Nonenergy Emission Reduction
Nonenergy-related sources of greenhouse gases include manufactured halocarbons, methane and nitrous oxide from agriculture, and methane from landfills.
"Halocarbon" is the general lable applied to chemicals such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), halons, and chlorocarbons (CCs). Halocarbons have the largest radiative impact per molecule of any of the greenhouse gases. However, halocarbon emission volumes are much lower than CO2 emission volumes, so that the total halocarbon contribution to global warming is less than that of CO2 from other sources. The CFCs also threaten the stratospheric ozone layer. Emissions of CFCs are scheduled to be eliminated under the Montreal Protocol, an international treaty signed in 1987 and strengthened in 1990, that commits nations to act to preserve the ozone layer. Positive action under the Protocolincluding bringing additional nations under its umbrellacontinues to be a visible demonstration of the possibility of global action on environmental questions.
More than 1 Mt of CFCs and halons were produced and consumed on a worldwide basis in 1986.1 Figure 25.1 shows that the United States is the largest consumer of CFCs in the world (approximately one-third). Other developed countries also consume large amounts of CFCs. During the 1970s, scientists became concerned about the potential impact of CFCs on the
ozone layer (Rowland and Molina, 1974). Concern continued, and in 1985 scientists detected unexpected seasonal losses in the stratospheric ozone layer above Antarctica (Farman et al., 1985). In 1987, these concerns resulted in the Montreal Protocolan international agreement to reduce by 1998 the production and use of CFCs, in developed countries, to 50 percent of their 1986 levels and to freeze halon production at 1986 levels by 1993. By 1988, research had shown that chlorine from man-made sources, primarily CFCs and CCs, contributed to the temporary early spring ozone losses above Antarctica. The Montreal Protocol was amended in 1990 to require a total phaseout of CFCs, halons, and carbon tetrachloride by the year 2000 in developed countries (2010 in developing countries). Not all countries have agreed to sign the Montreal Protocol, however, and this fact, along with the possibility that some countries may not comply with the agreement, has caused concern. More than 100 countries with over 67 percent of the global population and about 10 percent of current CFC useIndia and China includedhave not yet signed the agreement.
The United States has signed the Montreal Protocol. In addition, the 1990 amendment to the Clean Air Act will further regulate halocarbons in the United States. Figure 25.2 illustrates how CFC consumption will decline between now and 2010 because of the new Clean Air Act amendment.
Besides having a role in ozone depletion, CFCs are also greenhouse gases. Unlike the other greenhouse gases, which began to increase during the Industrial Revolution (1850), CFCs were not introduced until the early
1930s. Future use rates, and hence emissions, of fluorocarbons will be driven by societal use of goods and services employing CFCs (Table 25.1),which can be found in everything from mobile air conditioners to fire extinguishers to plastic foams in residential, commercial, and industrial applications. Over the last decade, the fractional contribution of CFCs to greenhouse warming has been about 20 percent. Because CFC concentrations began to increase significantly only after 1960, their fractional contribution to the increase since 1940 is about 15 percent, and since 1850 about 10 percent. The fractional contributions of CO2, CH4,N2O, and CFCs are shown for the three time periods in the pie charts shown in Figure 25.3.These charts illustrate how the CFC contribution to greenhouse warming relative to the contributions of the other greenhouse gases changed between the beginning of widespread use of CFCs in the 1940s (14 percent) and the1980s (19 percent). The areas of the pies are proportional to the calculated warming over the time periods given (F. A. Vogelsberg, Du Pont, personal communication to Deborah Stine, Committee on Science, Engineering and Public Policy, 1990).
TABLE 25.1 Primary Uses of CFCs and Halons
The goal of minimizing contributions to global warming should be considered in the context of other goals, including minimizing the potential for ozone depletion, maintaining safety standards for chemicals (low toxicity and low flammability), maintaining energy efficiency, and continuing to realize the substantial economic and societal benefits of CFC-using technologies while making the transition from CFCs to alternatives.
Several alternatives are being evaluated in an attempt to balance these goals. As a group, the HCFCs and HFCs under evaluation have about one-tenth the global warming potential of CFCs, and less than one-twentieth the ozone depletion potential of CFCs, because the hydrogen in these two alternatives destabilizes these chemicals and lowers their residence time in the atmosphere and thus their potential to contribute to greenhouse warming and ozone depletion. Furthermore, because HFCs contain no chlorine, they cannot contribute to ozone depletion (see Table 25.2). Thus, even with emission rates comparable to those of CFCs, the contributions to calculated global warming and ozone depletion would be significantly reduced, as shown in Figure 25.4.
TABLE 25.2 Global Warming Potentials of CFCs
Table 25.2 shows the atmospheric lifetimes, ozone-depleting potentials, global warming potentials, calculated equilibrium warming, and rate of increase of atmospheric concentration for CO2, CH4, N2O, fluorocarbons, and chlorocarbons. The global warming potentials are calculated on a mass basis relative to a global warming potential of 1.0 for CO2. These global warming potentials are estimates of the total cumulative (over time) calculated warming due to emission of 1 kg of a compound relative to the total cumulative calculated warming due to emission of 1 kg CO2. All of the
compounds have large global warming potentials compared to that ofCO2,but this fact can be misleading because it does not account for relative emission rates. This method of calculating global warming potentials differs slightly from that used by the Intergovernmental Panel on Climate Change (1990). They computed relative effects over the first 20, 100, and 500 years after instantaneous injections of 1 kg of each of the compounds into the atmosphere to derive the values in Table 2.8 of IPCC(Intergovernmental Panel on Climate Change, 1990). The values in Table 25.2 of this reportare based on the same atmospheric lifetimes and values for radiative forcing as used in the IPCC report, but relative effects are computed from totalintegrated forcing by assuming a CO2 lifetime of 120 years.
The last two columns of Table 25.2 can be used to estimate current contributions to calculated warming. Multiplying the values in these columns yields the 1986 contribution to global warming. Dividing the individual contributions by the sum of all the contributions yields an estimate of the relative contribution of each gas. This shows that although the global warming potential and calculated equilibrium warming for CO2 are small
per unit of CO2, it nevertheless contributed about 55 percent of the total calculated warming in 1986.
Figure 25.4 shows the projected calculated warming from fluorocarbon substitutes based on options for meeting a growing demand for goods and services that currently rely on CFCs. A comparison of the curve for continued use of CFCs with the lower curve demonstrates the effects of the decreased demand for fluorocarbons due to conservation and replacement by nonfluorocarbon alternatives, and also the lower global warming potentials of the HCFCs and HFCs targeted to replace CFCs. Global compliance with a CFC phaseout by 2000 (2010 in developing countries) and an HCFC phaseout from 2030 to 2060 (not yet required by treaty, but in a nonbinding agreement) would stabilize the contribution of fluorocarbons to global warming even though the demand for goods and services they provide is projected to increase at about 3.5 percent per year.
