This chapter provides a summary of presentations that address the broad topic of sustainable energy. Both presentations emphasize the need to consider energy sources or technologies from a systems perspective. Each energy source can be considered within the broader context of the energy milieu which includes other available energy sources, the potential benefits and potential damages across the life cycle and into the future, and the community context. The presentations emphasize a systems perspective that encourages understanding the relationships among different fuels and strategies and identifying optimal sources for the given context.
Steven Hamburg, Ph.D., M.F.S.
Chief Scientist, Environmental Defense Fund
Steven Hamburg began his presentation by pointing out the need to consider hydraulic fracturing in a broader context. Hydraulic fracturing, he said, is an issue of energy, energy independence, environmental quality, health impacts, and, finally, the integration of these matters. The challenge is to not think in terms of one specific energy source or one specific technology. Losing the broader perspective by focusing too narrowly will result in erroneous science, ill health, and unwanted outcomes, he said.
Potential Energy Options
Dr. Hamburg suggested that there are many options for the energy future that can be considered. One option is nuclear power. There are both advocates for and opponents against building more nuclear power plants. The opponents list rational health- and safety-based arguments against nuclear power. However, the data on nuclear power from the last several decades, including recent examples of disasters, reveal that the rate of mortality and morbidity is lower for nuclear power plants than for
coal-fired power plants. But that is not to say that there is not a small risk of something catastrophic occurring. A second option for energy is power derived from burning biomass. Similar to nuclear power, there are people who support using biomass for electricity, but there are plenty of people who believe burning biomass is a health disaster. A third option for energy is wind power. Again, some people support building onshore wind farms, coastal wind farms (e.g., Cape Wind), and, others fight the construction of these farms. Something similar is happening with hydraulic fracturing—some people support its use, and others oppose it. Dr. Hamburg posed two questions: Where should hydraulic fracturing fit among the energy mix utilized by the United States? And if advocates and adversaries of each energy source got together, what would be the outcome? Likely the status quo, he said, because there are legitimate issues with each one of these sources of power that have to be addressed. But they must be addressed in the context of the bigger picture—meeting our energy needs responsibly requires a suite of strategies in which negative impacts are minimized. If the energy future is focused too narrowly, it will not be successful, he said.
Every strategy mentioned, he noted, has a place in the energy future. This does not mean they are perfect, that they do not require good controls, or that more science is not needed. However, achieving a relevant balance through integration of these energy sources should be the objective.
Dr. Hamburg highlighted a state effort to reduce greenhouse gas emissions and consideration of a suite of potential strategies. California passed a climate change law, Assembly Bill 32 (California Environmental Protection Agency, Air Resources Board, 2013), which codifies the reduction of greenhouse gas emissions and calls for an energy future that will reduce emissions 80 percent below 1990 levels. Likely options to achieve this result include increasing energy efficiency, decarbonizing electricity generation, promoting smart growth, installing photovoltaic panels on rooftops, producing biofuels, electrifying vehicles and other entities currently not using electricity, and eliminating greenhouse gases from other sectors. He noted that there is a suite of approaches and they will likely need to proceed with all of them.
Shifting to climate change, Dr. Hamburg referred to work from Pacala and Socolow (2004) which divides the climate change problem into a series of different strategies. When mitigating climate change is the driver behind energy transitions, there is no specific solution or silver bullet. The approach is more akin to buckshot, and “all of the above” strategies to get reasonable outcomes. Certainly from a health standpoint, he said, it is important to curtail climate change because, going forward, climate change is likely to be one of the key drivers of negative health outcomes because of the disruption it will cause to social and biological systems.
Identifying Optimal Energy Sources
Dr. Hamburg suggested that moving forward, it is imperative to determine which energy sources are optimal in which situations. Achieving this requires more detail assessments. For example, electricity generated from coal combustion can be compared with electricity generated from natural gas combustion. Historically, only the emissions from smokestacks at the different power facilities were examined in this comparison. Now it is recognized that this is insufficient. Instead, how these fuels affect the environment and society throughout the supply chain must be considered. This includes the mining, production, and transport of coal and natural gas, as well as end use of the electricity generated, which for natural gas, includes use by industry and residential homes for heating.
