Science Energy What Is Biogas? Is It Sustainable? Discover the benefits and consequences of this renewable fuel. By David M. Kuchta David M. Kuchta Writer Wesleyan University, University of California, Berkeley David Kuchta, Ph.D. has 10 years of experience in gardening and has read widely in environmental history and the energy transition. An environmental activist since the 1970s, he is also a historian, author, gardener, and educator. Learn about our editorial process Published November 17, 2022 Share Twitter Pinterest Email Ralf Geithe / Getty Images Energy Renewable Energy Fossil Fuels In This Article Expand How Is Biogas Made? Environmental Benefits Consequences Is Biogas Carbon Neutral? Frequently Asked Questions Biogas is fuel gas made from biomass, either by decomposition or chemical processes. Biogas is 50% to 75% methane, while the remaining percentage is carbon dioxide and traces of other compounds. When it is reduced to nearly pure methane, biomethane can replace fossil fuel-based "natural gas" for electricity generation, transportation, heating, and home cooking. In the United States, nearly all biogas is produced for use in electricity generation. How Is Biogas Made? VectorMine / Getty Images Natural organic matter such as crop residues, animal manure, as well as forestry and wood processing waste, are broken down in biodigesters, which use anaerobic (oxygen-free) digestion to produce biogas. Biogas can also come from recovering methane from landfills and from wastewater treatment plant sludge. What Is Anaerobic Digestion? Anaerobic digestion uses microorganisms to break down biological material without oxygen. It is a multi-step process: Bacteria turn organic material into soluble derivatives, which are broken down by other bacteria into simple sugars, amino acids, and fatty acids. Then, they are converted further into acetic acid, ammonia, hydrogen, carbon dioxide, and other compounds, then finally into methane, carbon dioxide, and other trace compounds. Most biogas in the United States comes from municipal solid waste (landfills), while in Europe it comes from crop waste and animal manure, and in China primarily from manure. Environmental Benefits of Biogas Biogas can have environmental benefits, some more obvious than others. For example, unlike wind and solar energy, biogas is able to be used on demand when other renewable resources are unavailable. Developing renewable biofuels as a backup energy supply allows for the development of carbon-free wind and solar energy while eliminating, or at least reducing, the need for non-renewable fossil fuel energy. Reducing Landfill Emissions Landfills contribute up to 20% of anthropogenic methane emissions and, in the United States, are the third leading source of methane emissions. Capturing landfill gas and converting it to biogas is part of many countries' efforts to reduce their greenhouse gas (GHG) emissions. But transforming those sources of landfill gas into biogas before they reach the landfill is a more efficient use of resources and reduces other pollution problems as well. For example, turning wastewater sludge into biogas takes less energy than converting it into compost. Converting animal manure and crop wastes to biogas prevents runoff of these potential pollutants into waterways. Burning biogas from pre-treated leaves also produces fewer GHG emissions than composting them. The trade-off is a decrease in the availability of an important organic fertilizer. Sugarcane waste being transported to a biogas facility. Dinodia Photo / Getty Images Roughly 30% to 40% of food is wasted and ends up in landfills, making food waste the single largest category of landfill material. Giving wasted food an economic value decreases its presence in landfills and reduces municipal costs and methane emissions from rotting food. Combatting Deforestation Biogas can help reduce deforestation in areas of the world where firewood is the main source of home cooking and heating fuel. Half of all forest wood production worldwide is for fuelwood, one-third of which is harvested unsustainably. In sub-Saharan Africa, an estimated 70% of deforestation is due to fuelwood collection. Switching to biogas can reduce fuelwood consumption by nearly half. As a result, it also reduces by up to half the amount of time spent collecting firewood, a task most frequently performed by women and school-age children, reducing the labor burden on the former and increasing the educational opportunities of the latter. Cleaner Than Fossil Fuels Compared to diesel, using