Cellulose conversion in dry grind ethanol plants Michael Ladisch a,j, * , Bruce Dale b , Wally Tyner c , Nathan Mosier a,j , Youngmi Kim a , Michael Cotta d , Bruce Dien d , Hans Blaschek e , Edmund Laurenas h , Brent Shanks f , John Verkade g , Chad Schell i , Gene Petersen i a Laboratory of Renewable Resources Engineering, Purdue University, West Lafayette, IN 47907, USA b Department of Chemical Engineering, Michigan State University, E.Lansing, MI 48824, USA c Department of Agriculture Economics, Purdue University, West Lafayette, IN 47907, USA d USDA, NCAUR ARS, Peoria, IL 61604, USA e Department of Food Science and Human Nutrition, University of Illinois, Champaign-Urbana, IL 61801, USA f Department of Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, USA g Department of Chemistry, Iowa State University, Ames, IA 50011, USA h Genencor, Palo Alto, CA 94304, USA i US Department of Energy, Golden, CO 80401, USA j Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, USA Abstract The expansion of the dry grind ethanol industry provides a unique opportunity to introduce cellulose conversion technology to exist- ing grain to ethanol plants, while enhancing ethanol yields by up to 14%, and decreasing the volume while increasing protein content of distiller’s grains. The technologies required are cellulose pretreatment, enzyme hydrolysis, fermentation, and drying. Laboratory data combined with compositional analysis and process simulations are used to present a comparative analysis of a dry grind process to a process with pretreatment and hydrolysis of cellulose in distiller’s grains. The additional processing steps are projected to give a 32% increase in net present value if process modifications are made to a 100 million gallon/year plant. Ó 2007 Published by Elsevier Ltd. Keywords: Cellulose; Ethanol; Cellulose pretreatment; Cellulases; Corn co-products 1. Synopsis of key findings This special edition of the journal addresses pathways for introducing cellulose conversion to dry grind ethanol plants. The papers that make up this special volume give experimental results, an engineering framework, and eco- nomic analysis for incorporating cellulose conversion tech- nology into the dry grind pathway for fuel ethanol production from corn grain (Schell et al., 2007). The com- position of wet cake and distillers dried grains with solu- bles, and changes in composition upon pretreatment using liquid hot water (LHW) or ammonia fiber expansion (AFEX) are utilized to develop material balances for pro- cesses that incorporate pretreatment into an existing corn to ethanol plant (Kim et al., 2007a,b,c). The liquid hot water and AFEX pretreatment processes represent ‘‘wet to wet” and ‘‘dry to dry” approaches, respectively, for cel- lulose pretreatment. Both pretreatments minimize mono- saccharide formation during the pretreatment step itself. Formation of monosaccharides occurs after pretreatment when cellulases, hemicellulases, and/or other hydrolases are added (Fig. 1). A third type of pretreatment, based on chemical derivatization with phosphite esters results in some hydrolysis and nearly complete dissolution of DDGS in water (Oshel et al., 2007). 0960-8524/$ - see front matter Ó 2007 Published by Elsevier Ltd. doi:10.1016/j.biortech.2007.09.082 * Corresponding author. Address: Laboratory of Renewable Resources Engineering, Purdue University, West Lafayette, IN 47907, USA. Tel.: +1 765 494 7022; fax: +1 765 494 7023. E-mail address: carie@purdue.edu (M. Ladisch). Available online at www.sciencedirect.com Bioresource Technology 99 (2008) 5157–5159