologiesa

Category of Aggregate Damage Estimates (Cents/VMT)

2005

2030

1.10-1.19

 

CNG

Diesel with low sulfur and biodiesel

1.20-1.29

E85 herbaceous

E85 corn stover

CNG

Grid-independent HEV

E85 corn stover

E85 herbaceous

1.30-1.39

Conventional gasoline and RFG

E10

Hydrogen gaseous

Conventional gasoline and RFG

E10

E85 corn

1.40-1.49

Diesel with low sulfur and biodiesel

Grid-dependent HEV

Electric vehicle

1.50-1.59

E85 corn

Grid-independent HEV

Grid-dependent HEV

>1.60

Electric vehicle

Hydrogen gaseous

aCosts are in 2007 USD.

ABBREVIATIONS: VMT = vehicle miles traveled; CNG = compressed natural gas; HEV = hybrid electric vehicle; RFG = reformulated gasoline.

there are some differences that provide useful insight into the levels of damages attributable to different fuel and technology combinations in 2005 and 2030. Overall, the damage levels illustrate several things:

  • Among the fuel and technology choices, there are some differences in damages, although overall, especially in 2030, the different fuel and technology combinations have remarkably similar damage estimates.

    • Some fuels—E85 from herbaceous and corn stover and CNG—have relatively lower damages than all other options in both 2005 and 2030

    • Diesel, which has relatively high damages in 2005, has one of the lowest levels of damage in 2030. This is due to the substantial reductions in both PM and NOx emissions that a 2030 diesel vehicle is required to attain.

    • Corn-based ethanol, especially E85, has relatively higher dam-

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×
  • ages than most other fuels; this is in large measure due to the higher level of emissions from the energy required to produce the feedstock and the fuel.

  • Grid-dependent HEVs and electric vehicles have relatively higher damages in 2005. As noted above, these vehicles have significant advantages over all other fuel and technology combinations when considering only damages from operations. However, the damages associated with the current and projected mixes of electricity generation (the latter still being dominated by coal and natural gas in 2030, albeit at significantly lower rates of emissions) add substantial damages to these totals. In addition, the increased energy associated with battery manufacture adds approximately 20% to the damages from vehicle manufacture. However, further legislative and economic initiatives to reduce emissions from the electricity grid could be expected to improve the relative damages from electric vehicles substantially.

  • Although the underlying level of aggregate damages in the United States could be expected to rise between 2005 and 2030 because of projected increases in population and to increases in the value of a statistical life, the results in our analysis for most fuel and technology examples in 2030 are very similar to those in 2005 in large measure because of the expected improvement in many fuel and technology combinations (including conventional gasoline) as a result of enhanced fuel efficiency (35.5 mpg) expected by 2030 from the recently announced new national standards for fuel efficiency. (It is possible, however, that these improvements are overstated somewhat, because there is evidence that improved fuel efficiency can also lead to increased travel, probably resulting in higher aggregate damages than would otherwise be seen.)

  • As shown in Figure 3-7, these aggregate damages are not spread equally among the different life-cycle components. For example, in most cases, the actual operation of the vehicle is one-quarter to one-third of the aggregate damages, while the emissions incurred in creating the feedstock, refining the fuel, and making the vehicle are responsible for the larger part of aggregate damages.

Health and Other Non-GHG Damages on a per Gallon Basis

As illustrated in Tables 3-3, 3-10, and 3-14, the committee also attempted to estimate the health and non-GHG damages on a per gallon basis. This estimate is made somewhat more complicated by the fact that simply multiplying expected miles per gallon for each fuel and vehicle type by the damages per mile will tend to make the most fuel-efficient vehicles,

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×
FIGURE 3-7 Health effects and other nonclimate damages are presented by lifecycle component for different combinations of fuels and light-duty automobiles in 2005 (a) and 2030 (b). Damages are expressed in cents per VMT (2007 U.S. dollars). Going from bottom to top of each bar, damages are shown for life-cycle stages as follows: vehicle operation, feedstock production, fuel refining or conversion, and vehicle manufacturing. Damages related to climate change are not included. ABBREVIATIONS: VMT, vehicle miles traveled; CG SI, conventional gasoline spark ignition; CNG, compressed natural gas; E85, 85% ethanol fuel; HEV, hybrid electric vehicle.

