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Agriculture and Air Quality

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Background: Clean Air Act (CAA) -- Title I

Pursuant to Title I of the CAA, EPA has established national ambient air quality standards (NAAQSs) to limit levels of "criteria pollutants," including:
  • carbon monoxide,
  • lead,
  • nitrogen dioxide,
  • particulate matter,
  • ozone, and
  • sulfur dioxide.

EPA calls these pollutants "criteria air pollutants" because the agency has regulated them by first developing health-based criteria (science-based guidelines) as the basis for setting permissible levels. One set of limits (primary standard) protects health; another set of limits (secondary standard) is intended to prevent environmental and property damage.

A geographic area that meets or does better than the primary standard is called an attainment area; areas that don't meet the primary standard are called nonattainment areas. A single geographic area may have acceptable levels of one criteria air pollutant but unacceptable levels of one or more other criteria air pollutants; thus, an area can be both attainment and nonattainment at the same time.

Under Section 110 of the CAA, each state must develop a State Implementation Plan (SIP) to identify sources of air pollution and to determine what reductions are required to meet federal air quality standards. A State Implementation Plan is a detailed description of the programs a state will use to carry out its responsibilities under the Clean Air Act.

Telephone assistance from EPA

  • EPA's Control Technology Center - Call: 919-541-0800. The Center provides general assistance and information on CAA standards.

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Air Emissions from Agricultural Practices

Under Section 110 of the CAA, each state must develop a State Implementation Plan (SIP) to identify the sources of air pollution and to determine what reductions are required to meet federal air quality standards.

State implementation plans are collections of the regulations used by a state to reduce air pollution. The Clean Air Act requires that EPA approve each state implementation plan. Members of the public are given opportunities to participate in review and approval of state implementation plans.

The degree to which ambient air emissions from farming practices -- such as prescribed burning -- are allowed are location-specific (specific to a geographic area) within each State Implementation Plan. Visibility standards may also apply through the State Implementation Plan. Locations that are in areas that have been classified as "nonattainment areas" under the National Ambient Air Quality Standards (NAAQS) are subject to more restrictions.

The U.S. Department of Agriculture (USDA) has established the Agriculture Air Quality Task Force

EPA is an active participant in the Task Force. The Task Force has unanimously endorsed a listing of high priority research needs to improve the level of understanding of the impact of agriculture on air quality levels.

On February 25, 1998, the USDA and EPA announced a Memorandum of Understanding (MOU) to ensure that the two agencies work together to provide a healthy environment with clean air in harmony with a strong agriculturally productive nation. The MOU establishes a framework for the two agencies to share expertise and a process for involving the agricultural community in a cooperative effort to address agriculture-related air quality issues, including emissions from agricultural burning.

EPA will work with the task force to refine the distinction between wildland fires (which are covered by EPA's Interim Air Quality Policy on Wildland and Prescribed Fires) and agricultural burning.

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Particulate matter is the term for solid or liquid particles found in the air. Some particles are large or dark enough to be seen, such as soot or smoke. Others are so small they can be detected only with an electron microscope.

Concerns with particulates

  • breathing particulate matter can cause serious health problems,
  • particulates reduce visibility in many parts of the United States,
  • they can accelerate corrosion of metals,
  • they can damage paints and building materials such as concrete and limestone.

Sources of particulates

"Coarse" particles are larger than 2.5 micrometers and generally come from sources such as:
  • vehicles traveling on unpaved roads,
  • materials handling,
  • crushing and grinding operations such as cement manufacturing, and
  • combustion sources.

Fine particulates

Particles less than 2.5 micrometers (0.0004 inch) in diameter are known as "fine" particles. Fine particles result from:
  • fuel combustion in motor vehicles,
  • power plants,
  • industrial facilities,
  • residential fireplaces,
  • woodstoves,
  • wildfires,
  • prescribed forest burning,
  • fine particles can also be formed when combustion gases are chemically transformed into particles.

Health effects of particulates

Particulate matter less than 10 micrometers in size, including fine particles less than 2.5 micrometers, can penetrate deep into the lungs. On a smoggy day, one can inhale millions of particles in a single breath. Tens of millions of Americans live in areas that exceed the national health standards for particulates.