Emission Control Methods
Production and use of CFCs will probably be eliminated over the next 10 years (20 years in developing countries) because of concerns about ozone depletion. A variety of options can be used to meet growing demands for the goods and services as CFCs are eliminated:
• increased conservation of CFCs in the short term and of their replacements over the longer term,
• nonfluorocarbon alternative compounds for technologies not requiring a gas, and
• substitution of other compounds in the fluorocarbon familyHCFCs and HFCs.
Figure 25.5 illustrates how the demand for services now provided by CFCs could be satisfied in the year 2000 (deadline for phaseout under the amended Montreal Protocol). Conservation and recycling measures can reduce worldwide demand for CFC production by 30 percent and provide environmental benefits by reducing the need for virgin CFC production. Replacement of certain applications, primarily aerosols in Europe, with nonhalocarbon substitutes (''not-in-kind" options) can reduce CFC demand by an additional 30 percent. Fluorocarbon alternatives can replace CFCs in the remaining 40 percent of applications (Du Pont, 1989). However, some of the substitute chemicalsdeveloped to avoid reaction with ozone in the upper atmospheremay have radiative properties that would result in significant contributions to greenhouse warming (Shine, 1990).
Increased conservation and recycling of CFCs and their fluorocarbon replacements are initiatives that can provide benefits to consumers, industry, and the environment. United States tax legislation has more than doubled
the price of CFCs since January 1, 1990. Escalating tax rates will raise the price of CFCs by approximately 500 percent in the next 10 years. These price increases are exclusive of additional increases from producers due to mandated production cuts and higher fixed costs, increased raw materials costs, and the need for revenue to invest in alternatives. In addition, fluorocarbon alternatives are expected to cost up to 5 times as much as present(untaxed) CFCs. Clearly, economic incentives for conservation and recycling will grow rapidly with these price increases.
A review of the different industries that use CFCs illustrates the feasibility of each of the substitution options. The foam plastics industry uses CFC blowing agents in the insulation it produces. Conservation measures are difficult for this industry to implement because about 80 percent of the CFC blowing agent ends up in the bubbles of rigid foam insulation. The industry currently recovers 50 percent of the fugitive emissions that occur during manufacture (Aulisio, 1988). The best options for this industry are CFC substitutes such as HCFCs 22, 123, 141b and 142b, which will become available in increasing quantities in 1994 and 1995, when the market could be fully supported by HCFC alternatives. Higher prices may cause consumers to choose not-in-kind substitutes such as fiberglass and fiberboard insulation. Because these substitutes are less energy efficient, the net contribution to global warming may be adverse, a possibility that should be taken into account.
Appliance manufacturers put insulating foam in refrigerators to increase their energy efficiency as required by statute. Manufacturers will be able to
use some CFC substitutes such as HCFC-123. However, until these products are widely available, manufacturers will have to balance the need for energy efficiency with the availability of substitutes. Whirlpool has estimated that refrigerators with the new CFCs would cost about $100 more per unit to produce. CFCs are also used in refrigerators as refrigerants. Used refrigerant is currently being recycled, and manufacturers of commercial refrigeration and air conditioning equipment are working to reduce fugitive emission losses in the field (Cogan, 1988).
Mobile air conditioning is the largest market for CFC consumption in the United States; however, because new automobiles account for only 20 to 25 percent of the CFCs used in this sector, phaseout of CFCs by automobile producers will afford only a small reduction initially. Seventy-five percent of the consumption is in servicing the existing 125 million automobile air conditioners after the refrigeration fluid has leaked to the atmosphere (Putnam, Hayes, and Bartlett, 1987). Of the 120 million pounds used for replacement, 30 million pounds replaced fluid lost through normal operation, and 40 million pounds replaced fluids flushed out during servicing and repairs (Radian Corp., 1987). Therefore conservation and recycling of these CFCs are critical to reduce emissions from this industry.
The automobile industry has examined numerous alternative refrigerants. After independent analysis, mobile air conditioner manufacturers have agreed that HFC-134a is the best replacement for CFC-12. Significant technical issues need to be solved before HFC-134a can be used in new mobile air conditioning systems, most notably the development of a new system lubricant, hardware and elastomer modifications, toxicological testing of HFC-134a, and development of feasible chemical HFC-134a synthetics. Excellent progress has been made in all areas, such that domestic automobile manufacturers plan to switch to HFC-134a over a several-year period, with conversion expected to be complete by 1996. However, HFC-134a is not a drop-in replacement for CFC-12 in mobile air conditioning systems, and it is not expected to be retrofit option. The automobile industry is making serious efforts to minimize the release of CFC-12 from these air conditioning systems; for example, one major domestic producer (General Motors) is requiring that all of its dealerships use refrigerant recovery and recycling equipment by October 1990. Conversion from CFC-12 to HFC-134a will reduce the greenhouse impact of mobile air conditioners by more than 90 percent. Serious efforts at refrigerant recovery and recycling in the mobile air conditioning industry can further reduce this greenhouse contribution to less than 5 percent of its present level.
No nonfluorocarbon alternative air conditioning technology is currently suitable for this mobile market. The alternative technology most frequently considered is the Stirling gas refrigeration cycle (using helium or nitrogen), but there has been no demonstration of a high cooling capacity, energy
efficient, reasonably priced Stirling air conditioning system suitable for vehicle applications.
The electronics industry accounts for roughly one-fourth of CFC demand in the United States. This industry currently uses CFC-113 solvent to clean semiconductors and circuit boards. Recovery and recycling technology is available, and equipment is already in place for an estimated 50 percent of the applications; implementation of the best available equipment technology in the remaining 50 percent could reduce emissions by 25 percent or more. Water-based solvents are alternative cleaning agents used by a number of companies (ICF, 1987). These systems afford a trade-off of longer-lived CFCs for shorter-lived volatile organic carbon (VOC) emissions and increased waste-water treatment loads for municipal and industrial waste treatment facilities.
Halons are used to extinguish fires and are mainly contained within fire extinguishers, tanks, and so on, until released during testing or actual use. Seventy-five percent of halon emissions occurred during testing prior to the Montreal Protocol. Currently, the industry has ceased using halons as a requirement in the test. Not-in-kind substitutes are not yet available for these compounds (Cogan, 1988). Recently, two U.S. companies (Great Lakes Chemical Corporation and Du Pont) announced potential halocarbon substitutes for these halons. Large-scale demonstration of these substitutes has yet to be accomplished.
Carbon tetrachloride (CCl4) and methyl chloroform (CH3CCl3) emissions are controlled in the amended Montreal Protocol because of their potential contributions to ozone depletion. The use of CCl4 will be eliminated by 2000, and the use of CH3CCl3 by 2005. As can be seen from Table 25.2, both compounds are relatively small contributors to calculated global warming (<1 percent in 1986).