FIGURE 3-7 Health effects and other nonclimate damages are presented by lifecycle component for different combinations of fuels and light-duty automobiles in 2005 (a) and 2030 (b). Damages are expressed in cents per VMT (2007 U.S. dollars). Going from bottom to top of each bar, damages are shown for life-cycle stages as follows: vehicle operation, feedstock production, fuel refining or conversion, and vehicle manufacturing. Damages related to climate change are not included. ABBREVIATIONS: VMT, vehicle miles traveled; CG SI, conventional gasoline spark ignition; CNG, compressed natural gas; E85, 85% ethanol fuel; HEV, hybrid electric vehicle.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

which travel the most miles on a gallon, appear to have higher damages per gallon than a less fuel-efficient vehicle. With that caveat in mind, the committee estimated that in 2005 the mean damages per gallon for most fuels ranged from 23 cents/gallon to 38 cents/gallon, the damages for conventional gasoline engines being in approximately the middle of that range at approximately 29 cents per gallon.

Estimates of Aggregate National Health and Other Non-GHG Damages

Overall, and scaling up the per VMT damages reported here to reflect national VMT in 2005, we estimate that the aggregate national damages to health and other nonclimate-change-related effects would have been approximately $36 billion per year (2007 USD) for the light-duty vehicle fleet in 2005; the addition of medium-duty and heavy-duty trucks and buses raises the aggregate estimate to approximately $56 billion (2007 USD). These estimates are probably conservative, as they include but do not fully account for the contribution of light-duty trucks to the aggregate damages, and of course should be viewed with caution, given the significant uncertainties in any such analysis.

Limitations in the Health and Other Non-GHG Damages Analysis

It is important in interpreting these results to consider two major limitations in the analysis:

  • Emissions and damages that were not quantifiable. Although our analysis was able to consider and quantify a wide range of emissions and damages throughout the life cycle and included what arguably could be considered the most significant contributors to estimates of such damages (for example, premature mortality resulting from exposure to air pollution), there are many potential damages that could not be quantified at this time. Such damages include the following:

    • Overall: Impacts of hazardous air pollutants and damages to ecosystems (for example, from deposition), the full range of agricultural crops, and others.

    • Biofuels: Impacts on water use and water contamination, as well as any formal consideration of potential indirect land-use effects (see discussion of the latter in “Indirect Land Use and Externalities”).

    • Battery electric vehicles: Potential effects from exposures to air toxics in battery manufacture, in battery disposal, and during accidents.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×
  • Uncertainty. Any such analysis includes a wide set of assumptions and decisions about analytical techniques that can introduce uncertainty in the results. Although we did not attempt to conduct a formal uncertainty analysis, we have been cautious throughout our discussion of results—and urge the reader to be cautious—to not over-interpret small differences in results among the wide range of fuels and technologies assessed. Moreover, we engaged in limited sensitivity analyses to check the impacts of key assumptions.

Results of the Analysis: GHG Emissions

  • Similar to the damages estimates, the GHG emission estimates from each fuel and technology combination can provide relative estimates of GHG performance in 2005 and 2030. Although caution should be exercised in interpreting these results and in comparing the fuel and technology combinations, some instructive observations from Table 3-19 are possible:

    • Overall, the substantial improvements in fuel efficiency in 2030 (to a minimum of 35 mpg for light-duty vehicles) result in most technologies becoming much closer to each other in per VMT lifecycle GHG emissions. There are, however, some differences:

    • As with the damages reported above, the herbaceous and corn stover E85 have relatively low emissions; in terms of aggregate g/VMT of CO2-equivalent emissions, E85 from corn also has relatively low emissions.

