U.S. State-level Non-CO₂ Greenhouse
Gas Mitigation Potential: 2020-2080
(EPA-430-R-25-002)

About this Report

This web-based summary provides U.S. domestic technical and economic mitigation estimates of non-CO₂ GHGs from anthropogenic sources at the state level. The analysis includes information that can be used to understand sub-national contributions of GHG emissions and mitigation opportunities. It is intended to provide insight into abatement potential and costs of implementing specific abatement technologies. Readers interested in more technical details of the analysis should refer to the full Non-CO₂ Methodology Report.

Overview

Non-CO₂ Greenhouse Gases

Non-CO₂ greenhouse gases are more potent than CO₂ (per unit weight) at trapping heat within the atmosphere. Global warming potential (GWP) is the factor that quantifies the heat trapping potential of each GHG relative to that of carbon dioxide (CO₂). For example, methane has a GWP value of 28 which means that each molecule of methane released into the atmosphere is 28 more times effective at trapping heat compared to an equivalent unit of CO₂. Additionally, some non-CO₂ GHGs can remain in the atmosphere for longer periods of time than CO₂. The table shows the list of GHG gases with their GWP values that are considered in this report.

Greenhouse Gas GWP Factor (100-yr)
CO₂ 1
CH₄ 28
N₂O 265
HFCs 4 - 12,400
NF₃ 16,100
SF₆ 23,500
PFCs 6,630 - 17,400

Emission Projections and Mitigation Assessments

The emission projections were generated using a combination of the U.S. state-level greenhouse gas inventory data and the 2024 Biennial Transparency Report (BTR) U.S. projected emissions from the U.N. Framework Convention on Climate Change (UNFCCC). Historical emission estimates were incorporated from national reported data from 1990 through 2022 and emissions were projected through 2100. The greenhouse gas inventory’s state-level proportions were used to downscale the BTR national emission projections to display sub-national detail. The projections results are a “business as usual” (BAU) scenario with emission rates consistent with historical levels and do not include future effects of policy changes.

The mitigation estimates were generated using a bottom-up, engineering cost approach that analyzed the costs of a wide range of mitigation technologies for each sector and incorporated them into an economic tool called a marginal abatement cost curve (MACC).

MACCs represent emission reductions available at incrementally higher prices and provide information on the volume of emissions reductions that can be achieved, as well as an estimate of the costs of implementing the GHG abatement measures. Each point on the MACC reflects the average price and reduction potential (million metric tons of CO₂ equivalents, [MtCO₂e]) if a mitigation technology were applied across the sector.

This analysis accounts for state-level differences in the price of mitigation through a series of cost indices (labor, nonenergy materials, energy) to create a more heterogenous representation of emissions and mitigation costs and benefits at a state level. The MACCs that describe the mitigation estimates in this report represent the techno-economic mitigation potential for each source and technology evaluated.

Emission sources were grouped into four economic sectors: energy, industrial processes, agriculture, and waste. Although CO2 emissions are concentrated in the energy sector, agriculture, which includes non-CO2 emissions from livestock and manure management, croplands, and rice cultivation, accounts for the largest share of non-CO2 emissions throughout the time-period evaluated. The heat map shows the distribution of projected 2030 emissions across the United States for each sector.

The GHGs covered by this report include methane (CH4), nitrous oxide (N2O), and fluorinated greenhouse gases (FGHG). Total Non-CO2 emissions in 2030 are about 1,109 MtCO2e. Methane accounts for the largest percentage of total U.S. non-CO2 emissions in 2030 followed by nitrous oxide and fluorinated GHGs. The heat map shows the distribution of projected 2030 emissions across the United States for each gas.

In 2030, the agricultural sector accounts for 154 MtCO2e of mitigation potential followed by the energy sector at 96 MtCO2e. The waste and industrial sectors account for 19 and 15 MtCO2e of mitigation potential, respectively. The energy sector has the largest share of technical mitigation potential at 45%. The total technical mitigation potential from the agriculture sector accounts for 25% of baseline emissions in 2030, while the mitigation potential from the industrial and waste sectors each account for 12% of baseline emissions.

The mitigation at a given price represents the emission reductions that are economic, or the break-even point, at that price incentive (e.g., $0 per ton of CO2 equivalent [tCO2e]). The total technical potential is the maximum technically achievable emission reduction from a given source or mitigation option.

Energy Overview

The energy sector is projected to be the second largest contributing sector to U.S. emissions of non-CO₂ GHGs, accounting for 20% of emissions in 2030. U.S. energy-sector CH₄ and N₂O projected emissions and mitigation potential are estimated for the following source categories:

  • Coal mining (CH₄)
  • Natural gas and oil systems (CH₄)
  • Stationary and mobile combustion (Emissions only - CH₄, N₂O)

U.S. energy-sector non-CO₂ GHG emissions are projected to be 216 MtCO₂e in 2030. Natural gas and oil activities are projected to remain the largest contributor to non-CO₂ emissions from the energy sector. Emissions from natural gas activities are projected to slightly decrease through 2050 as the energy sector further transitions from coal to natural gas.

