Calif. dairy farmers give manure digesters ‘another whirl’

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cow digester

New manure digesters, used to convert methane from manure into electricity, have been developed that no longer emit the smog component nitrogen oxide, but persuading dairy farmers to try out the technology will be difficult.

More than 10 years ago, in response to concerns about the greenhouse gases emitted from cow manure, some California dairy farmers constructed million-dollar methane digesters on their properties. However, air pollution regulations and low rates caused most of these digesters to shut down after it was discovered that they were emitting nitrogen oxide. The cost of retrofitting the dairy digesters with catalytic converters was often cost-prohibitive.

“You have a lot of dairy farmers who put these things on and found themselves willy-nilly in the energy business,” said Stacey Sullivan, policy director at a San Francisco-based environmental group called Sustainable Conservation.

California produces more dairy than every other state with its 1.8 million cows. Now, officials in the state are making an aggressive push to increase renewable energy sources, and some experts say new dairy digesters show promise. The state’s Department of Food and Agriculture, California’s Environmental Protection Agency, and local air and water quality boards have not established a permitting process for the improved digesters.

“If these digesters run properly, they can reduce odors associated with manure, stabilize nitrogen and have a number of environmental benefits,” said California EPA climate change adviser John Blue.

Next year, renewable energy company CH4 Power Inc. aims to construct more than 40 manure digesters, but finding farmers to sign on to the projects after past failures has been a challenge.

The first digester will be installed at farmer Ron Koetsier’s land. Koetsier, who had attempted to run a digester in the past, will not run the operation. Instead CH4 is leasing the property and will take responsibility for the digester’s maintenance. CH4 will also purchase manure from Koetsier’s cows.

But Ray Brewer, president of CH4 Power, said Koetsier wasn’t easily convinced: “Talk about apprehensive,” Brewer said. “That was a little bit of an understatement” (ClimateWire, 6-18-2013)