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Chapter 7: Reducing Emissions of Non-CO2Greenhouse Gases
The Intergovernmental Panel on Climate Change's (IPCC) Third Assessment Report (IPCC 2001) states that "well-mixed" non-CO2gases, including methane, nitrous oxide, chlorofluorocarbons, and other gases with high global warming potentials (GWPs) may be responsible for as much as 40 percent of the estimated increase in radiative climate forcing between the years 1750 and 2000. [1] In addition, emissions of black carbon (soot), organic carbon and other aerosols, as well as tropospheric ozone and ozone precursors, have important effects on the Earth's overall energy balance.
Developing technologies for commercial readiness that can reduce emissions of these non-CO2GHGs is an important component of a comprehensive strategy to address concerns about climate change. A recent modeling study (Placet et al. 2004) showed that there is a considerable amount of uncertainty about future rate of growth of non-CO2emissions, but most models project that emissions will increase over time in the absence of constraints (see Chapter 3). One set of scenarios that included a wide range of advanced technologies2 for reducing emissions of non-CO2gases showed that emissions could potentially be reduced by a range of between 125 and 160 gigatons (Gt) of carbon-equivalent emissions (cumulatively) over a 100-year planning horizon, as shown in Figure 3-19 and highlighted on the figure above. Although bracketed by a range of uncertainties, this figure suggests both the potential role for advanced technology and a long-term goal for contributions from other GHGs in the future global economy. In the context of global warming, emissions of the non-CO2GHGs are usually converted to a common and roughly comparable measure of the "equivalent CO2emissions." This conversion is performed based on physical emissions, weighted by each gas' global warming potential (GWP). The GWP is the relative ability of a gas to trap heat in the atmosphere over a given timeframe, compared to the CO2reference gas (per unit weight). GWP values allow for a comparison of the impacts of emissions and reductions of different gases, although they typically have an uncertainty of �35 percent (EPA 2005). The choice of timeframe is significant and can change relative GWPs by orders of magnitude. All non-CO2gases are compared to CO2, which has a GWP of one. The GWPs of other GHGs, using a 100-year time horizon, range from 23 for methane to 22,200 for SF6, as shown in Box 7-2.
Non-CO2gases have different GWPs due to differences in atmospheric lifetimes and effectiveness in trapping heat. Methane and some HFCs have relatively short atmospheric lifetimes as compared to other non-CO2gases. Thus, emissions reductions among these gases manifest themselves as lower atmospheric concentrations in a matter of a few decades. PFCs and SF6, in contrast, can remain in the atmosphere for thousands of years. Emissions of these GHGs essentially become permanent additions to the Earth's atmosphere, with concomitant increases in the atmosphere's ability to capture and retain radiant heat. Finally, tropospheric ozone and black carbon aerosols (soot) are very short-lived in the atmosphere (i.e., remaining airborne for a period of days to weeks) and therefore do not become well-mixed in the atmosphere. Primarily for this reason, GWP metrics have not been assigned to these gases and aerosols, but they are nonetheless recognized as significant contributors to climate change. There is a strong record of successful collaboration between industry and government to reduce emissions of non-CO2gases, and these partnerships provide a solid foundation from which to pursue additional technological developments and more substantial future emission reductions. Some highlights of the current activities include:
These partnerships and others that are discussed in this chapter demonstrate the potential for significant near-term emission reductions from currently available technologies. In addition, longer-term analyses have identified the potential for current and future technologies to lead to even more significant emission reductions. Historically, non-CO2gases were either not included or were treated in a cursory manner in climate change modeling and scenario studies. This situation is changing, however, and many modelers are incorporating the non-CO2gases into their models and are developing the capability to assess the role of the non-CO2gases in addressing climate change. Studies published to date indicate that substantial mitigation of future increases in radiative forcing could be achieved by reducing emissions of these other GHGs. It is possible that such reductions could contribute as much as one-half of the abatement levels needed to stay within a total radiative forcing gain that would be consistent with commonly discussed stabilization ranges of CO2concentrations. [5] Achieving significant reductions in the emissions of the non-CO2gases is possible, taking into account the current achievements in reducing emissions as well as the results of detailed analyses of the technical and economic potential to reduce emissions from particular sources and sectors. Based on the information presented in this chapter, it is possible to achieve CH4 emissions reductions of 40 to 60 percent by 2050, and 45 to 70 percent by 2100. Emissions of N2O can be reduced by 25 to 30 percent by 2050, and 50 percent by 2100 (DeAngelo et al. forthcoming, Delhotal et al. forthcoming). In addition, it is possible to reduce emissions of high-GWP gases by 55 to 75 percent by 2050, and 60 to 80 percent by 2100 (Schaefer 2006). Target Areas for Reducing Emissions of Non-CO2GHGs (2000 Emissions in Tg CO2Equivalent)U.S. and Global Methane (CH4) Emissions from Energy and Waste (2000 Emissions in Tg CO2Equivalent)There are a number of potentially fruitful areas for technologies to mitigate growth in emissions of non-CO2GHGs and strong promise that over time emissions could be reduced substantially. The strategy for addressing non-CO2GHGs has two key elements. First, it focuses on the key emission sources of these GHGs and identifies specific mitigation options and research needs by gas, sector, and source. Given the diversity of emission sources, a generalized technology approach is not practical. Second, the strategy emphasizes both the expedited development and deployment of near-term and close-to-market technologies and expanded R&D into longer-term opportunities leading to large-scale emission reductions. By stressing both near- and long-term options, the strategy offers maximum climate protection in the near term and a roadmap to achieve dramatic gains in later years. The discussion of the key emission sources of other GHGs is organized around five broad categories-or "target areas"-listed in Table 7-1. Following the table, each target area is discussed in subsequent technology sections. Each of these technology sections includes a sub-section describing the current portfolio. The technology descriptions include a link to the CCTP Technology Options for the Near and Long Term (CCTP 2003). 7.1 Methane Emissions from Energy and WasteIn 2000, methane emissions from the energy and waste sectors accounted for 31 percent of global non-CO2GHG emissions (Table 7-2), and nearly 50 percent of global methane emissions. The major emission sources in these sectors include coal mining, natural gas and oil systems, landfills, and wastewater treatment. As Table 7-2 shows, among the energy and waste-related methane emission sources, oil and gas systems, and landfills are the largest emission sources, accounting for 9 and 11 percent, respectively, of global non-CO2emissions.The energy and waste sectors present some of the most promising and cost-effective near-term reduction opportunities. Reducing methane emissions, the primary component of natural gas, can be cost-effective in many cases due to the market value of the recovered gas. Efforts in the United States to voluntarily encourage these economically attractive opportunities have already been successful by focusing on the deployment of available, cost-effective technologies. As Table 7-3 shows, emissions from the key sources in the United States have declined in absolute terms by about 16 percent since 1990, equal to about 65 teragrams of carbon dioxide equivalent (Tg CO2equivalent). Despite this success, significant opportunities remain for further emission reductions through the expanded deployment of currently available technologies and the development of promising new technologies. These longer-term technologies could lead to substantial additional methane reductions in the future. The remainder of this section discusses these technical opportunities for the three major emission sources in this category: landfills, oil and gas systems, and coal mines. LandfillsMethane emissions from landfills result from the decomposition of organic material (yard waste, food waste, etc.) by bacteria in an anaerobic environment. Emission levels are affected by site-specific