Dairies Strive To Go Green: Turning Waste To Watts

Holsum Dairies in Wisconsin use a digestor to turn cow manure into electricity that powers more than 400 homes a year. iStockphoto.com hide caption

See A Video Of One Dairy's Efforts To Go Green
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Cows are big, they eat a lot, and, well, they produce a lot of manure. All this waste can have a negative impact on water and the environment, and some industrial dairies are working to make their facilities greener.

One way to keep cow manure from polluting the environment is to use a system called a digestor, in which the manure is funneled into a big vat, where it decomposes, producing methane that's then used to create electricity. The digestor at Holsum Elm Dairy in Wisconsin powers about 400 homes a year.

Holsum runs two dairy operations, Elm and Holsum Irish, both of which are Green Tier qualified, meaning they have voluntarily surpassed the environmental standards required by law. And for a dairy of Elm's size — about 4,000 cows — reducing pollution takes some serious engineering.

Holsum Elm is working to keep the dairy's cycle a closed loop — meaning it minimizes what goes in (like fossil fuels, food) and what goes out (manure). But a dairy this size produces more than 150 million pounds of manure each year, or the weight equivalent of nearly 60,000 Honda Civics. To keep the nitrogen and phosphorus in the manure from contaminating the environment, the dairy reuses it: After it's turned into electricity, the sterile, dry, leftover product is used for cow bedding. The wet waste is piped into a lined holding pool and eventually spread on nearby fields as fertilizer.

And the dairy buys all its feed from within a 10-mile radius, so it doesn't have to use a lot of fossil fuels to ship grains.

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