biomethane as a vehicle fuel reduces GHG emissions and particulate matter by up to 75%. Compared to burning fossil methane for electricity generation, biomethane reduced GHG emissions by 65% in one study and by 62–80% in another. Coupling a biogas-burning power plant with carbon capture technology can reduce GHG emissions even further (up to 87%), though carbon capture and storage technologies have yet to reach commercial viability. Consequences of Burning Biogas While it can be renewable and have environmental benefits, burning biogas still emits greenhouse gases and other pollutants into the atmosphere. Renewable, but How Sustainable? Transportation and storage of both biomass and biogas result in emissions of CO2 and particulate matter. As with fossil fuel methane, fugitive emissions are a concern at biogas plants. In both cases, methane emissions result when biogas is incompletely burned. When the storage of anaerobic digestion tanks goes uncovered, the GHG emissions benefits of biogas over fossil methane disappear. The carbon cycle involved in using agricultural products to produce biogas may be renewable. However, considering the entire life cycle of biogas production—including agricultural emissions, transportation, refining, and combustion—the use of biogas as a fuel source is by no means carbon neutral. Air Pollutants Biogas combustion can also lead to the emission of sulfur dioxide, carbon monoxide, volatile organic compounds (VOCs), and, most significantly, nitrous oxides, where biogas emissions are higher than those of natural gas combustion. Trace components of other pollutants at biogas plants, including carcinogens such as arsenic, have been found at higher levels than at natural gas plants as well. Manure-to-biogas and other biogas projects based on industrial animal agriculture are often cited adjacent to low-income communities or communities of color, exposing them to pollutants and discharging nitrates into the local groundwater. These instances make biogas production an environmental justice concern. Land Use Changes Biogas development should not come at the expense of forests. hohl / Getty Images As the market for biogas grows, so too do negative land use changes, where crops are grown specifically for biogas production. In Italy and Germany, biogas production expanded significantly in the first decade of the 21st century, leading to higher food and land rent prices, as land clearing for intensive agricultural production increased. In Indonesia, the use of palm oil effluent increases the profitability of the palm oil industry, encouraging the spread of oil palm plantations into one of the world’s most important old-growth forests. Is Biogas Carbon Neutral? Biogas is touted as "renewable," "sustainable," and "carbon neutral," mostly by its promoters. But calling biogas carbon neutral doesn't look at the whole life cycle of the product. The carbon that is released when biogas is burned comes from plants and other sources that originally pulled that carbon from the atmosphere, making the mere burning of the material itself carbon-neutral. But looking at the entire life cycle of biogas, including its production and transportation, as well as all the carbon embedded in the equipment used in those processes, makes the biogas industry a net contributor of carbon to the atmosphere. Frequently Asked Questions Is methane in biogas different from methane in natural gas? No, it is not different. Methane is CH4, whatever its source. But neither biogas nor natural gas is pure methane. Each contains other gaseous compounds. Is biogas recyclable? No. Once it's burned, it can't be recycled, and any unburned methane released when turning biogas into energy remains a potent greenhouse gas. Will more farmers grow crops for biogas, like many do for ethanol? There is currently less financial incentive to grow crops specifically for biogas, as the market is less predictable than traditional food crops. Farmers are able to grow and sell their main food crops, then sell their waste products to supplement that income. View Article Sources Da Costa Gomez, Claudius. “Biogas as an energy option: an overview.” The Biogas Handbook. Cambridge, U.K.: Woodhead Publishing Ltd., 2013. https://doi.org/10.1533/9780857097415.1. Christy, P. Merlin, L.R. Gopinath, and D. Divya. “A review on anaerobic decomposition and enhancement of biogas production through enzymes and microorganisms.” Renewable and Sustainable Energy Reviews 34 (2014), 167–173. doi: 10.1016/j.rser.2014.03.010. Arasto, A. et al. “Bioenergy's role