Evolution of an industry
The current dominant ethanol production process involves the fermentation of sugars and starches in food crops such as sugar cane, corn, potato and cassava. These raw materials have short molecules which are quite easily digested by enzymes and are the feedstock for the first generation ethanol industry.
Major research has taken place over the last decade to find a way to be able to use agricultural waste products, such as the corn stover (stalks, leaves and other residue) and sugar cane bagasse (plant mass after the removal of sugar). The unutilized sugars contained in these types of biomass are made up of long molecules of polysaccharides which cannot easily be converted into ethanol by simple fermentation. In addition, cellulose and hemicellulose are entrapped in a matrix of lignin, preventing the enzymes’ access to the sugars and thus their transformation into ethanol.
The key is a pre-treatment phase to be integrated into the production process. Numerous pre-treatment process designs were developed using either acid or enzymatic hydrolysis or a combination of both; or thermo-mechanical technologies. The challenge was to move such technologies from small scale pilot and demonstration plant production to cost-efficient commercial scale production.