factors such as waste composition, moisture, and landfill size. Landfills are the second largest anthropogenic methane emission source in the United States, releasing an estimated 131 Tg CO2equivalent to the atmosphere in 2003 (EPA 2005). Globally, landfills are also a significant emission source, accounting for an estimated 814 Tg CO2equivalent in 2000 or almost 10 percent of global non-CO2emissions (Table 7-2). The majority of emissions currently come from developed countries, where sanitary landfills facilitate the anaerobic decomposition of waste. Emissions from developing countries, however, are expected to increase as solid waste will be increasingly diverted to managed landfills as a means of improving overall waste management. By 2020, three regions are projected to each account for more than 10 percent of global methane emissions from landfills: Africa (16 percent), Latin America (13 percent) and Southeast Asia (12 percent) (EPA 2004).Change in U.S. Methane (CH4) Emissions from Energy and WastePotential Role of TechnologyThe principal approach to reduce methane emissions from landfills involves the collection and combustion (through use for energy or flaring) of landfill gas (LFG). LFG utilization technologies can be divided into two main categories: electricity generation and direct gas use. About 75 percent of the projects in the United States involve electricity generation, using reciprocating engines or combustion turbines. Direct use technologies account for about 25 percent of total projects, but their implementation has grown in recent years. Some of these technologies use LFG directly as a medium-Btu fuel, while others require the gas to be upgraded and delivered to a natural gas pipeline.Technology StrategyAdditional CH4 emission reductions at landfills can be achieved through RD&D efforts focused on improvements in LFG collection efficiency, gas utilization technologies, and alternatives to existing solid waste management practices. In the near term, RD&D efforts focused on improving collection efficiency and demonstrating promising emerging gas use technologies can yield significant benefits. These approaches could increase emission reductions from the waste currently contained in landfills, which will emit CH4 for 30 or more years. Longer-term reductions will result from research on advanced utilization technologies and development of solid waste management alternatives, such as bioreactor landfills.Current PortfolioThe current Federal portfolio focuses on three areas:
Future Research DirectionsThe current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. From diverse sources, suggestions for future research have come to CCTP's attention. Some of these, and others, are currently being explored and under consideration for the future R&D portfolio.Future applied research efforts in the near term could focus efforts to improve LFG collection efficiencies, including research on the design, construction, and operational effectiveness of horizontal wells and other new gas collection systems. Research could also be targeted on the development of additional economical gas utilization technologies and optimizing methane oxidation by cover soils or other advanced cover materials. Development and deployment of near-term technologies to recover LFG from current waste disposal sites could reduce emissions by 50 percent (Delhotal et al. forthcoming). Over the long term, emissions could theoretically be eliminated through the commercialization and deployment of advanced waste processing and treatment systems such as integrated systems approaches for waste management that could reduce the magnitude of landfill waste and nearly eliminate new landfill waste, such as:
Coal MinesCoal mines are a significant methane emission source in the United States and worldwide, accounting for about 10 percent of total anthropogenic methane emissions (EPA 2004). Methane trapped in coal deposits and in the surrounding strata is released during normal mining operations in both underground and surface mines. In addition, handling of the coal after mining (e.g., through storage, processing, and transportation) results in methane emissions. Underground mines are the largest source of coal mine methane (CMM) emissions.Emissions of CMM in the United States in 2000 were 56 Tg CO2equivalent and are projected to increase to 70 Tg CO2equivalent by 2010 (EPA 2005). Worldwide emissions of methane from the coal industry are estimated to be 432 Tg CO2equivalent and are expected to rise to 495 Tg CO2equivalent by the year 2010 as coal production increases (EPA 2004). Globally, almost all CMM emissions come from the major coal producing countries and regions of China; India; the United States; the Confederation of Independent States; Australia; Central, Eastern, and Western Europe; the United Kingdom; and Southern Africa. Underground mines present the greatest opportunities for reducing emissions; however, emission reductions are also possible at surface mines. Emissions from both underground and surface mines vary, depending on the technology used to mine the coal, the rate of coal production, the technologies employed to remove the methane from the mines, and the local geological conditions. Potential Role of TechnologyUpstream and downstream technologies are integral to reducing methane emissions from coal mines. The most important upstream technological contributions are in the recovery of methane from mine degasification operations and in the oxidation of low-concentration methane in mine ventilation air. Degasification systems are used to remove methane from the coal seams to provide for a safe working environment. These systems generally consist of boreholes drilled into the coal seams and adjacent strata, with in-mine and surface gathering systems used to extract and collect methane. CMM can be recovered in advance of mining or after mining has occurred, and recovery may consist of surface wells, in-mine boreholes, or some combination of the two.From a technical viewpoint, the most appropriate drainage technology depends on the surface topography, subsurface geology, reservoir characteristics, mine layout, and mine operations. Degasification technologies are used around the world and are commonplace in most of the aforementioned countries. Surface gob wells are used to extract methane after mining has occurred, and in-mine horizontal boreholes are standard at many gassy mines. However, advanced degasification employing long-hole in-mine directional drilling has only been successful in a limited number of countries, including the United States, Australia, China, Japan, United Kingdom, Germany, and Mexico; it is currently being tested in Ukraine. Only the United States and Australia have had success with pre-mine drainage using surface wells. Although gas drainage is practiced primarily at underground mines, drainage is also occurring at surface mines in some countries, including the United States, Australia, and Kazakhstan. Horizontal boreholes can be drilled into the coal seam ahead of mining and the methane extracted. In a number of countries, commercially applied technologies have led to large reductions in CMM emissions through use of the captured methane. These technologies have included the use of CMM as fuel for power generation (primarily internal combustion engines), injection into the natural gas pipeline system and local gas distribution networks, boiler fuel for use at the mine, local heating needs, thermal drying of coal, vehicle fuel, and as a manufacturing feedstock (e.g., methanol, carbon black, and dimethyl ether production). Technology advances in gas processing over the past decade have also resulted in projects to upgrade the quality of CMM and liquefy the gas, which in turn provide more end-use options and improve access to markets. Although considerable effort is still directed at improving methane drainage recovery efficiencies and broadening the application of end-use technologies, attention is also focused on the capture and use of coal mine ventilation air methane (VAM). Mine ventilation air generally contains less than 1 percent methane in accordance with regulatory standards. The low concentration greatly limits possible uses of the methane. However, VAM is the largest source of underground methane emissions, and presents a significant opportunity to further mitigate GHG emissions from coal mines if capture and use technologies can be successfully applied. Worldwide VAM emissions in 2000 were 238 Tg CO2equivalent and are expected to increase to 282 Tg CO2equivalent by 2010 and 308 Tg CO2equivalent by 2020. Emissions of VAM in the United States in 2000 were about 37 Tg CO2equivalent and are anticipated to rise slightly to 40 Tg CO2equivalent by 2010 and remain steady thereafter (EPA 2003a). Technology StrategyRD&D efforts aimed at emerging methane reduction technologies for coal mines could target VAM and advanced coalbed methane drilling techniques. The development of technologies to use VAM will enable overall emission reductions at underground mines to reach 