It has already proven its worth as a fertilizer and building material, and even as a secret ingredient in Ancient Egyptian ceramics. As it turns out, cow dung might also have a bright future as a plentiful source of clean electricity, thanks to the planet-warming methane it produces.
Few places encompass this potential future better than Bar 20 Dairy, a dairy farm in Kerman, California, which uses methane from cow manure to produce clean electricity with almost zero carbon emissions. It’s the first dairy farm in the U.S. to power its own clean energy “microgrid” using a biogas, and it could be a tantalizing sign of what the future of green energy might look like for companies with access to plenty of methane.
The technology isn’t all that hard to grasp. Manure and waste water from the farm’s nearly 7,000 cows are transported and sifted into a 25-million-gallon rectangular pit in the ground called a digester. The liquid sits for about 30 days while methane gas rises to the top of the closed digester. The gas then gets piped into a skid shifter, which separates the methane from hydrogen sulfide and other impurities. Finally, the methane is piped into fuel cells that harness it to produce electricity with little to no greenhouse gas emissions.
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https://www.thedailybeast.com/california-dairy-farm-has-microgrid-powered-by-clean-electricity-made-from-methane-from-cow-poop