The utilization of ethanol as an oxygenate has many benefits: higher oxygen content (lesser amount of required additive), high octane number (see Table 1.1), greater reduction in carbon monoxide emissions, and nonpollution of the water sources. Compared to methanol, ethanol is less hygroscopic, has a higher combus­tion heat, and has less heat from evaporation, and, most important, it is much less toxic. In addition, the acetaldehyde formed during ethanol oxidation is much less dangerous than the formaldehyde formed during methanol combustion. In fact, acetaldehyde predominates in comparison to formaldehyde in exhaust gas from vehicles using ethanol-gasoline blends (Rasskazchikova et al., 2004). Ethanol — gasoline blended fuels increase the emission of formaldehyde, acetaldehyde, and acetone 5.12 to 13.8 times more than gasoline. Although the aldehyde emissions will increase when ethanol is used as a fuel, the damage to the environment by the emitted aldehydes is far less than that caused by the polynuclear aromatics emitted from burning gasoline (Yuksel and Yuksel, 2004).

From the viewpoint of combustion properties, the autoignition temperature and flash point (temperature at which the liquid generates sufficient vapor to form a flammable mixture with the air) of ethanol are higher than those of gasoline, which makes it safer to transport and store. Ethanol has a latent heat of evaporation 2.6 times greater than that of gasoline, which makes the temperature of the intake manifold lower and increases the volumetric efficiency of the engine. Nevertheless, this property causes the engine’s cold start ability to be reduced because the alco­hols require more heat to vaporize than does gasoline in order to form an appropri­ate air-fuel mixture that can be burned. Ethanol heating value is also lower than that of gasoline and, therefore, it is necessary to have 1.5 to 1.8 times more fuel ethanol to release the same amount of energy if it is used in a pure form rather than in gasoline blends. On the other hand, the stoichiometric air-fuel ratio of ethanol is about two thirds to one half that of gasoline, hence, the required amount of air for complete combustion is less for ethanol (Yuksel and Yuksel, 2004).

From a socioeconomic point of view, the utilization of fuel ethanol presents important advantages as well (Chaves, 2004; Sanchez and Cardona, 2008a). Bioethanol contributes to the decrease of imports of gasoline or oil in consuming countries through the partial substitution of these fossil fuels. Thus, this biofuel has the potential of compensating and reducing the impact of periodical rises of oil prices in the context of exhausting national reserves. Therefore, significant currency savings can be achieved that otherwise would have to be directed to fos­sil fuel imports. In each country, ethanol usage favors the economic utilization of raw materials and renewable resources, such as sugarcane, cassava, corn, and sor­ghum, as well as a great amount of lignocellulosic residues having the potential to be converted into ethyl alcohol. The use of fuel ethanol boosts the economic and productive reactivation of many rural communities through the increase in demand for agricultural production. By means of the development of productive projects for obtaining fuel ethanol, the base for creating and expanding actual agro-industrial chains where several links are integrated with the participation of private and public sectors is provided. This integration spreads benefits to dif­ferent segments of the economy such as the energy, agricultural, industrial, and financial sectors. This makes possible the development of commercial relation­ships as well as the creation of jobs in depressed rural areas avoiding the migra­tion of population to urban centers, especially in developing countries. In addition, the large-scale utilization of ethanol will promote the scientific and technological development of many countries in the biofuel field even when turnkey technology is acquired. Once installed, this type of technology generates new challenges, such as increase in productivity, improvement of the different crops varieties that are used as feedstocks, enhancement of process efficiency, and reduction of the environmental impact caused in production facilities, as well as many others.

From the environmental point of view, the utilization of ethanol as a gasoline oxygenate offers net reductions in the amount of greenhouse gas emissions per traveled mile of 8 to 10% in gasoline blends containing 10% ethanol by volume (known as E10 blends). For blends containing 85% ethanol (E85 blends), this reduction can reach up to 68 to 91% (Wang et al., 1999). In general, it is considered that the greater the percentage of ethanol in gasoline blends, the better the envi­ronmental benefits mostly expressed through the net reduction of greenhouse gas emissions during the entire life cycle of ethanol. Numerous studies have proved the environmental benefits of fuel ethanol usage in terms of its impact on the emission of the combustion production from ethanol-gasoline blends. According to data compiled by the Canadian Renewable Fuels Association (2000), the gaso­line oxygenated with 10% ethanol reduces the levels of carbon monoxide by 25 to 30% as well as the net CO2 emission by 10%. The main benefits of using ethanol as an oxygenate are presented in Table 1.2. One of the features of ethanol lies in the fact that it can be utilized as a feedstock for ETBE production using isobutene obtained from the petrochemical industry. This duality converts the ethanol to a very promising product in the international energy market, especially if the leg­islation of different countries continues to be aimed at using renewable gasoline oxygenates (Ancillotti and Fattore, 1998) as in the case of the EU.