Photos: Barnyard energy

Five Star owner and General Manager Lee Jensen. Five Star sells the biogas produced by the digester to a utility. It will take about 10 years for the revenue from gas sales to pay off the digester, he said, but in the meantime, the farm can cut costs in other ways. The liquids at the end of the process can be used as fertilizer while the solids are comfy cow beds. Neither the liquids nor cow beds smell nearly as bad as the manure did the first time around.

Five Star Dairy

An aerial shot of Five Star. Yes, the digester is a pretty sizeable building to construct.

Five Star Dairy

Farmers check out the post-digester manure. Five Star says that cows actually prefer to sleep on manure over grass and it blows around less than hay.

Five Star Dairy

Here's a shot of a digester on the Wild Rose Dairy in Wisconsin. This farm sells the biogas generated by the digester to a utility. A large eight-digester project in Texas will produce a billion cubic feet of gas a year when complete.

American Images, Marshfield, WI

Biogas from the manure digester is fed into a generator (the yellow thing), which provides about 700 kilowatts of the electricity required at California's Joseph Gallo Farms, a major cheesemaker. The heat from the generator is then captured and used to run the boiler (the silver thing) that powers the boilers, where cheese is made.

Gallo Farms

Guess what's under the tarp? Seven acres of fresh cow manure. Gallo right now has a mesophilic, or ambient temperature, digester. The company, however, is also building a thermophilic one that creates energy by heating manure up to 130 degrees and mixing in the right microbes.

Gallo Farms

Manure separator. No, that's not a sun deck up there.

Gallo Farms

Moooo! This thermophilic digester at the Five Star Dairy in Wisconsin transforms cow manure and other waste products in 21 days into biogas. The farm doesn't smell nearly as bad after one of these goes in, according to Lee Jensen of the Five Star.

American Images, Marshfield, Wisc.

After the Five Star began to turn manure into gas, it invited farmers from the region to check it out. Because of the costs associated with managing manure, demand is growing.

American Images, Marshfield, Wisc.