The primary use of CCl4 is as a feedstock to produce CFCs 11 and 12. Only very small amounts (less than 1 percent of the quantity consumed) are emitted to the atmosphere during CFC production. However, based on atmospheric measurements of the concentrations of CCl4 and its model-calculated lifetime, atmospheric emissions of CCl4 are estimated at about 10 percent of the amount used for CFC production. This indicates that significant emissions occur from other uses. Carbon tetrachloride was used extensively as a solvent. However, in the United States and most other developed countries, CCl4 is currently used as a solvent in only very specialized applications with tight control on atmospheric emissions due to concerns about toxicity. Thus it appears unlikely that the United States, Japan, Western Europe are major sources of CCl4 emissions. Based on analysis of measurements of CCl4 and CFCs on the coast of Ireland, Prather (1985) concluded that Europe and, in particular, Eastern Europe might constitute a significant source of CCl4 emissions; however, uncertainties in the
results prevent a definitive assessment (Prather, 1985). Further work is needed to determine the sources of CCl4 emissions.
The primary use of CH3CCl3 is in industrial cleaning. It contributes only a small fraction of the calculated warming, but restrictions on CH3CCl3 could increase future contributions to global warming by decreasing energy efficiency. Producers of CH3CCl3 have stated that aqueous cleaning methods require more energy to dry the cleaned materials. The impact of CH3CCl3 regulations on energy use should be evaluated.
The analysis presented in this section deals only with the direct effect of CFCs on the chemical and radiative properties of the atmosphere. A more complete approach, beyond the scope of this analysis, would require an evaluation of the net change in contribution to global warming resulting from the use of different systems to meet a given societal need. For example, fluorocarbons are used in some applications because of their contributions to energy efficiency. In those cases, the energy saved, and hence the CO2 emissions prevented, may reduce the contribution to global warming by an amount that is greater than the direct contribution from emission of the fluorocarbon.
Chlorofluorocarbons will be replaced in most countries because of concerns over their potential contribution to ozone depletion. Costs of the transition will probably be high but are difficult to estimate. A recent study by the Department of Energy (Energy Information Administration, 1989) estimates the cost of one aspect of the CFC phaseoutthe cost of capital obsolescence in the United States over the next decade was estimated to be between $19 billion and $34 billion.
Appendix K attempts to estimate the additional cost for replacement of CFCs, both in the United States and throughout the world, with the options discussed earlier. Those options include meeting CFC demand by increased conservation and by use of not-in-kind or fluorocarbon substitutes. The costs reflect changes only in the cost for new equipment and new substitutes, and not in costs due to capital obsolescence. As determined in the calculation described in Appendix K, costs of the CFC phaseout are calculated to be approximately $2 billion per year in the United States and $6.3 billion per year throughout the world (in constant 1990 dollars at 6 percent). Cost estimates at other interest rates are also shown in Appendix K. Table 25.3 summarizes the cost of phasing out CFCs in the United States and the CO2-equivalent reduction of those CFCs. Figure 25.6 summarizes the abatement cost for each policy option.
These costs will be incurred regardless of global warming concerns; implementing the options that reduce contributions to global warming should constitute only a small incremental cost. Companies involved in research on substitutes are evaluating the potential contribution of these compounds to greenhouse warming in an attempt to obtain optimal solutions that take
TABLE 25.3 Cost Impact of CFC Phaseout in the United States
into account all safety and environmental concerns. Companies that will use the substitutes in their products are working to maximize energy efficiency and thus minimize potential contributions to global warming. Therefore most of the costs incurred due to global warming concerns will be hidden in the total transition costs. Initiation by government agencies such as the National Institute of Standards and Technology (NIST) and DOE of the type of systems analysis discussed in the preceding section would assist industry in obtaining optimal solutions.
Barriers to Implementation
Consumers are likely to be largely indifferent to the use of CFC substitutes, as long as substitutes do not raise prices significantly or suddenly, and as long as the technical capabilities of the substitutes match reasonably well those of the CFCs they displace. Both criteria may be satisfied, although some CFC substitutes will cost substantially more to produce and distribute.
Alternatives to CFCs constitute a significant market for chemical manufacturers, although several large firms are also likely to see their earnings erode as CFCs are phased out. A significant cost of phaseout is the replacement of equipment rendered obsolete by the elimination of CFCs.
According to estimates, future emissions of CFCs are dominated by contributions
from industrializing economies of the Third World. It is as yet unclear whether, and under what circumstances, large developing countries such as China would join any framework agreement on greenhouse warming. A significant inducement to joining a global management regime could be technology transfers financed by contributions from industrial nations, similar to recent provisions added to the Montreal Protocol for ozone depletion control (DeCanio and Lee, 1991). However, the cost of implementing new technology will be an important factor for any nation considering a CFC phaseout.
Within the United States, there have been embryonic discussions regarding a proposal for a global emissions tax, based on global warming potentials, to reduce carbon emissions. Currently, there is an excise tax on the Montreal Protocol CFCs, based on ozone depletion potential, applied at the production stage. Since CFCs are produced by a limited number of manufacturers, implementation of such a tax in the case of ozone depletion is not very difficult. However, actual application of a similar tax based on global warming potentials would be much more difficult because of the numerous methods by which greenhouse gases are generated.
For example, suppose the common denominator was equivalent CO2, and a tax was in place. If HFC-134a were used as a propellant, and there was no additional energy effect, it would be a simple matter to tax the compound based on its global warming potential relative to CO2. However, if the same compound, HFC-134a, was used as a coolant in a refrigerator, and HFC-134a had greater energy efficiency than an alternative refrigerant, the HFC-134a would result in less CO2 emissions from a power plant, due to lower energy consumption, and lower power usage in the refrigerator's 20-year life. How would that energy reduction be accounted for in a tax based on HCF-134a alone? Such questions and many more would need to be addressed in regulations, a considerable task because not only the production but also the consumption of products that generate greenhouse gases is involved.
To encourage world compliance, international policy should continue to be negotiated through processes, such as the Montreal Protocol, that recognize the differences in time tables for implementing these options in developed and developing countries. National policies should encourage an examination of available resources, an assessment of priorities, and implementation of the options within the Montreal Protocol framework in the most timely manner possible.
As mentioned above, the signatory nations of the Montreal Protocol have recently negotiated a new, more restrictive agreement, which will effect a
phaseout of CFC and halon production by 2000 for developed nations and by 2010 for developing nations. These nations have also issued a declaration of intent to phase out HCFCs by 2040. Global compliance with such an agreement would reduce atmospheric concentration of chlorine-containing compounds to pre-1978 levels by the end of the twenty-first century. At the same time, the agreement would have the effect of stabilizing the contribution of halocarbons to global warming.
The Montreal Protocol requires that parties establish mechanisms to ensure that developing nations (allowed 10-year delays in meeting all Protocol deadlines) obtain the financial and technological assistance necessary to facilitate compliance with the Protocol.
