Page 325 - Synthetic Fuels Handbook

FUELS FROM WOOD 311

(Enecon, 2002). Methanol was the first fuel from wood and is often called wood alco-
hol. Ethanol has been the focus of research at the Forest Products Laboratory. There has
been little attention to diesel fuel from wood, although there has been some research on
production from synthesis gas and through utilization of extractable materials from wood.
The United States accounts for about 23 percent of the world’s emissions of carbon
dioxide. Of the United States sources of carbon dioxide, electric power accounted for
35 percent, transportation 30 percent, industry 24 percent, and residences 11 percent.
Obviously, if we’re to do our share in reducing carbon dioxide emissions, we should
consider making a change in using more non-fossil fuels. The transportation industry is
based almost totally on the use of liquid fossil fuels and measures are under consideration
to reduce this consumption.
Liquid fuels that could be suitable for use in transportation vehicles have been made
from wood for a long time. Methanol was commonly called wood alcohol, and this term
is still used. Cellulose which is the largest wood component could be dissolved in con-
centrated acid solutions and converted to sugar, a precursor for making ethanol. A dilute
sulfuric acid hydrolysis process was used to make ethanol during World War I and wood
hydrolysis received considerable attention in Europe during the period between the World
Wars I and II. Wood hydrolysis plants continue to operate in Russia.
However, 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 biomass fuels, and closest to being competitive in current markets without
subsidy, are (a) ethanol, (b) methanol, (c) ethyl-t-butyl ether, and (d) methyl-t-butyl ether.
Other candidates include isopropyl alcohol, sec-butyl alcohol, t-butyl alcohol, mixed
alcohols, and t-amyl methyl ether.
Ethanol or grain alcohol is not restricted to grain as a feedstock. It can be produced from
other agricultural crops and ligno-cellulose compounds such as wood. It has often been
advocated as a motor fuel, and has been used frequently in times of gasoline scarcity. Today
Brazil is the only country that uses large quantities of ethanol as a motor fuel, but even in
the United States we use close to a billion gallons per year. In Brazil, 95 percent alcohol is
used as a neat fuel or anhydrous ethanol is used in admixture with gasoline. In the United
States we use anhydrous ethanol in mixtures of 10 percent ethanol with 90 percent gasoline.
The high cost of ethanol production in comparison to gasoline is a major disadvantage,
and in the United States only subsidies for biomass ethanol make it competitive. However,
because of the perceived ability of ethanol and other oxygenated fuels including alcohols
and ethers to reduce air pollution in 90 percent carbon monoxide and ozone nonattainment
areas in the United States, the cost disadvantage may become secondary, at least in these
areas. Other reasons for considering fuels alternative to petroleum include energy security
within national borders, balance of trade, and tax policies.
Another possibility for oxygenated fuels is methanol. Methanol could conceivably be
made from grain, but its most common source is natural gas. Use of natural gas is better for
reducing carbon dioxide production in comparison to other fossil fuels, but use of renew-
able fuels instead of natural gas would be still better. It can be made from coal or wood with
more difficulty and lower efficiency than from natural gas.
Methanol has long been used as the fuel for race cars at Indianapolis and some other
race tracks, not only because of its clean-burning characteristics, but also because of its
efficiency, low tire hazard, and high octane rating.
High octane rating is characteristic of all oxygenated fuels, including ethanol, methanol,
ethyl-t-butyl ether, and methyl-t-butyl ether. A large part of the success of ethanol from
grain in the current United States mix of motor fuels is due to its ability to raise octane
rating in a 10 percent mixture of ethanol with 90 percent gasoline. However, it is the recent
phenomenal growth in the use of methyl-t-butyl ether (MTBE) as an octane enhancer that
has captured worldwide attention. Methyl-t-butyl ether is made by reacting isobutylene