90 percent, as compared to the current technical recovery limit of 30 to 50 percent (EPA 1999). The most promising approach for recovering VAM emissions is through commercialization of technologies that convert the low-concentration (typically under 1 percent) methane directly into heat using thermal or catalytic flow reversal reaction processes. The heat can then be employed for power production or other heating. Demonstration projects in Australia, Canada, and the United Kingdom have shown that these technologies can be technically viable. The world's first commercial unit is expected to be operative in Australia in 2006, generating enough thermal energy to supply a 6-MW steam turbine. Future efforts will need to focus on continued testing and commercial deployment of VAM combined with market development support to ensure that it is seen by industry as an energy resource, rather than being vented to the atmosphere.The other potentially important approach to reduce emissions is the development of advanced drilling technologies. Over the 1990s, advances in steerable motors and stimulation techniques have increased the ability to recover a higher percentage of the total methane in coal seams. This methane, much of which is high quality, may then find a viable market. The most promising technologies include in-mine and surface directional drilling systems, which may enable fewer wells to produce more gas, and advanced stimulation techniques, such as nitrogen injection, that increase the recovery efficiency of surface wells. There is also considerable interest in CO2injection; however, this is currently not an option for mine degasification. Injecting the CO2into the coal seam renders the coal seams unmineable due to the hazard of releasing too much CO2into the mine workings. Although it is difficult to characterize the potential for enhanced gas drainage, these technologies have been shown to obtain drainage efficiencies of 70 to 90 percent (EPA 1999). Future RD&D activities will need to focus on the continued testing and commercial deployment of directional drilling and use of other gases in coalbed methane recovery. In addition, market development support will be needed to ensure that increased drained emissions are put to productive use, rather than vented to the atmosphere. Current PortfolioThe current Federal portfolio focuses on two areas:
Future Research Directions
Natural Gas and Petroleum SystemsMethane emissions from the oil and gas industry accounted for approximately 11 percent of global non-CO2emissions in 2000 (EPA 2004). Russia and the United States accounted for over 30 percent of global methane emissions from oil and gas systems. Emissions occur throughout the production, processing, transmission, and distribution systems and are generally process related. Normal operations, routine maintenance, and system upsets are the primary contributors. Emissions vary greatly from facility to facility and are largely a function of operation and maintenance procedures and equipment. However, over 90 percent of methane emissions from oil and gas systems are associated with natural gas rather than oil-related operations (EPA 2005, 2004).As demand for oil and gas increases, global methane emissions are projected to increase by more than 72 percent between 1990 and 2020 (EPA 2004). However, in many developed countries there is increasing concern about the contribution of oil and gas facilities to deteriorating local air quality, particularly emissions of non-methane volatile organic compounds (NMVOCs). Measures designed to mitigate NMVOC emissions, such as efforts to reduce leaks and venting, have the ancillary benefit of reducing methane emissions. In addition, as economies in many Eastern European countries undergo restructuring, efforts are underway to modernize gas and oil facilities. For example, Germany expects to reduce emissions from the former East German system through upgrades and maintenance. Russia also plans to focus on opportunities to reduce emissions from its oil and gas system as part of modernization. Potential Role of TechnologyReducing methane emissions from the petroleum and natural gas industries necessitates both procedural and technology improvements. Methane emission reduction strategies generally fall into one of three categories: (1) technologies or equipment upgrades that reduce or eliminate equipment venting or fugitive emissions, (2) improvements in management practices and operational procedures, or (3) enhanced management practices that take advantage of improved technology. Each of these technologies and management practices requires a change from business as usual in the schedule and conduct of daily operations. To date, over 90 emission reduction opportunities have been identified by corporate partners in EPA's Natural Gas STAR Program. In many cases, these actions are cost-effective and widely applicable across industry sectors.Technology StrategyDespite the current availability of cost-effective methane emission reduction opportunities in the natural gas and petroleum industry, RDD&D efforts could have an important impact on future methane emissions. Both in the near and long terms, RDD&D efforts could focus on increasing market penetration of current emission reduction technologies, improving leak detection and measurement technologies, and developing advanced end-use technologies.
Current PortfolioThe current Federal R&D portfolio primarily focuses on leak detection measurement and monitoring technologies for natural gas systems. Advanced leak detection and measurement technologies enable quick and cost-effective detection and quantification of fugitive methane leaks (Figure 7-3). Natural gas systems' RDD&D goals related to measurement and monitoring technologies are focused on completing of the development and deployment of advanced measurement technologies like the Hi-FlowTM and on advancing the development of imaging technology for methane leak measurement and facilitate demonstration and deployment. [12]Future Research DirectionsThe current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. From diverse sources, suggestions for future research have come to CCTP's attention. Some of these, and others, are currently being explored and under consideration for the future R&D portfolio.Pipelines carrying natural gas as well as facilities where natural gas is liquefied are a source of fugitive emissions of methane. Advances in materials, seals, and valve technology could eliminate or reduce these emissions at the source. Possible research may include:
Enhanced leak-detection and measurement efforts can yield significant methane emission reductions. Demonstration of improved technologies has indicated that emissions at compressor stations and gas-processing plants can be reduced cost effectively by as much as 80 to 90 percent. More importantly, an enhanced demonstration and deployment effort focused on currently available emission reduction technologies would encourage additional technology penetration. In the United States alone, this effort could reduce emissions by an estimated 37 Tg CO2equivalent in 2010. 7.2 Methane and Nitrous Oxide Emissions from AgricultureOver 40 percent of total U.S. non-CO2GHGs come from methane (CH4) and nitrous oxide (N2O) emissions from agriculture (EPA 2005). Globally, agricultural sources of methane and nitrous oxide contribute an estimated 5,428 Tg CO2equivalent, nearly 60 percent of global non-CO2emissions (EPA 2004). These emissions result from natural biological processes inherent to crop and livestock production and cannot be realistically eliminated, although they can be reduced. For example, emissions of oxides of nitrogen (NOX) can likely be decreased by 15 to 35 percent through programs that improve crop nitrogen use efficiency, through plant fertilizer technology, precision agriculture, and plant genetics (DeAngelo 2006). Table 7-4 shows N2O and methane emissions from agricultural sources (Tg CO2equivalent).Key research efforts have focused on the largest agriculture GHG emission sources:
Advanced Agricultural Systems for Nitrous Oxide Emissions ReductionsLow efficiency of nitrogen use in agriculture is primarily caused by large nitrogen losses due to leaching and gaseous emissions (ammonia, nitrous oxide, nitric oxide, and nitrogen). In general, N2O emissions from mineral and organic nitrogen can be decreased by nutrient and water management practices that optimize a crop's natural ability to compete with processes that result in plant-available nitrogen being lost from the soil-plant system.Potential Role of TechnologyKey technologies in the area of nutrient management can be applicable to N2O mitigation. They focus on the following areas:
Technology StrategyTechnologies and practices that increase the overall nitrogen efficiency while maintaining crop yields represent viable options to decrease N2O emissions. Focused RDD&D efforts are needed in a number of areas to develop new technologies and expanded deployment of commercially available technologies and management practices (Figure 7-4).
