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When the Audet family turns on the lights at Blue Farm, they are using electricity that comes from cows-cow manure (粪肥)， to be specific。

Cows produce a lot of wastes. One cow can create 30 gallons of wastes each day. Now imagine the output of over 1,000 cows at Blue Farm. That's really a big amount。

When farmers clean their barns, they put the wastes in a big heap, and spread some of them on their fields for fertilizer(肥料). But now places like Blue Spruce Farm have a new way of using cow wastes. They use them to produce electricity。

Here's how it works: A big machine moves back and forth cleaning the barn floor.