He pointed out that it is necessary to understand the implications that a transition from coal to natural gas will have on climate change. Methane is the main constituent of natural gas, and there is methane leakage at each point along the natural gas supply chain—production, processing, transport, and combustion. Methane is also a greenhouse gas, and its leakage should be accounted for in the comparison of natural gas and coal. The challenge is how to make methane leakage equivalent to carbon dioxide emissions—which persist in the atmosphere for very different lengths of time—for a true comparison. It is possible to use the 100-year global warming potential (GWP) of methane,1 which is 212 (EPA, 2013b), but GWP assumes that the short term is not relevant because the outcome is assessed 100 years from now. More specifically, GWP is the impact of a single pulse emission 100 years after it is released. A useful analogy for GWP is worrying about the impacts of renting a car today 100 years in the future. What are the implications 100 years from now of a pulse of emissions from a power plant? But a hundred years from now is an abstraction. There is a lot of time between now and then, and most people care about what happens between now and 100 years from now. What we really care about are the implications of owning a particular type of car for its lifetime, or even more important what are the implications of changing the characteristics of an entire fleet of cars (e.g., Corporate Average Fuel Economy [CAFE] standards). GWP, as traditionally applied, does not reveal much about the impacts of a power plant over time. Most people care about what the power plant does over its functional life or the effects of its emissions over the next 20 years, as well as its impacts over the longer term.
1 Global warming potential was developed to compare the ability of each greenhouse gas to trap heat in the atmosphere relative to carbon dioxide.
2 It should be noted that the Intergovernmental Panel on Climate Change uses 25 for the GWP (100-year) of methane; for a series of reasons, the U.S. Environmental Protection Agency uses an outdated factor.
Dr. Hamburg explained that when a comparison of the effects of a pulse emission from a coal power plant and a pulse emission from a natural gas power plant is performed, it is revealed that there is an immediate 20 percent reduction in net radiative forcing (the change in the balance between radiation coming into the atmosphere and radiation going out) by switching from coal to natural gas (Alvarez et al., 2012). Over 200 years, the benefit is a 45 percent reduction in net radiative forcing for the natural gas fueled electrical power plant in comparison to the one using coal. The climate impacts of fuel switching are best understood by considering their implications continuously over time for a large-scale shift in fuel. The concept of Technology Warming Potential introduced by Alvarez and colleagues (2012) allows one to make these comparisons simply. Using this more robust framework, Hamburg stated that there is a climate advantage from switching to natural gas from coal immediately and over time for the electricity sector. Yet it is important to note that the lower the methane leak rate across the supply chain the larger the climate benefits of such a shift, so long as the leak rates are below about 3 percent.
It should be noted, Dr. Hamburg said, that this calculation assumes methane leak rates estimated from the U.S. Environmental Protection Agency (EPA) data based on a natural gas study done nearly 20 years ago and updated with more recent activity factors (EPA, 2013a); even though industry techniques have changed radically since then, these are currently the best data available. Researchers and industry are working to complete a series of studies to collect empirical field data in order to populate these calculations with empirical numbers, rather than best estimates, allowing for a better assessment of the health impacts of these comparisons.
An interesting topic of political relevance, Hamburg suggested, is the comparison of natural gas versus gasoline for transport and its climate implications. When natural gas is compared with gasoline for the conversion of a fleet of cars, there is an immediate 30 percent disadvantage based on currently available data (e.g., EPA estimated leak rates and engine efficiency). It would take about 85 years before there is a climate change benefit to switching from gasoline to natural gas for a fleet of vehicles. He noted that a comparison of natural gas and diesel can also be performed. Because diesel holds more energy per unit of carbon dioxide emitted, the advantages of switching to natural gas are not as great. It would take more than 200 years to see any climate benefits assuming 2010 EPA estimated methane leak rates and literature estimates of engine efficiency (Alvarez et al., 2012).
Dr. Hamburg also suggested that from a policy standpoint, it would be helpful to know what leak rate is required to make these conversions beneficial relative to climate change. It is possible to compare well-to-wheels leak rates and the number of years that must elapse before a climate change benefit is realized. If the well-to-leak rate is 1 percent, a
benefit is realized immediately. Analytically, it is now possible to solve for when the benefit will be accrued, which allows society to decide which fuel is preferable. He stated that there may be a short-term disbenefit and a long-term benefit. But why not strive for a leak rate that makes benefits available continuously, especially if a significant capital investment is going to be made? Minimizing methane leaks would have health and climate benefits, and would represent a victory for society and for industry (because they collect more product and potentially reduce operating and maintenance costs through a better understanding of sources of leaks).
