Methanol

Methanol is a colorless, odorless and nearly tasteless alcohol with the simplest chemical structure of all the alcohols.

It is used as a chemical feedstock, extractant, solvent, a "neat" 85 percent by volume or more gasoline replacement and/or a feedstock for the manufacture of methyl tertiary butyl ether or MTBE.

Before modern production technologies were developed in the 1920s, methanol was obtained from wood as a co-product of charcoal production and, for this reason, was commonly known as wood alcohol. Methanol was often
used as a fuel for cooking, lighting and to power early automobiles. However, the yield from this method of production was very low. One ton of hardwood would only yield one or two percent, or about six gallons of methanol softwoods only half as much. This led to its eventual replacement by less expensive alternatives.

Methanol from coal could be a very important source of liquid fuel in our future. Although the costs are prohibitive at this time, the technology is fairly simple and easily implemented. The coal is first pulverized and cleaned, then fed to a gasifier bed where it is reacted with oxygen and steam to produce the synthesis gas. Once these steps have been taken, the production process is much the same as with the other feedstocks with some variations in the catalyst used and the design of the converter vessel in which the reaction is carried out.

Although coal's cost on a British thermal unit basis is less expensive than natural gas, it is not enough to offset the high capital cost associated with coal conversion plants. Some research projects are paving the way for making the coal-to-methanol process more economical, including efforts by the U.S. Department of Energy. Methanol from coal is attractive because coal reserves in the United States known and undiscovered are estimated to be about four trillion tons. A coal-to-methanol fuel industry producing one million barrels per day would require about 150 to 200 million tons of coal per year. Recent concerns about sulfur oxide emissions from coal combustion can be mitigated because, in coal-to-methanol gasification, sulfur is removed as a routine part of the process.

Natural gas will remain the least-expensive feedstock for methanol in the near term. Natural gas resources in the United States are estimated to be from 300 to 500 trillion cubic feet. Current U.S. consumption of natural gas is about 20 trillion cubic feet per year. The technology for making methanol from natural gas is already in place and requires only efficiency improvements and scale-up to make methanol an economically viable alternative transportation fuel.

Biomass resources can be used to produce methanol. Estimates of biomass resources available for use in the production of alcohol fuels range from one million to 4.7 million dry tons per day one ton equaling 100 gallons of methanol when biomass is also used to fuel the processing plant. Biomass resources include crop residues, forage, grass, crops, wood resources, forest residues, short-rotation wood energy crops and the cellulosic components of municipal solid waste. As a renewable resource, biomass represents a potentially inexhaustible supply of feedstock for methanol production. Contrary to popular belief, methanol is eligible for the same federal tax incentives as ethanol, in fact even a greater amount, if made from renewable resources. Current natural gas feedstocks are so inexpensive that even with tax incentives renewable methanol has not been able to compete economically. Technologies are being developing that may eventually result in commercial viability of renewable methanol.    

Methanol use in current-technology vehicles has some distinct advantages and disadvantages. On the plus side, methanol has a higher octane rating than gasoline. This reduces "knock" in today's engines and can result in greater fuel efficiency with proper adjustment of the engine's compression ratio. Methanol's high heat of vaporization results in lower peak flame temperatures than gasoline and lower nitrogen oxide emissions. Its greater tolerance to lean combustion higher air-to-fuel equivalence ratio results in generally lower overall emissions and higher energy efficiency. Dedicated-methanol-fuel vehicles would increase this advantage even further.

However, several disadvantages must be studied and overcome before neat methanol is considered a viable alternative to gasoline. Methanol's energy density is about half that of gasoline, reducing the range a vehicle can travel on an equivalent tank of fuel. Current-technology vehicles using neat methanol at temperatures below 45 degrees Fahrenheit are difficult to start because of methanol's lower vapor pressure and single boiling point. However, engineering solutions to these problems have been identified and are under development. For example, 85 percent methanol solves the cold start difficulties because of its 15 percent-gasoline component. The availability of 85 percent methanol is limited, but growing through a network of dozens of gasoline stations in the key, high-population areas of California.

Because methanol is a liquid fuel, fueling modes are consistent with those already used for gasoline. As DOE, other agencies and industry continue their demonstration and evaluation, answers will be found to mitigate barriers to the use of methanol as an alternative transportation fuel.