Current PortfolioAlthough many mitigation options for N2O emissions can be readily identified, their implementation has not been carried out on a large scale. Other than programs to limit nitrogen losses, programs that directly address the issue of N2O emissions from agricultural soil management are very limited. The current Federal portfolio focuses on N2O emissions from agricultural soil management; precision agriculture; understanding and manipulation of soil microbial processes; expert system management; and the development of inexpensive, robust measurement and monitoring technologies. Research for reductions in N2O emissions focus on improved production efficiencies and reduced energy consumption by developing and deploying precision agriculture technologies, sensors/monitors and information-management systems, and smart materials for prescription release utilized in major crops. An additional goal is to improve fertilizer efficiency and reduce nitrogen inputs by developing advanced fertilizers and technologies, methods of manipulating soil microbial processes, and genetically designed major crop plants. 13Future Research DirectionsThe current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. The current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. From diverse sources, suggestions for future research have come to CCTP's attention. Some of these, and others, are currently being explored and under consideration for the future R&D portfolio.In general, an improved understanding of the interaction and interrelationship among methane, carbon dioxide, and nitrous oxide emissions in agricultural environments is needed. This should involve a systems approach across gases and agricultural systems to synergize related technologies. Other possible further research activities include:
Other options could include improved utilization of the nitrogen in manure on croplands/pasturelands to offset use of synthetic nitrogen and decrease the quantity of nitrogen excreted from livestock by better matching the intake of nitrogen (e.g., protein) with the actual dietary requirements of the animals. A large portion of the N2O emissions from soils comes from livestock waste directly deposited on pastures, and this has significant mitigation potential both in the United States and globally. Wide-scale implementation of these technologies and improved management systems in the United States could lead to reductions in nitrous oxide emissions from agriculture of 15 to 35 percent. In some developing countries, where greater inefficiencies are identified and where potential use of nitrogen is likely to increase greatly in the future as the demand for more crop and pasture production increases, the potential is even greater. Methane and Nitrous Oxide Emissions from Livestock and Poultry Manure ManagementGlobally, nitrous oxide and methane emissions from livestock and poultry manure management totaled approximately 400 Tg CO2equivalent in 2000 (EPA 2004). Livestock and poultry manure has the potential to produce significant quantities of methane and nitrous oxide, depending on the waste management practices. When manure is stored or treated in systems that promote anaerobic conditions, such as lagoons and tanks, the decomposition of the biodegradable fraction of the waste tends to produce methane. When manure is handled as a solid, such as in stacks or deposits on pastures, the biodegradable fraction tends to decompose aerobically, greatly reducing methane emissions; however, this practice increases emissions of nitrous oxide, which has a greater global warming potential. Practices are needed that minimize both GHGs simultaneously.Potential Role of TechnologyMethane reduction and other environmental benefits can be achieved by utilizing a variety of technologies and processes. Aeration processes, such as aerobic digestion, auto-heated aerobic digestion, and composting, remove and stabilize some pollutant constituents from the waste stream. These technologies facilitate the aerobic decomposition of waste and prevent methane emissions. Anaerobic digestion systems, in contrast, encourage methane generation, and the collection and transfer of manure-generated off-gases to energy-producing combustion devices (such as engine generators, boilers, or odor control flares). Solids separation processes remove some pollutant constituents from the waste stream through gravity, mechanical, or chemical methods. These processes create a second waste stream that must be managed using techniques different from those already in use to manage liquids or slurries. Separation processes offer the opportunity to stabilize solids aerobically (i.e., to control odor and vermin propagation).Technology StrategyMethane collection from anaerobic digestion systems plays an important role in reducing emissions from livestock manure management (Figure 7-5). In addition, these systems can provide additional odor-control and energy benefits by collecting and producing electricity from the combustion of methane-using devices, such as engine generators and boilers. Although the use of commercial farm-scale anaerobic digesters has increased over the past five years due to private sector activities, significant opportunity remains. Currently there are only 12 companies that provide proven commercial-scale anaerobic digestion systems and gas utilization options for farm applications in the United States. As of 2003, an estimated 40 anaerobic digester systems, which produce about 1 million kWh/year, were in use at commercial swine and dairy farms in the United States (EPA 2003b).Expanded technology research and extension efforts could include commercial-scale demonstration projects and evaluation of emerging technologies to determine their effectiveness in reducing emissions, overall environmental benefits, and cost-effectiveness. For example, a number of emerging anaerobic digester systems adopted from the sewage industry are currently under evaluation for farm-scale applications. In addition, it is important to encourage research on odor and nitrogen emission control and ensure that it is coordinated with research on methane production and emission technology development. Current PortfolioMethane reduction and other environmental benefits can be achieved by utilizing a variety of technologies and processes, including aeration processes to remove and stabilize some pollutant constituents from the waste stream; anaerobic digestion systems that collect and transfer manure-generated off-gases to energy-producing combustion devises (such as engine generators, boilers, or odor control flares); and solids separation processes to remove some pollutant constituents from the waste stream. The goals of this research activity are to reduce costs and improve biological efficiencies of methane and nitrous oxide emissions by developing new types of digesters; developing separation processes for solid and liquid fractions; and on developing, applying, and evaluating process performance of aeration systems for manure waste streams. The current Federal portfolio focuses these technologies. 