Dr. Hamburg explained that the analytical work described here is necessary to understand the relationships among different fuels and strategies. This work will allow a clearer understanding of what will meet social and legal goals and what will not, and when they affect health. This is only possible when all types of fuels are analyzed across the landscape in a comparative way—requiring one to understand the lifecycle implications of diverse fuels in greater detail than currently available.
Including Biomass in the Energy Future
Another energy source that is hotly contested because of its potential impacts on health is bioenergy, Dr. Hamburg said. A forest may be considered a pristine place, but it might have been a pasture in the previous 100 years. It is important to think of many of the forests of the United States as cultural landscapes—a landscape heavily influenced by people. The way a landscape is used can be affected by the political economy and can have social effects. The concept of the cultural landscape allows us to understand that often there is much less of a perceived conflict between nature and people than might otherwise be the case. It also allows one to understand how people have used the land and how they might use it in the future with or without negatively impacting the environment.
Biomass energy plants can convert municipal forest waste from urban environments to energy, burning material that might otherwise simply decay, and use it for heat in a highly efficient manner. There are health effects of particulate emissions, but if larger biomass plants implement effective particulate controls there is an opportunity for a win-win: low carbon energy with limited health and environmental impacts. Understanding if such plants can actually be deployed represents the kinds of issues and trade-offs that need to be considered.
Dr. Hamburg emphasized that the bottom line in developing a lowcarbon economy is not about deploying a single strategy. It is not about a single fuel. It is about optimization among them all, deploying a mixed fuel strategy is more complicated and thus more difficult, but has the potential to more effectively meet our climate goals while reducing
health impacts. It is important to understand the context of each fuel, its implications, when it is appropriate to deploy, when it is better than another fuel, and when it is worse. It is about “all of the above.”
Daniel S. Greenbaum, M.S.
President, Health Effects Institute
Daniel S. Greenbaum began his presentation by reiterating Dr. Hamburg’s point that discussions about shale gas extraction need to be considered in the larger context of a comprehensive energy discussion where comparisons are made across all energy forms. America’s production and use of energy result from a complex system of supply and demand. It also creates a complex web of potential health, environmental, and other effects throughout the life cycle. Any one component of the system (e.g., shale gas hydraulic fracturing) must be placed in the context of the whole system. This approach requires that effects be evaluated throughout the system, and the effects be compared on an “apples-to-apples” basis across different energy sources and uses.
One example of a broad, systems approach to energy analysis is the National Research Council (NRC) report, Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use (NRC, 2010). Congress requested this study as part of the Energy Policy Act of 2005 (Public Law 109-58). The task of the report was to “evaluate key external costs and benefits—related to health, environment, security, and infrastructure—that are associated with the production, distribution, and use of energy but not reflected in the market price or fully addressed by current government policy.” That is the essence of what economists consider an “externality”—an effect that is not paid for, but that has a cost.
The report concluded that, in the United States, there are many externalities related to energy production and use. The committee that authored the NRC report assigned monetary values to a wide range of damages, although an equal number or perhaps greater number of external effects could not be monetized. This approach allowed for some degree of “apples-to-apples” comparison between different forms of energy. The overall monetized damages in 2005 were $120 billion, but that number does not incorporate damages due to climate change, Mr. Greenbaum noted.
To assess the monetary values of damages, the report focused on several key components of the energy system. These areas included
electricity generation, transportation, and heating for buildings and industrial processes. These three areas combined account for approximately 80 percent of the energy use in the United States. The report also described sets of external costs for infrastructure and national security that are not always embedded in the market price. Whenever possible, the report examined the full life cycle of the energy source and external costs. To provide a longer-term view, the report looked at both actual damages in 2005 and projected damages in 2030.
For the nonclimate damages, a fairly conventional method of looking primarily at air pollution was used, because those data were most readily available. Emission levels and ambient concentrations of air pollutants could be estimated. Exposures of people to these pollutants and the effects of these exposures could also be calculated. These evaluations permitted the assignment of monetary damage values to these effects. Modeling was used to estimate damages based primarily on sulfur dioxide (SO2), nitrogen oxides (NOx), and particulate matter (PM) emissions across the 48 contiguous states. The effects that were examined included damages to human health; grain, crop, and timber yields; building materials; recreation; and visibility of outdoor vistas. The single largest contributor to the damage estimates was related to human mortality, despite the fact that the highest value for a statistical human life (recently used by the EPA and others) was not used in this assessment (NRC, 2010).
