So-called ‘Biogas’ from Intensive Animal Farming Threatens a Clean Energy Future

So-called ‘biogas,’ an energy source generated from the anaerobic decomposition of organic waste, is growing as a source of energy in the US. Unfortunately, biogas is increasingly linked to the most environmentally damaging forms of animal agriculture.

Most animals raised for food in the US are confined in intensive facilities such as concentrated feeding operations (CAFOs) that generate vast amounts of animal waste, which is collected as dry poultry litter or stored in liquid form in massive hog and cow manure lagoons. Storing and processing so much manure poses an overwhelming problem for industrial animal agriculture operations, which often fail to adequately manage it, allowing contaminants to leach into waterways, groundwater, air, and soil.[1]

Current so-called ‘biogas’ systems use this farmed animal waste as one of the raw materials for natural gas production. Biogas from industrial animal farming uses the language of the natural gas industry to cast itself as a source of renewable clean energy, despite its myriad human and environmental harms. Biogas from industrial animal farms is more appropriately called factory farm gas to distinguish its production and harms from other, more benign forms of biogas production.

In 2021, the US biogas industry had 2,200 operational projects covering all 50 states, including about 300 located on industrial farms. Revenues of the eight largest biogas companies (which build and sell the systems) grew by 300% that year. The American Biogas Council sees the potential for at least 15,000 additional systems, including 8,574 new systems on intensive dairy, poultry, and swine farms.

“Renewable” is not the whole story

The world “renewable” often describes energy sources like wind, solar, and hydropower that generate electricity from natural phenomena without the environmental consequences of burning finite supplies of fossil fuels. Although any fuel source that can be replenished can be considered renewable, not all “renewable” fuel sources are low-emission or environmentally friendly. For example, while not of finite fossil origin, the “renewable natural gas” (RNG) produced from refined industrial animal manure has a significant environmental footprint and contributes harmful greenhouse gases that drive climate change. Moreover, factory farm biogas used for power generation is typically mixed with fracked natural gas of fossil origin. Classifying factory farm biogas as ‘renewable’ ignores the environmental harm caused by industrial animal farming and the climate consequences of continued reliance on carbon-intensive natural gas.

The agriculture industry promotes factory farm gas as a sustainable alternative to fossil fuels that can help solve the problems of disposing of agricultural waste while generating clean energy. The federal government supports these claims and encourages the production of factory farm gas as a source of on-farm energy and also for conversion to vehicle fuel for the consumer energy grid.

In reality, factory farm gas operations have devastating negative consequences that make biogas production from animal agriculture a false solution. They pollute and degrade air, water, and soil, perpetuate environmental injustice and cruelty to farmed animals, and further entrench damaging forms of industrial agriculture and their many harms within the US food system. Furthermore, by providing natural gas to the existing fossil fuel energy system, factory farm gas operations increase dependence on fossil fuels. Factory farm biogas projects rely on revenue from carbon trading schemes to make financial sense, meaning that factory farm gas is not economically viable as a standalone energy source. Before reaching the fuel market, factory farm gas is most frequently mixed with environmentally destructive fracked natural gas. Its distribution also depends on existing fossil fuel pipeline infrastructure, the same pipelines that have garnered international opposition for serious human and environmental harms. When the human, animal, and environmental damage associated with intensive animal farming are also taken into account, factory farm gas is revealed as a fuel source that is incompatible with a sustainable energy future.

REquest OUR Factory Farm Gas Roadmap

This Roadmap is a collaborative product written by the members of the Factory Farm Gas working group with facilitation by Stray Dog Institute. The Roadmap examines the many threats posed by future factory farm biogas expansion and opportunities for factory farm gas opposition to create positive systemic change.


Biogas as a category includes both factory farm gas, which is harmful in every aspect of its production and application, and biogas produced from other organic waste sources, which may be less polluting and can have some beneficial applications.

