We've made some changes to EPA.gov. If the information you are looking for is not here, you may be able to find it on the EPA Web Archive or the January 19, 2017 Web Snapshot.

AgSTAR

Guidelines and Permitting for Livestock Anaerobic Digesters

Many of the links on this page exit the site Exit
You will need Adobe Reader to view some of the files on this page. See EPA’s About PDF page to learn more.

Biogas recovery systems that use anaerobic digestion are sophisticated systems. To help you plan and optimize your anaerobic digester, AgSTAR provides the following information:


Anaerobic Digester Guidelines

These resources can help you evaluate anaerobic digester designs, build and implement an anaerobic digester, and operate and maintain the system:

Top of Page


Codigestion Guidelines

Photograph of a garbage truck driving down a city streetCodigestion occurs when more than one type of organic waste is fed into an anaerobic digester. Codigestion can increase methane production from low-yielding or difficult to digest farm-based feedstocks.

Codigestion Feedstocks

Codigestion feedstocks can be collected from other nearby sources including restaurant or cafeteria food wastes; food processing wastes or byproducts; fats, oil and grease from restaurant grease traps; energy crops; crop residues; and others. Codigestion feedstocks should be carefully selected to enhance—not inhibit—methane production.

Testing potential codigestion feedstocks helps owners understand the potential for biogas production, effects on methane production and other attributes. Methods for testing attributes of codigestion feedstocks include:

The composition of feedstocks in anaerobic digesters also has a significant influence on the biogas produced. This resource discusses energy from common codigestion feedstocks:

Laboratories that Conduct Testing of Anaerobic Digester Feedstocks

To find a university or private laboratory that tests anaerobic digester feedstocks, contact your system designer for references or contact your state university’s agriculture department.

Top of Page


Interconnection GuidelinesInterconnection Power Lines

Interconnection is the physical linking of a biogas recovery system to the electrical power grid.  Biogas recovery systems connected to the electrical power grid generate renewable energy, which is distributed to energy consumers on the grid.  The sale of electricity can generate revenue for biogas recovery system owners. Additionally, renewable energy certificates (RECs) and other environmental credits can be earned from producing and distributing the energy.

Interconnection Guidelines provide general guidance for connecting a biogas recovery system to the electrical power grid.

Top of Page


Permitting

Anaerobic digesters must meet local, state and federal regulatory and permitting requirements for air, solid waste and water. These requirements are in addition to permitting requirements for Concentrated Animal Feeding Operations (CAFOs). Anaerobic digester permit requirements vary by location and change frequently. Local, state and federal resources can help you navigate the permit process.

Local Permit Requirements

Anaerobic digesters may be subject to local government permit requirements for a range of municipal issues, such as construction, zoning and stormwater management. Contact your local government to determine current rules before constructing or operating anaerobic digesters.

State Permit Requirements

In addition to administering federal regulations, state agencies also administer their own state air, solid waste and water permit requirements.

Consolidated or General Permit Process

Some states provide the option of a consolidated permit process, which has several benefits:

  • Allows permit applicants to have all of their state environmental permits coordinated by one agency;
  • Makes the process easier by providing a single point of contact for multiple permits;
  • Identifies needed permits earlier in the process; and
  • Decreases duplicate information to various agencies.

Contact your state environmental agency to determine current rules before constructing or operating anaerobic digesters.

Air

  • Combustion devices used for energy generation may require state air permits if the devices operate over federal thresholds.
  • Some states have additional state-specific thresholds that require state air permits.

Solid Waste

  • Waste processing facilities are required to meet Resource Conservation and Recovery Act (RCRA) Subtitle D requirements (which cover non-hazardous solid wastes) and 40 CFR Part 258 (which covers landfills).
  • Many states exempt manure-only anaerobic digesters from solid waste permit requirements.

    • Some states may exempt all farm digester systems or only some systems based on the type and volume of feedstocks processed. For example, farms may require permits if they rely on codigestion, accept any offsite waste or accept offsite waste above a threshold amount.

Water

  • The presence of an anaerobic digester on a CAFO does not change the federal CAFO requirements, which some states administer.

  • EPA regulates CAFOs by size.

    • EPA considers large CAFOs as point sources of water pollution. Therefore, CAFOs require National Pollutant Discharge Elimination System (NPDES) permits. CAFOs also must develop and maintain Nutrient Management Plans to ensure appropriate land application of manure. Anaerobic digesters with solids separation may give farms more control over how they apply nutrients.

