Hi Joseph,
As I have no hands on
experience with ethanol,
wood gas, or steam, I'll focus on biodiesel.
Waste fryer oil (aka yellow grease) is probably the best all around feedstock for the small scale biodiesel producer. It can often be collected for free from restaurants, and its use as a liquid fuel is, in my opinion, a higher use for it than as an animal
feed additive or use in the cosmetic industry.
Most agricultural crops, like soy or canola can make fine fuel, but as you say, markets for them typically fetch higher prices than for use as a liquid fuel feedstock.
That being said, I know a number of farmers who divert some of their soy or canola crop to make their own fuel on farm, and they are happy to be able to control the availability of fuel on their own farm.
In the battle of food vs fuel - food will usually win the price war. This is why biodiesel from algae is not likely to ever be commercially viable. If you're growing algae commercially - food and nutraceuticals are the markets of choice.
Bob
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