Methane and nitrous oxide are the two main greenhouse gases emitted by agricultural sources. EPA has several direct regulatory tools available to reduce emissions of these greenhouse gases, including recognizing the harm or “endangerment” caused by these pollutants and promulgating regulatory programs to require or support their reduction.

These regulatory programs could include direct limits, prohibitions on certain activities or practices known to emit significant amounts, or increased support for known practices that reduce emissions.

As we discuss in Chapters II and III, agriculture is now highly consolidated in the United States. The largest 0.4% of farms in the United States produce more than a third of all agricultural products in the country, while the top 7% are responsible for more than 80%.² The top 7% of producers also owns 60% of the harvested cropland,³ receives almost half of all government farm payments,⁴ and takes in almost 90% of all net farm income.⁵ Policymakers should be attentive to the genuine challenges farming operations face when transitioning to climate-friendly practices, but most of these large commercial farms, which often earn millions each year, can afford to adopt basic conservation practices. As we discuss in Chapter V, Congress and USDA should require large-scale operations to curb their most environmentally damaging practices in exchange for support from government programs, while maintaining a robust regulatory approach focused on the largest farms. Small and midsized farms should also be required to adopt basic conservation practices in order to receive government support, but additional funds should be made available to provide them with the financial means to adopt climate-friendly practices.

CAFO air pollution regulation.

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Section 111 of the CAA requires the EPA Administrator to set and revise “a list of categories of stationary sources” that “cause, or contribute significantly to, air pollution which may reasonably be anticipated to endanger public health or welfare.”⁷ After the EPA Administrator lists a category, the CAA requires that EPA set standards of performance for new and modified (e.g., expanded) sources in that category.⁸ These standards must reflect “the best system of emission reduction” that has been “adequately demonstrated” taking into account “the cost of achieving such reduction and any non-air quality health and environmental impact and energy requirements.”⁹ Further, when a category is listed, the CAA then requires that states develop plans with “standards of performance” to be achieved by existing sources in that category.¹⁰

In 2009, the Humane Society and other groups petitioned to set emissions standards for CAFOs on the grounds that they are stationary sources that emit significant quantities of a number of air pollutants, including the greenhouse gases methane and nitrous oxide.¹¹ Although EPA had already recognized that these greenhouse gases endanger public health and welfare and that enteric fermentation and livestock manure are responsible for a large portion of overall methane and nitrous oxide emissions,¹² EPA denied the petition in 2017 citing “the EPA’s current comprehensive strategy to address CAFO emissions and the agency’s limited resources and the need to prioritize its regulatory activity and to use its resources efficiently.”¹³ In 2021, Public Justice and other environmental organizations revived this issue and petitioned EPA to “list industrial dairy and hog operations as source categories” that cause or contribute significantly to dangerous pollution,” noting

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that they are major sources of methane … and [account] for 33 percent of agricultural methane emissions.”¹⁴

In setting emissions standards, EPA could assess achievable limits by looking at a number of actions new CAFOs can take to reduce methane emissions, including methane-reducing feed additives,¹⁵ grazing animals,¹⁶ cover and flare manure management systems (a cost-effective method of reducing GHG emissions while reducing odor and protecting water quality),¹⁷ or using anaerobic digestors to convert the methane into energy.¹⁸ The Public Justice petition, for example, urges EPA to “base subsequent regulations on the emission reductions achievable with widespread application of sustainable, pasture-based practices [that] not only significantly reduce methane, [but] also remove carbon dioxide from the atmosphere through healthy soils [and] reduce nitrous oxide emissions from feed crops and manure disposal.”¹⁹ If a standard of methane emissions for new CAFOs proves to be impractical (for instance if emissions monitoring difficulties precluded adequate enforcement), the CAA also allows the EPA Administrator to promulgate a “design, equipment, work practice, or operational standard, or combination thereof” to limit emissions.²⁰ For example, EPA implemented work practice standards to control particulate matter emissions from open coal piles at preparation and processing plants, rather than numerical emissions limitations, on the basis that it would be “difficult and prohibitively expensive to measure actual emissions from individual open storage piles or roadways.”²¹ This approach could be used to require, for example, dry manure handling practices, which generate less methane.

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While EPA’s regulatory oversight responsibilities would be increased by the addition of a new category of sources, EPA could minimize this burden by prioritizing regulation of the largest CAFOs. The largest 10% of CAFOs emit around 80% of CAFO greenhouse gas pollution. Section 111 allows for EPA to “distinguish among classes, types, and sizes within categories of new sources for the purpose of establishing … standards.”²² EPA could distinguish sizes based on animal units, as EPA does under the Clean Water Act,²³ or amounts of pollution emitted as it does under §114 of the CAA (see below).