    • Medium CAFOs may face similar requirements as large CAFOs. Some states include smaller farms in their animal feeding operations programs depending on past performance or other site conditions.

    • Smaller farms must comply with the NPDES requirements if they discharge to waters of the U.S. through a manmade device or through direct contact of the animals with waters of the U.S.

    • Some states have additional water permit requirements for farm-based anaerobic digester operations that codigest other feedstocks with manure.

State-Specific Requirements

View a summary overview

Overview of State Permitting Requirements Specific to Anaerobic Digestion Systems

This table summarizes state-specific air, solid waste and water permitting requirements as of May 2015 for livestock farm anaerobic digesters in the states with the most operating anaerobic digesters.

Note: Even if there is no state specific anaerobic digester permitting requirement or there is no check in the table, state or federal regulations still may apply for air, solid waste and water.
NMP – regulated under the facility’s nutrient management plan

State Consolidated or General Permit Process Air Solid Waste Water
State-Specific Thresholds General Permit Permit Required if Codigestion Additional Requirements
Processing Only Manure Codigestion Accepting Offsite Waste
California      
Idaho       NMP    
Illinois            
Indiana      
Iowa          
Maine          
Massachusetts        
Michigan        
Minnesota          
Nebraska            
New York        
Ohio        
Oregon      
Pennsylvania          
Texas            
Vermont          
Washington      
Wisconsin            
  • California

    Consolidated or General Permit Process

    • The California Environmental Protection Agency (Cal/EPA) offers a consolidated permit process (PDF) (2 pp, 437K) for dairy digester projects. If requested, Cal/EPA will have one state agency coordinate environmental permits for a facility, which can make the process easier.
    • Cal/EPA’s Dairy Digesters website provides permit resources for dairy digesters, such as flow charts for permit processes.

    Air

    • State-specific Thresholds: The California Air Resources Board (CARB) oversees 35 districts. Each district has different requirements depending on whether or not the district meets the National Ambient Air Quality Standards (NAAQS) for criteria pollutants. For example, the San Joaquin Valley Air Pollution Control District is an ozone non-attainment area, which means anaerobic digesters must meet additional requirements under the district’s permit process (PDF) (1 p, 47K).
    • Combustion devices may require permits depending on the requirements of the specific air district. If organic feedstocks are added, the type of organic feedstocks may cause additional permit requirements.

    Solid Waste

    Water

    • The California State and Regional Water Boards manage and regulate water resource quality and waste discharges, including digester discharges. The State Water Resources Control Board map provides a list of the nine Regional Water Quality Control Boards.
    • The Central Valley Region has the majority of the state’s dairy farms. This region developed general permits for dairy manure anaerobic digesters and codigestion facilities, either at a single site or in a centralized location.
  • Idaho

    Air

    Solid Waste

    Water

  • Illinois

    Solid Waste

    • Manure-only Exemption: Anaerobic digesters processing only manure do not require solid waste permits.
    • Codigestion, Offsite Waste Acceptance: Illinois EPA considers anaerobic digesters as waste processing facilities if they process offsite feedstocks and requires permits unless they meet certain exemptions. Illinois State code 415 ILCS 5, Section 3.330(a)(19) lists these exemptions
  • Indiana

    Air

    • IDEM’s Air Quality Permit Guide website contains information on air permits and application forms.
    • State-specific Thresholds: New emission sources with combustion devices require air permits prior to construction and operation.

    Solid Waste

    • IDEM’s Office of Land Quality requires facilities with anaerobic digesters to have one of the following: 1) solid waste processing facility permit, 2) CFO/CAFO approval or 3) biomass registration.

    Water

    • Codigestion: Anaerobic digesters processing organic feedstocks in addition to manure may be required to perform additional screening of either the anaerobic digester influent or effluent.
  • Iowa

    Solid Waste

    • Manure-only Exemption: Anaerobic digesters processing only manure do not require solid waste permits.
    • Codigestion: Anaerobic digesters processing non-manure organic feedstocks may require solid waste permits. Iowa evaluates facilities on a case-by-case basis.

