5. Cow Manure
Most of us are more familiar with the smell of cow manure than any information about it as a source of renewable energy, but researchers are working on ways to convert the methane gas contained in cow manure into diesel and other fuels. This fuel is of a high quality and burns cleaner than other fuels. Converting cow waste into energy allows gallons of fuel to be manufactured while cleaning both the odor and waste from land and water sources.