Cost effective mitigation potential from the energy sector is approximately 7 MtCO₂e in 2030, accounting for 6% of coal emissions and 4% of oil and gas emissions. Total mitigation in the energy sector is 96 MtCO₂e, with 16 MtCO₂e of mitigation coming from coal emissions and the remaining 80 MtCO₂e from natural gas. Cost effective (less than $0/tCO₂e) mitigation potential in the energy sector represents 3% of total U.S. Non-CO₂ mitigation potential in 2030.

Energy Emissions in 2030

The heat map shows the distribution of projected 2030 emissions from the energy sector across the United States.

Energy Emissions in 2030

The bar chart shows the reductions available at no cost, the total technical potential at increasing costs, and the residual emissions after applying all feasible mitigation options. 3% (7 MtCO₂e) of baseline emissions can be reduced through mitigation opportunities at no cost. The total technical mitigation potential from the energy sector accounts for 44% (96 MtCO₂e) of projected baseline emissions in 2030.

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Industrial Processes Overview

The industrial processes sector is the fourth largest contributing sector to emissions of non-CO₂ GHGs in the U.S., accounting for 11% of emissions in 2030. F-GHGs are important because the gases tend to have large heat-trapping capacities and long atmospheric lifetimes. This section presents N₂O and F-GHG (HFCs, SF₆, PFCs, and NF₃) projected emissions and mitigation potential from the industrial processes sector, including the following categories:

  • Nitric and adipic acid production (N₂O)
  • Electronics (HFCs, PFCs, SF₆, NF₃)
  • Electric power systems (EPS) (SF₆)
  • Metals (PFCs, SF₆)
  • Substitutes for ozone-depleting substances (ODSs) (HFCs)

Industrial process emissions are projected to reach 124 MtCO₂e in 2030. The largest source of emissions from industrial processes is refrigeration and air conditioning, which is estimated to reach 62 MtCO₂e in 2030. The South Atlantic has the greatest emissions in 2030 with 33 MtCO₂e, followed by the West South Central and East North Central with 24 MtCO₂e and 13 MtCO₂e, respectively.

Mitigation potential from the industrial processes sector is estimated to be approximately 15 MtCO₂e in 2030. This mitigation potential is 12% of the industrial processes sector’s emissions and 5% of total U.S. non-CO₂ mitigation potential in that year. The West South Central has the greatest potential for mitigation, can abate 4 MtCO₂e in total. The largest source of mitigation potential from industrial processes sector is semiconductor manufacturing at 7 MtCO₂e with nitric and adipic acid production following at 5 MtCO₂e in 2030.

The heat map shows the distribution of projected 2030 emissions from the industrial sector across the United States.

The bar chart shows the reductions available at no cost, the total technical potential at increasing costs, and the residual emissions after applying all feasible mitigation options. In 2030, less than 1% of projected emissions (less than 1 MtCO₂e) can be abated from industrial processes at no cost. An additional 9% (14 MtCO₂e) can be abated at increasing cost, leaving 91% in residual emissions.

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Agriculture Overview

The agriculture sector is the largest contributing sector to U.S. non-CO₂ GHG emissions, accounting for 55% of emissions in 2030. Agriculture-sector CH₄ and N₂O projected emissions and mitigation potential are estimated from the following source categories:

  • Livestock (CH₄, N₂O)
  • Croplands (CH₄, N₂O)
  • Rice cultivation (CH₄, N₂O)

National agriculture-sector emissions are projected to reach 608 MtCO₂e in 2030. Emissions from rice cultivation and livestock production are projected to increase by the largest margins.

Emissions in the agriculture sector are projected to increase because of increased fertilizer consumption, crop production, and livestock populations, which are driven by demand for animal products. National demand for animal products is expected to grow modestly over the next decade. 1

1 https://www.usda.gov/sites/default/files/documents/USDA-Agricultural-Projections-to-2030.pdf

Mitigation potential from the agriculture sector is estimated to be approximately 154 MtCO₂e in 2030. This mitigation potential is 29%, 22%, and 26% of livestock, croplands, and rice cultivation emissions, respectively; 25% of overall agriculture-sector emissions; and 54% of total national non-CO₂ mitigation potential in that year.

The heat map shows the distribution of projected 2030 emissions from the agriculture sector across the United States.

The bar chart shows the reductions available at no cost, the total technical potential at increasing costs, and the residual emissions after applying all feasible mitigation options. 7% (45 MtCO₂e) of baseline emissions can be reduced through mitigation opportunities at no cost. The total technical mitigation potential from the agriculture sector accounts for 25% (154 MtCO₂e) of projected baseline emissions in 2030.

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Waste Overview

The waste sector is the third largest contributing sector to national emissions of non-CO₂ GHGs, accounting for 15% of non-CO₂ emissions in 2030. National waste-sector CH₄ and N₂O projected emissions and mitigation potential are estimated from the following source categories:

  • Landfills (CH₄)
  • Wastewater (CH₄, N₂O)

Through 2030 emissions from landfills and wastewater are projected to grow at similar rates, reaching 161 MtCO₂e in 2030. Projected increases in population and per capita waste generation are underlying drivers of emission growth overtime. However, implementation of regulations on municipal solid waste landfills has resulted in widespread adoption of landfill gas recovery for flaring and/or beneficial use has tempered this increase.

Mitigation potential from the waste sector is estimated to be approximately 19 MtCO₂e in 2030, representing 8% of landfill emissions and 24% wastewater emissions.

The heat map shows the distribution of projected 2030 emissions from the waste sector across the United States.

