Trivia question: Do you know the total weight of the livestock--i.e. all of the pigs, chickens, and cows-- in the United States? If you guessed 95 billion pounds, you'd be right. (Cows account for 80.7 billion of the total). And annually, the annual manure output from these collective animals contains 928 trillion BTUs a year, according to a study from the University of Texas. (Read more here.) Interest in manure power has been growing. Earlier this year, Microgy, after a few delays, managed to get its large manure-to-gas facility in Texas operational. Pacific Gas & Electric is running manure trials. Meat packers like Swift & Co. are also experimenting. The plan is to sell...