In both forms, biogas is an energy-rich gas that is produced as a byproduct when anaerobic microorganisms break down animal manure or other wastes. Biogas can be burned for fuel, used as cooking gas, turned into electricity via combustion engines or gas turbines, or refined and used as natural gas vehicle fuel.


Farms that generate and use factory farm gas install tanks called digesters. Anaerobic bacteria in the digester decompose the organic materials found in animal manure, releasing methane and carbon dioxide. As the gasses accumulate in the digester, water vapor is removed and disposed of through sloping pipes and condensate traps. Hydrogen sulfide, a highly toxic gas, must be removed using chemical or biological scrubbers. The resulting factory farm gas is then used as a fuel source.

Digesters can be designed to process only one type of input or multiple inputs. Many types of waste require pre-processing before entering the digester. The materials in the digester must have a pH of around 7, and the ratio of nitrogen and carbon must be balanced to maintain production efficiency: too much nitrogen can kill bacteria, and too little will halt carbon digestion. Often the process must be carefully balanced to yield sufficient factory farm gas; in a study examining factory farm gas produced from a mixture of horse and cow waste, increasing cow manure levels resulted in significant decreases of biogas yields.[3] High levels of heavy metals, a common supplement in pig feed in the US and other parts of the world,[4] inhibit factory farm gas production and increase environmental pollution risks.[5]

Since 2014, the US government has been offering subsidies, loans, and education to encourage agribusinesses to generate factory farm gas despite the environmental and animal welfare concerns it generates. The 2018 Farm Bill Energy Title authorized $2 million to educate farmers on installing biogas systems, and the Rural Energy for America Program provides grants to promote factory farm gas production. AgStar is a program jointly headed by the Environmental Protection Agency (EPA), the US Department of Agriculture (USDA), and the Department of Energy (DOE) to promote anaerobic digester use in animal agriculture operations.


Despite its reputation as a renewable source of energy, factory farm biogas is not a clean or emission-free fuel source. Biogas contains methane and carbon dioxide, two potent greenhouse gases. Biogas contains 50–70% methane, 30–40% carbon dioxide, and small amounts of hydrogen sulfide, particulates, water vapor, and other trace elements. Digesters can also produce toxic gasses including carbon monoxide, sulfur dioxide, and nitrogen oxides as byproducts.[2]

Despite its toxicity, the greatest harms to humans from so-called biogas come from the industrial farms that generate it.


Both farmed animal waste and other significant sources of organic waste may be used to produce biogas, with different environmental impacts depending on the sources of organic wastes.


CAFOs in the US collectively produce over 8 billion pounds of animal manure per day and over 3 trillion tons per year.[6] Given the large environmental footprint of disposing of this waste, USDA has targeted animal manure as a primary source of biogas in its Biogas Opportunities Roadmap. USDA developed this roadmap, along with EPA and DOE, in response to the 2014 federal Strategy to Reduce Methane Emissions, part of the government’s Climate Action Plan.[7] State efforts, like California’s Low Carbon Fuel Standard, have likewise targeted waste from intensive animal farming as an environmentally friendly fuel source. Unfortunately, converting animal manure into biogas carries devastating costs for animals and the environment, making so-called ‘biogas’ a false solution to environmental impacts from industrial animal farming.


Crop residues are the unused parts of plants left over from harvesting processes (stalks, straw, and plant trimmings). Due to high crop yields from industrial monocropping, particularly from crops used to feed farmed animals, crop residues have been increasing; in 2017, DOE estimated that 104 million tons were available for sale. Although crop residues are proposed as a fuel source, their high lignan content makes them difficult to break down in digesters. They need to be combined with other inputs, like manure.[8]


Up to 40% of food is wasted in the US, equaling around 133 billion pounds of food annually. Much of this ends up in landfills. In 2018 the US had 66 standalone biogas systems digesting food waste. EPA and USDA prioritize source reduction as the best way to reduce food waste and have set a goal of reducing food waste at its sources by 50% by 2030.