The bar chart shows the reductions available at no cost, the total technical potential at increasing costs, and the residual emissions after applying all feasible mitigation options. 1% (2 MtCO₂e) of baseline emissions can be reduced through mitigation opportunities at no cost. The total technical mitigation potential from the waste sector accounts for 12% (19 MtCO₂e) of projected baseline emissions in 2030.

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Uses and Applications for Non-CO₂ Abatement Data

The emission projections and mitigation datasets in this report are intended to provide technical information that can be useful in economic modeling and climate mitigation analysis. The results have not been evaluated with respect to their fitness for particular applications. These non-CO₂ datasets are of particular use to economic and integrated assessment models that evaluate the effect of GHG emissions and the cost and availability of mitigation from the non-CO₂ GHG sectors. Marginal abatement cost curves disaggregated at the state-level highlight differences in mitigation potential and cost, thereby providing valuable data for spatially disaggregated models and supporting the design of more effective climate mitigation policies.

The results in this report are generally presented at aggregate source and sector levels with regional and subsource-level detail. The underlying non-CO₂ emission and mitigation data are available at the source and state levels. Many states produce their own official GHG inventories which differ from the EPA state-level GHGI on which these estimates are based. State-level MACs reflect variability in costs and technical potential to the extent possible.

Details about each source and mitigation option modeled, as well as specific information about the estimation of emission projections, are available in the accompanying methodology document to this report, Global Non-CO₂ Greenhouse Gas Emission Projections & Marginal Abatement Cost Analysis: Methodology Documentation.

Emission Projections and Mitigation Potential

This figure shows the total BAU emission projections (dashed line), and residual emissions by sector at various user selectable price points. The figure shows that over time non-CO₂ emissions can be greatly reduced by deploying available mitigation technologies (i.e. at higher costs). These emissions that remain after mitigation options are implemented are called “residual” emissions. Achieving long-term reductions of non-CO₂ emissions below the 2020 level would require development of new or more effective mitigation technologies.

Coal Mining

CH₄ is produced during the process of coalification, where vegetation is converted by geological and biological forces into coal. Coal seams and the surrounding rock strata store CH₄. Natural erosion, faulting, or mining can reduce pressure above or surrounding the coal bed and liberate the CH₄. Because CH₄ is explosive, the gas must be removed from underground mines high in CH₄ as a safety precaution.

This analysis considered six abatement measures for CH₄ emissions in underground coal mining: recovery for pipeline injection, power generation, process heating, flaring, and catalytic or thermal oxidation of ventilation air methane (VAM). These reduction technologies consist of one or more of the following primary components: (1) a drainage and recovery system to remove CH₄ from the underground coal seam, (2) the end use application for the gas recovered from the drainage system, and (3) the VAM recovery or mitigation system.

High-quality CH₄ is recoverable from coal seams by drilling vertical wells from the surface up to 10 years in advance of a mining operation or drilling in-mine horizontal boreholes several months or years before mining. However, most mine operators exercise just-in-time management in developing new operations; subsequently, horizontal cross-panel boreholes are installed and drain gas for 6 months or less.

Once recovered, CH₄ can be used for energy purposes, and can either be injected into a natural gas pipeline or used on-site for electricity or heat generation. Recovered CH₄ that is not used for energy can be flared instead of released into the atmosphere. At mines where the ventilated mine air has a low concentration of CH₄ (0.25% to 1.25%), the recovered gas can be oxidized and combusted. The by-products of the combustion process are water and CO₂.

Total CH₄ emissions from coal mining are projected to be 27 MtCO₂e in 2030. The largest source of emissions is the South Atlantic, with 9 MtCO₂e in 2030 (33% of total U.S. coal mining emissions).

Total emissions from coal mining are 27 MtCO₂e in 2030, with a total mitigation potential of 16 MtCO₂e. In the coal mining industry, 6% of total coal mining emissions (2 MtCO₂e) can be abated at no cost. An additional 52% (14 MtCO₂e) of total emissions can be reduced at increasing costs. The remaining 42% of emissions are residual. Multiple technologies can be implemented to reduce emissions at no cost, such as degasification for pipeline injection and power generation and on-site use in coal drying. Stand-alone VAM technology results in the largest reduction potential at costs greater than $0/tCO₂e.

The South Atlantic region has the greatest potential for abatement with 6 MtCO2e of available abatement in 2030.

Oil and Natural Gas Systems

CH4 is the principal component of natural gas and is emitted during natural gas production, processing, transmission, and distribution. Oil production and processing upstream of oil refineries can also emit CH4 in significant quantities as natural gas is often found in conjunction with petroleum deposits. In both systems, CH4 is a fugitive emission from leaking equipment, system upsets, deliberate flaring and venting at production fields, processing facilities, natural gas transmission lines and compressor stations, natural gas storage facilities, and natural gas distribution lines.

In total, this analysis evaluated over 150 abatement measures (combinations of mitigation activity and recovered gas usage) for their potential to mitigate CH4 emissions associated with the four natural gas and oil system segments—production, processing, transmission, and distribution. Abatement measures documented by the EPA's Natural Gas STAR Program served as the basis for estimating the costs of abatement measures used in this analysis. Measures typically fall into three categories: equipment modifications or upgrades; changes in operational practices, including directed inspection and maintenance (DI&M); and installation of new equipment. Abatement measures are available to mitigate emissions associated with a variety of system components, including compressors, engines, dehydrators, pneumatic controls, pipelines, storage tanks, wells, and others.