in balancing the electricity grid and providing storage options: An EU perspective.” IEA Bioenergy: Task 41P6 Vol. 2017 No. 1; Bedoić, Robert, et al. “Beyond energy crops and subsidised electricity— A study on sustainable biogas production and utilisation in advanced energy markets.” Energy 201 (2020), 117651. doi: 10.1016/j.energy.2020.117651. Singh, Chander Kumar, Anand Kumar, and Soumendu Shekhar Roy. “Estimating Potential Methane Emission from Municipal Solid Waste and a Site Suitability Analysis of Existing Landfills in Delhi, India.” Technologies 5:4 (2017), 62–78. doi: 10.3390/technologies5040062; United States Environmental Protection Agency. Inventory of U.S. Greenhouse Gas Emissions and Sinks, 1990-2015 (2017). Morsink-Georgali, Phoebe-Zoe, et al. “Compost versus biogas treatment of sewage sludge dilemma assessment using life cycle analysis.” Journal of Cleaner Production 350 (2022), 131490. doi: 10.1016/j.jclepro.2022.131490. de Jesús Vargas-Soplín, Andrés, et al. “The potential for biogas production from autumn tree leaves to supply energy and reduce greenhouse gas emissions – A case study from the city of Berlin.” Resources, Conservation & Recycling 187 (2022), 106598. doi: 10.1016/j.resconrec.2022.106598. Hagman, Linda, et al. “The role of biogas solutions in sustainable biorefineries” Journal of Cleaner Production 172 (2018), 3982–3989. doi: 10.1016/j.jclepro.2017.03.180. Bailia, Robert, et al. “The carbon footprint of traditional woodfuels.” Nature Climate Change 5 (2015), 266–272. doi: 10.1038/NCLIMATE2491. Subedi, Madhu, et al. “Can biogas digesters help to reduce deforestation in Africa?” Biomass and Bioenergy 70 (2014), 87–98. doi: 10.1016/j.biombioe.2014.02.029. Desta, Getnet Alemu, et al. “Biogas technology in fuelwood saving and carbon emission reduction in southern Ethiopia.” Heliyon 6 (2020) e04791. doi: 10.1016/j.heliyon.2020.e04791. Meeks, Robyn, Katherine R. E. Sims, and Hope Thompson. “Waste Not: Can Household Biogas Deliver Sustainable Development?” Environmental & Resource Economics 72:3 (2019), 763–794. doi: 10.1007/s10640-018-0224. Pérez-Camacho, María Natividad, Robin Curry, and Tomas Cromie. “Life cycle environmental impacts of biogas production and utilisation substituting for grid electricity, natural gas grid and transport fuels.” Waste Management 95 (2019) 90–101. doi: 10.1016/j.wasman.2019.05.045; Feiz, Roozbeh, et al. “The biogas yield, climate impact, energy balance, nutrient recovery, and resource cost of biogas production from household food waste—A comparison of multiple cases from Sweden.” Journal of Cleaner Production 378 (2022) 134536. doi: 10.1016/j.jclepro.2022.134536. Esquivel-Patiño, Gerardo G. and Fabricio Nàpoles-Rivera. “Environmental and energetic analysis of coupling a biogas combined cycle power plant with carbon capture, organic Rankine cycles and CO2 utilization processes.” Journal of Environmental Management 300 (2021) 113746. doi: 10.1016/j.jenvman.2021.113746. Buratti, C., M. Barbanera, and F. Fantozzi. “Assessment of GHG emissions of biomethane from energy cereal crops in Umbria, Italy.” Applied Energy 108 (2013), 128–136. doi: 0.1016/j.apenergy.2013.03.011. Paolini, Valerio, et al. “Environmental impact of biogas: A short review of current knowledge.” Journal of Environmental Science and Health 53:10 (2018), 899–906. doi: 10.1080/10934529.2018.1459076. Li, Yin, et al. “Composition and Toxicity of Biogas Produced from Different Feedstocks in California.” Environmental Science & Technology 53 (2019), 11569–115769. doi: 10.1021/acs.est.9b03003. Gittelson, Phoebe, et al. “The False Promises of Biogas: Why Biogas Is an Environmental Justice Issue.” Environmental Justice (2021), doi: 10.1089/env.2021.0025. Britz, Wolfgang, and Ruth Delzeit. “The impact of German biogas production on European and global agricultural markets, land use and the environment” Energy Policy 62 (2013), 1268–1275. doi: 10.1016/j.enpol.2013.06.123; Bartoli, A. et al. “The impact of different energy policy options on feedstock price and land demand for maize silage: The case of biogas in Lombardy.” Energy Policy 96 (2016), 351–363. doi: 10.1016/j.enpol.2016.06.018. Gaveau, David L.A. et al. “Slowing deforestation in Indonesia follows declining oil palm expansion and lower oil prices.” PLoS One 17:3 (2022), e0266178. doi: 10.1371/journal.pone.0266178; Sodri, Ahyahudin, and Fentinur Evida Septriana. “Biogas Power Generation from Palm Oil Mill Effluent (POME): Techno-Economic and Environmental Impact Evaluation.” Energies 15 (2022), 7265. doi: 10.3390/en15197265.