14Future Research DirectionsThe current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. From diverse sources, suggestions for future research have come to CCTP's attention. Some of these, and others, are currently being explored and under consideration for the future R&D portfolio.Expanded extension efforts to the livestock, agricultural, energy, and regulatory communities in a number of key livestock-producing states (for example, by expanding the activities currently conducted through the AgSTAR Program 15), could lead to additional emissions reductions in the United States. In addition, research that utilizes new technological developments in analytical instrumentation and molecular biology related to a commercial farm's operational ability would be useful. If such activities were undertaken globally, the emission reductions could be substantial. Methane Emissions from Livestock Enteric FermentationMethane emissions from enteric fermentation are the second largest global agricultural GHG source, contributing an estimated 1712 Tg CO2of emissions in 2000 (EPA 2004). Methane emissions occur through microbial fermentation in the digestive system of livestock. The amount of methane emitted depends primarily on the animal's digestive system, and the amount and type of feed. Ruminant livestock such as dairy cattle, beef cattle, and buffalo emit the most methane per animal, while non-ruminant livestock such as swine, horses, and mules emit less. Because methane emissions represent an economic loss to the farmer-where feed is converted to methane rather than to product output-viable mitigation options can entail efficiency improvements to reduce methane emissions per unit of beef or milk.Potential Role of TechnologyReductions in this energy loss can be achieved through increased nutritional efficiency. The goal of much livestock nutrition research has been to enhance production efficiency in order to indirectly reduce methane per unit of product through breed improvements, increased feeding efficiency through diet management, and strategic feed selection. Without reductions in national herds, however, this approach will not result in net decreases of enteric methane. Historic and near-term projected trends show both a decreasing herd size and reduced methane emissions on a per unit product basis.Technology StrategyTechnologies that would likely reduce methane emissions in addition to enhancing production efficiency include precision nutrition; and improvements in grazing management, feed efficiency, and livestock production efficiency. Research includes but is not limited to investigating between-animal differences to determine if traits for reduced methane production can be inherited, and dietary manipulation of grains, oils, and fats that reduce methane production. Key technologies include the following:
Current PortfolioThe current Federal research portfolio focuses on improved feed and forage management and treatment practices to increase the digestibility and reduce residence digestion time in the rumen, best-management practices to increase animal reproduction efficiency, and use of growth promotants and other agents to improve animal efficiency. Enteric emissions reduction goals focus on improved production efficiencies for forage and feedstuffs; increased digestibility; means to reach these goals include genetically designed forages; manipulation of ruminal microbial processes to sequester hydrogen, making it unavailable to methanogens; and genetically designed bacteria that can compete with natural microbes.Future Research DirectionsThe current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. The current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. From diverse sources, suggestions for future research have come to CCTP's attention. Some of these, and others, are currently being explored and under consideration for the future R&D portfolio.In general, an improved understanding of the interaction and interrelationship among methane, carbon dioxide, and nitrous oxide emissions in agricultural environments is needed. This should involve a systems approach across gases and agricultural systems to synergize related technologies. Possible research activities include:
It is estimated that an increase in production efficiency of approximately 25 percent could be realized if maximum implementation were to occur. A large potential exists as well in developing countries, where the livestock population is expected to increase significantly over the next few decades and where production efficiency is currently low (i.e., high methane per unit product). Methane Emissions from Rice FieldsAnother significant source of global anthropogenic methane is rice production. Rice is the dietary staple of a large proportion of the world's population. It is generally grown in flooded paddy fields, where methane is generated by the anaerobic decomposition of organic matter in the soil. Traditional wet cultivation emits an estimated 642 Tg CO2equivalent of methane (EPA 2004). Emissions from this source have leveled off in the past two decades.Although water management, fertilizer selection, cultivar selection, and nutrient management are potential options for limiting methane emissions from rice fields, further research and development is needed to determine their cost-effectiveness and feasibility. Currently, there is no research ongoing in this area. A number of opportunities for future research exist in this area, some of which include plant genetics, water management, and nutrient management. In general, the greatest challenges for mitigating methane emissions from rice fields arise from uncertainties in effecting changes in cultivation management, which affects rice yields; and developing feasible management practices that reduce methane emissions without increasing nitrogen losses and reducing yields. In addition, reduction of methane emissions could be difficult to implement because, in many cases, the necessary actions could involve significant changes in agricultural practices (e.g., shifting to different water management regimes). In principle, application of known techniques could reduce methane emissions by 30 to 40 percent by the year 2020. Achieving these large emission reductions would, however, require finding suitable incentives and delivery mechanisms to induce changes in current practices. 7.3 Emissions of High Global-Warming Potential GasesIn 2000, high-GWP gases represented 13 percent of total U.S. non-CO2GHG emissions and 4 percent of global non-CO2emissions (Table 7-5). There are two different types of emission sources in this category, and each has different R&D priorities. As discussed below, emissions of high-GWP gases used as substitutes for ozone-depleting substances (ODSs) that are being phased out under the Montreal Protocol are currently increasing. High-GWP gases are also used or emitted by several other industries, and in many cases these emissions can be readily managed or eliminated. Table 7-5 shows emissions of substitutes for ODSs and high-GWP gases (Tg CO2equivalent).Substitutes for Ozone Depleting SubstancesHigh-GWP gases used as substitutes for ODSs are a growing emissions source in the United States and globally. These high-GWP gases are being used as replacements for chemicals (like CFCs) that deplete the stratospheric ozone layer (Box 7-2). ODSs, which are also GHGs, are being phased out under the Montreal Protocol and, thus, are not counted in national inventories. To address ozone depletion, the refrigeration, air conditioning, fire suppression, foam blowing, solvent cleaning, and other industries are in the midst of the ODS phaseout.Potential Role of TechnologyFor many industries, the ODS phaseout is accomplished by switching to alternative chemicals. For most industries, the most popular and highest performing alternatives are chemicals like HFCs, which do not deplete the ozone layer but are potent GHGs. At the same time, the phaseout is providing industries with an opportunity to improve processes and practices related to chemical use, management, and disposal in ways that reduce the emissions of HFCs and PFCs, where those chemicals are used as alternatives. As the ODS phaseout continues, opportunities exist to find better life-cycle climate performance alternatives and/or continue reducing emissions.Technology StrategyTo reduce emissions of GHGs used as ODS substitutes, focus might be given to the following: (1) finding alternative gases with lower or no GWP to perform, safely and efficiently, the same function currently served by the HFCs and PFCs; (2) exploring technologies that can reduce the use of these chemicals and/or the rate at which they are emitted; and (3) supporting responsible handling practices and principles that reduce unintended and unnecessary emissions.Current PortfolioThe Federal R&D portfolio is focused on the two largest sources of hydrofluorocarbon emissions. These emissions arise from the supermarket refrigeration and motor vehicle air conditioning sectors.
Future Research DirectionsThe current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. The current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. From diverse sources, suggestions for future research have come to CCTP's attention. Some of these, and others, are currently being explored and under consideration for the future R&D portfolio.