DI&M programs present mitigation opportunities across all segments of natural gas and oil with no up-front capital costs and high technical effectiveness, in some cases unlocking a 95% reduction in targeted emissions. Installing plunger lift systems in gas wells has a small capital cost and technical effectiveness of only 40%, but they generate an annual revenue stream from captured gas in excess of the initial capital costs, resulting in a payback period of less than 1 year. Replacing wet seals with dry in centrifugal compressors also generates revenue but has much higher capital costs and a longer payback period. The most expensive mitigation options considered in this analysis are open flaring in offshore platforms and replacement of aging or unprotected pipeline infrastructure.

These results assume implementation of the 2024 New Source Performance Standards for the Oil and Natural Gas Sector, which reduces projected baseline emissions and mitigation potential.

CH₄ emissions from natural gas and oil systems are projected to reach 152 MtCO₂e in 2030. The region with the largest oil and natural gas emissions is West South Central, with 57 MtCO₂e in 2030 (37% of U.S. emissions). The second largest is the Mountain region, with 30 MtCO₂e (20% of U.S. emissions).

Total emissions of oil and natural gas systems are 152 MtCO2e in 2030, of which 81 MtCO2e can be abated. In the oil and gas sector, 4% (6 MtCO2e) of total emissions can be abated at no cost. Another 49% (75 MtCO2e) of total emissions can be reduced at increasing prices. The remaining 47% of emissions are residual. Multiple DI&M practices could be implemented to reduce emissions at no cost. Other measures such as installing catalytic converters and replacing iron pipelines can reduce emissions at increasing costs.

The West South Central region has the greatest potential for abatement with 30 MtCO₂e of available abatement in 2030.

Combustion of Fossil and Biomass

CH4 and N2O emissions result from the combustion of fossil fuels and biomass in both stationary and mobile sources. CH4 emissions are primarily a function of the CH4 content of the fuel and the overall combustion efficiency. N2O emissions vary according to the type of fuel, combustion technology, size and vintage, pollution control equipment used, and maintenance and operating practices.

CH4 and N2O emissions from stationary and mobile combustion are projected to reach 37 MtCO2e in 2030. The region with the largest stationary and mobile combustion emissions is South Atlantic, with 7 MtCO2e in 2030 or 18% of stationary and mobile combustion. The second largest is the East North Central region, with 6 MtCO2e or 16% of stationary and mobile combustion emissions.

Other

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Nitric and Adipic Acid Production

Nitric acid is an inorganic compound used primarily to make synthetic commercial fertilizer. Adipic acid is a white crystalline solid used as a feedstock in the manufacture of synthetic fibers, coatings, plastics, urethane foams, elastomers, and synthetic lubricants. The production of these acids results in N₂O emissions as a by-product.

This analysis considered four abatement measures applied to the chemical process used to produce nitric and adipic acid to reduce the quantity of N₂O emissions released during production. Three abatement measures— catalytic decomposition, catalytic reduction, and homogeneous decomposition—were modeled for nitric acid production. Catalytic decomposition and reduction can be applied as tertiary measures. Catalytic and homogeneous decomposition are considered secondary processes, which are applied inside or immediately following the ammonia burner. Homogeneous decomposition is better suited for new facilities because of the associated design changes and capital costs. Some primary measures, which are applied at the beginning of the production process to prevent the formation of N₂O, exist, but they were not modeled in this analysis because of data limitations.

Adipic acid facilities direct the flue gas to a reductive furnace in a thermal destruction process to reduce nitric oxide (NOX) emissions. Thermal destruction is the combustion of off-gases (including N₂O) in the presence of CH₄. The combustion process converts N₂O to nitrogen, resulting primarily in emissions of NO and some residual N₂O. The heat generated from this process can also be used to produce process steam, offsetting more expensive steam generated using just fossil fuels.

Total N₂O emissions from nitric and adipic acid production are projected to be 17 MtCO₂e in 2030. The largest source of emissions is the South Atlantic, with 9 MtCO₂e in 2030 or 50% of nitric and adipic acid production emissions in the U.S.

The national emission reduction potential in the nitric and adipic acid production source category is 5 MtCO₂e in 2030, or 26% of projected baseline emissions from nitric and adipic acid production. There are no available no cost abatement opportunities for nitric and adipic acid production emissions in 2030. All mitigation (5 MtCO₂e) is available at prices less than $50/tCO₂e. The remaining 74% of emissions are residual. Tail-gas catalytic composition technology has the largest abatement potential in 2030 at some costs. The region with the greatest potential abatement is South Atlantic, with 2 MtCO₂e of total potential abatement. The region with the next largest abatement potential include West South Central with 1 MtCO₂e.

The region with the largest nitric and adipic acid production emissions is the South Atlantic with 9 MtCO₂e, followed by West South Central with 5 MtCO₂e.

Electronics

Electronics consists of emissions from the manufacturing of semiconductors, flat panel displays (FPDs), and photovoltaics (PV) . During the manufacture of these electronics, F-GHGs, including HFCs, PFCs, SF₆, and NF₃, are emitted from two repeated activities: (1) cleaning of chemical vapor deposition chambers and (2) plasma etching (etching intricate patterns into successive layers of films and metals). Because there are no PV or FPD manufacturers located in the US we only have emissions and mitigation potential for semiconductors.