In recent studies, exposure to particulate pollution -- either alone or with other air pollutants -- has been linked with:
  • premature death,
  • difficult breathing,
  • aggravated asthma,
  • increased hospital admissions and emergency room visits, and
  • increased respiratory symptoms in children.
People most at risk from exposure to fine particulate matter are:
  • children,
  • the elderly, and
  • people with chronic respiratory problems.

Environmental effects of particulates

Fine particles scatter and absorb light, creating a haze that limits our ability to see distant objects. Particle plumes of smoke, dust, and/or colored gases that are released to the air can generally be traced to local sources such as industrial facilities or agricultural burning. Regional haze is produced by many widely dispersed sources, reducing visibility over large areas that may include several states.

The Clean Air Act established special goals for visibility in some national parks and wilderness areas. In 1994, EPA began developing a regional haze program that is intended to ensure that continued progress is made toward the national visibility goal of "no manmade impairment." Such control efforts would likely result in improved public health protection and visibility in areas outside national parks as well.

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Backyard Burning

Backyard burning refers to the burning of household trash by residents on their own property.

Trash typically burned can include:
  • paper,
  • cardboard,
  • food scraps,
  • plastics,
  • yard trimmings
  • essentially any materials that would otherwise be recycled or sent to a landfill.
Burning usually occurs in:
  • a burn barrel,
  • homemade burn box,
  • wood stove,
  • outdoor boiler,
  • or open pit.

Air emissions from backyard burning are released directly to the atmosphere without being treated or filtered.

Backyard burning is common in many areas of the country. People burn trash for various reasons—either because it is easier than hauling it to the local disposal site or to avoid paying for regular waste collection service. Most people who burn their waste do not realize how harmful this practice is to their health and to the environment. Current research indicates that backyard burning is far more harmful to our health than previously thought.

Backyard burning can:
  • increase the risk of heart disease,
  • aggravate respiratory ailments such as asthma and emphysema,
  • cause rashes, nausea, or headaches.

Backyard burning is particularly dangerous because it releases pollutants at ground level where they are more readily inhaled or incorporated into the food chain. Backyard burning is of particular health concern because it produces significant quantities of dioxins.

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Prescribed Burning

Prescribed burning is a land treatment, used under controlled conditions, to accomplish natural resource management objectives. It is one of several land treatments, used individually or in combination, including chemical and mechanical methods.

Prescribed fires:
  • are conducted within the limits of a fire plan and prescription that describes both the acceptable range of weather, moisture, fuel, and fire behavior parameters, and the ignition method to achieve the desired effects.
  • are a cost-effective and ecologically sound tool for forest, range, and wetland management.
  • reduce the potential for destructive wildfires and thus maintains long-term air quality.
  • remove logging residues,
  • control insects and disease,
  • improve wildlife habitat and forage production,
  • increase water yield,
  • maintain natural succession of plant communities,
  • reduce the need for pesticides and herbicides.

The major air pollutant of concern is the smoke produced. Smoke from prescribed fires is a complex mixture of carbon, tars, liquids, and different gases. This open combustion source produces particles of widely ranging size, depending to some extent on the rate of energy release of the fire.

The major pollutants from wildland burning are:
  • particulate,
  • carbon monoxide, 
  • volatile organics,
  • nitrogen oxides are emitted at rates of from 1 to 4 g/kg burned, depending on combustion temperatures,
  • emissions of sulfur oxides are negligible.
Some pollution prevention practices that can be used during prescribed burning operations include:
  • Carefully plan burning to adhere to weather, time of year, and fuel conditions that will help achieve the desired results and minimize impacts on water quality.
  • Intense prescribed fire for site preparation should not be conducted in the streamside management areas.
  • Avoid conditions requiring extensive blading of firelines by heavy equipment.
  • Revegetate firelines with adapted herbaceous species.
  • Avoid burning on steep slopes with high erosion hazard areas or highly erodible soils.
  • Construct firelines in a manner that minimizes erosion and sedimentation and prevents runoff from directly entering watercourses.

