Dairy farmer says he saves money by converting cow manure to electricity . Remaining waste from 600 cows is used as fertilizer and mulch . Score: 6 He says process also helps cut dairy farm 's odor .
Dairy farmer says he saves money by converting cow manure to electricity . Remaining waste from 600 cows is used as fertilizer and mulch . Anaerobic digestion became popular in United States in 1970s . He says process also helps cut dairy farm 's odor .