    Water

    • Codigestion: Codigestion of offsite organic feedstocks may trigger additional requirements in the AFO’s discharge permit and adjustments to the nutrient management plan. This does not apply to manure-only digesters.
  • Maine

    Solid Waste

    • Manure-only Exemption: Anaerobic digesters processing only manure and agricultural feedstocks do not require a DEP license.
    • Offsite Waste Acceptance: Anaerobic digesters processing offsite feedstocks, including only manure, require a DEP license.
    • Chapter 419 of Maine’s Waste Management Rules provides detailed rules on farm use of offsite feedstocks.
  • Massachusetts

    Consolidated or General Permit Process

    Solid Waste

  • Michigan

    Air

    • State-specific Thresholds: Michigan DEQ generally exempts manure-based anaerobic digesters from air permitting requirements. Anaerobic digesters may not be exempt if the onsite combustion device 1) produces more than one pound of sulfur dioxide an hour, or 2) has a heat input capacity of greater than 10 million Btu per hour.

    Solid Waste

    • Manure-only Exemption: Anaerobic digesters processing only manure do not require solid waste permits.
    • Codigestion: Michigan encourages facilities to work with the Michigan DEQ to determine what permits might be required.
      • Farms adding non-manure feedstock to anaerobic digesters may need authorization before composting solids or applying to the land.
      • MDEQ exempts several materials from permitting (PDF) (4 pp, 465K), including food processing residuals, syrup from ethanol production, grease trap wastes that do not contain septic tank sludge, and fish wastes. However, to be exempt, the anaerobic digester must not accept more than 20 percent of these other organics.

    Water

    • In general, anaerobic digesters accepting only manure are not required to obtain additional water discharge permits.
    • Codigestion: Anaerobic digesters including non-manure organic feedstocks may require permits or land application authorization. Michigan DEQ encourages each facility to contact the Water Resources Division to discuss requirements.
    • CAFO: Permitted CAFOs must include the anaerobic digester in their Nutrient Management Plan.
  • Minnesota

    Solid Waste

    • Manure-only Exemption: Anaerobic digesters processing only manure do not require solid waste permits.
    • Codigestion: MPCA determines the need for a solid waste permit on a case-by-case basis for anaerobic digesters that process manure and other organic feedstocks. Project developers should contact MPCA solid waste staff to determine the need for an individual permit.

    Water

    • Codigestion: Anaerobic digesters processing non-manure organic feedstocks require individual permits.
  • Nebraska
  • New York

    Solid Waste

    • New York regulations for Quality Services, Part 360-5 applies to composting facilities. Subpart 360-5.3 lists exemptions, including exemptions for anaerobic digester facilities.
      • Manure-only exemption: Anaerobic digesters that accept manure, bedding, crop residues and farm waste do not need Part 360 permits.
      • Codigestion:
        • Anaerobic digesters located on CAFOs having a Comprehensive Nutrient Management Plan may accept up to 50 percent non-manure feedstocks (by volume of their annual feedstock received) to qualify for an exemption from permit requirements.
        • Anaerobic digesters processing more than 50 percent non-manure feedstocks require permits.

    Water

  • Ohio

    The Ohio Environmental Protection Agency (Ohio EPA) oversees compliance with environmental laws. Use the Ohio EPA Permit Wizard to identify the permits, licenses and other requirements needed for anaerobic digesters.

    Air

    • The Ohio EPA issues air permits and provides general permits for anaerobic digestion systems. The Ohio EPA provides model general permits for the following:
      • Biomass digesters using a flare
      • Digesters with a gas-fired boiler
      • Digesters with a gas-fired, spark ignition internal combustion engine.

    Solid Waste

    • Codigestion:
      • The Ohio Department of Agriculture issues permits for, and oversees, anaerobic digesters that accept
        • Only manure, and  
        • Non-manure organic feedstocks less than 25 percent by volume.
      • The Ohio EPA permits facilities that accept more than 25 percent (by volume) non-manure feedstocks.
      • Facilities with anaerobic digesters must comply with their Nutrient Management Plan.

    Water

  • Oregon

    Air

    Solid Waste

    Water

    • Anaerobic digesters processing only manure at permitted CAFO facilities do not require additional permits. Digesters need to be incorporated into existing permits and Nutrient Management Plans.
    • Anaerobic digesters operating at unpermitted CAFO facilities may require water permits, depending on the facility.
    • Codigestion: Oregon DEQ reviews anaerobic digesters processing non-manure organic feedstocks. To date, Oregon DEQ has not required additional permits for anaerobic digesters at permitted CAFOs that accept non-manure organic feedstocks.
  • Pennsylvania

    Consolidated or General Permit Process

    • A General Permit (WMGM042) (PDF) (8 pp, 51K) authorizes anaerobic digestion of waste mixtures that include animal manure, grease trap waste, pre-consumer food, and wastewater from dairy farms. To obtain approval to operate under the general permit, facilities must obtain a “Determination of Applicability” from the appropriate regional office (see permit standard conditions for details).

