Biogas, also called renewable natural gas (RNG), is touted as an environmentally-friendly energy solution, and it’s become big business, garnering hundreds of millions of dollars in federal and state grants, loans, and tax credits. But a close look at biogas reveals that it is far less green than proponents would like you to believe.
What is biogas?
Biogas is made from the anaerobic digestion of organic material like animal manure or crop residues. The gas is further refined into biomethane, which can be used in vehicles or to heat homes like any other gas.
What is the problem with biogas?
The biogas industry is on a growth trajectory, but is falsely represented as renewable energy. Biogas has long been generated for use of on-site, localized power at farms and at wastewater treatment plants. However, technology has evolved to allow for gas to be shipped long distances, which increases its profitability. In 2021, the global biogas market was valued at nearly $26 billion, and is expected to grow by another $11 billion by 2028. But biogas profits come with a big cost, as biogas is produced from gas emitted from large amounts of decomposing organic matter, including the lagoons used to store manure at concentrated animal feeding operations (CAFOs). Biogas production is not possible without a large quantity of waste.
While biogas could be viewed as a solution to an existing waste problem, instead biogas profits are driving the growth and expansion of industrial-scale livestock operations. At some industrial dairy facilities, biogas from manure is the primary profit-making product, with milk having become a value-added product. The negative impacts on people, communities, and the environment associated with the confinement of tens of thousands of animals in one place are significant, and cannot be dismissed when considering a clean energy future. Biogas is one of the major greenwashed renewable energy myths of contemporary climate discussions.
Myth #1: Biogas is a green energy source
Before it is refined, biogas contains 50–70% methane, a greenhouse gas many times more potent than carbon dioxide. The rest is primarily carbon dioxide, along with small amounts of hydrogen sulfide and particulates, and potentially toxic gasses including carbon monoxide, sulfur dioxide, and nitrogen oxide. Refined biomethane is a cleaner fuel but still releases carbon dioxide when it burns, making it not carbon neutral by definition.
According to the Environmental Protection Agency (EPA), capturing methane from agricultural operations in the United States reduced direct emissions equivalent to that of nearly 1 million cars in 2020. Unfortunately, CAFO biogas systems can leak up to 15 percent of the gas they produce. This means that in normal leakage conditions, so-called renewable natural gas could be more climate-intensive than fossil natural gas.
Biogas production from large livestock operations also does nothing to reduce the high levels of nitrogen or phosphorus in manure. Instead these nutrients are concentrated in biogas digestate, a byproduct of anaerobic digestion, which is disposed of as field fertilizer. High concentrations of nitrogen and phosphorus spread on fields can significantly contribute to water pollution. Biogas also does not reduce the air-polluting ammonia, hydrogen sulfide, non-point source methane, volatile organic compounds, and dust from CAFOs, or the environmental impact of additional acres of intensively-grown corn and soybeans as livestock feed.
Myth #2: Biogas is a renewable energy source
Biogas proponents point to its potential for keeping existing methane from being emitted into the atmosphere. However, research has shown that only a very small portion of producible fossil gas alternatives come from methane that is already being emitted. One study estimates that existing capturable waste methane (e.g., from landfills and wastewater treatment plants) is less than 1% of current gas demand. Growing the biogas industry will require intentionally producing more methane-producing waste, with all the risks of methane leakage and other pollution that come with those activities.
Proponents point to CAFO biogas as a win-win: it keeps methane from the atmosphere and produces energy. The reality is more of a lose-lose, as biogas industry demands for waste drive the development of more and larger CAFOs.
In reality, there are many ways to reduce livestock emissions, which all require smaller operations rather than larger. With smaller herds, livestock operators can maintain regenerative pasture-based systems, produce waste amounts that can be nutritionally beneficial for nearby cropland, or more feasibly use dry handling manure systems to compost the waste, all of which would eliminate or significantly reduce methane emissions.
Myth #3: Biogas is efficient and cost effective
The fact is, biogas production is rarely economically feasible without public subsidies, particularly when construction and operation costs are taken into account. As noted, once a biogas facility is operational, it requires an enormous volume of manure, which will need to come from ever-larger CAFOs or trucking of manure from several operations to a centralized biogas plant, increasing carbon emissions, costs, and impacts on the local community.
Anecdotal evidence from the Eastern Shore of Maryland indicates that on-farm biogas digesters at even the largest CAFOs are sitting empty because they are too expensive to properly construct and operate. Some research indicates that steady biogas production would require more manure to operate efficiently than even what is produced by the largest of CAFOs.
Myth #4: Biogas will help us transition off of fossil fuels
In fact, investment in biogas is further investment in fossil fuel infrastructure like pipelines, refineries, and gas stations. Major oil and gas companies have invested in biogas as key to their own future. For example, the American Biogas Council (ABC) includes members like Enbridge Energy, a Canadian oil company responsible for a 2010 oil spill in Michigan that was the largest inland oil spill in US history.
In 2021, the US biogas industry had 2,200 projects in all 50 states, including about 300 on industrial farms, and the ABC sees the potential for at least 15,000 additional systems, including nearly 8,600 on intensive dairy, poultry, and swine farms. These developments only extend the need for infrastructure that can also be used for fossil fuels. The only way to transition more rapidly off of fossil fuels is through investments in the electrical grid, batteries, and charging stations required for solar and wind power.
What can state legislators do to push back against these false narratives?
Since digesters are not renewable energy sources, they should not receive tax credits or subsidies or be included in state renewable energy portfolios. In 2021, Oregon allowed the expiration of a tax credit for manure, which was intended to promote manure-to-energy projects.
State officials should also work to strike any existing manure-to-energy components of a state renewable energy portfolio. New York (2019 NY S 6599) recently passed a bill that would prohibit waste-to-energy projects to be included in its future renewable energy platform.