When I was in graduate school at Texas A&M in the early 90's, I selected chemical engineering Professor Mark Holtzapple as my research advisor. His work was exactly in my area of interest: Biofuels from cellulose. Even then, I was very concerned about the unsustainable lifestyle we were living, and I was hoping to save the world. For a very good overview on what we were doing, see this PowerPoint presentation (note the Hubbert slide) or this article. In brief, what we were doing was searching for naturally occurring biological systems that convert cellulose to organic chemicals.

The primary system we studied was the bovine digestive system. Cattle are very efficient digesters of cellulose. They eat grass, and break it down via microorganisms that live in their digestive systems. So what we did was extract those microorganisms and attempt to convert cellulose in reactors that emulated the chemistry of the cow's stomach. And while we did have success, the conversion was never as efficient as it was inside the cow.