The Regulatory Landscape of Livestock Anaerobic Digesters and Renewable Natural Gas (RNG) Article Now Published In the Journal of Animal and Environmental Law
The Regulatory Landscape of Livestock Anaerobic Digesters and Renewable Natural Gas (RNG) Article Now Published In the Journal of Animal and Environmental Law
Authors: Ekrem Korkut, Michael D. Helbing, Lara B. Fowler, Lisa A. Schulte, J. Gordon Arbuckle, Forrest Stagner, and Frank Montabon
Introduction
Anaerobic digestion is a critical tool to address multiple challenges associated with livestock manure. According to the U.S. Greenhouse Gas Inventory Report, in 2021, the greenhouse gas (GHG) emissions from the agriculture sector were 598.1 MMT CO2Eq. or 9.4% of total U.S. GHG emissions.1 Methane (CH4) emissions from agriculture are of particular concern because the sector is a major source of this GHG, which is 28–34 times more potent than carbon dioxide (CO2) at trapping heat over a 100-year period. Livestock production contributed 35.9% of U.S. 2021 anthropogenic CH4
emissions, while management of associated manure represented 9.1% of total U.S. anthropogenic CH4 emissions and 11.0% of all GHG emissions from U.S. agriculture.
In addition to GHG emissions caused by manure management, poor handling of manure can degrade local water resources, create nuisance odors, and
be a source of harmful ammonia (NH3) emissions and particulate matter (PM). Anaerobic digestion (AD) of livestock manure can be used to manage these problems while also producing biogas and renewable natural gas (RNG, also known as biomethane) as an additional source of energy and revenue. While anaerobic digestion is an important tool, it is also not a panacea.
At this point in the United States, the installation of anaerobic digesters—also known as biodigesters— is widely incentivized by federal and state
programs. The federal Renewable Fuel Standard (RFS) program establishes the federal regulatory framework. Under the RFS, RNG produced from agricultural biodigesters can be classified with “D3 RINs” or Renewable Identification Numbers" this, in turn, provides funding opportunities (see Section III.A for an in-depth discussion of the RFS and D3 RINs). Biogas can also be used as a biointermediate to produce other renewable fuels, another potential source of income for farmers under the RFS program. Similarly, low-carbon fuel standard programs in California, Oregon, and Washington offer credit for renewable natural gas produced from agricultural biodigesters. Finally, state Renewable Portfolio Standard programs offer credit for electricity produced from eligible renewable energy resources, including anaerobic digesters.
There are numerous federal and state funding opportunities meant to foster the installation of livestock anaerobic digesters for manure management, with funding for these programs increasing over time. For example, the federal Natural Resource Conservation Service (NRCS) provided funding assistance to 49 anaerobic digesters between 2003 and 2017.5 More recently, the 2022 Inflation Reduction Act scaled up potential funding by allocating approximately $20 billion for the NRCS conservation programs.
This review paper examines how livestock-based anaerobic digesters and the resulting biogas and RNG are regulated and incentivized under these programs. Section II summarizes how anaerobic digestion (AD) and digesters work, with a focus on digesters that predominantly process livestock manure. Section III reviews federal programs, grants, and tax credits for installing livestock anaerobic digesters, while Section IV examines state incentives. Finally, Section V concludes that while livestock AD is not a silver bullet to address concerns associated with larger-scale livestock production, it provides many environmental benefits, including a reduction in GHG emissions, prevention of nuisance odors, improved water quality, and better soil health and quality. Current federal and state programs discussed in the paper offer various financial incentives for livestock AD projects. This review also examines connections between these different programs and includes a detailed appendix summarizing federal program requirements.
This review paper is funded by C-CHANGE (the Consortium for Cultivating Human and Naturally reGenerative Enterprises), a multi-institutional
consortium working to develop new ways for farmers to produce RNG from AD of perennial and winter biomass crops and animal manure.6 While this paper focuses on livestock anaerobic digesters, there is also discussion of the regulatory framework for including various waste products and/or biomass.