    • The tar-sand-based fuels have the highest GHG emissions of any of the fuels.

    • As shown in Figure 3-8 and in contrast to the damages analysis above, the operation of the vehicle is in most cases a substantial relative contributor to total life-cycle emissions. This is not the case, however, with either the grid-dependent technologies (for example, electric or grid-dependent hybrid) or the hydrogen fuel-cell vehicles, where the dominant contributor to life-cycle emissions is the processing of the fuel in the grid or in the production of hydrogen.

Results of the Analysis: Heavy-Duty Vehicles

The committee also undertook a more limited analysis of the damages and GHG emissions associated with heavy-duty vehicles. Although this analysis included operations, feedstock, and fuel components of the life cycle, it could not include a vehicle-manufacturing component because of the

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

TABLE 3-19 Relative Categories of GHG Emissions in 2005 and 2030 for Major Categories of Light-Duty Fuels and Technologies

Category of Aggregate CO2-Equivalent Emission Estimates (gal/VMT)

2005

2030

150-250

E85 herbaceous

E85 corn stover

E85 herbaceous

E85 corn stover

250-350

Hydrogen gaseous

E85 corn

Diesel with biodiesel

Hydrogen gaseous

CNG

350-500

E85 corn

Diesel with biodiesel

Grid-independent HEV

Grid-dependent HEV

Electric vehicle

CNG

Grid-independent HEV

SI conventional gasoline, RFG

Grid-dependent HEV

Electric vehicle

Diesel with low sulfur

E10 herbaceous, corn stover

SIDI conventional gasoline

E10 corn

SI tar sands

500-599

Conventional gasoline and RFG

E10

Low-sulfur diesel

 

>600

Tar sands

 

Costs are in 2007 USD.

ABBREVIATIONS: GHG = greenhouse gas; VMT = vehicle miles traveled; CNG = compressed natural gas; HEV = hybrid electric vehicle; RFG = reformulated gasoline.

wide range of vehicle types and configurations. In sum, and as illustrated in Figures 3-9 and 3-10, there are several conclusions that can be drawn:

  • The damages per VMT in 2005 are significantly higher than those shown above for light-duty vehicles, although they accrue to a much higher weight of cargo and number of passengers being carried per mile as well.

  • Damages drop significantly in 2030 because of the full implementation of the 2007-2010 Highway Diesel Rule, which requires substantial reductions in PM and NOx emissions.

GHG emissions are driven primarily in these analyses by the operations component of the life cycle and do not change substantially between 2005 and 2030 (except for a modest improvement in fuel economy). EPA

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×
FIGURE 3-8 Greenhouse gas emissions (grams CO2-eq)/VMT by life-cycle component for different combinations of fuels and light-duty automobiles in 2005 (a) and 2030 (b). Going from bottom to top of each bar, damages are shown for life-cycle stages as follows: vehicle operation, feedstock production, fuel refining or conversion, and vehicle manufacturing. One exception is ethanol fuels for which feedstock production exhibits negative values because of CO2 uptake. The amount of CO2 consumed should be subtracted from the positive value to arrive at a net value. ABBREVIATIONS: g CO2-eq, grams CO2-equivalent; VMT, vehicle miles traveled; CG SI, conventional gasoline spark ignition; CNG, compressed natural gas; E85, 85% ethanol fuel; HEV, hybrid electric vehicle.

