Methanol and ethanol are not the only transportation fuels that might be made from wood. A number of possibilities exist for producing alternatives. The most promis­ing bio-oxygenated fuels, and closest to being competitive in current markets with­out subsidy, are ethanol, methanol, ethyl-tert-butyl ether, and anti-methyl-tert-butyl ether. Other candidates include isopropyl alcohol, sec-butyl alcohol, tert-butyl alco­hol, mixed alcohols, and tert-amylmethyl ether.

Another possibility for bio-oxygenated fuels is methanol. Methanol could con­ceivably be made from grain, but its most common source is natural gas. The use of natural gas is better for reducing carbon dioxide production in comparison to other fossil fuels, but the use of renewable fuels instead of natural gas would be better still. It can be made from coal or wood with more difficulty and lower efficiency than from natural gas. The cost of making methanol from natural gas is around US$ 0.40 per gallon. It could probably be sold as a motor fuel for about US$ 0.60 to $ 0.70 per gallon. This would be equivalent to gasoline selling at about US$ 0.92 to $ 1.03 per gallon. Methanol was once produced from wood as a byproduct of charcoal manufacture, but overall yields were low. To produce methanol from wood with a significantly higher yield would require production of synthesis gas in a pro­cess similar to that used for production of methanol from coal. Such processes for gasifying wood are less fully developed than the two-stage hydrolysis process for the production of ethanol.

A high octane rating is characteristic of all oxygenated fuels, including ethanol, methanol, ethyl-tert-butyl ether (ETBE), and MTBE. MTBE is made by reacting isobutylene with methanol. ETBE is made by using ethanol instead of methanol. Thus either ethanol or methanol from either grain or wood could be a factor in making tert-butyl ether octane enhancers. The characteristics of ethers are generally closer to those of gasolines than those of alcohols. Ethers are benign in their effect on fuel system materials and are miscible in gasoline; therefore, they are not subject to phase separation in the presence of water, as are methanol and ethanol.