The biggest trick is getting the used oil. I have debated "cracking" used cooking oil for some time now for biodiesel. I think it may prove to be a stop gap until some other form of energy is found/harnessed. Ethanol and BioDiesel are both good ideas but I don't think they are the answer long term. The used oil will be free only until the 2nd guy comes around asking for it, and as far as doing it on a commercial basis it just can't work (growing crops for use as biomass fuel). Fuel to plant soybeans/corn, fuel to grow/harvest it, fuel to process it, fuel to deliver it. I remember 7th grade physical science: You never get more energy OUT of a system than you put INTO it.
But, lots of things that weren't "Cost Effective" 10 years ago are starting to look more economical now. I am not knocking BioDiesel or Ethanol. I would run them if available. But I think they will only buy us time until we perfect some other energy source.
Don't mean to hijack the thread, got on a rant there for a second. /forums/images/graemlins/grin.gif