Damages from Electricity Generation
Mr. Greenbaum discussed the monetary value of damage associated with energy sources and by sectors. In 2005, coal used for electricity generation accounted for $62 billion in nonclimate damages. Of 406 power plants, 10 percent (the oldest, largest—which produced 25 percent of net generation) were responsible for 43 percent of the damages. This variation in damages is primarily due to a disparity in the tonnage of emitted pollutants. The total amount of nonclimate damages equates to an external cost of 3.2 cents per kilowatt-hour, which is not an insignificant addition to the cost of electricity. For the analysis carried out to 2030, it is assumed that existing rules will be successful in reducing emissions of traditional air pollutants: emissions of SO2 and NOx per kilowatt-hour are expected to fall by 64 percent and 50 percent, respectively. The 2030 external cost decreases to 1.7 cents per kilowatt-hour, despite rising incomes and an increase in the value of a human life. Thus, it is possible to internalize those external costs and reduce them.
A very different outcome was observed with natural gas. For the 498 natural gas-fired plants, which account for approximately 71 percent of domestic natural gas generation, there were $740 million in nonclimate damages. This is slightly more than 1 percent of the damages associated with coal. This finding is due to the much lower levels of pollutants
emitted during natural gas combustion. The 10 percent of power plants with the greatest damages were older plants; these accounted for 65 percent of the damages. The cost per kilowatt-hour for natural gas is onetwentieth that associated with coal, or 0.16 cent. By 2030, when newer, cleaner plants come online, the cost will decrease to 0.11 cent per kilowatt-hour. This decrease is due to an expected 19 percent reduction in NOx emissions and 32 percent reduction in PM emissions per kilowatthour (NRC, 2010).
It is beneficial to put these data in a different perspective and investigate where the damages are localized, which is also helpful for health impact assessments. The majority of coal-fired power plants are in the eastern United States. In contrast, natural gas plants (and their concomitant damages) are spread more widely across the country, Mr. Greenbaum said.
Damages from Transportation
When examining the transportation sector, the committee focused on highway vehicles, which account for 75 percent of energy use within this sector. Various fuels were considered: oil (both petroleum gasoline and diesel), natural gas, biomass or biofuels, and electricity. A full wells-towheels analysis was performed that incorporated the extraction of the feedstock, the transport of the feedstock to the refinery, the fuel conversion and refining process, the transport of the fuel to the pump, the manufacturing of the vehicle (which is often not included), and the tailpipe and evaporative emissions from operating the vehicle.
It was determined that the aggregate nonclimate damages in 2005 from transportation were $56 billion. Light-duty vehicles accounted for 60 percent of these damages. Per gallon, damages were estimated to be 23 to 38 cents per gallon, which is 1.1 to 1.7 cents per vehicle-mile traveled. This cost may not seem high when the price of a gallon of gasoline is $3.80, but the costs accumulate when more than 3 billion barrels of gasoline are used for transportation annually (EIA, 2012).
Mr. Greenbaum highlighted the finding of minimal variation across the different technologies and fuels analyzed. Some (electricity and corn ethanol) had marginally higher levels of damages whereas others (cellulose and natural gas) had slightly lower life-cycle damages. This finding should be interpreted cautiously: the damages associated with electric cars are mainly due to the coal-fired power that supplies electricity in much of the country and is associated with considerably higher damages. It is also noteworthy that damages were not spread evenly among the different life-cycle phases. In most cases, vehicle operation accounted for less than one-third of the total damage. Vehicle manufacturing was a significant contributor to damages.
Looking forward to 2030, the minimal variation among fuels and technologies will shrink even further. This shift is due to new fuel
economy standards that will increase vehicle efficiency, diesel emission rules that will reduce NOx and PM levels, and electricity-generating power plants that will become cleaner and more efficient (as discussed previously).
Damages from Greenhouse Gas Emissions
The committee that authored the NRC report also estimated climaterelated emissions for the sectors described above. However, a specific damage estimate was not ascribed for climate damages. The committee instead reviewed a range of analyses in the climate-change literature that have used integrative assessment models to try to assess the social cost of carbon. One of the limitations in estimating the value of specific damages, and a reason why the committee did not pursue this further, came from the wide range of values assigned to the cost per ton of carbon dioxide equivalent (ranging from $1 to $100). The committee found that the key factors responsible for this variation were (a) the rate at which future damages are discounted and (b) how fast damages (as a percentage of gross domestic product) were predicted to increase with temperature.
