In a groundbreaking effort to reduce agriculture’s significant contribution to climate change, the Inflation Reduction Act (IRA) supports agricultural practices that reduce the sector’s greenhouse gas emissions. Given that our food system causes about a third of climate change, it is imperative that the IRA’s support goes to practices that provide real climate benefits. Anaerobic digesters, which capture some of the methane from manure storage in industrial animal factories to produce so-called biogas, are not among these practices.

Earlier this month, Earthjustice and 51 other organizations told the Treasury Department that they did just that. The department administers the IRA’s Clean Electricity Tax Credits, which apply to power generation facilities that have a greenhouse gas emission rate of zero or less, meaning the department has determined they emit no greenhouse gases at all. For facilities that use biogas from animal manure, the agency must evaluate their emissions, including all emissions and reductions associated with their fuel source, to ensure their overall greenhouse gas emission rate is zero or less. As our comments explain, facilities that use biogas from animal manure cannot meet this standard.

To understand biogas and its enormous greenhouse gas emissions, one must understand today’s meat and dairy production. Most of our meat and dairy comes from huge, industrial animal factories, commonly referred to as concentrated animal feedlots, or CAFOs. These factories often keep many thousands of animals in crowded buildings. These animals generate a lot of waste. According to the Centers for Disease Control and Prevention, livestock in the United States generate up to 20 times more manure than the amount of waste produced by the human population. Dairy and hog farms typically move the manure with water and store it in liquid form in huge pits and dispose of it by spreading it on fields. As the manure decomposes, it releases methane and nitrous oxide, two climate pollutants. Methane is over 80 times more potent than carbon dioxide on a 20-year timescale, and nitrous oxide is nearly 300 times more potent on a 100-year timescale.

Anaerobic digesters at factory farms typically consist of plastic covers over the pits that capture some of the methane and then direct it either to a burner to generate electricity on-site or, after the gas is cleaned, to a pipeline to burn elsewhere. (They are usually much more rudimentary than digesters at sewage treatment plants, which are usually steel tanks.)

Chloe Waterman and Molly Armus, Biogas or nonsense? The deceptive promise of manure biogas as a methane solution (2024).

Digesters are touted as an effective method of reducing methane emissions from manure and as a source of “clean” energy because they use organic waste instead of fossil fuels. But what happens in the waste pit is not the whole story, and biogas is far from clean. Congress wisely directed the Treasury Department to look beyond the waste pit and consider greenhouse gas emissions from the entire life cycle of biogas production. This makes it clear that biogas production generates enormous greenhouse gas emissions from the following sources:

• Animal feed production. Producing grain for the animals confined in industrial factory farms consumes over 127 million acres of land in the United States. Converting native forests and grasslands to cropland releases stored carbon from the soil and original native vegetation and, when used for feed production, increases demand for land for food elsewhere. This opportunity cost of carbon is well known in science (see Opportunity costs increase the carbon footprint advantage of grain-fed beef, The CO2 opportunity costs of agricultural production of animal foodsAnd Consideration of the CO2 impacts of land use in life cycle assessments – method and example for animal products), significantly increases the climate impact of feed production. And the application of nitrogen fertilizer to crops releases large amounts of nitrous oxide, in addition to the significant emissions generated during the production of the fertilizer and other agrochemicals.
• Enteric fermentation. Unlike humans, cows and other ruminants produce huge amounts of methane when they digest food, and every breath and burp releases this methane. Nationwide, cows burp almost as much methane as the entire oil and gas industry.
• Leaks and disruptions in the infrastructure for transporting digesters and biogas. On average, digesters lose 3 to 5 percent of the methane they originally absorbed. And during repairs, maintenance, breakdowns, or other performance degradations, digesters can release 13 to 25 percent of the methane they originally absorbed. In addition, there are also leaks in the infrastructure used to transport biogas, which releases even more methane.
• Combustion of biogas to generate electricity. Burning biogas to generate electricity produces carbon dioxide (not to mention other air pollution).
• Storage and disposal of fermentation residues. The sludge that remains in the pits after methane extraction, called digestate, emits both methane and nitrous oxide when stored in pits and spread on fields. In fact, digestate emits more nitrous oxide than non-digested manure.

Digesters ignore the majority of the greenhouse gas emissions described above. The following figures, showing the average life-cycle greenhouse gas emissions from producing 1 kilogram (kg) of milk and 1 kg of pork, show that emissions from manure account for less than a quarter of the total emissions. Consequently, even if digesters could reduce all emissions from manure, they cannot compensate for the significant life-cycle emissions from biogas.

Average life cycle greenhouse gas emissions from dairy production in the United States.

Average life cycle GHG emissions for pork production in the United States.

The reduction in greenhouse gas emissions from digesters seems even less convincing when compared to other options for manure management. Digesters are only suitable for farms that store manure in open pits, which generate the most methane. Other processes – such as solid-liquid separation, aeration, acidification, reduced storage time, composting, optimising storage temperature and dry manure management – generate much less methane in the first place.

Not only does promoting biogas plants not help reduce greenhouse gas emissions from factory farms, it also creates perverse incentives. First of all, promoting the purchase of biogas from factory farms for electricity producers would create incentives for them to continue producing methane instead of reducing or eliminating it. In fact, this would reward them for choosing the most polluting system and continuing to use it. Some dairies in California that already subsidize biogas production profit more from methane production than from milk. In addition, recent evidence suggests that subsidizing biogas production incentivizes operators to increase their herds so they can generate more manure methane, causing even more pollution.

Promoting biogas has many other unacceptable consequences, too. Funding biogas favors larger, more polluting factory farms over smaller operations at a time when industrial animal production is already decimating small farms. With programs to fund climate-friendly practices already heavily oversubscribed, funding digesters—which can cost over a million dollars each—diverts limited public money from practices that provide real climate benefits. And installing digesters on factory farms exacerbates the environmental injustice they cause. Ample evidence shows that factory farms disproportionately harm communities of color and low-income communities across the country. Digesters, which also create air and water pollution, will only make this environmental injustice worse.

We hope the Treasury Department does not follow the example of other agencies that have mistakenly decided to use taxpayer money to subsidize biogas. For example, Earthjustice and other organizations have called on the Natural Resources Conservation Service not to include digesters on its annual list of agricultural practices eligible for “climate-friendly” funding. And at the state level, Earthjustice and others have called on the California Air Resources Board to stop investing in biogas through California’s Low Carbon Fuel Standard.

These and other programs can play an important role in addressing the climate crisis, but only if they support practices that actually reduce or eliminate greenhouse gas emissions and do not lead to additional pollution and injustice. Anaerobic digesters in industrial animal factories are a false climate solution that fails to meet these needs.