Industrial Use of High-GWP GasesHigh-GWP synthetic gases are generally used in applications where they are critical to highly complex manufacturing processes and provide safety and system reliability, such as in semiconductor manufacturing, electric power transmission and distribution, and magnesium production and casting. High-GWP gases are also emitted as byproducts from the manufacture of refrigerants (HCFC-22) and from the production of primary aluminum.Potential Role of TechnologyIncremental improvements to current technology have been made through the initiation of voluntary public-private industry partnerships. EPA's partnerships with industries, including the U.S. primary aluminum producers, HCFC-22 manufacturing, electric utility industry, magnesium producers, and semiconductor industry, are identifying new technologies and process improvements that not only reduce emissions of high-GWP gases but also improve production efficiency, thereby saving money. With continued support, production technologies are expected to further improve, allowing these industrial sectors to cost effectively reduce and possibly eliminate emissions of high-GWP gases.Technology StrategyHigh-GWP gas-emitting industries are implementing an RDD&D strategy focused on pollution prevention. The industries have established long-term goals of reducing, and in some cases eliminating high-GWP emissions, and are pursuing these goals by investigating and implementing source reduction, alternative process chemicals, high-GWP gas capture and reuse, and abatement.While the U.S. sources of high-GWP emissions are well defined, they are also very diverse, and thus a customized approach for each industry is required. New and enhanced R&D will accelerate and expand options to stabilize and reduce emissions. Opportunities exist for both near- and long-term RD&D on technologies, including alternative chemicals for plasma etching for semiconductors and magnesium melt protection, as well as continued demonstration of advanced plasma abatement devices for the semiconductor industry. Current PortfolioThe current Federal portfolio for reducing industrial emissions of high-GWP gases focuses on five areas:
Future Research DirectionsThe current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. The current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. From diverse sources, suggestions for future research have come to CCTP's attention. Some of these, and others, are currently being explored and under consideration for the future R&D portfolio.Long-term research might focus on technologies that hold the most potential for reducing or eliminating total GHG emissions, including associated energy production emissions, and that are practical for their applications. Many of these research efforts may prove to be high risk due to unknown commercial viability, and thus are unlikely to be pursued by the industry without significant government funding. Possible research activities include:
Significant opportunities exist to reduce emissions. A focused RD&D program to develop safe, high-performing, cost-effective climate protection technologies could result in emission reductions of 40 percent or more over the near term and a dramatic reduction and, in some cases, elimination of emissions by key industries within a few decades. U.S. and Global N2O Emissions from Combustion and Industrial Sources (2000 Emissions in Tg CO2Equivalent)7.4 Nitrous Oxide Emissions from Combustion and Industrial SourcesStationary and mobile source combustion and the production of various industrial acids account for about eight percent of non-CO2emissions in the United States and four percent globally (EPA 2005, 2004). U.S. emissions of N2O associated with industrial acid production declined significantly after 1996 due to voluntary industry action and could remain relatively stable. Although generally not accounted for in N2O emission inventories, significant emissions of NOX from combustion sources are chemically transformed in the atmosphere and are eventually deposited as nitrogen compounds, which subsequently result in emissions of N2O in a manner similar to emissions from fertilizer application (Figure 7-8). In 2000, the U.S. N2O emissions from combustion and industry accounted for nearly 10 percent of total non-CO2GHG emissions, with the combustion sources accounting for over 70 percent of these (EPA 2005). Table 7-6 shows N2O emissions from combustion and industrial sources. R&D priorities differ between N2O combustion and industrial sources. The priorities for reducing N2O emissions for each of the sources are discussed below.CombustionCombustion of fossil fuels by mobile and stationary sources is the largest non-agricultural contributor to N2O emissions. Nitrous oxide can be formed under certain conditions during the combustion process and during treatment of exhaust or stack gases by catalytic converters. Since N2O emissions do not contribute significantly to ozone formation or other public health problems, N2O has not been regulated as an air pollutant and has historically not been a focus of emission control research.Potential Role of TechnologyA better understanding is needed of how and when N2O forms and how N2O emissions can best be prevented and reduced. For both stationary and mobile combustion sources, N2O emissions appear to vary greatly with different technologies and under different operating conditions, and the phenomena involved are poorly understood. For stationary sources, catalytic NOX reduction technologies can reduce N2O emissions. Other NOX control technologies either have no impact or can increase N2O.Technology StrategyA key to identifying the most promising approaches and technologies for reducing N2O emissions is understanding how N2O is formed during combustion and under what circumstances catalytic technologies contribute to N2O emissions. The main research thrust in the near term is to improve scientific understanding of these basic questions.Current PortfolioThe current Federal research portfolio on N2O emissions from combustion is focused on better understanding the formation and magnitude of N2O emissions from fuel combustion and catalytic-converter operation; evaluating the climate-forcing potential of atmospheric nitrogen deposition, especially from combustion; and developing emission models to assess the potential climate benefits from changes in emissions from nitrogen oxide. The goal in this area is to determine linkages of NOX emissions from transportation combustion and catalytic-converter operation to climate-change impacts due to nitrogen deposition and develop enhanced modeling capabilities. [23]In addition, Federal research on advanced engine/combustion technologies and alternative fuel vehicles will contribute to a reduction in N2O emissions. Research in these areas is described in the Transportation section of Chapter 4 (Reducing Emissions from Energy End-Use and Infrastructure). Future Research DirectionsThe current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. The current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. From diverse sources, suggestions for future research have come to CCTP's attention. Some of these, and others, are currently being explored and under consideration for the future R&D portfolio.Limited but recent additional collection of nitrous oxide test data have provided statistically reliable emissions estimates for most gasoline-powered passenger cars and light duty trucks. It will be important to develop vehicle- and engine-testing programs to generate nitrous oxide emissions data for a variety of vehicles and engines equipped with a range of current and advanced emission-control technologies and operated over a range of real-world operating conditions, particularly for diesel engines. In addition, future research could determine the effect of catalyst formulation including noble metal loadings and compositions for alternative catalysts that result in less nitrous oxide formation. Also, an intensified research effort is needed to assess the role of airborne nitrogen compounds emitted from combustion and deposited onto the ground, and how they interact with soil-generated nitrous oxide emissions. The development of new combustion technologies and catalyst formulations that reduce or eliminate nitrous oxide emissions will require new Federal efforts to facilitate joint public-private RD&D activities that can effectively address the reduction of nitrous oxide emissions from combustion and industrial sources. This could include research that would form the basis for identification of new technologies in the future. Some areas for near-term study are outlined below:
