I make biodiesel myself during the summer months. The main reason for the lack of availability is the cost to produce the product commercially. Those of us who run around getting waste oil for free are able to produce the stuff for our private use very cheap. My average is ~$.65 per gallon. Commercially the refiners are going to have to build a proper processing plant, buy land, pay employees, pay for transport, convince environazies that they aren't building a future superfund site, buy oil as well as the other materials to process, etc. All of this stuff costs, and the result is higher costs vs. pump fuel in the commercial market. They would also have to effect road use taxes.