Abatement measures can be applied in the electronics source category throughout processes for the manufacturing of semiconductors. This analysis considered six abatement measures across the two manufacturing processes: central abatement, catalytic wet abatement, high-pressure plasma wet abatement, low-pressure plasma abatement, combustion and wetchamber cleaning, and combustion and wet etching. These technologies reduce emissions from either etch or chamber-cleaning processes (or in some cases both). The measures focus on reducing F-GHG (i.e., HFCs, PFCs, SF₆, or NF₃) emissions that are released during production.

Across the technologies used in the electronics manufacturing industry, thermal abatement, NF₃ remote chamber cleaning, and catalytic abatement tend to have the highest market penetration, meaning that manufacturers are implementing these abatement technologies most often. These technologies have high reduction efficiencies.

Total F-GHG emissions from electronics are projected to be 15 MtCO₂e in 2030. The largest source of emissions is the West South Central, with 5 MtCO₂e in 2030 or 33% of electronics emissions, followed by the Mountain region with 3 MtCO₂e or 22% of electronics emissions.

Abatement potential in the electronics source category is estimated to be 47% (7 MtCO₂e) of the projected 15 MtCO₂e of F-GHG emissions in 2030. At $20/tCO₂e or below, 97% of abatable emissions can be abated in 2030, increasing to 100% at $50/tCO₂e. There are no technologies that provide reductions emissions at no cost. Thermal abatement technology would result in the largest reductions at increasing costs in 2030. The West South Central is the region with the greatest potential for abatement of electronics emissions at more than 2 MtCO₂e in 2030.

The West South Central is the region with the greatest potential for abatement of electronics emissions at 0.5 MtCO₂e in 2030.

Electric Power Systems

SF₆ is used for absorption of energy from electric currents flowing between conductors and as an insulating medium in electric power systems. SF₆ emissions occur through leakage and handling losses. Manufacturing equipment for electrical transmission and distribution also results in SF₆ emissions, but this report does not include this source. The type and age of SF₆-containing equipment and the handling and maintenance protocols used by electric utilities affect SF₆ emissions from electric power systems.

This analysis considers five main abatement technologies and measures for the electric power system. The first measure, SF₆ recycling, reduces emissions by technicians transferring SF₆ to special gas carts before maintenance or decommissioning to reuse the gas. The second measure, known as leak detection and repair reduces emissions in a two-step process: (1) identifying the leaks through either a camera or a hand-held gas detector and (2) later sealing the leak or completely replacing the broken component. The third measure, equipment refurbishment, is a method that reduces longer term leakage problems by disassembling and possibly upgrading equipment with clean or new components, but this abatement measure can be costly to implement. Another abatement measure uses a combination of different gases to form a class of g3 mixtures that have a GWP less than SF₆. The final and most cost-effective measure is improving SF₆ handling. Properly training employees to handle SF₆ can reduce and avoid instances of accidentally venting the gas; using inappropriate fittings to connect transfer hoses to cylinders or equipment; and misplacing gas cylinders, which result in handling losses.

National SF₆ emissions from electric power systems (EPS) are expected to be 7 MtCO₂e in 2030. Projected emissions increase over time, with emissions more than doubling to about 16 MtCO₂e by 2050. In 2030, EPS emissions make up less than 6% of IPPU emissions. The largest source of emissions is the Pacific, with 1.3 MtCO₂e in 2030 (19% of total U.S. electric power systems emissions). As infrastructure ages it is anticipated that utilities will phase out the use of SF₆ in high-voltage gas-insulated equipment over time. Additionally, there are state and regional regulations aimed at reducing equipment leakage of SF₆ through specific repair and refurbishment practices and early retirement and replacement of SF₆ containing equipment.

Significant reductions are available at relatively low cost in the EPS sector. Total available abatement in 2030 is 2.4 MtCO₂e, 34% of baseline emissions. All of this potential abatement can be achieved at under $5/tCO₂e. Improved SF₆ handling practices would result in the largest reduction at some costs. The West North Central and Mountain regions have the largest abatement potential at about 16.5% for each.

The South Atlantic and Mountain regions have the largest abatement potential at 16% and 14% respectively.

Metals

Emissions from metal production include PFCs emitted as by-products of aluminum production and SF₆ emitted from magnesium production.

During the aluminum smelting process, high voltage anode effect events emit tetrafluoromethane (CF4) and hexafluoroethane (C2F6). Recent research has shown that low-voltage anode effect events also emit PFCs;65 however, such emissions are not accounted for in this analysis.

The magnesium production and casting industry uses SF₆ to prevent spontaneous combustion of molten magnesium in the presence of air. Fugitive SF₆ emissions occur mostly during primary production, die-casting, and recycling-based or secondary production. Additional processes may use SF₆; however, these processes are believed to be minor emission sources.

Abatement measures for metals come from aluminum and magnesium production. Abatement options considered in the primary aluminum production industry involve (1) a minor retrofit to upgrade the process computer control systems and (2) a major retrofit to the process computer control systems coupled with the installation of alumina point-feed systems. The analysis does not include the installation of alumina point-feed systems on its own because it would be very unlikely that an aluminum production facility would install alumina point-feed systems without also installing or upgrading process computer control systems.