Industrial SourcesNitric acid is an inorganic compound used primarily to make synthetic commercial fertilizer. As a raw material, it also is used for the production of adipic acid and explosives, for metal etching, and in the processing of ferrous metals. Facilities making adipic acid used to be high emitters of nitrous oxide, but now that adipic acid plants in the United States have implemented nitrous oxide abatement technologies, nitric acid production is the largest industrial source of nitrous oxide emissions.Potential Role of TechnologyThe nitric acid industry currently controls NOX emissions using both non-selective catalytic reduction (NSCR) and selective catalytic reduction (SCR) technologies. NSCR is very effective at controlling nitrous oxide while SCR can actually increase nitrous oxide emissions. NSCR units, however, are generally not preferred in modern plants because of high energy costs and associated high gas temperatures. A catalyst to reduce nitrous oxide emissions from SCR plant is being developed in the Netherlands, and a manufacturer of nitric acid is testing a catalyst for use in the ammonia burners in nitric acid plants. Both research groups claim to be capable of reducing nitrous oxide emissions by up to 90 percent and their technology can be easily installed on existing plants. These technologies could be available for commercial application by 2010. Another manufacturer has developed an integrated destruction process; however, this process is only considered suitable for use on new plants because of the high capital costs and long operational down times needed to retrofit existing plants.Technology StrategyAdditional research is needed to develop new catalysts that reduce nitrous oxide with greater efficiency, and to improve NSCR technology to make it a preferable alternative to SCR and other control options.Current PortfolioThe current Federal portfolio focuses on developing catalysts that reduce nitrous oxide to elemental nitrogen with greater efficiency and promoting the use of NSCR over other NOX control options such as SCR and extended absorption. The goal in this area is to focus on development of catalysts that reduce nitrous oxide to elemental nitrogen with greater efficiency and to promote the use of NSCR over other NOX control options such as SCR and extended absorption.24Future Research DirectionsThe current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. The current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. From diverse sources, suggestions for future research have come to CCTP's attention. Some of these, and others, are currently being explored and under consideration for the future R&D portfolio.The use of a catalyst that can reduce a higher percentage of nitrous oxide emissions might be a promising avenue for future research. Current technology is primarily implemented to reduce NOX emissions, not to reduce nitrous oxide. In the longer term, in order to achieve further reductions in nitrous oxide emissions from nitric acid production, an advanced NSCR technology that is not energy intensive will likely need to be developed and implemented at most nitric acid production facilities. 7.5 Emissions of Tropospheric Ozone Precursors and Black CarbonUnderstanding of the role of black carbon (BC) and tropospheric ozone in climate change is still evolving. Large uncertainties remain with regard to emission levels, atmospheric concentrations, net climatic effects, and mitigation potential. However, research to date indicates that these substances influence the global radiation budget, particularly at regional scales. Complicating our understanding is that BC, which tends to have a warming effect, is co-emitted with organic carbon (OC), which tends to have a cooling effect on climate, much like sulfate aerosols.Mitigation options for BC and tropospheric ozone can already be identified in various sectors. However, for particular emission sources it is often difficult to precisely quantify the emission implications of different mitigation scenarios for these substances, and even more difficult to quantify the climatic implications of such scenarios. Activities to reduce tropospheric ozone precursors and BC will have large public health and local air quality benefits, in addition to their role in mitigating climate change. In fact, it is expected that even in the absence of climate-change-driven mitigation actions, reductions in tropospheric ozone and BC will be achieved as local and regional air quality concerns are addressed, in the United States and many other countries. Potential Role of TechnologyOzone and particulate matter (PM), of which BC is a component, have been key targets of air pollution control efforts in the United States for many years. National, State, and local regulations have aimed at reducing the significant human health and environmental impacts from high levels of tropospheric ozone and particulate matter. Emission control programs directed toward reducing ozone have focused on the primary precursors that contribute to formation of 1-hour peak ozone concentrations in and near urban centers, such as i.e., emissions of NOX and volatile organic compounds (VOC).Programs aimed at reducing PM have led to significant advances in emission control technologies in the transportation, power generation, and industrial sectors, which have and will continue to reduce emissions of BC in the United States. Power plants and other large combustion sources use control technologies such as high-efficiency electrostatic precipitators, fabric filters, and scrubbers to reduce particulate matter, including BC. Regulatory efforts for other stationary sources have addressed biomass burning and include new source performance standards for residential wood heaters and limits on open and agricultural burning. Technology StrategyThe approach to address the most significant sources of tropospheric ozone precursors and BC involve the following abatement technology areas:
Current PortfolioThe current Federal portfolio focuses on the representative technologies listed below. Transportation goals are focused on developing cost-effective NOX and PM (black carbon) engine and vehicle controls, especially for diesel engines, hybrid-diesel, and gasoline drive trains for medium- and heavy-duty vehicles (Figure 7-9). Goals for temperature reduction in cities are focused on understand and quantifying the impacts that heat island reduction measures have on local meteorology, energy use, GHG emissions, and air quality. Basic research goals are focused on better understanding of the joint role of BC and OC in climate change, including establishing linkages between air pollution and climate change by enhancing modeling capabilities; designing integrated emissions control strategies to benefit climate, regional and local air quality simultaneously. 25
Future Research DirectionsThe current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. The current portfolio supports the main components of the technology development strategy and addresses the highest priority current investment opportunities in this technology area. For the future, CCTP seeks to consider a full array of promising technology options. From diverse sources, suggestions for future research have come to CCTP's attention. Some of these, and others, are currently being explored and under consideration for the future R&D portfolio.Basic research is needed to both better understand the role of black and organic carbon and tropospheric ozone precursors in climate change, and to achieve emission reductions in the near and long terms. Much of this research is a focus of the Administration's Climate Change Science Program. Some of the areas where basic research is needed include the following:
