Bioethanol production: Feedstock and current technologies

Fossil fuels such as oil, coal and natural gases have become the prime sources of energy in the current era. However, it is anticipated that these sources will deplete within the next 40–50 years. The expected environmental damages like global warming, acid rain and urban smog have tempted us to reduce the carbon emissions by 80% (v/v) and shift toward utilizing a variety of renewable energy resources such as solar, wind, biofuel, etc. that are less environmentally harmful in a sustainable way. Ethanol is one of the most promising alternative biofuel. Although the energy equivalent of ethanol is 68% lower than that of petroleum fuel, the combustion of ethanol is cleaner (because it contains oxygen) and thus it recognize as a potential biofuel alternative to gasoline. Ethanol has been frequently used for the blended gasoline in the concentration range 10–85% (v/v). More recently, ethanol is identified as a fuel for the direct ethanol fuel cells (DEFC) and biofuel cells. Sugarcane and corn feedstock, are the main source of ethanol. Nevertheless, it is barely sufficient to meet the current demand. Lignocellulosic biomass is an alternative source but its availability is poorly documented. This review discusses the current status of ethanol production from different feedstocks and the state of technologies involved in ethanol production from such different feedstock.