FIGURE 3-8 Greenhouse gas emissions (grams CO2-eq)/VMT by life-cycle component for different combinations of fuels and light-duty automobiles in 2005 (a) and 2030 (b). Going from bottom to top of each bar, damages are shown for life-cycle stages as follows: vehicle operation, feedstock production, fuel refining or conversion, and vehicle manufacturing. One exception is ethanol fuels for which feedstock production exhibits negative values because of CO2 uptake. The amount of CO2 consumed should be subtracted from the positive value to arrive at a net value. ABBREVIATIONS: g CO2-eq, grams CO2-equivalent; VMT, vehicle miles traveled; CG SI, conventional gasoline spark ignition; CNG, compressed natural gas; E85, 85% ethanol fuel; HEV, hybrid electric vehicle.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×
FIGURE 3-9 Aggregate operation, feedstock, and fuel damages of heavy-duty vehicles from air-pollutant emissions (excluding GHGs) (cents/VMT). (Top) Estimated damages in 2005; (Bottom) estimated damages in 2030.

FIGURE 3-9 Aggregate operation, feedstock, and fuel damages of heavy-duty vehicles from air-pollutant emissions (excluding GHGs) (cents/VMT). (Top) Estimated damages in 2005; (Bottom) estimated damages in 2030.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×
FIGURE 3-10 Aggregate operation, feedstock, and fuel damages of heavy-duty vehicles from GHG emissions (cents/VMT). (Top) Estimated damages in 2005; (Bottom) estimated damages in 2030.

FIGURE 3-10 Aggregate operation, feedstock, and fuel damages of heavy-duty vehicles from GHG emissions (cents/VMT). (Top) Estimated damages in 2005; (Bottom) estimated damages in 2030.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

and others are investigating possible future enhanced requirements for fuel economy among heavy-duty vehicles.

Results of the Analysis: Damage and GHG Emission Comparisons

Although energy use and emissions generally track one another quite closely, the comparisons above indicate that they do not uniformly distinguish among the fuel and technology combinations. In general, there are few fuel and technology combinations that have significantly lower damages than gasoline in 2005 (Table 3-10), although several combinations have significant advantages in global warming potential (GWP). (The former is in part due to the GREET model, which assumes all fuel and vehicle combinations must at least meet similar emissions standards.) The electric and fuel-cell options have somewhat higher life-cycle damages than gasoline even though they have significantly lower GWP in most cases.

The conclusions to be drawn from the 2030 analysis are similar, although some diesel options begin to exhibit improvements in damages over gasoline damages because of the substantial mandated reduction in emissions, and the overall difference in damages is somewhat smaller as fuel efficiency among the fuel and technologies converge.

Overall Implications of the Results

Perhaps the most important conclusion to be taken from these analyses is that, when viewed from a full life-cycle perspective, the results are remarkably similar across fuel and technology combinations. One key factor contributing to this result is the relatively high contribution of emissions to health and other non-GHG damages in life-cycle phases (such as those in the development of the feedstock, the processing of the fuel, and the manufacturing of the vehicle) other than in the phase of vehicle operation.

There some differences though, and from these, some conclusions can be drawn:

  • The gasoline-driven technologies have somewhat higher damages and GHG emissions in 2005 than a number of other fuel and technology combinations. The grid-dependent electric options have somewhat higher damages and GWP than other technologies, even in our 2030 analysis, in large measure due to the continued conventional and GHG emissions from the existing and likely future grid at least as of 2030. (See below for mention of possible pathways for reducing those emissions.)

  • In 2030, with the move to meet the enhanced 35 mpg requirements now being put in place, those differences among technologies tend to converge somewhat, although the fact that operation of the vehicle is

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

generally less than a third of overall life-cycle emissions and damages tends to dampen the magnitude of that improvement. Further enhancements in fuel efficiency—the likely push for an extension beyond 2016 to further improvements—would improve the GHG emission estimates for all liquid-fuel-driven technologies.

  • The choice of feedstock for biofuels can significantly affect the relative level of life-cycle damages, herbaceous and corn stover having some advantage in this analysis.