Additionally, EPA could regulate ammonia emissions, which could also lead to decreased nitrous oxide emissions, depending on the control technology. One option is for EPA to designate and regulate ammonia under CAA §§108 and 109. Section 108 requires EPA to designate pollutants generated by “numerous or diverse mobile or stationary sources” that “may reasonably be anticipated to endanger public health or welfare” as “criteria” pollutants.²⁴ Under §109, this designation further requires EPA to establish a national ambient air quality standard (NAAQS) for the pollutant.²⁵ Following this, states must provide a plan to implement, maintain and enforce the NAAQS.²⁶ Ammonia is emitted in large quantities by CAFOs and poses significant health risks.²⁷ As a result, Environmental Integrity Project and other organizations petitioned EPA to list ammonia as a criteria pollutant in 2011.²⁸ However EPA failed to respond and litigation to compel a response was dismissed on procedural grounds.²⁹

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A second option is regulation under §112, the Hazardous Air Pollutants (HAP) program. Under §112, EPA can undertake rulemaking to add pollutants that “present, or may present, through inhalation or other routes of exposure, a threat of adverse human health effects…or adverse environmental effects …” to the HAP list.³⁰ Once a pollutant is listed, EPA must set maximum achievable control technology (MACT) standards for “major sources” of the HAP (emitting 10 tons per year or more of any single HAP or 25 tons per year of any combination of HAPs).³¹ For new major sources, MACT standards for a category must be equally or more stringent than “the emission control that is achieved in practice by the best controlled similar source.”³² For existing major sources, MACT standards for a given category must be at least as strict as the average emissions limitation achieved by a best performing subset of that category.³³ In addition to major sources, EPA can also regulate “area sources” (groups of sources whose aggregate emissions present a threat to health) by imposing a less strict requirement that the sources use generally available control technologies to limit their emissions.³⁴

Such limitations on ammonia emissions could also limit nitrous oxide emissions depending on the method of reduction.

To effectively regulate CAFO emissions, EPA will need to establish methods by which CAFOs can measure and monitor their emissions. Accordingly, Congress should direct EPA to complete its development of emission-estimating methodologies (EEMs) for CAFOs, as the agency committed to do by 2009 under a 2005 consent agreement.³⁵ In addition, EPA should adopt a process-based modeling approach to developing the EEMs, since, as its Science Advisory Board has stated, such a model is better able to “represent the chemical, biological and physical processes and constraints associated with emissions.”³⁶ These steps will allow the public and policymakers to more

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accurately evaluate the role of CAFOs in the climate crisis, while giving regulators the tools they need to reduce their emissions.

Row crop air pollution regulation. Row crop agriculture is a major source of nitrous oxide emissions (as well as particulate matter pollution which can be regulated by states to achieve the particulate matter NAAQS). One approach to address nitrous oxide would be under §615 of the CAA. Section 615 states that:

If, in the Administrator’s judgment, any substance, practice, process, or activity may reasonably be anticipated to affect the stratosphere, especially ozone in the stratosphere, and such effect may reasonably be anticipated to endanger public health or welfare, the Administrator shall promptly promulgate regulations respecting the control of such substance, practice, process or activity, and shall submit notice of the proposal and promulgation of such regulation to the Congress.³⁷

Currently, nitrous oxide is considered “the most important ozonedepleting substance emission”³⁸ and is projected to be the most significant contributor to stratospheric ozone pollution during the twenty-first century.³⁹ In addition, stratospheric ozone-depletion increases human exposure to UV radiation.⁴⁰ This results in health impacts including an increased prevalence of skin cancers,⁴¹ cataracts and other eye diseases,⁴² and immune system suppression.⁴³ Agriculture is responsible for more than 80% of U.S.

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drainage, irrigation, and fallowing of land.⁴⁵ EPA could prescribe regulations for these activities to reduce the emissions of nitrous oxide. In this context, “regulations” could require work practices rather than any numerical emission limit, which would likely be infeasible.⁴⁶ Some work practices with demonstrated efficacy in reducing nitrous oxide emissions include matching fertilizer and manure application rates to crop nitrogen requirements⁴⁷ and planting cover crops.⁴⁸

Greenhouse gas regulation under water pollution programs. Federal and state governments can also reduce greenhouse gas emissions as incidental to their regulation of water or other pollution. Programs to reduce nitrate runoff from fields into rivers would (depending on the precise practices incentivized) likely reduce nitrous oxide emissions; programs to reduce erosion and sediment pollution from grazing could increase soil carbon; and programs to change manure management could reduce methane emissions.

