It's literally under our very noses. The possibility of harnessing animal waste to generate energy:
Rosamond Gifford Zoo (USA) is looking at the possibility of collecting dung from its 6 asian elephants to generate energy to alleviate its energy comsumption used in heating land electricity.
The zoo's 6 asian elephants produces about 1000 pounds (roughly 453kg) of dung per day and this cost the zoo US$10 000 per year to clean up.
If the plan succeeds, the zoo can save money from the waste disposal and also cut down its energy bill which amounts up to US$400,000 per annum.
"Answer to zoo's power needs may be right under their nose." AP report on CNN, 03 May 2005.