The main disadvantage of producing fuel ethanol is that its production is more expensive than the production of fossil fuels. From a technical viewpoint, gasoline

Source: Canadian Renewable Fuels Association. 2000. Environmental Benefits of Ethanol.

blended with ethanol conducts electricity and its RVP is higher than nonblended gasoline. This implies a higher volatilization rate that can lead to ozone and smog formation (Thomas and Kwong, 2001). Although the addition of ethanol increases the evaporation rate of organic volatile compounds, many experts consider that the reduction of CO emissions effectively offsets the volume losses due to the volatility increase (Ghosh and Ghose, 2003).

One of the most troubling issues regarding the utilization of gasoline blends is the tendency of ethanol to form two liquid phases in the presence of water: one aqueous phase with an important ethanol content and one organic phase. If water contaminates the fuel, the water dissolves into the ethanol and disperses through the tank. Once it exceeds the tolerance level, the alcohol-water mixture will sepa­rate from the gasoline. Depending on individual conditions, about 40 to 80% of the ethanol will be drawn away from the gasoline by the water, forming two distinct layers. The top layer will be a gasoline that is a lower octane and perhaps out of specification, while the bottom layer is a mix of water and ethanol that will not burn (Central Illinois Manufacturing Company, 2006). To avoid the phase separation, ethanol-gasoline blends are not directly transported by pipelines. In general, ethanol is added to gasoline in bulk terminals (retail outlets, the end link of the supply chain for wholesale distribution) or in tanker trucks at the terminal immediately before delivery to the service station. In these points, reception and storage tanks are steel-made to minimize the exposure to water that can infil­trate into the distribution and storage systems for gasoline as well. This problem can be overcome by using stabilizing additives such as higher alcohols, fusel oils (mixture of higher alcohols, fatty acids, and esters), aromatic amines, ethers, and ketones. For instance, the addition of 2.5 to 3% isobutanol ensures the stability of ethanol-gasoline blends containing up to 5% water at temperatures down to -20°C. In fact, the phase stability of gasoline blends increases with high ethanol concentrations (Rasskazchikova et al., 2004). Another approach for stabilization
of these gasoline blends is the modification of the carburetor that also can allow the utilization of blends with higher ethanol contents (Yuksel and Yuksel, 2004).

On the other hand, ethanol, like all the alcohols in general, is highly corrosive, depending on water content. The higher the molecular weight of the alcohol, the less corrosive it is. To neutralize this effect, corrosion inhibitors can be added. Among these inhibitors are hydroxyethylated alkylphenols, alkyl imidazolins, and different oils obtained during cyclohexane production. Ethanol can have a negative effect on rubber and plastic materials because it penetrates hoses and tight seals, which increases fuel losses due to evaporation. Nevertheless, the cur­rent level of development of the polymer industry makes it possible to select mate­rials resistant to penetration of alcohols so that fuel losses are eliminated. These new polymers are being used in the automobile parts industry (Rasskazchikova et al., 2004).

From an economic point of view, fuel ethanol also presents some drawbacks that depend on the situation in all countries of the world. Particularly, in the case of the sugar sector, there exists the risk that sugar producers involved in ethanol production can reduce the amount of ethanol produced when sugar prices are especially high on the international market. For this reason, some governments, like Colombia’s for instance, have adopted measures to avoid this situation by link­ing the international sugar price to the value paid to ethanol producers. However, several authors and nongovernmental organizations (NGOs) have expressed their concern regarding the fact that this price structure and related tax exemptions favor the economic groups controlling sugar markets in each country (Chaves, 2004). Another great concern, when an ethanol oxygenation program for gasoline is being implemented, is in the pressure over food prices related to feedstocks from which ethanol is produced, especially sugar and corn. In particular, the bio­fuels were hardly criticized when both oil and food commodities prices reached their historical peaks during 2008. Specifically, it was estimated that the “bio­fuels effect” could have provoked an increase in the international price of food commodities and crops of about 35% in that year. This statement was weakened when the oil price fell at the end of 2008 (corresponding to the beginning of the global financial crisis) and the price of food commodities also fell to a percentage higher than 35%. This could indicate than the elevated value of food feedstocks was more linked to the oil price than to the biofuels prices. However, it should be pointed out that the price of biofuels in the international market depends on the oil price as well. In any case, the effect of producing bioethanol and biodiesel from agricultural resources on food and feed prices cannot be neglected and should be thoroughly assessed. In this regard, the production of the so-called second-gener­ation biofuels represents an important option for producing biofuels from sources other than those related to food and feed production. In this case, bioethanol can be produced from lignocellulosic residues or by-products, such as cane bagasse, corn stover, or wheat straw, that have no influence on food production structure.

Considering the effect of bioethanol production on the environment, some con­cerns have been expressed based on the fact that ethanol usage in gasoline blends increases the aldehyde level, mostly acetaldehyde, compared to the combustion

of conventional gasoline. The aldehydes are formed during the incomplete com­bustion of ethanol and have been linked to some potentially harmful effects on human health. Nonetheless, it should be emphasized that all oxygenates form higher amounts of aldehyde emission than nonoxygenated gasoline. Furthermore, the effect on the health is negligible as proven by the Royal Society of Canada tak­ing into account, in addition, that the catalytic convertors of new vehicles reduce these aldehyde levels to a higher degree (Canadian Renewable Fuels Association, 2000). In the case of old automobiles that do not have this kind of convertor, the level of formed aldehydes, although increased when ethanol is employed as the gasoline oxygenate, is always below the permissible limits. Actually, the emission of this type of organic compound is very low compared to other types of danger­ous emissions (e. g., aromatic hydrocarbons), which are effectively reduced when fuel ethanol is used (see Table 1.2).

There exists a great debate on the environmental suitability of ethanol usage as an oxygenate, especially when blends with low ethanol contents are employed. Reviewing various literature sources, Niven (2005) points out that gasoline blends with 10% content of ethanol (E10) offer few advantages in terms of greenhouse gas emissions, energy efficiency, or environmental sustainability. In addition, this author indicates that E10 blends increase both the risk and severity of soil and groundwater contamination, although greenhouse gas benefits for 85% etha­nol blends (E85) are recognized. By contrast, the Argonne National Laboratory (USA) estimates that an 8 to 10% reduction in greenhouse gas emissions per vehicle mile traveled is achieved when biomass ethanol is used in E10 blends and 68 to 91% reduction when used in E85 blends (Wang et al., 1999). This contro­versy has arisen in countries with an important ethanol industry, as in the case of the United States. Authors such as Pimentel (2003) have maintained for several years that the energy required for producing ethanol is greater than the energy contained in the ethanol itself, particularly when starchy materials like corn are used. This implies that important natural resources of a national economy are being squandered by maintaining an artificial biofuels program. Nevertheless, most studies have concluded that the energy invested in ethanol production is less than its energy content, which allows achieving significant environmental ben­efits. These studies have been accomplished by both independent research groups and governmental centers and have belied Pimentel’s arguments, as shown in the works of Shapouri et al. (2003) and Wang et al. (1999).