Technology transfer to developing nations can be divided into two areas: "in-use" technology and manufacturing technology. In-use technology refers to application, equipment maintenance, service, and so on. This is anticipated to be the more important technology, and the more difficult to transfer, as it requires expertise in several applications. Changeover in developed countries, however, will facilitate the transition of technology to developing countries, as lessons will have been only recently learned (Du Pont, 1989).
Manufacturing technology will be transferred once economic incentives are created, and financing will come from the private sector. It is important to realize the role that creating economic incentives will play in the creation of indigenous demand for such technology. There will be no natural economic incentive for buying equipment using HCFCs or HFCs, because equipment intended for new compounds will be more expensive than equipment designed for CFC use. (Several decades of product optimization, fixed cost depreciation and write-off, and expertise cannot be matched in a few short years.) Economic incentives therefore must come from other sources, and several mechanisms can be employed at the national and international levels to help create them. Most promising among these are marketable emissions permit systems and a price structure that reflects environmental impacts. International environmental and trade agreements are logical vehicles for introducing these mechanisms (U.S. Environmental Protection Agency, 1990b).
Finally, financial aid from the developed countries will be a necessary part of technology transfer. It is anticipated that the need for a coordinated worldwide approach for ozone protection will enable mechanisms to form naturally as a function of that worldwide cooperation. Additionally, much of the incentive for cooperative effort in providing financial aid will come from the strong desire for developing countries not to undermine the efforts of developed countries (United Nations Environment Programme, 1989).
The subject of financial aid is still being addressed on a world scale. The Economic Panel Report on the Montreal Protocol and Substances That Deplete the Ozone Layer (United Nations Environment Programme, 1989)
makes no recommendation as to the amount or the sources of the funds that might be made available for this purpose. It does, however, make some recommendations as to where the funding for technology transfer could be generated:
• Industrial nations could set aside a percentage of the national product.
• Industrial nations could set aside a fixed amount of money.
• Governments could implement a tax on CFC and halon use, and use those tax revenues for technology transfer.
Such monies generated could be regulated and managed by the World Bank, which is set up for such a purpose.
Other Benefits and Costs
The obvious benefit of moving to CFC alternatives is a reduction in stratospheric ozone depletion. However, although nonfluorocarbon alternatives provide an important option to meet CFC demands, care must be taken that such options provide adequate safety and environmental acceptability as well. For example, conversion of aerosol applications to hydrocarbons may lead to an increase in the formation of local photochemical smog.
Research and Development
Significant research and development programs will be required to implement "third-generation" heat pump, refrigeration, and insulation technology in support of a phaseout of HCFCs as early as 2015 to 2020 (the dates specified in the Clean Air Act, agreed to by the House/Senate Conference Committee). A "systems" approach should be employed to ensure that third-generation technologies do not lead to a net increase in calculated warming. Unless the energy efficiency of the third-generation technology is at least as great as that of the HCFC technology it would replace, the added contribution from increased CO2 emissions due to increased energy consumption could offset the decreases due to elimination of HCFCs.
Finding and implementing suitable third-generation technology could prove to be a significant challenge, and it is currently unclear what that technology might be. Producers and users of CFCs are evaluating alternatives that would minimize environmental effects while maintaining the safety and performance standards of CFCs. The atmospheric lifetime of a gas chosen to replace CFCs is a major factor in determining its potential environmental effects. If its lifetime is less than 6 months, some of the gas can decompose near the point at which it escapes to the atmosphere, possibly contributing to local environmental problems (such as smog). Many gases with short atmospheric lifetimes are also flammable or toxic, and thus worker and consumer safety concerns are associated with their use.
If the lifetime of a gas is longer than about a year, the gas will disperse before significant decomposition occurs; however, if emission rates are large enough, the compound's global concentrations can build to the point at which it has the potential to contribute to global environmental concerns. If the gas contains chlorine, it may potentially contribute to ozone depletion; if it absorbs infrared radiation, it may contribute to greenhouse warming.
The HCFCs and HFCs have been chosen to replace CFCs because of their shorter atmospheric lifetimes. To date, no one has identified an alternative that meets the safety and performance standards of CFCs and also has no potential to contribute to either local or global environmental concerns. The HCFCs and HFCs provide a near-term option to balance societal needs, environmental concerns, consumer and worker safety, and efficiency and performance standards.
Global compliance with the 1990 revisions to the 1987 Montreal Protocol would stabilize the contribution of CFCs to calculated global warming by the end of the twenty-first century. Reducing CFCs as required by the Protocol will be achieved most effectively by a combination of increased conservation and recycling; replacement of CFCs with not-in-kind substitutes (e.g., replacement of CFCs in aerosol products by lower-cost, but flammable, hydrocarbons); and switching some 40 percent of existing essential uses of CFCs (e.g., refrigeration, air conditioning, and medical) to HCFCs and HFCs, which have lower global warming effects because of their shorter atmospheric lifetimes. The Montreal Protocol provides a mechanism to monitor and manage this result to ensure protection of the stratospheric ozone shield. Policymakers must provide incentives to encourage and support global compliance.
The agricultural sector is relevant to greenhouse gas emissions in five contexts:
1. The agricultural sector includes two major worldwide sources of CH4 gas: decomposition in rice paddies and digestion in ruminants in livestock production.
2. Agriculture uses nitrogenous fertilizer and is thus a source of N2O emissions.
3. Agricultural production decisions alter land use, which in turn affects greenhouse gas emissions.
4. Agricultural production uses fossil fuel energy sources and provides potential for reduced energy-related emissions.
5. Agriculture offers biomass fuel potential.
The agricultural sector is responsible for only a small portion of greenhouse gas emissions in the United States. Therefore reduction of greenhouse gas emissions from the agricultural sector in the United States is unlikely to have a major impact on greenhouse warming. On a global basis, however, agriculture contributes a substantial portion of global greenhouse gases. Thus, although the reduction of greenhouse gases from the agricultural sector may be relatively small within the United States, these reductions may represent a large portion of the global greenhouse gas emissions.
Contexts 1, 2, and 3 are discussed in this section. Land use changes (context 3) are also discussed in the context of deforestation policies in Chapter 27 and Appendix O. Energy efficiency (context 4) is extensively treated in Chapters 21, 22, and 23, and Appendixes C, D, and E. Context 5 is discussed in Chapter 24.
Agricultural emissions can be reduced by using a variety of methods. In the case of livestock production, methods include proper handling of manure to reduce CH4, eliminating overproduction of livestock and feed, reducing energy and agrochemical use, and improving the conversion of feed to milk and meat through breeding, hormones, and vaccines to reduce feed requirements. Agricultural practices can also be improved through reducing biomass burning, conserving tillage and using advanced machinery to reduce use of energy and agrochemicals, and increasing the use of on-farm sources of nitrogen fertilizers through better manure management and nitrogen-fixing plants to reduce the need for commercial nitrogen fertilizers (U.S. Department of Energy, 1989).
