Many of the bio-bugs being explored to create synthetic fuels require temperatures higher than those found in nature, so the risk with the ones I know about (e.g. Swift Fuel) are probably safe. However, a room-temperature bug certainly poses risks.
The other factor is that alcohols do not contain the same energy density as 100LL, and thus you will get fewer miles per gallon.
Hope they find something soon, though - wouldn't it be great if you could just sprinkle this stuff on a pond, come back at the end of the summer, and pump the results into 55 gallon drums?