Research and development of alternative, non-carbon based fuels could lead to significant reductions in emissions of tropospheric ozone precursors and BC in the longer term. Additional longer-term research needs include the following:
SummaryThis chapter reviews various forms of advanced technology, their potential for reducing emissions of non-CO2GHGs, and the R&D strategies intended to accelerate the development of these technologies. Although uncertainties exist about both the level at which GHG concentrations might need to be stabilized and the nature of the technologies that may come to the fore, the long-term potential of advanced technologies to reduce emissions of non-CO2GHGs is estimated to be significant, both in reducing emissions (as shown in the figure at the beginning of this chapter) and in reducing the costs for achieving those reductions, as suggested by Figure 3-21. Further, the advances in technology development needed to realize this potential, as modeled in the associated analyses, animate the R&D goals for each technology area focused on reducing emissions of non-CO2GHGs.As one illustration among many hypothetical cases analyzed, 26 GHG emissions were constrained to a high level over the course of the 21st century in such a way that a stabilized GHG concentration levels could ultimately be attained. The lowest-cost arrays of advanced technology to reduce emissions of non-CO2GHGs, when compared to a reference case, resulted in reduced or avoided emissions of about 150 Gt of carbon equivalent over the 100-year planning horizon. This amounted to roughly 25 percent of all GHG emissions reduced, avoided, captured and stored, or otherwise withdrawn and sequestered needed to attain this level. Similarly, the costs for achieving such emissions reductions were reduced by roughly a factor of 3. See Chapter 3 for other cases and other scenarios. As described in this chapter, CCTP's technology development strategy supports achievements in this range. The overall strategy is summarized schematically in Figure 7-10. Advanced technologies are seen entering the marketplace in the near-, mid-, and long-terms, where the long-term is sustained indefinitely. Such a progression, if successfully realized worldwide, would be consistent with attaining the potential for reducing emissions of non-CO2GHGs portrayed at the beginning of this chapter. The timing and pace of technology adoption are uncertain and must be guided by science and supported by appropriate policies (see Approach 7, Chapters 2 and 10). In the case of the illustration above, t he first GtC per year (1GtC/year) of reduced or avoided emissions, as compared to an unconstrained reference case, would need to be in place and operating, roughly, around 2050. For this to happen, a number of new or advanced technologies to reduce emissions of non-CO2GHGs would need to penetrate the market at significant scale before this date. Other cases would suggest faster or slower rates of deployment. See Chapter 3 for other cases and other scenarios. Throughout Chapter 7, the discussions of the current activities in each area support the main components of this approach to technology development. The activities outlined in the current portfolio sections address the highest-priority investment opportunities for this point in time. Beyond these activities, the chapter identifies promising directions for future research, identified in part by the technical working group and assessments and inputs from non-Federal experts. CCTP remains open to a full array of promising technology options as current work is completed and changes in the overall portfolio are considered. Technologies for Goal #4: Reduce Emissions of Other GasesFootnotes1 The radiative forcing due to increases in the well-mixed GHGs between the years 1750 and 2000 is estimated to be 2.43 Wm-2: 1.46 Wm-2 from CO2; 0.48 Wm-2 from CH4; 0.34 Wm-2 from the halocarbons (CFC and HCFC); and 0.15 Wm-2 from N2O.2 The technologies discussed in this chapter were included in this set of scenarios. 3 The Landfill Methane Outreach Program, Natural Gas STAR Program, AgSTAR Program, Coalbed Methane Outreach Program, SF6 Emission Reduction Partnership for Electric Power Systems, Voluntary Aluminum Industrial Partnership, SF6 Emission Reduction Partnership for the Magnesium Industry, PFC Reduction/Climate Partnership with the Semiconductor Industry, and HCFC-22 Partnership Program. 4 Results from this study, EMF 21, are to be published in a special issue of the Energy Journal in 2005. 5 U.S. Climate Change Science Program, Prospectus for Synthesis and Assessment Product 2.1. 6 For this chapter, the GWP-weighted emissions of methane (estimated at 21) are presented in terms of equivalent emissions of carbon dioxide (CO2), using units of teragrams of carbon dioxide equivalents (Tg CO2equivalent). To convert the emission estimates included in this chapter to gigatonnes of carbon (GtC), multiply the emissions estimate by .000272. For example, 200 Tg CO2equivalent X (.000272) = .054 GtC. 7 See Section 4.1.1 (CCTP 2005). 8 See Section 4.1.2 (CCTP 2005). 9 See Section 4.1.3 (CCTP 2005). 10 See Section 4.1.4 (CCTP 2005). 11 See Section 4.1.5 (CCTP 2005). 12 See Section 4.1.6 (CCTP 2005). 13 See Section 4.2.1 (CCTP 2005). 14 See Section 4.2.2 (CCTP 2005). 15 For additional information on the AgSTAR Program. 16 See Section 4.2.3 (CCTP 2005). 17 See Section 4.3.6 (CCTP 2005). 18 See Section 4.3.1 (CCTP 2005). 19 See Section 4.3.2 (CCTP 2005). 20 See Section 4.3.3 (CCTP 2005). 21 See Section 4.3.4 (CCTP 2005). 22 See Section 4.3.5 (CCTP 2005). 23 See Section 4.4.2 (CCTP 2005). 24 See Section 4.4.1 (CCTP 2005). 25 See Section 4.5.1 (CCTP 2005). 26 In Chapter 3, various advanced technology scenarios were analyzed for cases where global emissions of GHGs were hypothetically constrained. Over the course of the 21st century, growth in emissions was assumed to slow, then stop, and eventually reverse in order to ultimately stabilize GHG concentrations in the Earth's atmosphere at levels ranging from 450 to 750 ppm. In each case, technologies competed within the emissions-constrained market, and the results were compared in terms of energy (or other metric), emissions, and costs. ReferencesDeAngelo, B., F. de la Chesnaye, R. Beach, A. Sommer, and B. Murray. Forthcoming. Methane and nitrous oxide mitigation in agriculture. Energy Journal.Delhotal, K. Casey, F. C. de la Chesnaye, A. Gardiner, J. Bates, and A. Sankovski. 2006. Mitigation of methane and nitrous oxide emissions from waste, energy and industry. Energy Journal. Intergovernmental Panel on Climate Change (IPCC). 2001. Climate change 2001: the scientific basis. Cambridge, UK: Cambridge University Press. Placet, M., K.K. Humphreys, and N.M. Mahasenan. 2004. Climate change technology scenarios: energy, emissions and economic implications. Richland, WA: Pacific Northwest National Laboratory. Schaefer, D., D. Godwin, and J. Harnish, 2006. Estimating Future Emissions and Potential Reductions of HFCs, PFCs, and SF6. Energy Journal (forthcoming). U.S. Climate Change Technology Program (CCTP). 2003. Technology options for the near and long term. DOE/PI-0002. Washington, DC: U.S. Department of Energy. Update is at website. U.S. Environmental Protection Agency (EPA). 1999. U.S. methane emissions 1990 � 2020: inventories, projections, and opportunities for reductions. #430-R-99-013. Washington, DC: U.S. Environmental Protection Agency. U.S. Environmental Protection Agency (EPA). 2003a. Assessment of the worldwide market potential for oxidizing coal mine ventilation air. #430-R-03-002. Washington, DC: U.S. Environmental Protection Agency. U.S. Environmental Protection Agency (EPA). 2003b. Current status of farm-scale digesters. AgSTAR Digest. #430-F-02-028. Washington, DC: U.S. Environmental Protection Agency. U.S. Environmental Protection Agency (EPA). 2004. Global emissions of non-CO2greenhouse gases, 1990 � 2020. Washington, DC: Environmental Protection Agency. U.S. Environmental Protection Agency (EPA). 2005. Inventory of U.S. greenhouse gas emissions and sinks: 1990 � 2003. #430-R-05-003. Washington, DC: U.S. Environmental Protection Agency.
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