I have been saying that someone should do this for a long time...

Wired science has a story about how a simple contraption is using dog poop (yes, that's the technical scientific term) to power the lights at a local park in Cambridge, Mass.  Most people don't think about the carbon footprint that their pets can have, but it is pretty substantial.  In fact, it has been estimated that owning a medium sized dog is twice as bad for the environment as owning a gas guzzling SUV.  The main reason for this is that dogs (in fact all animals, including us) take in carbon in the form of food (think CARBOhydrates and fats, which are made of long carbon strains) and expel carbon dioxide and methane when we breathe, fart, and poop (yup, again, all accepted scientific terms).  Of course the carbon dioxide that we breathe out is not so bad, but the methane that we produce, is pretty bad.  In fact, the EPA estimates that methane is 21 times more harmful to the environment than carbon dioxide.  So what can we do about the methane released by dog poop?  We can burn it.  That's right, burn it.  When methane is burned, it not only produces energy, but water and carbon dioxide, thus, reducing the environmental impact.  Put all this together in a dog-friendly park and here's what you get:

"Dog owners collect their dog waste in a special biodegradable bag and throw it into the digester –- an air-tight cylindrical container, where the dog feces are broken down by anaerobic bacteria. A byproduct from that process is methane, which can then be released through a valve and burnt as fuel. In this case it is being used to power an old-fashioned gas-burning lamppost in a park."
Read More http://www.wired.com/wiredscience/2010/09/dog-poop-powers-park-lights/#ixzz0zehGO9Zz