For the production and processing of magnesium, replacing SF₆ with an alternative cover gas is the principal abatement measure. The three options for alternative cover gas in magnesium production are SO₂, HFC-134a, and Novec™ 612. Although toxicity, odor, and corrosive properties are a concern of using SO₂ as a cover gas, it can potentially eliminate SF₆ emissions entirely through improved containment and pollution control systems. HFC-134a, along with other fluorinated gas, contains fewer associated health, odor, and corrosive impacts than SO₂, but it does have a GWP. The replacement of SF₆ with Novec™ 612 is under evaluation and is currently being used in one remelt and die-casting facility in the United States. Each of the three cover gases has a reduction efficiency between 95% and 100%.

Combined PFC and SF₆ emissions from metal production decreased steadily for the last several decades. Emissions from metal production are projected to remain static through 2050. The metals source category emits less than 0.20% of the national baseline non-CO2 emissions, and less than 2% of baseline IPPU emissions in 2030, making this source a small emitter relative to the others. The largest source of emissions is the East North Central, with 1.09 MtCO₂e in 2030 (57% of U.S. emissions).

Metals production’s abatement potential is estimated to be approximately 1.5 MtCO₂e in 2030, or 74% of the source's baseline emissions. Break-even prices of $5/tCO₂e can deliver over 60% mitigation potential. Over half of the mitigatable emissions in the metals sector comes from the East North Central region of the U.S.

The largest share of reduction potential at 43% comes from the East North Central region of the U.S. Two abatement practices, minor retrofit and alternate cover gas (SO₂), can achieve reductions at costs less than $0/tCO₂e.

Substitutes for Ozone-Depleting Substances

HFCs are used as alternatives to several classes of ODSs that are being phased out under the terms of the Montreal Protocol. ODSs, which include chlorofluorocarbons (CFCs), halons, carbon tetrachloride, methyl chloroform, and HCFCs, have been used in a variety of industrial applications, including refrigeration and air-conditioning equipment (ref/AC), aerosols, solvent cleaning, fire extinguishing, foam production, and sterilization. HFCs are not harmful to the stratospheric ozone layer, but they are powerful GHGs.

These results assume implementation of the 2020 American Innovation in Manufacturing Act, which reduces the projected baseline emissions, as well as leaving minimal mitigation potential in this sector.

Refrigeration and air conditioning accounts for 79% of national emissions from ODS sector. Foams and aerosols account for 11% and 6% of ODS emissions respectively. The largest source of emissions for refrigeration and air conditioning is the South Atlantic, with 16 MtCO₂e in 2030 or 26% of baseline emissions.

Emissions from refrigeration and air conditioning are the largest source of potential abatement; measures targeting ref/AC emissions have the potential to abate 91 MtCO₂e of emissions, representing a 34% reduction in baseline emissions. Aerosols offer additional abatement of 15 MtCO₂e or an additional 6% reduction in baseline emissions from the ODS sector.

The South Atlantic region has the largest share of mitigation potential at 22% with West South-Central following at 17%.

HCFC-22 Production

Trifluoromethane (HFC-23) is generated and emitted as a byproduct during the production of chlorodifluoromethane (HCFC-22). HCFC-22 is used primarily as a feedstock for production of synthetic polymers and in emissive applications, primarily ref/AC. Facilities that produce HCFC-22 in the United States either already control HFC-23 emissions or have announced plans to install control measures. For that reason, we have not modeled mitigation opportunities for this source.

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Livestock

Emissions from livestock include enteric fermentation and manure management. Enteric fermentation is a normal mammalian digestive process, where gut microbes produce CH₄ that the animal exhales. Livestock manure management produces CH₄ emissions during the anaerobic decomposition of manure and N₂O emissions during the nitrification and denitrification of the organic nitrogen content in livestock manure and urine.

The analysis considers nine enteric fermentation CH₄ abatement measures: improved feed conversion efficiency, antibiotics, bovine somatotropin (bST), propionate precursors, antimethanogen vaccines, intensive grazing, asparagopsis (red algae), 3-nitrooxypropanol (3-NOP), and cattle methane-reducing wearable technology. Some of the currently available enteric fermentation abatement options work directly to reduce enteric fermentation and some work indirectly by increasing animal growth rates and reducing time to finish (or increasing milk production for dairy cows). These abatement measures achieve emission reductions because increased productivity means fewer animals are required to produce the same amount of meat or milk. Furthermore, several of the abatement measures are inexpensive to implement and are cost-effective at reducing emissions.

In the case of manure management (CH₄ and N₂O), this analysis considers four largescale abatement measures that are applied in developed regions: complete-mix, plug-flow, fixed-film digesters, and covered lagoons. We consider options for producing electricity through an on-site generator or, with additional processing, renewable natural gas production (and associated incentives). Small-scale dome digesters are also included to provide a lower cost abatement measure and exhibit a measure used in developing regions. These digesters mitigate emissions from manure but also generate revenue for farms by generating heat and electricity from captured CH₄ gases.

Methane emissions represent over 93% of the total emissions in this sector while N₂O accounts for the balance of livestock emissions from manure management. Combined emissions are 286 MtCO₂e in 2030. The largest regional contribution to national emissions is the West North Central, with 82 MtCO₂e in 2030 (29% of U.S. emissions).

