Biogas energy systems have typically been considered a source of renewable electricity and/or combined heat and power, but several projects across the U.S. are demonstrating the suitability of biogas as a transportation fuel. Using biogas as a supply source of lower-carbon, domestic, renewable fuel is an exciting prospect, even in the face of abundant natural gas supplies and low prices.
Since biogas can be converted to a product that is very similar to natural gas, biogas offers an alternative transportation fuel for vehicles converted or designed to run on natural gas. Given the historically low price for natural gas, many truck and heavy duty vehicle fleets are switching from diesel to natural gas. The build-out of additional natural gas refueling infrastructure and fleet conversions could accelerate the development of biogas as a transportation fuel, which provides diversity to the overall fuel mix and offers greater levels of carbon reductions.
Biogas as a transportation fuel is also bolstered by the federal renewable fuel standard (RFS). This policy, passed by Congress and signed into law by President George W. Bush in 2007, sets a national production goal of 36 billion gallons of renewable fuel by 2022. Biogas is designated as an advanced biofuel under the law. The overall framework for the RFS provides more of a market pull for other renewable fuels like conventional and cellulosic ethanol, but the contribution that biogas can make in achieving the ambitious RFS targets should not be overlooked.
In 2011, the American Gas Foundation commissioned a study by the Gas Technology Institute to determine the total national potential for renewable natural gas. Renewable natural gas is the term of art for defining biogas, a mixture of carbon dioxide and methane, to an upgraded or cleaned form that is mostly methane or substantially similar to natural gas. My organization, the Great Plains Institute, used the analysis from the American Gas Foundation to calculate the potential number of renewable fuel gallons that could be produced from biogas. Under an aggressive scenario, if the U.S. successfully converted 40 to 75 percent of the available livestock, municipal solid waste (MSW), wood residue and agriculture residue feedstocks to renewable natural gas, as much as 29 billion equivalent gallons of renewable fuel could be supplied.
Obviously, this is an ambitious goal, and does not fully consider the economic or technical potential. However, the analysis demonstrates that biogas could supply a considerable amount of renewable fuel, while greatly reducing greenhouse gas emissions, and should not be dismissed or overlooked.
The potential of biogas as a transportation fuel is already being demonstrated by projects across the country. Fair Oaks Dairy in Indiana is successfully displacing 1.5 million gallons of diesel fuel per year by collecting, cleaning and compressing biogas from a large herd of dairy cows. Biogas-based renewable fuel is used to run a fleet of milk delivery trucks and fuel for a public compressed natural gas (CNG) refueling station.
In Ohio, Quasar Energy Group is working with the Solid Waste Authority of Central Ohio and Kurtz Bros. Inc. to collect biogas from municipal wastewater biosolids and food/beverage waste fats, oils and greases to displace approximately 1.3 million gallons of diesel fuel per year. A CNG refueling station is available onsite and is also available to public.
Numerous municipal waste haulers are implementing projects to collect, clean and compress gas from landfills to provide renewable fuel for MSW vehicles. The possibilities are endless, and in addition to producing a lower-carbon source of fuel, materials that would otherwise be a strain on wastewater treatment facilities or livestock producers are transformed into a stable source of domestic, renewable fuel. Biogas is already contributing to the RFS and is positioned to make an even larger impact in the future.