However, in looking at the agricultural sector from a technical perspective, it is difficult to say that a particular practice will work in all types of agriculture. Many promising technologies do not work in practice or do not work everywhere. Therefore, rather than focusing on the potential of particular technologies as in previous chapters, this analysis attempts to determine the impact of various taxes and subsidies on agricultural practices. In that way, each agricultural source of greenhouse gas can reduce emissions in the way that is most technically acceptable in any particular part of the country, and according to consumer desire for a particular product. The analysis in this chapter reviews both the potential of reducing emissions during production and the desire of the consumer for agricultural goods that generate greenhouse gas emissions.
The primary agricultural sources of CH4 in the United States are paddy rice and ruminants. Information on reducing emissions from both of these sources is discussed in this section.
The United States contributes a relatively small share of the global CH4 emissions from paddy rice (Barker and Herdt, 1985). Most paddy rice is produced in Asia, with China and India contributing half the world's total and Asian countries accounting for almost 90 percent (Crutzen et al., 1986). Ruminants (e.g., cattle, buffalo, horses, and sheep) are also major contributors of CH4 and constitute the largest source of U.S. agricultural CH4 emissions. Ruminants are used as work animals in parts of Asia and Africa, with some use in Latin America, but are used for food, leather, and wool in high-income countries. Biomass burning is another agricultural source of CH4 (and N2Osee the ''Nitrous Oxide" section below).
Table 25.4 shows emission reduction parameters on a per-hectare or per-head basis for paddy rice, draft animals, and other ruminants. For purposes of assessing the relative impacts of U.S. emission controls and controls in other countries, the range of emission reduction (million tons of carbon) from a 10 percent reduction in rice production or ruminant production in different regions is shown. Here it can be seen that the United States is a minor contributor of CH4 from rice paddies and contributes virtually nothing from work animals. It is an important source of CH4 from other ruminant animals (as are other industrialized countries).
Emission Control Methods
Methods for controlling CH4 emissions include the following:
1. Improving the biological efficiency of rice plants and of ruminant animals.
2. Improving waste and residue management.
3. Changing agricultural practices.
4. Reducing consumption and production of paddy rice and ruminant animals.
The biological efficiency of both rice and ruminant animals can be improved. For example, the biological efficiency of paddy rice has improved in recent decades. Most of the world's irrigated and shallow-water-rainfed rice area is currently planted to the more-efficient modern varieties. However, further progress, while possible, is not likely to be dramatic. In the case of ruminant animals, agricultural scientists and farmers themselves have achieved improvements in animal efficiency through selective breeding. This work has resulted in improved animals that convert grains and roughage into meat, milk, and other products more efficiently. In this case, there is considerable scope for further improvement.
TABLE 25.4 Methane Mitigation Policy Options in Agriculture
Waste management in some livestock systems could be improved through regulations, and some animal wastes could be converted to biogas use. For many livestock systems, these options are not feasible, however. Improved residue straw management in rice paddies offers some scope for CH4 reduction, but this is limited because rice straw provides nutrients to soils that would otherwise come from fertilizer, which itself entails N2O emissions.
Agricultural practices can also be changed so that greenhouse gas emissions are reduced. Since work animals provide a considerable part of the world's energy for agriculture, the development of improved tractors and implements could bring about a reduction in work animals. This would reduce CH4 emissions, but at the cost of increased CO2 emissions. A number of logging and agricultural practices include the burning of crop residues, grasses, or shrubs, increasing the emissions of a number of greenhouse gases. Alternatives to biomass burning can be encouraged through information dissemination campaigns. Regulations and taxes can be used to discourage biomass burning.
Both suppliers and consumers can be discouraged from producing or consuming products that increase greenhouse gas emissions. Alternatively, substitutes for these products can be encouraged. For example, consumption of paddy rice and ruminant products can be reduced either by enhancing the supply of substitute products or by making paddy rice and ruminant products more costly than substitutes to consumers (through taxes and other price-increasing practices). Methods for enhancing the supply of substitutes for paddy rice include the improvement of upland (nonpaddy) rice production as well as the improvement of other cereal grain production. For ruminant products the methods include the development of cereal substitutes for meats. Methods for inducing consumers to consume less rice and ruminant products require that the prices of these commodities rise relative to prices of substitute commodities. This can be achieved through taxes, quotas, and regulations or "buyouts" of production reserves. Consumer education programs may also affect meat and egg consumption.
Barriers to Implementation
The barriers to improving the biological efficiency of rice plants and of animals are technological. Virtually every country in the world has an active program of agricultural research to achieve these goals. A system of International Agricultural Research Centers support these efforts.
Regulation of residue and waste management requires an efficient regulatory system, and such systems do not exist in most developing countries. This is also the case for regulation of biomass burning. For developed countries, the necessary systems are in place.
Enhancing the supply of substitute products is the object of a number of
research programs and initiatives in many countries. As with the improvement of biological efficiency, the limitations are technological. The question is whether upland rice is likely to replace paddy rice. Since technological improvements in paddy rice have been achieved at a more rapid pace than for upland rice, it is unlikely that upland rice will displace paddy rice.
Programs to intervene in markets to raise the price of rice and ruminant products will generally be in conflict with welfare concerns. This is particularly likely to be the case for rice, the staple food for most of the world's poor. These programs may be in conflict with or in harmony with current U.S. farm policies with objectives (i.e., incentives to reduce production) related to greenhouse gas concerns. In general, most developed countries, including the United States, intervene in markets to raise prices to the consumer for the purpose of raising producer incomes. They are thus amenable to raising the prices of agricultural goods, but not necessarily to raising the relative prices of rice and ruminant products. Most developing countries, by contrast, resist raising prices to consumersespecially for staple commodities such as rice.
Consumption and production of paddy rice and ruminant products could be reduced by increasing the price of these goods. When prices to consumers increase, it is well established that consumption shifts to substitute products. Price increases to consumers can be achieved through (1) elimination of subsidies to consumers, (2) taxes on the product, and (3) reduced supply of the product. The first option is generally limited to low-income farm countries, where rice consumption may be subsidized. Most low-income countries seek to provide urban consumers with low-priced staple foods. In many cases, imports of rice are subsidized. Removal of these subsidies would curtail consumption and reduce imports. However, a nongreenhouse-gas-producing food crop would need to be developed to replace the rice.
All developed market economies, in contrast, have policies in place that are designed to raise net incomes to farmers. These policies are designed to raise both producer and consumer prices above normal market levels. Taxes on production or sales are not used because these would result in lower producer prices. Importing countries typically impose import tariffs or quotas to reduce supplies, and this causes higher domestic producer and consumer prices. Japan, for example, limits rice imports to such a degree that domestic prices are more than 5 times world prices. South Korea and Taiwan and most European economies also protect domestic producers through import controls. These same countries pursue similar policies with respect to beef and milk production. These policies have a cost to the economy
because they cause resources to be inefficiently allocated. The value that consumers place on the protected products (as measured by the prices consumers pay) exceeds the real cost to the economy (as measured by world prices).
