The rising cost of gas makes one consider alternative sources of fuel. Lately I’ve been hearing a great deal about biodiesel fuels. I found a recipe for cooking up a batch. Unfortunately making biodiesel still appears to be more expensive than ordinary petroleum (at least when made from fresh soy), so it might be a while before this catches on, but the chemistry is at least mildly interesting. I was trying to sort out the potential for using waste fats and oil, but it seems rather obvious that even when my diet consisted largely of fried food, I used more gasoline by volume than cooking oil. Thus, while using waste oil may be temporarily cheap, there simply isn’t enough supply to make it more than a curiousity on the path to renewable energy.