California cow manure to supply gas energy

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California is blessed with many renewable sources of energy, from surging Sierra rivers to strong coastal winds.Now, add another source to that list -- cow manure.Pacific Gas and Electric Co. is unveiling its latest renewable energy project this week, a system that collects methane from manure on a Fresno County dairy farm and refines it into biogas, virtually identical to natural gas. The biogas then flows into a PG&E natural gas pipeline for use in homes and power plants.The San Francisco utility gets a new source of fuel. The farm gets a new source of income. And the methane, a potent greenhouse gas, stays out of the atmosphere.Other farmers have tried capturing methane and burning it on site to create electricity. But those systems tend to be expensive and inefficient, said David Albers. He is both the president of the company that built the new system, BioEnergy Solutions, and a partner in Vintage Dairy, whose 5,000 cows will supply the manure."This makes much more sense," Albers said. "We're not generating electricity at all. PG&E's doing that."This isn't PG&E's only foray into cow power. The company signed an agreement in 2006 with another company, Microgy, to do much the same thing. That project is expected to begin construction in June, a PG&E spokeswoman said. PG&E estimates that biogas could one day supply 5 percent of all the natural gas the utility needs.The BioEnergy system will collect manure in a holding pit three stories deep and allow naturally occurring microbes to break down the waste, releasing methane bubbles in the process. The trapped gas will feed into a series of steel tanks where corrosive compounds such as hydrogen sulfide will be removed. Under its contract with PG&E, BioEnergy will supply the utility with about 3 billion cubic feet of biogas per year, enough to meet the needs of 50,000 customers, according to PG&E. The companies did not disclose terms of the contract.E-mail David R. Baker at dbaker(at)sfchronicle.com.(Distributed by Scripps Howard News Service, www.scrippsnews.com.)