Thus most food-importing countries are already limiting rice and ruminant product consumption, and this generally means less production and CH4 emissions. They bear costs in doing so, but the motives for doing so are not to reduce CH4 emissions. Further CH4 emission reduction could be achieved by increased protection at a cost of $16 to $20/t CH4 mitigated for rice and $50/t CH4 mitigated for ruminant products (see Appendix L for calculations).
For countries that are exporters of rice and ruminant products, the policy options are different. Thailand is the only low-income rice-exporting country, and Thailand has actually used a rice tax on producers to raise government revenue. This tax reduces production and income and CH4 emissions at a cost of $20/t CH4 mitigated. Thailand has lowered this tax in recent years, however.
High-income rice-exporting countriesthe United States is the chief exampleseek to protect the incomes of rice producers. They can do this by subsidizing exports or by making direct payments to producers. In recent years in the United States, producer prices have been maintained at roughly 30 percent above world export prices. Indirect export subsidization and direct payments to producers are made. Irrigation water is heavily subsidized in California. The direct payment schemes do require acreage restrictions. The net effect of this mix of policies is that total rice production is probably higher than it would be in the absence of the policies. Thus some CH4 mitigation could be achievable if these policies were eliminated, but they exist for reasons having little to do with CH4 emissions, and direct CH4 policies would require either more acreage restrictionscompensated by direct paymentor land buyouts. The costs per ton CH4 mitigated through further acreage restrictions are probably in the range of $10 to $200. The buyout options range in cost from $50 to $150 (see Appendix L).
Buyout programs could be pursued in developing countries as well. International agencies could seek to buy paddy rice land out of production by making payments to farmers. This policy would have two complications and is probably not very feasible. First, if the buyouts were substantial, rice prices would rise, and this would affect the welfare of rice consumers. Second, the rise in rice prices would induce the farmers who had not been bought out to plant more rice unless a system of controls was in place (as is feasible in the United States). Thus buyout programs are likely to be quite costly.
For ruminant products, the agricultural policies of developed exporting countries are more complex than for rice. For products that can be stored at
low cost (e.g., dry milk), most OECD countries attempt to reduce supply to achieve higher prices. Supply reduction programs are often ineffective and produce surpluses. Some reduction in CH4 emissions is probably achieved for dairy products. For beef cattle the costs of carrying surpluses are sufficiently high that few direct programs are attempted.
A ruminant tax could be imposed on ruminant products to achieve reduced consumption and production. The imposition of the tax would create an adjustment problem, but once the adjustment was made the implications for producers would not be great. The cost of attaining CH4 mitigation via a ruminant tax in the United States would be approximately $100/t CH4 (see Appendix L).
Waste and residue management in the United States can be improved by reviewing current waste regulations. For many systems, tightened regulations may be in order. For other countries, this will not be feasible in the short term, but increased awareness of CH4 problems is likely to produce long-term gains. Further experiments with biogas systems in livestock production systems and selective subsidies to achieve more experience with such systems could be productive.
Biomass burning in the United States could be reduced by tightening burning regulations. Taxes might be used in some instances. The costs will vary greatly from case to case and should be carefully considered in drawing up new regulations. For developing countries, educational programs and technical assistance from developed countries could be helpful. In some cases, subsidies from international agencies could be used to achieve reduced burning. Such programs need to be sensitive to each situation.
Table 25.4 summarizes CH4 mitigation policy options in agriculture. For each option, the effect per hectare (or animal) and the total ton of carbon mitigated are estimated, along with an estimated range for dollars per ton of carbon mitigated. More information on the way in which these estimates were calculated is given in Appendix L.
Price policy reforms would probably have no real effect on greenhouse gas emissions except in U.S. rice production. Taxes or regulatory quotas by the United States and other countries would reduce greenhouse gas emissions at moderate costs. The lowest costs per ton of carbon mitigated are for limited annual buyouts of rice producers. These options affect production very little. Permanent buyouts are more costly. Ruminant product options are generally more costly than rice options. They, too, are limited in terms of total reductions but do offer some scope for U.S. policies.
None of these calculations considers the distributional consequences of these options. Because these policy options lead to higher rice, meat, and milk prices and because low-income households spend a higher proportion of their incomes on these goods than do high-income households, these policies have undesirable distributional consequences.
Soil cultivation (tillage and fertilizing) in conventional agriculture leads to the release of N2O as well as CO2. N2O is also released in land clearing (Wuebbles and Edmonds, 1988).
The major biogenic source of atmospheric N2O growth is the use of nitrogenous fertilizer to increase crop yields: 34 percent of anthropogenic N2O emissions by one estimate (Krause et al., 1989). Although the accuracy of these values is questionable due to lack of worldwide information on biogenic sources, they do indicate the importance of the contribution to N2O emissions from fertilizer application in relation to that from fossil fuels. The IPCC estimates that N2O was responsible for approximately 5 percent of the greenhouse gas contribution during the 1980s (see Chapter 19 for more details; Intergovernmental Panel on Climate Change, 1990). The U.S. N2O emissions from nitrogenous fertilizers can be estimated at approximately 0.9 teragrams (Tg) of nitrogen per year by taking the total world N2O emissions and dividing by the land area of the United States.
Available data (see, for example, Eicher, 1990) show that the magnitude of N2O emissions varies greatly with the form in which nitrogen fertilizer is applied and suggest that magnitudes may also depend on agricultural practices, biogenic processes, soil properties, and climate. The form of, and application method for, nitrogen are factors that could be managed if further analysis were to confirm that they are important variables in N2O control.
Emission Control Options
There apparently is some scope for changing N2O emissions by choosing different fertilizers and by altering fertilizer and other chemical application practices. There are currently many types of chemical fertilizer, and more may be developed. Researchers may develop improvements, but as with energy and other activities, costs will be a factor. If the lowest-cost fertilizer is the heaviest emitter, then a tax or regulation would be required to limit its use (which is costly). Scientists have been working on nitrogen-fixing crops for many years, but additional progress is possible and needs to be made.
Therefore reduction of fertilizer use is probably the least costly method for significantly lowering the growth of agricultural sources of atmospheric N2O emissions. There are many approaches, including altering planting and tillage practices, to reduce the amount of fertilizer application required. One of the most attractive is crop rotation, interspersing legumes (which are
efficient extractors of atmospheric nitrogen) with grains. More organic waste recycling would also be helpful, and its use could be effectively increased. An alternative mitigation approach is the application of additional chemicals that reduce N2O emissions from soils.
