Cellulosic ethanol via biochemical processing poses a challenge for developers and implementors

In the future liquid biofuels will need to be renewable, sustainable, as well as technically and economically viable. This paper provides an overview of the challenges that the biochemical production of cellulosic ethanol process still faces. The main emphasis of the paper is on challenges that emerge from the scale of liquid biofuel production. These challenges include raw material availability, other consumables, and side stream handling. The pretreatment, C5 fermentation, and concentration of sugars in processing need improvements, too. Sustainability issues and greenhouse gas reduction also pose a challenge for implementation and require development of internationally recognized sustainability principles and standards, and certification of sustainable operation. Economics of cellulosic ethanol processes are still also an area under development and debate. Yet, the Energy Independence and Security Act mandate together with the European Union Renewable Energy Directive and other local targets are driving the development and implementation forward towards more significant contribution of biofuels in the transportation sector.

[1]  K Sipilae,et al.  Status and Outlook for Biofuels, Other Alternative Fuels and New Vehicles , 2008 .

[2]  W. Glasser,et al.  Steam-assisted biomass fractionation. II. fractionation behavior of various biomass resources , 1998 .

[3]  L. Lynd,et al.  Hot Liquid Water Pretreatment of Lignocellulosics at High Solids Concentrations , 1997 .

[4]  D. Kilburn,et al.  Evaluation of cellulase preparations for hydrolysis of hardwood substrates , 2006, Applied biochemistry and biotechnology.

[5]  Kelly N. Ibsen,et al.  Lignocellulosic Biomass to Ethanol Process Design and Economics Utilizing Co-Current Dilute Acid Prehydrolysis and Enzymatic Hydrolysis for Corn Stover , 2002 .

[6]  Dennis Anderson,et al.  Sustainable Biofuels: Prospects and Challenges , 2008 .

[7]  Carlos A Cardona,et al.  Fuel ethanol production: process design trends and integration opportunities. , 2007, Bioresource technology.

[8]  Venkatesh Balan,et al.  Ethanolic fermentation of hydrolysates from ammonia fiber expansion (AFEX) treated corn stover and distillers grain without detoxification and external nutrient supplementation , 2008, Biotechnology and bioengineering.

[9]  C. Wyman,et al.  Impact of fluid velocity on hot water only pretreatment of corn stover in a flowthrough reactor , 2004, Applied biochemistry and biotechnology.

[10]  Robert C. Brown,et al.  Comparative economics of biorefineries based on the biochemical and thermochemical platforms , 2007 .

[11]  Charles E Wyman,et al.  What is (and is not) vital to advancing cellulosic ethanol. , 2007, Trends in biotechnology.

[12]  M. Taherzadeh,et al.  Acid-based hydrolysis processes for ethanol from lignocellulosic materials: A review , 2007, BioResources.

[13]  J. Saddler,et al.  Acid‐catalyzed steam pretreatment of lodgepole pine and subsequent enzymatic hydrolysis and fermentation to ethanol , 2007, Biotechnology and bioengineering.

[14]  L. Ingram,et al.  Efficient ethanol production from glucose, lactose, and xylose by recombinant Escherichia coli , 1989, Applied and environmental microbiology.

[15]  R. Elander,et al.  A Comparison of Aqueous and Dilute-Acid Single-Temperature Pretreatment of Yellow Poplar Sawdust , 2001 .

[16]  M. Galbe,et al.  Energy considerations for a SSF-based softwood ethanol plant. , 2008, Bioresource technology.

[17]  T. Jeffries,et al.  Engineering yeasts for xylose metabolism. , 2006, Current opinion in biotechnology.

[18]  G. Lidén,et al.  A short review on SSF – an interesting process option for ethanol production from lignocellulosic feedstocks , 2008, Biotechnology for biofuels.

[19]  Joseph J. Bozell,et al.  Chemicals and materials from renewable resources , 2001 .

[20]  L. Lynd,et al.  Consolidated bioprocessing of cellulosic biomass: an update. , 2005, Current opinion in biotechnology.

[21]  Jacinto F. Fabiosa,et al.  Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change , 2008, Science.

[22]  D. Leak,et al.  Effect of nutrient limitation on product formation during continuous fermentation of xylose with Thermoanaerobacter ethanolicus JW200 Fe(7) , 2003, Applied Microbiology and Biotechnology.

[23]  David K. Johnson,et al.  Biomass Recalcitrance: Engineering Plants and Enzymes for Biofuels Production , 2007, Science.

[24]  Anneli Petersson,et al.  Increased tolerance and conversion of inhibitors in lignocellulosic hydrolysates by Saccharomyces cerevisiae , 2007 .

[25]  Diane Greer.  Spinning straw into fuel , 2005 .

[26]  Luís C. Duarte,et al.  Hemicellulose biorefineries: a review on biomass pretreatments , 2008 .

[27]  Mark Holtzapple,et al.  Coordinated development of leading biomass pretreatment technologies. , 2005, Bioresource technology.

[28]  John N. Saddler,et al.  Steam pretreatment of douglas-fir wood chips , 2000, Applied biochemistry and biotechnology.

[29]  Ignacio Ballesteros,et al.  Ethanol production from steam-explosion pretreated wheat straw , 2006, Applied biochemistry and biotechnology.

[30]  Warren Mabee,et al.  Biorefining of softwoods using ethanol organosolv pulping: preliminary evaluation of process streams for manufacture of fuel-grade ethanol and co-products. , 2005, Biotechnology and bioengineering.

[31]  Mette Hedegaard Thomsen,et al.  Complex media from processing of agricultural crops for microbial fermentation , 2005, Applied Microbiology and Biotechnology.

[32]  M. Zhang,et al.  Development of an arabinose-fermenting Zymomonas mobilis strain by metabolic pathway engineering , 1996, Applied and environmental microbiology.

[33]  Mark J. Spencer,et al.  Conversion of Lignocellulosics Pretreated with Liquid Hot Water to Ethanol , 1996 .

[34]  Bryce J. Stokes,et al.  Biomass as Feedstock for A Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply , 2005 .

[35]  G. Lidén,et al.  Variability of the response of Saccharomyces cerevisiae strains to lignocellulose hydrolysate , 2008, Biotechnology and bioengineering.