Several alcohols have been or are being used as motor fuel in limited applications where their unique properties provide a specific benefit. Recently, proposals have been made to manufacture methyl and ethyl alcohols from nonpetroleum feedstocks for use as a primary energy source. Such a program, it is claimed, would reduce U.S. dependence on foreign oil; manufacturing ethanol would also stabilize prices of farm commodities.
An economical and abundant feedstock for methanol manufacture is North Dakota lignite. In a plant consuming lignite and self-sufficient in utilities, energy in the methanol would represent about 45 per cent of the energy in the feedstock. The cost of energy from the methanol produced would be about twice that from gasoline at 1979 prices. Liquefaction of lignite or coal to a synthetic crude with subsequent refining by conventional processes would provide motor fuel at somewhat higher energy efficiency and lower cost than by methanol synthesis. Municipal solid wastes could also be used as feedstock for methanol manufacture, but the cost would be even higher than with lignite as feedstock.
The lowest cost and most abundant feedstock for ethanol manufacture is corn. With current farming and ethanol manufacturing practices, which use mainly petroleum-based fuels, energy in the ethanol plus that in the byproducts is only about 55 per cent of the energy in the petroleum fuels consumed. If the ethanol plant used only nonpetroleum fuels such as coal or agricultural wastes for process energy, the efficiency based on just the petroleum fuels used in farming and collection of wastes would range from 130 to 160 per cent; overall efficiency would remain at 55 per cent or less. Energy in the byproducts represents about 40 per cent of the energy output, which greatly complicates evaluation of the efficiency of the plant. In any event, the cost of energy from the ethanol produced would be at least four times that from gasoline. The high cost results from large capital charges, large operating costs and, especially, large raw material costs.
While both methanol and ethanol have characteristics that complicate distribution and detract from product quality, poor energy yield and high cost are the most serious deterrents to commercialization of either alcohol. Methanol is definitely preferred, but neither represents a practical alternative unless the price of petroleum-based fuels rises markedly relative to that of the alcohols.