A summary of possible mitigation techniques includes the following:
• controlling erosion,
• improving crop varieties,
• matching available nitrogen to crop needs,
• using the lowest-emitting nitrogen fertilizers whenever suitable,
• adding nitrification inhibitors to fertilizers,
• limiting fertilizer use, and
• extending no-tillage or low-tillage farming using nitrogen-fixing plants.
Barriers to Implementation
Fertilizer use has long been essential to efficient agricultural production. Many improvements in crop varieties have depended on an enhanced responsiveness to fertilizers to achieve greater productivity. For many less-developed countries a reduction in nitrogen fertilizer use would be seen as a strong and direct threat to their capacity to produce food. Many countries have been actively seeking to increase fertilizer use (Barker and Herdt, 1985; Hayami and Ruttan, 1985).
In developed countries where there is an interest in controlling production of commodities as part of farm programs designed to achieve higher prices, a nitrogen tax, provided it applied to all farmers for all uses, would probably be politically feasible. The political feasibility of such programs is discussed in the section on "Methane" above.
Nitrogen fertilizer use is widespread, being heaviest in Europe. Some crops in some countries use little fertilizer (cassava and legumes), but cotton, paddy rice, and maize rely heavily on nitrogen fertilizer. A ban on nitrogen fertilizer would have a major impact on the production of these crops. Thus a tax to reduce N2O emissions could be quite costly. In most developing countries, extension advisors to farmers usually recommend more nitrogen fertilizer use than farmers actually apply. In general, the value of the increase in crops produced by nitrogen fertilizerthe "marginal product"is higher than the price of the fertilizer applied (Hayami and Ruttan, 1985).
Several studies of fertilizer demand estimate that a 10 percent increase in price (from a tax) would decrease use by roughly 5 percent (Gardner, 1987).
If such a tax were applied on all nitrogen fertilizer in the United States, it would have a cost of $25 million and would reduce N2O emission by 50,000 t N/yr at a cost of $500/t N.
Research and Development
Biological efficiency can be improved by supporting and strengthening agricultural research programs. CH4 reduction objectives can be incorporated directly into research programs. Specific programs for animal improvement can be implemented. Past experience with agricultural research programs indicates that most programs have been highly productive (Evenson, 1990). Expanded support for CH4 concerns is likely to be effective. Paddy rice production and consumption can be reduced by enhancing substitutes such as upland rice. The production of such rice could be improved through research programs. It should be recognized, however, that the substitute crops for upland rice are other upland crops, not paddy rice. More upland rice production will increase rice supplies and lower rice prices generally, however, thus having a small discouragement effect on paddy rice production.
Ruminant products could be replaced with cereal-based substitutes with additional development. Given that substantial research and development activities directed toward this objective are in place, it is unlikely that a specific subsidy to such research and development would speed up the process significantly. Subsidies to substitutions for rice and ruminant products would reduce CH4 but could be more costly than other policies (see below).
Naturally produced or fixed nitrogen by plants is quite important and may be enhanced by further research. Legumes (e.g., beans, soybeans, and lentils) fix nitrogen. The Azolla fern is used in parts of Asia to fix nitrogen in rice fields, but its use is limited by high labor requirements and temperature sensitivity.
The agricultural sector constitutes a major sink for sequestering of carbon, and because this carbon is constantly recycled, the sink is a long-term one. The sector is a major source of CH4 and N2O, and to the extent that agricultural production uses fossil fuels it is also a small source of CO2. Land use change also leads to direct emission of CO2.
The political climate for policies (e.g., taxes, subsidies, and buyouts) to reduce CH4 and N2O emissions through reductions in supply of ruminant products and rice in the United States is favorable because farm interest groups seek higher prices; however, there is some concern regarding the efficiency and effectiveness of such mechanisms. For other industrialized
countries, the political situation is similar and would likely not constitute a major barrier to the implementation of greenhouse gas emission control options.
Developing countries, on the other hand, offer quite a large scope for potential greenhouse gas mitigation. Political and distributional concerns are barriers to mitigation options in these countries because they often reduce production and consumption of vital goods. International mechanisms for sharing costs would be required to realize mitigation in many developing economies.
Finally, although there are few impending breakthroughs in technology, the potential for improved technology from research and development in both food and biomass fuel production is good in the long run.
On a worldwide basis, municipal landfills are a relatively small but increasing source of CH4 emissions to the atmosphere. The EPA estimates that worldwide landfill emissions account for approximately 3 percent of total global CH4, but that this would increase to roughly 7 to 9 percent by 2025 in the absence of new abatement measures (Lashof and Tirpak, 1990). For the United States, however, landfills are the largest source of CH4 emissions, as seen in Chapter 19.
Landfill CH4 is produced primarily by the decomposition of municipal and industrial solid wastes under anaerobic conditions (i.e., a lack of oxygen). The quantity and rate of CH4 production depend on a number of factors, including composition of the waste; age, moisture and oxygen content, temperature, and acidity (pH); and the presence of nutrients or biological inhibitors that either stimulate or repress the activity of bacteria responsible for decomposition. Biological decomposition in landfills is typically accompanied by other chemical reactions and by vaporization of some landfill constituents. Thus ''landfill gas" includes not only CH4, but CO2, nitrogen, and a variety of non-CH4 organic compounds. The average composition of waste at active U.S. landfills is shown in Table 25.5. Household waste at approximately 72 percent (by weight) is the largest contribution by far.
Figure 25.7 depicts the typical evolution of landfill gas constituents, illustrating the dominant biochemical processes over time (U.S. Environmental Protection Agency, 1990a). Actual elapsed time is measured in decades and depends on landfill composition. As a rough approximation, most studies assume that landfill gas is 50 percent CH4 and 50 percent CO2 by volume, with trace amounts of other constituents.
The time required for significant production of CH4 can vary from 10 to 100 years or more, depending on the landfill properties noted above. The
TABLE 25.5 Average Composition of Waste in Active Municipal Waste Landfills
EPA estimates typical rates of CH4 production at 1000 to 7000 cubic feet per ton of municipal solid waste deposited (Lashof and Tirpak, 1990).
Estimates of landfill CH4 and CO2 generally are based on population estimates for a particular region, together with assumptions about the quantity and composition of refuse associated with that population. Table 25.6 summarizes the assumptions employed by Barnes and Edmonds (1990) in a study for DOE. These estimates are based on the work of Bingemer and Crutzen (1987), who estimate current landfill CH4 emissions at approximately 30 to 70 Mt/yr worldwide. Note that the model described by Barnes and Edmonds (Table 25.6) does not include a time lag between waste generation and landfill gas emissions.
In the United States, more detailed estimates of CH4 generation rates have recently been developed by EPA as part of a proposal for controlling air emissions from municipal solid waste (MSW) landfills (U.S. Environmental Protection Agency, 1990a,c). Table 25.7 summarizes EPA estimates of CH4 and non-CH4 organic compound emissions for new and existing landfills in 1997 in the absence of any regulatory action. A simple two-parameter model is used to estimate CH4 generation rates as a function of the landfill opening and closing dates and of the annual average refuse acceptance. The two chemical parameters in the model reflect the type of
refuse in each landfill and the various dependency factors (temperature, moisture, and so on) listed earlier.
