You know, they turned sewer waste into cooking oil in china. Maybe some sort of methane-based engine cycling? I'm not an expert but something for an expert to ruminate on, there'll be shitloads of it- quite literally.
I haven't done it yet but I know regular testing is something that should be done.
I think, depending on what you're trying to do, dogs can hurt and help you. They require food and water, they're loud, and not all breeds can fight, but if you want a food-powered alarm system, to hunt down birds you've shot, find prey, etc. You'll have to train one, basically, for your purposes.