The Toronto Zoo is planning to convert the feces from the animals at the zoo into energy.  The feces can be used to create methane, which can then be used to produce electricity.

In order to convert the feces into usable energy, the zoo must build a facility which would cost $13 million. By using the electricity produced by the facility and selling the excess electricity, zoo officials believe they can make their money back in five years.

For more info: http://www.cbc.ca/technology/story/2008/11/15/zoo-poo.html