Renewable Natural Gas (Biogas)

Biogas—also known as biomethane, swamp gas, landfill gas, or digester gas—is the gaseous product of anaerobic digestion (decomposition without oxygen) of organic matter. In addition to providing electricity and heat, biogas is useful as a vehicle fuel. When processed to purity standards, biogas is called renewable natural gas and can substitute for natural gas as an alternative fuel for natural gas vehicles.

Biogas is usually 50% to 80% methane and 20% to 50% carbon dioxide with traces of gases such as hydrogen, carbon monoxide, and nitrogen. In contrast, natural gas is usually more than 70% methane with most of the rest being other hydrocarbons (such as propane and butane) and traces of carbon dioxide and other contaminants.

More than half the gas used in Sweden's 11,500 natural gas vehicles is biogas. Germany and Austria are targeting 20% biogas in natural gas vehicle fuel. In the United States, biogas vehicle activities have been on a smaller scale.

Production

Biogas is a product of decomposing organic matter, such as sewage, animal byproducts, and agricultural, industrial, and municipal solid waste. Biogas must be upgraded to a purity standard to fuel vehicles and be distributed via the existing natural gas grid.

Biogas from Landfills

Landfills are the third-largest source of human-related methane emissions in the United States. Methane can be captured from landfills and used to produce biogas. Methane gas collection is practical for landfills at least 40 feet deep with at least 1 million tons of waste.

Find examples of landfills using biogas for vehicle fuel from the Sanitation Districts of Los Angeles County.

Biogas from Livestock Operations

Biogas recovery systems at livestock operations can produce renewable energy in cost-effective ways. Animal manure can be collected and delivered to an anaerobic digester to stabilize and optimize methane production. The resulting biogas can be used to fuel natural gas vehicles.

The U.S. Environmental Protection Agency (EPA) estimates 8,200 U.S. dairy and swine operations could support biogas recovery systems with the potential to generate more than 13 million megawatt-hours and displace about 1,670 megawatts of fossil fuel-fired generation collectively per year. Biogas recovery systems are also feasible at some poultry operations.

An example of converting livestock manure to biogas to fuel vehicles is the Western United Resource Development project.

Distribution

After biogas is produced, it must be refined to meet pipeline specifications. Currently, there are no specifications for natural gas as a vehicle fuel. Refining biogas means increasing the proportion of methane and decreasing the proportion of carbon dioxide and contaminants through absorption, adsorption, membrane separation, or cryogenic separation.

Renewable natural gas can be distributed via existing natural gas distribution routes. Because these technologies are not developed and tested fully yet, distributing renewable natural gas via the pipeline grid is not common practice.

Benefits

Biogas can be an alternative to conventional transportation fuels. The benefits of biogas are similar to the benefits of natural gas. Additional benefits include:

  • Increased Energy Security—Biogas offsets non-renewable resources, such as coal, oil, and fossil fuel-derived natural gas. Producing biogas creates U.S. jobs and benefits local economies.
  • Fewer Emissions—Biogas reduces emissions by preventing methane release in the atmosphere. Methane is 21 times stronger than carbon dioxide as a greenhouse gas.
  • Better Economics—Biogas reduces the cost of complying with EPA combustion requirements for landfill gas.
  • Cleaner Environment—Producing biogas through anaerobic digestion reduces landfill waste and odors, produces nutrient-rich liquid fertilizer, and requires less land than aerobic composting.

Research and Development

Research and development efforts are reducing the costs of biogas production and purification, producing higher-quality natural gas from biogas, and evaluating the performance of biogas-fueled vehicles. Some federal and state programs assist in these efforts, including EPA's Landfill Methane Outreach Program and AgSTAR Program. Learn more about landfill gas research and development projects from the Natural Gas Vehicle Technology Forum.

More Information

Learn more about methanol from the links below. The AFDC and U.S. Department of Energy do not necessarily recommend or endorse these companies (see disclaimer).

The AFDC also provides a publications search and a database of related links.