Within the electricity sector, natural gas produces half the carbon dioxide emissions of coal—coal emits 1 ton of carbon dioxide per megawatt-hour of power generated, and natural gas emits 0.5 ton of carbon dioxide per megawatt-hour. This is not anywhere near the discrepancy observed for the nonclimate change damages, where damages were 20 times greater for coal compared with natural gas. Nuclear, wind, solar, and biomass sources were also investigated. Lifecycle emissions of greenhouse gases from these energy sources were so small as to be negligible compared with those from fossil fuel-generated electricity.
For transportation vehicles, there was no major variation across the technologies in terms of greenhouse gas emissions. Some benefits were observed for cellulosic ethanol, but tar sands petroleum and Fischer-Tropsch diesel emitted more carbon dioxide per vehicle-mile traveled. Vehicle operation, in most cases, is a substantial contributor to the total life cycle of greenhouse gas emissions. The projections for 2030 show even closer estimates in the greenhouse gas emissions per vehicle-mile traveled between fuels and technologies; this is due to substantial improvements in fuel efficiency.
As mentioned above, the damages per ton of carbon dioxideequivalent ranged from $1 to $100 and the committee did not estimate climate damages. However, a few arrays are presented for a point of reference (see Table 7-1). In selecting $30 per ton—a moderate estimate of climate damages—and combining this with the nonclimate damages, the impact of coal-fired electricity generation nearly doubled to approximately 6 cents per kilowatt-hour (compared with 3.2 cents when
TABLE 7-1 Combining Nonclimate and Climate Change Damage Estimates (2005)
|Energy-Related Activity (fuel type)||Nonclimate Damages||Climate Damages (per ton CO2 equivalent)|
|@ $10||@ $30||@ $100|
|Electricity Generation (coal)||3.2 cents/kWh||1 cent/kWh||3 cents/kWh||10 cents/kWh|
|Electricity Generation (natural gas)||0.16 cent/kWh||0.5 cent/kWh||1.5 cents/kWh||5 cents/kWh|
|Transportation||1.2 to ~1.7 cents/VMT||0.15 to ~0.65 cent/VMT||0.45 to ~2 cents/VMT||1.5 to ~6 cents/VMT|
|Heat production (natural gas)||11 cents/MCF||7 cents/MCF||70 cents/MCF||700 cents/MCF|
NOTE: kWh = kilowatt-hour, MCF = thousand cubic feet, VMT = vehicle miles traveled.
SOURCE: NRC, 2010.
nonclimate damages were considered alone). For electricity generated by natural gas, climate damages (based on $30 per ton of carbon dioxide equivalent) resulted in an external cost of 1.5 cents per kilowatt-hour, which, given that the nonclimate damages were so low originally, is a vast increase in damages. The transportation sector also experienced an increase in the damage estimate, to approximately 1.6–3.7 cents per kilowatt-hour, when climate impacts were considered.
Evaluating Energy with a Systems Approach
The Hidden Costs of Energy report found that nonclimate damages from electricity generation and transportation exceeded $120 billion in 2005. These damages were principally related to emissions of SO2, NOx, and PM. The committee believed that the total value was a substantial underestimate because it did not include damages related to climate change effects, the health effects of hazardous pollutants, ecosystem effects, or the external effects on infrastructure and national security.
Economists assert that estimating a cost does not imply that the cost needs to go to zero. It is important to consider the marginal costs—the cost of diminishing a burden compared with the value added from the reduction. For instance, if it costs $100,000 to get the next $1,000 of reduction, this might not be the best option for society as a whole. Still, there was evidence from these analyses that showed decreasing
emissions, improving energy efficiency, and shifting to cleaner methods of generating electricity could reduce damages and have a substantial benefit.
Returning to the topic of hydraulic fracturing, it is important to place natural gas in the larger—and life-cycle—context. In the analyses found in the NRC report, natural gas was a favorable option in the nonclimate area and even somewhat beneficial in the climate area; however, there are still significant data challenges and questions that remain. For example, much is still unknown about the upstream effects of natural gas and coal, and it is not yet possible to quantify many environmental effects (such as water requirements for biofuel production) on a national scale. The bottom line is that energy cannot be handled with a “one solution by one solution” approach. Systems approaches to these energy questions—like the one outlined here and the “all of the above” approach presented by Dr. Hamburg—are needed to make fully informed decisions in the future.
