BIOMASS ETHANOL: Technical Progress, Opportunities, and Commercial Challenges

TLDR: In this article, the authors discuss the benefits of cellulose and hemicellulose fractions and the major challenges to realizing the great benefits of biomass ethanol without subsidies, and propose to use genetically engineered bacteria to ferment all five sugars in biomass to ethanol.

Abstract: ▪ Abstract Ethanol made from lignocellulosic biomass sources, such as agricultural and forestry residues and herbaceous and woody crops, provides unique environmental, economic, and strategic benefits. Through sustained research funding, primarily by the U.S. Department of Energy, the estimated cost of biomass ethanol production has dropped from ∼$4.63/gallon in 1980 to ∼$1.22/gallon today, and it is now potentially competitive for blending with gasoline. Advances in pretreatment by acid-catalyzed hemicellulose hydrolysis and enzymes for cellulose breakdown coupled with recent development of genetically engineered bacteria that ferment all five sugars in biomass to ethanol at high yields have been the key to reducing costs. However, through continued advances in accessing the cellulose and hemicellulose fractions, the cost of biomass ethanol can be reduced to the point at which it is competitive as a pure fuel without subsidies. A major challenge to realizing the great benefits of biomass ethanol remains ...