Biofuels enthusiasts mean well but I often wonder if they truly understand the sustainability of their efforts. The Resource Insights blog does a good job articulating the pro's and con's of each side. Needless to say, Cobb finds that the con's arguments usually win out, i.e. no free lunch.
In particular, the scavenging biofuel crowd need to realize that their "free lunch" run will have a short lifetime. I would classify their efforts on par with early investors in faddish antique markets. As a rather pitiful analogy, discarded vegetable oil will (although common now) become as rare as 19th-20th century telephone insulators dotting the countryside. I spent much time in my youth shimmying up poles collecting these emerald-colored glass jewels, but heck if you can find them anymore. Once they started becoming more rare, insulators became more valuable, which caused more people to track them down, a rather abbreviated ad infinitum.
And this outcome occurs for something that has absolutely no intrinsic value1. On the other hand, everyone uses fuel. Old saying: "The early bird gets the worm ... until the drought comes"
1 Aside from well-engineered electric dog fences.