Landfills are the third-largest producer of human-related methane emissions in the US. Instead of allowing the methane to escape into the atmosphere, 652 landfills currently use onsite digesters to turn it into a biological energy source, collectively generating about 17 billion kilowatt-hours of electricity per year.


Wastewater treatment plants can also be sources of biogas, and many already have digesters installed to treat sewage. But, because water treatment plants typically lack the appropriate equipment to repurpose biogas, most of it is disposed of by burning in a process called flaring. In 2017 the US had 1,269 wastewater treatment plants using digesters, but only 860 were equipped to repurpose the biogas they created.


So-called ‘biogas’ from intensive animal farms is harmful to humans in several ways. The factory farm gas generated by on-farm digesters is flammable, toxic, and potentially explosive.[9] Hydrogen sulfide, one of the gases present in biogas before it is processed, can cause ocular and respiratory irritation, nausea, headaches, pulmonary edema, collapse, unconsciousness, and death. When burned, it creates the toxic gas sulfur dioxide.

However, despite its toxicity, the greatest harms to humans from so-called biogas come from the industrial farms that generate it. Hog and cattle waste used to produce factory farm gas is stored in vast manure pits, or lagoons, that create significant hazards for farmworkers and the surrounding community. In the state of North Carolina alone, satellite imagery analysis has revealed over 4,000 manure lagoons covering 7,000 acres. More than 100 of these lagoons were within half a mile of a public well, presenting dangers for water quality. A 2018 study of North Carolina residents who lived in proximity to manure lagoons found elevated rates of infant mortality, anemia, kidney disease, septicemia, and tuberculosis. Manure lagoons pollute nearby water sources, release noxious gases into the air, and create strong unhealthy odors that reduce quality of life for nearby residents.

Manure lagoons also pose fatal hazards to farmworkers and are just one factor in the high occupational fatality rates in agriculture. The pits are often uncovered, and workers have fallen into them and drowned or choked in the thick liquid. Manure lagoons also produce dangerous gases, including methane, hydrogen sulfide, carbon dioxide, and ammonia, which can cause disorientation, difficulty breathing, rapid fatigue, impaired judgment, and sometimes death. Workers have asphyxiated in or near manure pits, and other workers have died trying to rescue them. More than half of accidents involving manure pits result in death, and over one-third of fatalities were of children five years old or younger.[10]

Through the existing agricultural subsidy system, US taxpayers pay unfairly for agribusinesses’ unethical practices around manure disposal and biogas production. Through biogas energy schemes that overlook the pollution and cruelty inherent in confined animal farming, large industrial animal farms can also receive carbon-offset credits for installing digesters, even if they are not in compliance with environmental or health regulations.[11]


Factory farm gas is not an environmentally sustainable answer to contemporary energy needs, nor is it a clean energy source. Like other sources of natural gas, the manure that creates factory farm gas generates greenhouse gas emissions that drive climate change. Furthermore, so-called ‘biogas’ production on industrial animal farms is devastating to the surrounding environment.

In recent years manure lagoons have overflowed during floods, putting soil, groundwater, and wildlife at risk. Runoff and leakage from manure lagoons have killed wildlife through poisoning and drowning, caused massive fish fatalities, and generated algal blooms that damage aquatic environments. Animal waste also produces around 70% of US ammonia emissions, a toxic gas that affects plant biodiversity by damaging leaves, causing soil acidification, and heightening plant susceptibility to frost, drought, and disease. Methane emissions from manure in industrial dairy and pig farms have increased by 134% and 29%, respectively, over the past 27 years.[12]

Biogas production on industrial animal farms also harms the environment by entrenching—and even promoting—large-scale animal agriculture. Finding ways to turn animal waste into a marketable product makes large industrial animal farms more profitable, and the availability of factory farm gas encourages power grids to rely on energy produced from industrial animal manure. Furthermore, factory farm gas production systems can incentivize industrial animal operations to increase their herd sizes, since the financial efficiency of biogas digesters depends on economies of scale.