Technologically feasible abatement potential from livestock is estimated at 83 MtCO₂e in 2030, a 29% reduction compared with the baseline. In 2030, 14% of emission reductions are achievable at break-even prices below $0. West North Central has the largest abatement potential at 29 MtCO₂e with West South Central following at 10 MtCO₂e in 2030.

West North Central has the largest abatement potential at 20 MtCO₂e with Pacific and East North Central following at 12 MtCO₂e in 2030.

Croplands

A number of land management activities add nitrogen to soils, thus increasing the amount of N₂O emitted, including various cropping practices and livestock waste management. Indirect additions of nitrogen occur through volatilization and atmospheric deposition of ammonia and oxides of nitrogen that originate from (1) the application of fertilizers and livestock wastes onto agricultural land and (2) surface runoff and leaching of nitrogen from these same sources.

This analysis considers nine abatement measures for croplands. For the first measure, no-till management, the analysis does not consider any cultivation or field preparation except for seeding. The second analyzed measure is split nitrogen fertilization application, which applies fertilizer2 times in equal amounts instead of only once on the initial planting day. The third measure is the application of nitrification inhibitors simultaneously with the annual nitrogen fertilizer application, which reduces nitrification by 50% for 8 weeks. The fourth and fifth abatement measures considered the impacts of either increasing or decreasing nitrogen fertilization by 20% above or below the baseline. The sixth abatement measure is switching applications to slow-release fertilizer=. The planting cover crop through the winter or fallow season. The final measure, 100% residue incorporation, assumes that all residue remains after harvest and allows for evaluating how reducing residue removal could affect soil organic carbon stocks.

Each of the abatement measures can lower or raise farm costs, depending on changes in farm labor and equipment usage. Use of 100% residue incorporation has no associated costs, and reducing fertilization is expected to lower costs because less fertilizer will be purchased. In contrast, increasing fertilization and split nitrogen fertilization could raise costs because more fertilizer is used and labor increases. Furthermore, using no-till management could lower labor costs because less direct labor is needed due to the reduction in field preparation. However, purchasing equipment for direct planting is a potential increase in capital costs associated with no-till management.

N₂O emissions from agricultural soils are projected to be 299 MtCO₂e in 2030. The largest regional contribution to national emissions is the West North Central, with 114 MtCO₂e in 2030 (38% of U.S. emissions).

Of the 299 MtCO₂e of projected emissions in 2030 technology is available to mitigate 22%, or 65 MtCO₂e. In 2030, about half of that potential mitigation is available at break-even prices below $0/tCO₂e. Additional reductions are possible with the inclusion of more costly abatement measures. Three practices, 20% reduced fertilizer, no till, and split fertilization, can be implemented to reduce emissions at no cost. Mitigation potential increases to 65 MtCO₂e by including abatement measures with an implementation cost greater than $0/tCO₂e. The region with the largest mitigation potential for agricultural soils is West North Central at 27 MtCO₂e with East North Central following at 12 MtCO₂e in 2030.

The region with the largest mitigation potential for agricultural soils is West North Central at 5 MtCO₂e with East North Central following at 3 MtCO₂e in 2030.

Rice

Rice cultivation is associated with CH₄ emissions . The anaerobic decomposition of organic matter (i.e., decomposition in the absence of free oxygen) by methanogenic bacteria in flooded rice fields produces CH₄. Several factors influence the amount of CH₄ produced, including water management practices and the quantity of organic material available to decompose.

This analysis considered water management, as well as fertilizer application options. However, the fertilizer changes were ineffective at reducing non-CO₂ GHGs and were eliminated from the final analysis. The water management options are: paddy flooding (continuous flooding, midseason drainage [MD], alternating wetting and drying [AWD], and dryland production), crop residue incorporation (50% and 100%), tillage (conventional and no-till), Properly managing tillage, residue, and fertilizer techniques is crucial for growing a quality crop while reducing GHG emissions. Conventional tillage tills 20 cm deep before the first crop rotation and 10 cm deep for following rotations, whereas no-till mulches the residue and does not till the land. Residue incorporation leaves either 50% or 100% of the above-ground residue to be incorporated in the next tillage. Nitrogen fertilizers are applied in the form of urea or ammonium sulfate and sometimes alongside nitrogen inhibitors.

Rice cultivation, which is largely restricted to Gulf Coast states and California, is projected to account for 2% of total non-CO₂ emissions in 2030. The largest regional contribution to national emissions is the West South-Central states near the Mississippi Delta, with 14 MtCO₂e in 2030 (63% of U.S. emissions). The Pacific region accounts for an additional 6 MtCO₂e (26% of U.S. emissions).

In 2030, the total abatement potential from rice is estimated at 6 MtCO₂e. Approximately 2% of the potential abatement, less than 1 MtCO₂e, can be abated at prices below $0/tCO₂e in 2030, rising to a 26% reduction from baseline available at prices greater than $0/tCO₂e. Dryland rice can be implemented to reduce emissions at no costs. Changes in irrigation practices such as alternate wetting & drying; utilization of nitrification inhibitors; and reduced fertilizer utilization with mid-season drainage offer an additional mitigation potential at prices greater than $0/tCO₂e. Rice production is limited to only a few states in the near the Mississippi river and parts of California. As a result, over 80% of the abatement potential are associated with the West South Central (3 MtCO₂e) and Pacific (2 MtCO₂e) regions.

