Ethanol from cellulosics

Investigates simulation studies on the conversion of cellulosic waste which indicate that ethanol yields are higher with prehydrolysis than without, and formation of by-product is minimized. Argues that the current major RandD effort in the US to improve technology for the conversion of cellulosic waste is justified by the potential utilization of hundreds of millions of tons per year of agricultural and forest wastes that otherwise have little or no economic value, in contrast with the use of corn. Cellulose must first be hydrolyzed to hexose monosaccharides (mainly glucose) before it can be fermented to ethanol. Diagram shows process logic and tables compare sales price to by-product value and glucose concentration in fermentor feed. Guidelines offered include pretreatment steps prior to acid hydrolysis should be minimized, as there is little or no economic benefit to their use; prehydrolysis is the most useful pretreatment; solvent delignification is uneconomic, unless the recovered lignin has a high market value; recycle of unreacted solids to hydrolysis is economical only up to 50%; and concentration of glucose prior to fermentation is not necessarily economical.