Ethanol is a grain alcohol that is produced by fermenting starch and sugar crops. It has an energy content of about two third that of gasoline. Ethanol made from food crops would be the most expensive of the major alcohol fuels. Even so, it has managed to gain support because of its potential contribution to the agricultural economy. Every year, nearly I billion gallons of ethanol are added to U. S gasoline stock to create gasohol. The addition of small quantities of ethanol to gasoline is viewed primarily as a means to reduce carbon monoxide emissions.
The use of one hundred percent ethanol is viewed as a means to reduce concentrations of ozone in urban areas. However, before fuel ethanol can be introduced commercially, the production cost must be competitive with that of fossil fuels. The greatest costs in the conversion of biomass to ethanol are those of the raw material(1) Hence, it is important to utilize all the carbohydrate components present in the wood to make the process cost-effective(6)
Many experts have argued that public health considerations do not require ambient air quality standards at the current level of stringency, and many more experts have seriously questioned the usefulness of determining attainment by measuring short-tem peak concentrations rather than longer averages. (10) Even Los Angeles, the city with the nations dirties air, meets ozone standards more than 97 percent of the time.
However, apart from the fact that the Bush administration treated the standards as sacrosanct, and apart from the questioned of whether attainment in a technical sense is a good measure of effective clean air policy, the simple fact is that in contrast to what may have been the case in 1970, today‘s air pollution problems defy a standard-setting, command and control solution, whether the standards apply to tailpipes or fuels. One reason for this is the law of diminishing marginal returns.
Since automobile hydrocarbon emissions have already been reduced by 96 percent over their 1969 levels, further emission reductions are difficult to attain and exceedingly expensive. The tailpipe standards of the 1990 Amendments will already increase the price of new vehicles by $100 to $600; the alternative fuel provisions will increase sticker prices even more(11). This is not simply a matter of economic costs. Dramatically higher sticker prices discourage consumers from buying new cars and thus extended the life of older cars which account for an overwhelming portion of air pollution from mobile sources.
(12). The Amendments could slow fleet turnover to such an extent as to offset the benefits that might be gained from running a portion of the automotive fleet on alternative fuels. A clean fuels policy is marred by another fundamental difficulty. There is no such thing as a truly clean fuel. Any alternative fuels policy will involve tradeoffs between different emissions, all of which can have negative environment effects. The most widely touted clean fuel is ethanol, an alcohol fuel typically made from corn. Ethanol helps reduce carbon monoxide emissions by increasing the fuel’s oxygen content.
The widespread use of gasohol, a blend of 10 percent ethanol and 90 percent gasoline, could possibly reduce CO emissions by as much as 22 percent nationwide while reducing fuel mileage by two percent. (13). Ethanol could also cause a slight reduction in lead emissions. However, ethanol is hardly an environmentally sound fuel . In fact; it may be the most polluting of the so-called clean fuels. Ethanol is more volatile than gasoline, meaning that it evaporates more quickly. Relative to gasoline, ethanol could increase evaporative hydrocarbon emissions by as much as fifty percent and total VOC emissions by as much as twenty five percent.
The use of gasohol would increase VOC emissions by as much as twenty percent and NOx emissions by about eight to fifteen percent. (14), because VOC are among the most common smog precursors, widespread ethanol use would increase urban smog. (15). Moreover, ethanol is water soluble and cannot be transported via pipeline; most gasohol is produced by adding ethanol to gasoline at locations near the point of retail sale. This process known as splash blending may exacerbate the problem of evaporative emissions.