According to information supplied by dairy organizations and agriculture departments in the West, there are four commercial dairy manure digesters operating in Washington state, two in Oregon, three in Idaho and seven to 10 in California.

Renee A. Rippchen, vice president of sales and marketing for BioEnergy Solutions in Bakersfield, Calif., said that most digesters in the state are set up on the premise of capturing the gas and running it through an on-site generator to provide power for the individual dairy farm.

But Rippchen said the problem this model has run into in California is that the mono-nitrogen oxide emissions from the generators violate air-quality standards.

While several generators are being tested, Rippchen said there doesn't appear to be a generator on the market today that has been proven to meet California's air-quality standards for mono-nitrogen oxide emissions when biogas from dairy cows is used as a fuel.

Rippchen said that the regulation impacts all of the generators in the state, regardless of size.

-- Cookson Beecher

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