How many dairy cows does it take to make a kilowatt of electricity, enough to power a small apartment? Four, according to GHD, Inc. The company, based in Chilton, Wis., makes methane from cow poop using a technique called anaerobic digestion. Four cows make about 64 gallons of manure a day. This manure can be fed to bacteria that once lived in a cow's gut. These microorganisms break down undigested fatty acids in the manure over weeks to make methane gas. Methane is then burned onsite at the farm to make electricity that can be sold to utility companies. To be economical the operation needs about 600 cows, and the largest operations include more than 10,000 cows.
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