AutoBlog points to an article on Japanese research into alternative energy sources, including Ethanol. Now we've heard of several sources for Ethanol, crops like corn, soybean and switchgrass as well as Algae. But the Japanese are looking elsewhere.
Here, is where they're looking, cow manure. I don't think this is really a new idea. I mean..
Ask this guy nicely, and he may tell you how he made fuel from pig manure.
From what I've read online, algae seems to give the most output per acre, but what ever it takes.