While digesters are often promoted to farmers as a clean way to convert excess animal waste into profitable energy for the grid, in reality, factory farm gas increases reliance not only on industrial agriculture with all of its hazards but also on fossil-fuel infrastructure. Transporting factory farm gas requires building and using gas pipelines that damage the environment and local communities, trucks that depend on fossil fuels, and connections to fossil-fuel dependent local power grids. Methane leakage from pipelines negates any decrease in emissions that may be derived from biogas, regardless of source.[13] Furthermore, combining factory farm gas produced under the name ‘biogas’ with fracked natural gas allows fossil fuel producers to disguise their reliance on the environmentally devastating process of fracking.


So-called ‘biogas’ from intensive animal agriculture perpetuates environmental injustice by expanding intensive agriculture in rural communities. CAFOs are disproportionately located near low-income and/or BIPOC[i] communities.[14] Because industrial farms are almost universally opposed by local populations, agribusinesses target areas with little political clout where farms can operate without resistance.

Industrial animal agriculture impacts the health, mental wellbeing, and economic viability of rural areas. Animal agriculture waste exposes farming communities to antibiotics, hormones, disease-causing pathogens, and heavy metals by contaminating groundwater and drinking sources. Heavy antibiotic use in farmed animals leads to antibiotic-resistant pathogens, with profound implications for human health and disease treatment.[15]

Factory farm gas can also include carcinogens, including arsenic and vinyl chloride, that can poison the air of local communities.[16] It can spread noxious air pollutants that may impair brain development in children[17] and may lead to reduced fertility, increased miscarriages, reproductive system cancer, and suppressed immune systems in women.[18]

Communities living near CAFOs have reported higher rates of sleep and mood disorders, anxiety, depression, and appetite loss. Pollutants and odors place additional burdens on low-income, predominantly BIPOC, rural communities whose members already face inequities in healthcare access and other quality-of-life resources. Industrial agriculture operations also drive down local property values, resulting in community loss of capital. Installing so-called ‘biogas’ schemes on intensive animal farms requires building additional pipeline infrastructure, further burdening communities already facing deleterious health impacts from industrial animal agriculture.


For the reasons mentioned above, factory farm gas is not a sustainable solution to renewable energy needs. Instead, it further entrenches harmful industrial animal-farming practices, keeps the US energy grid dependent on fossil fuels, accelerates climate change, degrades the environment, and impairs the health and wellbeing of both humans and animals.

Moreover, it fails to fulfill its core promise of sustainably redressing the massive amounts of manure generated by animal agriculture, instead proposing a stopgap measure that only perpetuates the root problems. In addition, factory farm gas causes the following harms:

  • Supports an inequitable food system in which resources go to feeding farmed animals rather than people
  • Allows agribusinesses to claim they are helping the environment while continuing to pursue destructive practices
  • Increases dependence on polluting fossil fuel infrastructure such as pipelines and truck transport
  • Exploits low-income, BIPOC communities and impacts their physical, mental, and economic health, perpetuating a system of environmental injustice


Factory farm gas fails to provide any real solutions to society’s pressing needs for clean energy and sustainable waste management. While it may appear to be an innovative solution to industrial agriculture waste, in reality, factory farm biogas perpetuates the harms of industrial animal agriculture and the fossil fuel industry. Sustainable farming that does not depend on raising animals presents a far better prospect for decoupling alternative energy sources from both industrial agriculture and fossil fuels.

[i] Stray Dog Institute uses the term BIPOC to recognize the lived histories of oppression and resistance experienced by Black, Indigenous, and People of Color. This term is not universally embraced, particularly because it can erase the experiences of individual groups by lumping them together. Additionally, the language of this term reflects the specific historical social context of the United States and may not accurately reflect current or past racial and ethnic descriptions elsewhere. We recognize these drawbacks and use the term BIPOC only when a statement is truly applicable to Black, Indigenous, Latinx, Middle Eastern, North African, East Asian, South Asian, Southeast Asian, and Pacific Islander communities in the US. When an experience or condition is applicable only to a specific group, we use specific rather than general language.