The Clean Water Act (CWA) establishes a national pollutant discharge elimination system (NPDES) to regulate operations that discharge pollutants directly into waters. While most field operations and irrigation water return flows are exempted from direct regulation,⁴⁹ other agricultural operations including CAFOs that do, or are likely to, discharge are covered.⁵⁰ The law requires point source dischargers to obtain an NPDES permit from EPA or authorized state authorities in order to operate.⁵¹ States that have been authorized to act as a permitting authority may impose more stringent requirements than the federal government.⁵² In addition, the CWA requires states to develop programs to address nonpoint source (runoff) pollution, including agricultural sources.⁵³

EPA should strengthen its nationwide regulations in ways that would reduce greenhouse gas emissions as well as water pollution.

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example, NPDES programs should clearly prohibit CAFOs from spreading manure on frozen or saturated lands, insist on vegetated buffer zones along water courses, limit application rates, or require dry manure management, which can also reduce methane emissions. Similarly, management of crop production should require or incentivize buffer zones to reduce nitrate emissions, and thus also nitrous oxide emissions.

Greenhouse gas regulation under waste programs. Other statutes also give EPA regulatory options for reducing agricultural greenhouse gas emissions. The most common waste management systems at industrial livestock facilities produce massive quantities of toxic fumes of ammonia and hydrogen sulfide in addition to the greenhouse gases methane and nitrous oxide. EPA estimates that livestock facilities are responsible for 73% of the country’s ammonia air emissions.⁵⁴ Many of the practices that would reduce these hazardous air emissions would also reduce methane and nitrous oxide emissions, and EPA should thus use its regulatory tools to achieve such reductions.

The Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) and the Emergency Planning and Community Right-to-Know Act of 1986 (EPCRA) require all facilities that release hazardous substances to report these emissions to federal, state, and local governments and emergency responders.⁵⁵ In 2008, EPA exempted livestock facilities from this reporting requirement.⁵⁶ In 2017, the D.C. Circuit struck down EPA’s loophole as illegal.⁵⁷ Responding to pressure from the animal production industry, Congress passed a rider to the March 2018 budget bill excluding livestock facilities from CERCLA reporting requirements.⁵⁸ The following month, EPA asserted that, as a result of the CERCLA exemption, the facilities were also exempt from EPCRA reporting, an action that has been challenged by community organizations.⁵⁹ Congress should pass new legislation eliminating both exemptions, ensuring that an estimated 33,000 facilities are covered, or, at a minimum, require reporting by medium and

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large CAFOs, which would impose reporting only on the largest facilities that produce the vast majority of the waste.⁶⁰ Of course, reporting alone does not reduce emissions, but it can raise awareness of the issue, leading to reductions of waste.

Similarly, the Resource Conservation and Recovery Act (RCRA)⁶¹ has been successfully used by neighbors of a large animal facility to require the better management of stored and spread manure to limit groundwater contamination.⁶² As a result of this case, industry is urging Congress to amend RCRA to exempt animal manure, and EPA and Congress must resist this pressure as this law provides an important opportunity to reduce water and air pollution. As noted, manure management changes instigated by concerns for groundwater, including more significant changes such as switching to dry manure handling or installation of digesters, can also reduce greenhouse gases.

Renewable fuel standard. In 2017, close to 30 million acres of corn were grown in the United States as feedstock for ethanol.⁶³ As noted above, the purported climate change benefits of corn ethanol are widely disputed and modest at best. Ideally, Congress should reform the renewable fuel standard (RFS) to support only those biofuels with significant climate benefits. Short of congressional reform of the RFS program, however, EPA should revise its “aggregate compliance” mechanism to ensure that nonagricultural land is not converted to growing corn as ethanol feedstock.

Conversion of native ecosystems for cultivation releases vast amounts of CO₂. A 2008 study found that converting forest, grassland, or peatland for biofuel production can release 17-420 times more CO₂ than the annual greenhouse gas reductions these biofuels would provide by replacing fossil fuels.⁶⁴ To prevent this conversion of natural ecosystems, Congress in 2007

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revised the 2005 RFS to exclude crops “harvested from land cleared or cultivated” after December 19, 2007, from its definition of “renewable biomass.”⁶⁵

