Alternative fuels revisited

Got Manure? These Trucks Run on It

A California dairy has converted a pair of 18-wheelers to run on biomethane produced from cow manure, creating what is believed to be the nation's first cow-pie–powered trucks.

Hilarides Dairy will use manure produced by 10,000 cows to generate 226,000 cubic feet of biomethane daily — enough to reduce the Central Valley farm's diesel fuel consumption by 650 gallons a day.

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The bio-gas manufacturing process involves flushing manure and other waste from the cows' stalls into a covered lagoon where bacteria breaks it down. Methane is pumped out of the lagoon to a refinery that removes carbon dioxide, hydrogen sulfide and other impurities. The purified methane is pressurized before being pumped into the trucks; the Cummins engines have been converted from compression-ignited diesels to spark-ignited methane-burners.

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Using cow manure to produce bio-methane cuts greenhouse gas emissions in two ways. Burning biomethane produces less pollution than conventional fuel, and producing it cuts down on the methane released into the atmosphere by the manure itself....

"The technology is here and public-private partnerships can make this work. Biomethane is the only vehicle fuel that is carbon negative."