I noticed a press release which fits well with the other "energy" postings of the past week. MWK Biogas North America Corp. of Rensselaer is the US branch of a German company. They market "digester" systems which harvest biogas from manure and other organic feedstocks, generating electricity and heat via anaerobic fermentation.
Their technology is said to produce 1.2-1.3 kW per cow. According to a recent article about a proposed greenhouse gas tax on farm animals, New York State has about 627,000 dairy cows. That's a lot of energy waiting to be captured - about 750-800 megawatts. For comparison, Maple Ridge Wind Farm in Lowville produces 320 MW of electricity with 195 turbines, which they claim is enough to power 160,000 average New York homes.
The article Farm Digesters For Small Dairies In Vermont tells how "Cow Power" provides renewable energy from dairy farm "output", as well as from other organic waste like whey from the Ben & Jerry's ice cream factory.