As noted earlier, CO2 emissions are roughly comparable in magnitude to CH4 emissions on a volume basis. Adjusting for the differences in molecular weight, CO2 mass emissions thus are approximately 2.75 times greater than the CH4 values in Table 25.7.
Emission Control Methods
Reduction of CH4 from active or inactive landfills requires that the gas first be collected and then utilized in an energy recovery system or simply burned (flared). Either alternative produces CO2 and water vapor, but a net benefit in terms of greenhouse effects still results because CH4 contributes more radiative forcing than CO2 (see Chapter 19, Table 19.4) and because with CH4 as an energy source, some use of an alternative fuel has been displaced.
TABLE 25.6 Parameters for Estimating Landfill Gas Emission Rates
In the United States, approximately 17 percent of the operating municipal landfills employ some form of CH4 recovery and mitigation system, although less than 2 percent of the sites recover CH4 for energy use (Lashof and Tirpak, 1990). Recently, however, EPA announced its intent to require the collection and control of landfill gases under Section 111 of the Clean Air Act (which pertains to new sources). The EPA standards (for new sources) and guidelines (for existing sources) currently being drafted would apply to all municipal landfills emitting more than 100 t/yr of non-CH4 organic compounds (U.S. Environmental Protection Agency, 1990c). Such facilities would be required to design and install gas collection systems and then combust the captured landfill gases (with or without energy recovery). The combustion control device would have to be capable of reducing non-CH4 organic compounds in the collected gas by at least 98 percent.
As background to its draft regulatory proposal, EPA analyzed three regulatory options for new and existing landfills. The three alternatives were based on cutoff sizes of 25, 100, and 250 t/yr of non-CH4 organic compounds from a given landfill. The lowest cutoff level would influence the greatest number of facilities. For each regulatory alternative, engineering and economic models were used to estimate the overall emission reductions and costs of landfill gas mitigation. The assumed control technology was an active gas collection system coupled with either a flare or an energy
TABLE 25.7 National Baseline CH4 and Non-CH4 Organic Compound Emission Estimates, 1997
recovery system for gas combustion. Because the latter option entails higher capital costs, its economical viability depends on the site-specific nature of by-product energy use or markets, which EPA was not able to evaluate. Thus the costs reported by EPA are based on application of active gas collection systems and flares to all landfills above the specified emission level cutoffs (U.S. Environmental Protection Agency, 1990c).
The control cost results for new and existing landfills are presented in Table 25.8. The average CH4 emission reduction encompassed by the three regulatory alternatives ranges from 39 to 82 percent at costs of $9 to $29/t CH4 removed. The current EPA draft proposal calls for implementing "regulatory
TABLE 25.8 Landfill CH4 Reduction Control Costs
alternative No. 2," which would reduce CH4 emissions by 60 to 65 percent over the life of U.S. landfills.
Because emissions, as well as capital and operating costs, vary significantly over the life of a facility, EPA's analysis employs a two-stage discounting procedure to calculate cost-effectiveness. First, capital costs are annualized over the useful life of the equipment by using a 10 percent rate of return. Then, the annual capital costs, operating costs, and emission reduction are brought back to a reference year (1992) by using a 3 percent social discount rate. Cost-effectiveness is calculated by dividing the total annualized cost by the total annualized emission reduction. Landfill lifetimes employed in the calculation range from 64 to 119 years, depending on the type of facility and the regulatory stringency. Although this calculation procedure differs from one used earlier in this report for CO2 reduction measures (where emissions do not vary from year to year), the discount rate assumptions employed by EPA are similar to those employed in earlier chapters. Note, however, that 1992 (the effective date for regulation) rather than 1990 is used as the basis for EPA's cost results.
The panel's analysis of landfill gas cost-effectiveness in terms of CO2 equivalence, which is based on the EPA results in Table 25.8, is presented in Appendix M.
Barriers to Implementation
Of primary interest here are barriers to the utilization of landfill gas as an energy resource. The economic viability of this option is hampered both by the quantity of gas available and by the fact that the energy content of landfill gas is only about half that of natural gas. Thus, under present conditions, landfill gas is economically viable as a fuel only if used close to the landfill site (e.g., within 2 to 3 miles). One such option could involve coupling directly to an electricity grid via a co-generation plant. Landfill operators have not traditionally been concerned with by-product recovery and utilization, however. Most landfills also tend to be in relatively remote locations. Another significant impediment to energy recovery is that some existing state regulations establish unlimited liability for any potential contamination problems at landfill resource recovery projects (Lashof and Tirpak, 1990).
As discussed above, EPA already plans to require collection and combustion of landfill gas from large facilities. This policy will reduce the emissions of greenhouse gases. The magnitude of the reduction will depend on a final determination of the size of facilities affected.
In the long term, landfill gas emissions can be reduced through increased recycling so that less waste is available for decomposition. Alternative methods of waste disposal also could be promoted. For example, an analysis could be conducted that evaluated the relative greenhouse gas benefits of incineration versus landfill disposal. Policy incentives to encourage wider use of energy recovery systems could also be devised and implemented.
Other Benefits and Costs
The U.S. Environmental Protection Agency (1990a,c) lists four major health and welfare effects that motivate the regulation of landfill gas emissions: (1) human health and vegetation effects caused by tropospheric ozone, which is formed from non-CH4 organic compound emissions; (2) carcinogenicity and other health effects associated with air emissions of toxic species; (3) global warming effects of CH4; and (4) gas explosion hazards. Additional consequences cited by EPA are odor nuisance and hazardous effects on soil and vegetation (U.S. Environmental Protection Agency, 1990a). Policies that reduce waste generation would also help communities that are running out of landfill space.
Research and Development
One important focus for research and development is to explore and improve techniques for enhancing CH4 gas production yield from landfills. Methods such as the controlled addition of nutrients and moisture, control of landfill acidity, and bacterial seeding could help improve the economic viability of landfill gas recovery as an alternative to flaring (Lashof and Tirpak, 1990).
Major conclusions emerging from the above discussion on the potential mitigation of landfill gas are the following:
• Municipal landfills account for a small but growing fraction of CH4 emitted from the decomposition of organic materials in refuse worldwide.
• In the United States, EPA is about to promulgate new measures that would require the collection and combustion of landfill gas from larger facilities, thus reducing overall emissions from new and existing landfill sites.
• The utilization of landfill gas as an energy resource is currently quite low. Increased research and development could enhance the economic feasibility of this energy option.
1. Throughout this report, tons (t) are metric; 1 Mt = 1 megaton = 1 million tons; 1 Gt = 1 gigaton = 1 billion tons.
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