EPA regulations implementing this provision, however, have rendered it meaningless. Though EPA’s proposed rule required crop producers to comply with recordkeeping requirements to verify that feedstocks met Congress’ definition, the agency then worked with USDA to write a final rule that differed significantly from that proposal. In the final rule, the agency adopted an “aggregate compliance” approach that instead deems all producers compliant with the standard as long as the net land area used for agriculture in the United States does not exceed its 2007 level of 402 million acres.⁶⁶ This approach has demonstrably failed to prevent significant land conversion. A 2016 analysis of satellite data estimated that 4.2 million acres of land have been converted to agriculture for biofuel production since the adoption of the standard, and EPA itself found in a 2018 report that there has been “an increase in actively managed cropland by roughly 4–7.8 million acres” since 2007, some amount of which is attributable to biofuel production.⁶⁷ An earlier study estimated that between 2008 and 2012, 1.6 million acres of longterm grasslands (that is, grasslands that were uncultivated since 1992 and likely earlier) were converted.⁶⁸ Separately, the World Wildlife Fund (WWF) estimated that between 2009 and 2015, 53 million acres of uncultivated grassland in the United States were converted.⁶⁹ (The WWF estimate likely exceeds the other estimates because it did not account for grassland that, while uncultivated in 2008, had been cultivated in earlier years.)

This “aggregate compliance” approach is also facially ineffective as millions of acres of agricultural land are taken out of production each year for many reasons, such as urban development, roads, or energy production. Thus, a static acreage cap on cropland cannot prevent conversion. Given that this approach violates both Congress’ stated intent and clear language by eliminating the requirements on what land may be used to produce renewable biomass, EPA should repeal the “aggregate compliance” standard and replace it with a mandate to demonstrate feedstock was produced on land cleared before December 7, 2007, replace the static acreage cap with one reflecting current active cropland acreage, or otherwise reform the program.

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Nitrogen fertilizer standards. Conventional nitrogen fertilizer practices are quite inefficient—more than half of the nitrogen applied does not contribute to plant or animal growth.⁷⁰ In addition to regulating nitrogen runoff and other on-farm behavior contributing to nitrous oxide pollution, policymakers can lower emissions by increasing the market share of so-called enhanced-efficiency fertilizers, which are designed to reduce emissions relative to conventional fertilizers. Enhanced-efficiency fertilizers take one of two forms: inhibitors, which can help retain nitrogen in soil for longer periods; and slow- and controlled-release fertilizers, which delay the release of nitrogen into the soil.⁷¹ Despite their potential to reduce emissions, these products have been understudied and underutilized, and researchers do not expect their use to increase through voluntary initiatives alone.⁷² As a result, a pair of researchers have proposed applying new requirements to gradually increase the proportion of enhanced-efficiency fertilizers sold over time, while simultaneously providing incentives for companies to improve the climate profile of their products.⁷³ They propose modeling the program on the Corporate Average Fuel Economy (CAFE) standards, which set field consumption standards for vehicles, and have proven to be a durable and effective tool for increasing fuel economy.⁷⁴

The researchers propose two possible mechanisms for enhanced-efficiency fertilizer standards. One approach would be to require that manufacturers increase the share of enhanced-efficiency fertilizer sales over time.⁷⁵ Alternatively, regulators could set a national average efficiency level, which would take into account both the share of enhanced-efficiency fertilizer sold as well as how effective those enhanced-efficiency fertilizers are at reducing emissions.⁷⁶ As discussed in Chapter IV.A.1, there are concerns regarding the environmental impacts of nitrification inhibitors, which should be studied further.⁷⁷ In addition, as the researchers warn, such standards must be coupled with other actions to reduce nitrous oxide emissions. Nonetheless, the CAFE standards provide an intriguing model for reducing nitrous oxide emissions.

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State and local regulatory tools. Finally, state and local governments should improve on current federal regulations by passing their own legislation designed to reduce emissions from agricultural operations. The California State Legislature, for example, passed a law in 2014 directing the California Air Resources Board (CARB) to develop a comprehensive strategy to reduce short-lived climate pollutants, including methane.⁷⁸ Subsequent legislation required CARB to begin implementing the plan by 2018.⁷⁹ CARB’s strategy calls for significant decreases in emissions from dairy manure management with reductions of at least 20% in 2020, 50% in 2025, and 75% in 2030.⁸⁰ In 2015, Minnesota passed a pioneering law requiring permanent vegetative buffers on farmland abutting lakes and streams.⁸¹ The law was designed to reduce runoff, but will also increase soil carbon sequestration on the new strips, thereby reducing greenhouse gas emissions within the state. There are a variety of practices that state legislatures and environmental agencies and local governments should require, such as riparian buffers, or prohibit, such as spreading manure on frozen land, in order to further reduce the environmental harms of modern industrial agriculture. This would provide models for future federal initiatives, while also producing immediate climate and environmental benefits.