Bioethanol production: insight into past, present and future perspectives

The use of ethanol as liquor since ancient times and later in the twentieth century as fuel has sparked a widespread interest in its production, more so since it shows great potential in areas including good biodegradability, and reduction in carbon dioxide (10-100%), carbon monoxide (25-30%) and particulate matter emission, as well as high-octane value (research octane number (RON)/motor octane number (MON), 108.6/88.6). The production of bioethanol from renewable resources and the combustion advantages for greener alternatives have led scientists around the world to develop cutting-edge technologies to achieve higher biomass conversion and, consequently, industrial-level yield and purity. Thus, production of bioethanol can also reduce the consumption of crude oil. Global ethanol production has increased to almost 41,000 million gallons, if recent market reviews are to be believed. Recent advances in technologies such as the use of agricultural wastes containing polysaccharides, or algal polysaccharides, and genetic manipulation to develop crops containing high carbon content, or to contain cellulase in their leaves, have opened a new horizon in bioethanol production. This review highlights the evolution in bioethanol development from first-generation production to the futuristic fourth-generation bioethanol production, the various constraints and challenges involved, and the scope for development.