Rice production is limited to only a few states in the near the Mississippi river and parts of California. As a result, over 90% of the abatement potential are associated with the West South Central (6 MtCO₂e) and Pacific (2 MtCO₂e) regions.

Landfills

Landfilling of solid waste includes emissions associated with the disposal of municipal solid waste (MSW) and industrial solid waste. Landfills produce CH₄ and other landfill gases, primarily CO₂, through the natural process of bacterial decomposition of organic waste under anaerobic conditions.

These results assume implementation of 2019 Emission Guidelines for Municipal Solid Waste Landfills, which reduces projected baseline emissions and mitigation potential in this sector.

This analysis considers 12 abatement options to control landfill emissions, which are grouped into three categories: (1) collection and flaring, (2) landfill gas (LFG) utilization systems (LFG capture for energy use), and (3) enhanced waste diversion practices (e.g., recycling and reuse programs). Collection of LFG is feasible at most engineered landfills. It prevents high concentrations of gas in the landfill, which addresses public health and facility safety concerns. After collecting LFG, the least capital-intensive way to reduce emissions is flaring, which burns off the gas. However, flaring does not deliver any economic benefits for landfill operators.

Energy production represents a potential revenue stream for landfills. It includes electricity generation, anaerobic digestion, and direct use. A variety of engine types and waste-to-energy processes can achieve electricity generation. Anaerobic digestion provides CH₄ for on-site electricity or for selling to the market. Direct use implies that a landfill transports captured methane to a facility, which uses it for electricity generation, as process heat, for transportation fuel, or as an input into other processes.

Furthermore, enhanced waste diversion practices redirect biodegradable components of the waste stream from the landfill for reuse through recycling or conversion to a value-added product (e.g., energy or compost). Diverting organic waste components lowers the amount of CH₄ generated at the landfill. Other benefits from the measures under this category include the sale of recyclables, electricity, and cost savings in avoided tipping fees.

CH₄ emissions from waste sector are projected to be 161 in 2030. The largest regional contribution to national emissions is the South Atlantic, with 36 MtCO₂e in 2030 (22% of U.S. emissions). The regional contributions to national emissions are largely determined by population and relative climate (i.e. average annual temperature and humidity).

National abatement potential from solid waste landfills is estimated to be approximately 9 MtCO₂e in 2030, or 8% of the baseline emissions. About 76% of all potential abatement can be achieved at break-even prices below $20/tCO₂e; 21% of reductions can be achieved at prices below $0/tCO₂e, suggesting a substantial share of abatement could generate revenue for landfill operators. The South Atlantic and East North Central regions have the largest share of abatement potential at approximately 2 MtCO₂e each. Landfill gas recovery for direct use technology can be implemented to reduce emissions at no costs. Implement electricity generation with a reciprocating engine represents the largest abatement potential at costs greater than zero in 2030.

The South Atlantic and East North Central regions have the largest share of abatement potential at approximately 2 MtCO₂e each. Landfill gas recovery for direct use technology can be implemented to reduce emissions at no costs. Implement electricity generation with a reciprocating engine represents the largest abatement potential at costs greater than zero in 2030.

Wastewater

Wastewater originates from a variety of residential, commercial, and industrial sources. It can be a source of CH₄ when organic material present in the wastewater-flows decomposes under anaerobic conditions. Most urban and suburban communities in the United States rely on centralized aerobic wastewater treatment systems that limit CH₄ generation, while more rural areas often rely on a broader suite of wastewater treatment technologies. N₂O emissions occur primarily as indirect emissions from wastewater after disposal of effluent into waterways, lakes, or the sea.

Upgrades to infrastructure and equipment can reduce CH₄ emissions from wastewater. No proven and reliable technologies for mitigating N₂O from wastewater treatment exist. Abatement measures available for wastewater include (1) implementing centralized collection of wastewater for treatment, (2) constructing aerobic wastewater treatment plants (WWTPs), and (3) constructing anaerobic WWTPs with cogeneration.

This analysis also considers the mitigation potential of a WWTP that uses an anaerobic sludge digester with co-generation. However, adding co-generation increases the capital cost of the technology.

National wastewater emissions are projected to increase modestly over time, reaching 43MtCO₂e in 2030. Projected emissions reflect population growth and an increasing contribution of emissions from fast growing urban populations. The region with the largest wastewater emissions is South Atlantic, with 9 MtCO₂e in 2030 (20% of U.S. emissions). The second largest is the Pacific region, with 6 MtCO₂e (14% of U.S. emissions).

National abatement potential of CH₄ from wastewater treatment is 10 MtCO₂e in 2030. High-cost abatement measures from wastewater treatment significantly constrain the abatement achievable at lower prices.. There are no cost-effective emission reductions, or reduction at prices below $0/tCO₂e in 2030. The region with the greatest potential abatement is South Atlantic, with 2 MtCO₂e of total potential abatement. The regions with the next largest abatement potential include West North Central and East North Central at more than 1 MtCO₂e of abatement potential each.

The region with the greatest potential abatement is South Atlantic, with 2 MtCO₂e of total potential abatement. The regions with the next largest abatement potential include West North Central and West South Central at approximately 1 MtCO₂e of abatement potential each.