Brown gold: the great American manure rush begins

The energy industry is turning waste from dairy farms into renewable natural gas - but will it actually reduce emissions?

On an early August afternoon at Pinnacle Dairy, a farm located near the middle of California's long Central Valley, 1,300 Jersey cows idle in the shade of open-air barns. Above them whir fans the size of satellites, circulating a breeze as the temperature pushes 100F (38C). Underfoot, a wet layer of feces emits a thick stench that hangs in the air. Just a tad unpleasant, the smell represents a potential goldmine.

The energy industry is transforming mounds of manure into a lucrative carbon negative fuel" capable of powering everything from municipal buses to cargo trucks. To do so, it's turning to dairy farms, which offer a reliable, long-term supply of the material. Pinnacle is just one of hundreds across the state that have recently sold the rights to their manure to energy producers.