Renewable Natural Gas from Agricultural-Based AD/Biogas Systems

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What is Renewable Natural Gas?

Renewable Natural Gas, often called RNG or biomethane, is a term used to describe biogasGas resulting from the decomposition of organic matter under anaerobic conditions. The principal constituents are methane and carbon dioxide. that has been upgraded for use in place of conventional natural gas. The biogas used to produce RNG comes from a variety of sources including livestock farms, municipal solid waste landfills, water resource recovery facilities (wastewater treatment plants), waste products from food and beverage production, and organic waste management operations. RNG can be used for thermal applications, electricity generation, bio-plastic feedstock or vehicle fuel.

To upgrade biogas to RNG, the methane content is increased by removing water vapor, carbon dioxide, hydrogen sulfide and other impurities. It can then be injected and transported via natural gas pipelines and used as a substitute for natural gas. RNG is essentially indistinguishable from natural gas but is derived from biological materials rather than from fossil fuel deposits.

RNG Basics

  • RNG can be produced from the degradation of manure and organic matter in an anaerobic digestion (AD) system. RNG is different than fossil-based natural gas because it comes from renewable sources.
  • Federal and state public policy initiatives have helped kickstart the RNG market by incentivizing renewable, carbon-negative energy. See information on the U.S. Renewable Fuel Standard Program and the California Low-Carbon Fuel Standard (LCFS) and Oregon LCFS programs.
  • The number of farm-based AD projects generating RNG is increasing; in California alone there are over 50 projects planned or under construction.

Why the Interest in RNG?

Use of RNG can provide benefits in terms of fuel security, economic revenues or savings, local air quality and greenhouse gas emission reductions. Read more about RNG benefits here: https://www.epa.gov/lmop/renewable-natural-gas#benefits.

Federal and state programs for renewable fuels have provided incentives for projects to convert biogas into RNG. Congress created the Renewable Fuels Standard (RFS) program in 2007 to expand the nation’s use of renewable fuels while reducing reliance on imported oil. The RFS provides a market-based monetary value for renewable fuels, including RNG.

Several states have created similar programs focused on the reduction of fossil fuel-based fuel. For example, California and Oregon have Low-Carbon Fuel Standard (LCFS) incentive programs. The state of Washington has proposed a program designed to reduce the carbon intensity of fuels and to provide additional value for biofuels, including RNG. The value of the LCFS credits can be monetized in California and Oregon if the fuel, regardless of origin, is conveyed (via pipeline or other means) and used as a transportation fuel in the state. Therefore, fuel can be generated in a non-LCFS state, conveyed, and later utilized in a LCFS state to obtain credits.

The federal RFS and state LCFS incentives are additive, meaning both incentives can be earned for a specific project.

Methane Mitigation Facts

  • Methane has a 12-year lifetime in the atmosphere and traps 28-36 times more heat than carbon dioxide over a 100 year time scale, resulting in a stronger influence on global warming.
  • Capturing methane and using it as an energy sources has a positive impact on the environment, as it avoids methane emissions and displaces conventional fossil fuels.

How Does RNG Become Monetized?

Because of market values for renewable fuels/low carbon fuels at the federal and state level, RNG has a greater value than conventional natural gas. If a party can demonstrate that RNG is used as transportation fuel and meets appropriate requirements at the federal or state level, a Renewable Identification Number (RIN) and/or LCFS credit are generated and can be sold.

There are several factors and steps involved in monetizing (selling and buying) RINs. As shown in the table below, RNG is currently characterized under two different RIN categories:  cellulosic (or D3 RINs) or advanced biofuel (or D5 RINS). Not all biogas from AD projects qualify as D3 RINs.

Transportation Fuel Feedstock or Source RIN "D" Code
Renewable Natural Gas (Compressed or Liquefied) Biogas from landfills, municipal wastewater treatment facility digesters, agricultural digesters, and separated MSW digesters; and biogas from the cellulosic components of biomass processed in other waste digesters 3
Biogas from waste digesters (e.g., organic fraction of municipal solid waste or food waste) 5

To learn more about the RFS and how to register to meet the requirements, visit the EPA Office of Transportation and Air Quality (OTAQ) RFS Program website. For additional details on the RFS program, refer to the Code of Federal Regulations.

Similarly, an RNG project must meet state-specific carbon intensity standards in order to qualify for state LCFS credits. The value of the LCFS credits for a project depends on several factors as determined by state guidance. To learn more about the California LCFS, see California’s LCFS Program Guidance.

Agricultural RNG Projects in the United States

As of June 2024, there are 191 manure-based AD systems producing RNG (includes pipeline injection and compressed natural gas (CNG) projects) in the United States with 69 RNG projects under construction (source: EPA AgSTAR Livestock Anaerobic Digester Database).

Visit the EPA RNG web page for a map of all landfill and anaerobic digester-based RNG projects in the United States.

Agricultural RNG Activities in California

The state of California has provided many incentives for creating and using RNG. In addition to the LCFS, legislation adopted in 2017 requires the state to reduce methane emissions by 40 percent by 2030. The California Department of Food and Agriculture (CDFA) created the Dairy Digester Research and Development Program (DDRDP) which awards competitive grants to implement AD dairy projects that result in methane emission reductions and minimize or mitigate adverse environmental impacts. From 2015-2018 the DDRDP allocated $11.1M (2015), $35.3M (2017), and $72.4M (2018) to AD dairy projects. This program has been instrumental in transforming the agricultural-based AD industry. Most of these projects are focused on the generation of RNG to be utilized in California and are sourced from clusters of multiple farms.

In December 2018, three state agencies (California Public Utilities Commission, California Air Resources Board, and CDFA) announced that California would fund six pilot projects (PDF)(2 pp, 307K) in the San Joaquin and Sacramento Valleys to demonstrate generation of RNG from dairy digesters as part of the state’s overall strategy to reduce emissions. A total of 45 dairies are participating in the pilot projects, which will significantly reduce methane-related greenhouse gas emissions from dairy manure by putting it to beneficial use as RNG. RNG from cluster projects will be consolidated into one RNG plant prior to injection into the pipeline. The six projects will receive approximately $319 million in infrastructure investments and operation expenses over the next 20 years.

Industry Innovations in RNG

  • Smithfield Foods, Inc. The world’s largest pork processor and hog producer, Smithfield Foods, Inc. (Smithfield), announced in 2016 that it had set a goal of reducing its corporate carbon-equivalent emissions by 25 percent by 2025. The goal includes incorporating renewable energy and developing AD projects to capture methane emitted from hog farms.
  • Dominion Energy. In 2018, Dominion Energy and Smithfield created a new joint-venture named Align RNG to unify and accelerate Smithfield’s carbon reduction and renewable energy efforts. Projects will be implemented on more than 90 hog farms located in Virginia, North Carolina, and Utah.
  • Calgren Dairy. Biogas produced at Calgren’s dairy digester in Pixley, California is being injected as RNG into SoCalGas pipelines. Read more here: https://ngtnews.com/rng-now-flowing-into-socalgas-pipelines-from-calgren-dairy-digester
  • Roeslein Alternative Energy. In April 2019, Smithfield signed a joint venture with Roeslein Alternative Energy called Monarch Bioenergy; this partnership is focused on conversion of manure via AD into biogas and RNG from Smithfield’s Missouri farms. Smithfield and Roeslein Alternative Energy (RAE) also operate biogas to RNG facilities at Ruckman, Locust Ridge, and Valley View farms in Missouri.

More Information on RNG

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Last updated on September 30, 2024