Biomethane—natural gas made by upgrading biogas produced by the controlled decomposition of dairy manure or similar waste products—can serve as a cost-effective renewable substitute for natural gas, according to a study published earlier this year.
The study, Biomethane from Dairy Waste: A Sourcebook for the Production and Use of Renewable Natural Gas in California, surveys the most effective and economical technologies for producing biomethane, as well as specific applications and markets for the gas.
Project partners on the study, which was funded by the USDA, include Sustainable Conservation, Western United Dairymen, Institute for Environmental Management, Great Valley Center, CalStart and RCM Digesters.
The authors conclude that manure from about half the cows in California would provide enough biomethane to power all the natural gas vehicles currently operating in the state. Furthermore:
There are 8.5 million cows in the United States, each producing enough manure to potentially generate about 30 cubic feet of biomethane per day, which could replace significant amounts of natural gas at today’s prices. If used as vehicle fuel, biomethane could power a million cars.
The technologies for converting dairy manure to biomethane are already used at several landfills around the United States. Sweden has 20 plants producing biomethane and runs 2,300 buses on it. As natural gas prices continue to rise, biomethane fuel is becoming cost-competitive with natural gas and diesel, and is much cheaper than hydrogen.
Switching to biomethane improves air quality, reduces greenhouse gas emissions, improves water quality and strengthens rural economies.Allen Dusault, Biofuels Project Manager for Sustainable Conservation
California has particularly good reasons for using biomethane. The state is home to more than 1.7 million dairy cows, with a technically feasible potential for producing about 18 billion cubic feet of methane a year, equivalent to over 150 million gallons of gasoline.
The San Joaquin Valley, where most of the cows reside, has some of the nation’s most polluted air. A dairy biomethane industry along Highway 99 could serve as the start for a renewable fuel highway.
Unlike ethanol and biodiesel, biomethane receives no direct government funding or incentives. To quickly achieve the full potential of biomethane, the federal and state governments must support development of the technology, markets, programmatic infrastructure and regulatory environment that will allow rapid use of this practical, domestic energy resource.—Michael Marsh, CEO, Western United Dairymen
|Stages and technologies in biomethane production. Click to enlarge.|
The report deals with five major areas:
Producing biogas from dairy wastes with anaerobic digesters.
Upgrading biogas to fuel-grade biomethane by removing hydrogen sulfide, moisture, and carbon dioxide.
Using and distributing biogas and biomethane.
Meeting regulatory requirements and obtaining access to government incentives.
Determining the financial, economic, and business environment for the development of a biomethane industry.