Poo is powerful stuff. That's cow poo to be exact, though scientists say other animals' waste could also be used as an environmentally friendly energy source. 121 facilities in the U.S. are already turning their manure into electricity, and a report from the university of Texas says that the total potential across the country from existing cows could potentially serve 3% of our national energy use. And, a new bill was recently proposed asking for tax incentives for even more biogas production. This poo power stuff is really catching on.