    Solid Waste

    • Anaerobic digesters, including those that digest food processing feedstocks, do not require solid waste permits for land application.

    Water

    • Although not specific to farms with anaerobic digesters, farms producing or using manure require a Nutrient Management Plan. PA DEP does not require additional permits.
  • Texas

    Air

    • State-specific Thresholds: The Texas CEQ requires Permits by Rule (PBR) for facilities that produce some emissions but not enough to trigger federal permit requirements.

    Solid Waste

    Water

    • Texas CEQ determines permit requirements on a case-by-case basis depending on the location, how the anaerobic digester fits within the permitted activity at that location, and the type of materials digested.
  • Vermont

    Air

    • The Vermont Department of Environmental Conservation (DEC) administers air permits.
    • Vermont DEC generally does not require permits for anaerobic digesters as long as they meet the following requirements:
    • Vermont DEC typically does not require additional permits for anaerobic digesters using non-manure feedstocks but reviews additional feedstocks on a case-by-case basis.

    Solid Waste

    • The Vermont DEC administers solid waste permits.
    • Manure-only exemption: Anaerobic digesters processing only manure do not require permits.
    • Codigestion: Anaerobic digesters require permits if adding offsite food wastes that are more than one percent of the digester design capacity.

    Wastewater

    • The Vermont Agency of Agriculture administers permits for anaerobic digesters used for manure management.
    • Anaerobic digesters processing only manure do not require additional permits.
    • Codigestion: Anaerobic digesters that include food-processing residuals may require indirect discharge permits. The VT DEC Drinking Water and Groundwater Protection Division coordinates with the Agency of Agriculture for projects with land application on farms to determine: 1) additional storage needs for the non-manure feedstocks and 2) amount of nutrients allowed in the wastewater released by the farms. Indirect discharge permits (per 10 V.S.A. §1263), which are issued to those producing the food-processing residuals, include the name of the farms receiving the food-processing residuals.
  • Washington

    Air

    • Washington’s Department of Ecology (Ecology) regulates counties without an air pollution control agency. The Regulatory Handbook provides information for those counties that Ecology regulates, which includes Adams, Asotin, Chelan, Columbia, Douglas, Ferry, Franklin, Garfield, Grant, Kittitas, Klickitat, Lincoln, Okanogan, Pend Oreille, San Juan, Stevens, Walla Walla, and Whitman counties. Other counties have local clean air agencies that may have stricter requirements.
    • State-specific Thresholds: Ecology requires a Notice of Construction air quality permit for new or modified sources that produce over a certain amount of air pollution. See Table 110(5) in the New source review (NSR) for sources and portable sources (Washington Administrative Code (WAC) 173-400-110(5)) for the levels of various pollutants that trigger permits.
    • General Order Permits apply to new or modified dairy manure anaerobic digesters that meet certain conditions and operate in a county that Ecology regulates.

    Solid Waste

    Water (CAFO General Permit information)

    • Codigestion: CAFOs with anaerobic digesters do not require additional water quality permits. If the system digests non-manure organic feedstocks, the Nutrient Management Plan must reflect these wastes.
  • Wisconsin

    Solid Waste

    • Codigestion: CAFOs must get approval before adding non-manure feedstocks to anaerobic digesters. There may be additional permit requirements if the anaerobic digesters contain less than 90% manure. The state may also require permits depending on what is added, even if less than 10%.

Federal Regulatory Requirements

The federal government issues regulations. These regulations establish the minimum guidelines a state can use for permitting. More restrictive state regulations replace federal regulations.

Air

Onsite combustion devices used for energy generation may require federal permits if the devices trigger federal emissions thresholds and other federal regulatory permit requirements. Conversely, if air emissions from these devices are below federal thresholds they may be exempt from permit requirements. The following regulations establish the federal thresholds:

Solid Waste

  • Waste processing facilities must meet Resource Conservation and Recovery Act (RCRA) Subtitle D requirements (which cover non-hazardous solid wastes) and 40 CFR Part 258 (which covers landfills). See Managing Non-Hazardous Municipal and Solid Waste.
  • Federal laws do not require solid waste permits for the anaerobic digestion of manure at farms. However, the acceptance of other organics may designate farms with anaerobic digesters as waste processing facilities in some states.

Water

There are no national water-related permit requirements specifically triggered by use of anaerobic digesters.

Top of Page