gut

The termite gut, which contains ~200 different microbes, is an exceptionally efficient bioreactor; it can produce up to 2 liters of hydrogen from a single sheet of paper. Further research is being done to see if it can be recreated as a renewable energy source. – WTF Fun Facts

Source: https://web.archive.org/web/20060922180946/http://www.jgi.doe.gov/education/bioenergy/bioenergy_4.html