[1] Jorge Sigler et al., “Distribution of Animals Used for Agriculture and Manure Generated: Ratio of Manure to Land Application” (Humane Party, August 2017),

[2] Valerio Paolini et al., “Environmental Impact of Biogas: A Short Review of Current Knowledge,” Journal of Environmental Science and Health Part A, 53, no. 10 (April 2018): 899–906,

[3] Meshach Ileanwa Alfa et al., “Evaluation of Biogas Yield and Kinetics from the Anaerobic Co-Digestion of Cow Dung and Horse Dung: A Strategy for Sustainable Management of Livestock Manure,” Energy, Ecology and Environment 6 (2021): 425–434,

[4] Julius J. Medardus et al., “In-Feed Use of Heavy Metal Micronutrients in US Swine Production Systems and Its Role in Persistence of Multidrug-Resistant Salmonellae,” Applied and Environmental Microbiology 80, no. 7 (2014): 2317–2325,

[5] Shuyu Xiang et al., “Pretreated Rice Straw Improves the Biogas Production and Heavy Metals Passivation of Pig Manure Containing Copper and Zinc,” Journal of Cleaner Production 315 (September 2021),

[6] See endnote 1.

[7] USDA, EPA, and DOE, “Biogas Opportunities Roadmap” (Washington, DC: USDA, August 2014),

[8] Sagarika Mothe and Venkateswara Rao Polisetty, “Review on Anaerobic Digestion of Rice Straw for Biogas Production,” Environmental Science and Pollution Research 28 (2021): 24455–24469,

[9] Phoebe Gittelson et al., “The False Promises of Biogas: Why Biogas Is an Environmental Justice Issue,” Environmental Justice (May 2021),

[10] Mahmoud M. Nour et al., “Farm-Related Injuries and Fatalities Involving Children, Youth, and Young Workers During Manure Storage, Handling, and Transport,” Journal of Agromedicine 26, no. 3 (July 2021): 323–333,

[11] See endnote 9.

[12] Patricia M. Gilbert, “From Hogs to HABs: Impact of Industrial Farming in the US on Nitrogen and Phosphorus and Greenhouse Gas Pollution,” Biogeochemistry (August 2020),

[13] See endnote 9.

[14] Ji-Young Song et al., “Distribution of Environmental Justice Metrics for Exposure to CAFOs in North Carolina, USA,” Environmental Research 195 (April 2021),

[15] Christy Manyi-Loh et al., “Antibiotic Use in Agriculture and Its Consequential Resistance in Environmental Sources: Potential Public Health Implications,” Molecules 23, no. 4 (April 2018),

[16] See endnote 9.

[17] Sam Brockmeyer and Amedeo D’Angiulli, “How Air Pollution Alters Brain Development: The Role of Neuroinflammation,” Translational Neuroscience 7, no. 1 (March 2016): 24–30,

[18] Mariana Matera Veras et al., “Impacts of Air Pollution on Reproductive Health,” in Air Pollution and Health Effects, S. Nadadur and J. Hollingsworth, eds. (Singapore: Springer, 2015), 25–50,

About the author

Stray Dog Institute

To cultivate dignity, justice, and sustainability in the food system, Stray Dog Institute provides nonprofit allies with funding, strategic research, and opportunities for collaboration. Together, we hope to build a more compassionate world for people, animals, and the environment.

About the Author

To cultivate dignity, justice, and sustainability in the food system, Stray Dog Institute provides nonprofit allies with funding, strategic research, and opportunities for collaboration. Together, we hope to build a more compassionate world for people, animals, and the environment.

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