More information from EPA

  • EPA Control Technology Center Hotline: 919-541-0800

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State Programs and Information on Prescribed Burning, Particulates, and Smoke Management   

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Solid Waste Incineration

New Source Performance Standards and Emission Guidelines for Existing Sources: Other Solid Waste Incineration (OSWI) Units

In response to the requirement to publish a schedule for regulation of other categories of solid waste incineration units, a Federal Register notice (58 FR 31358, June 2, 1993) was published that proposed a regulatory schedule and a draft list of potential subcategories for consideration of regulation under OSWI standards. After receiving comments on the June 1993 notice, another Federal Register notice (58 FR 58498, November 2, 1993) was published to include comments received on the draft category list and proposed regulatory schedule. The November 1993 notice listed the following potential subcategories of OSWI:

  • Very small municipal waste combustion units;
  • Residential incinerators;
  • Agricultural waste incinerators;
  • Wood waste incinerators;
  • Construction and demolition waste incinerators;
  • Crematories; and
  • Contaminated soil treatment facilities.

Assessment of the above categories

None of the three agriculture-related categories were included by EPA as a subcategory of Other Solid Waste Incinerators for regulation at this time.

Grain Terminal Elevators

  • Any grain terminal elevator having a permanent storage capacity of more than 2.5 million U.S. bushels or any grain storage elevator having a permanent storage capacity of more than 1.0 million U.S. bushels must comply with the New Source Performance Standard for grain elevators.
  • Process emissions from loading, unloading, and grain handling are required to be ventilated and conveyed to a control device and meet a PM limit of 0.023 g/dscm.
  • Fugitive emissions from grain elevators take the form of grain dust and can be emitted from almost any point in the grain elevator process.
  • Depending on the fugitive emission source, the standard either requires compliance with an equipment standard and/or meeting a 0% opacity limit.

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Animal Feeding Operations

Air Monitoring at Agricultural Operations

Some activities and equipment on farms release pollutants into the atmosphere. The Air Monitoring at Agricultural Operations site explains how EPA works to study these emissions and the federal standards that limit emissions. It also describes common practices that can be used to reduce emissions from crop and animal farms.

Air Emissions Monitoring Study for Animal Feeding Operations (AFOs)

EPA collaborated with farmers on the first-ever nationwide study of air emissions from animal feeding operations (AFOs).

Researchers from eight universities took part in a two-year, $14.6 million study to measure levels of
  • hydrogen sulfide,
  • particulate matter,
  • ammonia,
  • nitrous oxide,
  • volatile organic compounds,
  • other gases from poultry, dairy, and swine facilities

The study was conducted at 24 sites in nine states as part of an innovative and voluntary consent agreement EPA developed with the AFO industry. This agreement established a framework for farmers to participate in a monitoring study in which over 2,600 agreements were signed, representing approximately 14,000 swine, dairy, egg-laying, and broiler chicken (meat-bird) farms (an AFO can include more than one farm).

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Air Quality Conservation Practices

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Reporting Requirements for Air Releases from Animal Waste

Reporting Requirements for Air Releases of Hazardous Substances from Farm Animal Waste

Two environmental laws, the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and Emergency Planning and Community Right-to-Know Act (EPCRA), require reporting of releases of hazardous substances that exceed reportable quantities within a 24-hour period. The purpose of the notification is for federal, state, and local officials to evaluate the need for an emergency response to mitigate the effects of a release to the community.

However, due to legislative changes in the “Fair Agricultural Reporting Method Act” or “FARM Act” in March 2018, “air emissions from animal waste at a farm” are exempt from reporting under CERCLA. These types of releases also do not need to be reported under EPCRA.

For more information, please see:  CERCLA and EPCRA Reporting Requirements.

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Emission Standards for Farm Equipment - Boilers

Boilers (Steam Generating Units) are commonly used as a source of energy on farms. For more information, please see the emission standards for boilers.

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Emission Standards for Farm Equipment - Engines

Stationary internal combustion engines use pistons that alternatively move back and forth to convert pressure into rotating motion. Many types of stationary engines exist and are found on farms, including diesel engines, spark ignited engines, and reciprocating internal combustion engines. Air quality requirements vary for stationary engines, depending on whether the engine is new or existing, where the engine is located, and what type of ignition system is used. 

For more information, please see the emission standards for engines.

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Ozone (O3) Air Quality Standards

The Clean Air Act requires EPA to set national ambient air quality standards (NAAQS) for ozone and five other pollutants considered harmful to public health and the environment (the other pollutants are particulate matter, nitrogen oxides, carbon monoxide, sulfur dioxide and lead). The law also requires EPA to periodically review the standards to ensure that they provide adequate health and environmental protection, and to update those standards as necessary.

For more information, please see: Ozone (O3) Air Quality Standards

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