  • Additional regulatory actions or changes in the mix of electricity generation can significantly affect levels of damages and GHG emissions. This result was illustrated in this analysis by the substantial reduction in diesel damages from 2005 to 2030. Similarly, major regulatory initiatives to reduce electricity-generation emissions or legislation to reduce carbon emissions would significantly improve the relative damages and emissions from the grid-dependent electric options. A shift to electricity generation with lower emissions (for example, natural gas, renewables, and nuclear) would also further reduce the life-cycle emissions and damages of the grid-dependent technologies.

  • Overall, the differences are somewhat modest among different types of vehicle technologies and fuels, even under the likely 2030 scenarios, although some technologies (for example, grid-dependent electric) had somewhat higher life-cycle emissions. Therefore, some breakthrough technologies (such as cost-efficient conversion of advanced biofuels; cost-efficient carbon capture and storage, and much greater use of renewable resources for electricity generation) appear to be needed to dramatically reduce transportation-related externalities.

These results must be viewed in the context of a large number of potential damages noted above that cannot at this time be quantified and substantial continued uncertainties. There is a need for additional research to attain the following:

  1. At the earliest possible stage in the research and development process, better understanding of the potential negative externalities for new fuels and technologies should be obtained to avoid these externalities as the fuels and technologies are being developed.

  2. Understanding of the currently unquantifiable effects and potential damages should be improved, especially as they relate to biofuels (such as effects on water resources and ecosystems) and battery technology (such as effects throughout the battery life cycle of extraction through disposal).

  3. More accurate emissions factors should be obtained for each stage of the fuel and vehicle life stages. In particular, there is a need, in the context of enhancing even further EPA’s recent shift to the Motor Vehicle

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
×

Emission Simulator (MOVES) model for mobile-source emissions, to make measurements to confirm or refute the assumption that all vehicles will only meet but not exceed emission standards. In actual practice, there can be significant differences between on-road performance relative to emissions requirements and some alternative-fuel vehicles may do better or worse than expected.

  1. The issue of indirect land-use change is central to current debates about the merit of biofuels. Regardless of whether this impact is regarded as an externality associated with U.S. or foreign biofuels production, it is important to obtain more empirical evidence about its magnitude and causes, as well as to improve the current suite of land-use change models.

  2. Because a substantial fraction of life-cycle health impacts comes from both vehicle manufacture and fuel production, it is important to improve and expand the information and databases used to construct emissions factors for these life stages. In particular, there is a need to understand whether and how energy-efficiency improvements in these industrial components might change the overall estimates of life-cycle health damages.

  3. As better data become available, future studies should also focus on other transportation modes—both those that are alternatives to automobiles and light trucks (transit), as well as air, rail, and marine, which are alternatives for long-distance travel and for freight.

Suggested Citation:"3 Energy for Transportation." National Research Council. 2010. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use. Washington, DC: The National Academies Press. doi: 10.17226/12794.
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Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use Get This Book
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Despite the many benefits of energy, most of which are reflected in energy market prices, the production, distribution, and use of energy causes negative effects. Many of these negative effects are not reflected in energy market prices. When market failures like this occur, there may be a case for government interventions in the form of regulations, taxes, fees, tradable permits, or other instruments that will motivate recognition of these external or hidden costs.

The Hidden Costs of Energy defines and evaluates key external costs and benefits that are associated with the production, distribution, and use of energy, but are not reflected in market prices. The damage estimates presented are substantial and reflect damages from air pollution associated with electricity generation, motor vehicle transportation, and heat generation. The book also considers other effects not quantified in dollar amounts, such as damages from climate change, effects of some air pollutants such as mercury, and risks to national security.

While not a comprehensive guide to policy, this analysis indicates that major initiatives to further reduce other emissions, improve energy efficiency, or shift to a cleaner electricity generating mix could substantially reduce the damages of external effects. A first step in minimizing the adverse consequences of new energy technologies is to better understand these external effects and damages. The Hidden Costs of Energy will therefore be a vital informational tool for government policy makers, scientists, and economists in even the earliest stages of research and development on energy technologies.

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