Following the presentations, Lynn Goldman began the discussion by asking the presenters to comment on energy renewability, energy security, and incentives. That is, the energy sources that are renewable and also can be produced domestically and are the focus of large tax incentives to encourage them. The presenters were also asked to comment on biomass combustion, which has also been incentivized by tax policy and encourages the growing and burning of trees. Dr. Hamburg responded that there is feedstock (biological material that can be used directly as fuel) that is available and that has minimal impacts on the climate and that would be beneficial to the economy of the forest. Hamburg pointed out that the wood pulp industry, for example, is hurting because the public is reading fewer newspapers and this is causing problems for the low-grade wood market. If low-grade wood is not going to pulp for newspapers, then bioenergy is a great use for it; you can produce bioenergy. It is a matter of having the right rules and the incentives aligned with the rules so that the forest of today is not turned into the forest of the past century. In the past, there was a wave of cutting down almost every tree from East Coast to West Coast. That could be repeated with bad incentives. He stated that this does not mean that there should be no incentives or no use of forest material, but that incentives should be considered for their potential to create perverse outcomes.
John Balbus asked the presenters how to use systems thinking to produce policies that are not just economically optimized but that balance trade-offs (produce energy but not at the expense of environmental justice, for example). Dr. Hamburg responded that a criterion to address local impacts is needed. For example, a local heating and
distribution biomass plant is located in the middle of downtown St. Paul, Minnesota. It provides cheap, local heating but must abide by their air pollution permit. Without the right permits, it would increase pollution and morbidity in the local area. The challenge is finding the sweet spot of balance between the two—pollution controls that are not so high that they produce barriers to siting the plant in the community and the protection of the local community.
Richard Jackson noted that the use of gas for heat in homes is very high, yet there is not a focus on producing high-quality gas for homes. He asked the presenters to comment on the lack of progress in this area. Dr. Hamburg responded that Dr. Jackson’s question implied that the gas used in homes is a low-grade end product, but the real issue is that highefficiency furnaces are needed. He commented that if you have a boiler or furnace that is at 97 percent and it provides direct heat and there are good controls so that it is used wisely—that is optimal thermodynamically. Investment in efficient boilers and furnaces, he noted, is far more efficient (given that heat is not lost through window leaks) than burning electricity and bringing electricity into the home.
Luiz Galvão asked the presenters to think about key policy recommendations they felt would be impactful. Both presenters emphasized that they are not in a position to make policy recommendations and they do not speak for their agencies. That said, Mr. Greenbaum said that his focus would be on greening the electricity system. He noted that there is a problem as long as there are coal-fired plants and they are not being replaced by renewable and other sources of energy. There are immediate health issues associated with coal versus other sources of electricity; further, the relative benefit of electric vehicles is undermined because the electricity these vehicles run on is generated by coal. The life-cycle damage from those vehicles is affected if energy is ultimately generated by coal. Dr. Hamburg offered the development of technology-neutral incentives and a set of pollution filters and other criteria to test new technologies (e.g., thermodynamic system implications for health and other local impacts) as his policy suggestion.
Henry Anderson asked the presenters if it was better to encourage the use of plentiful biomass for home heating, especially in less populated areas with available wood resources or move to gas. Shifting to gas would require adding gas lines to low-density areas and would have associated economic costs. On the other hand, continuing to use a wood fire boiler, for example, is not as energy efficient and contributes to pollution. Dr. Hamburg responded that, although not an expert in this area, he believed that for larger institutional settings (such as schools and universities) heating with biomass (with good pollution control on institutionally based boilers) would be a net winner financially and environmentally for the communities described. As long as the waste is harvested, it would have a minimal net impact on the forest and still provide jobs and money.
Nicholas Jones, a public health physician from New Zealand, told the panel that a large oil plate had been discovered in his area. He was attending the workshop to learn about the potential health issues associated with natural gas. He told the panel that in New Zealand the electricity supply is based on about 60–70 percent renewable energy. He asked whether the benefit of a shift to natural gas would be less given this context. Mr. Greenbaum responded that the single largest advantage of natural gas in the U.S. context has been in comparison to coal as a source of electricity because of its contribution to air pollution and other factors. He stressed that Dr. Jones was asking the right question—How would the energy source work within the given context? He noted that even within the U.S. context, there are few coal-fired plants in the West, so the benefit from shifting to natural gas would not be as beneficial as in the East, which has many more coal-fired plants.
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