Ethanol

However, there are several problems with the use of ethanol as an alternative fuel. First, it is costly to produce and use. At 1987 prices, it cost 2.5-3.75 times as much as gasoline. The United States Department of the Environment (DOE) is funding a research program aimed at decreasing the cost to $0.60/gallon by the year 2000; in the last decade or so, the cost has dropped from $3.60/gallon to $1.27/gallon. There are also costs associated with modifying vehicles to use methanol or gasohol, but these costs vary, depending on the number of vehicles produced.

Another problem is that ethanol has a smaller energy density than gasoline. It takes about 1.5 times more ethanol than gasoline to travel the same distance. However, with new technologies and dedicated ethanol-engines, this is expected to drop to 1.25 times.

An important consideration with ethanol is that it requires vast amounts of land to grow the crops needed to generate fuel. The process for conversion of crops to ethanol is relatively inefficient because of the large water content of the plant material. There is legitimate concern, especially in developing countries, that using land for ethanol production will compete directly with food production.

Another problem is that ethanol burning may increase emission of certain types of pollutants. Like any combustion process, some of the ethanol fuel would come out the tailpipe unburned. This is not a major problem since ethanol emissions are relatively non-toxic. However, some of the ethanol will be only partially oxidized and emitted as acetylaldehyde, which reacts in air to eventually contribute to the formation of ozone. Current research is investigating means to reduce acetylaldehyde emissions by decreasing the engine warm-up period.

Finally, ethanol production, like all processes, generates waste products that must be disposed. The waste product from ethanol production, called swill, can be used as a soil conditioner on land, but is extremely toxic to aquatic life.