Research Interests

Renewable energy, fuels and chemicals • bioprocessing • process engineering

Current Research

Characterization of Accumulation Trends for Carbohydrate, Lignin and Extractive Degradation Products in Lignocellulose Pretreatment

One of the most well-studied and near-commercial technologies for converting biomass to ethanol is to use a thermochemical pretreatment followed by enzymatic hydrolysis and fermentation to produce ethanol. Challenges in realizing this approach have been to reduce the cost of the pretreatment, reduce the production of microbial inhibitors in the hydrolysate, and to ferment the complete variety of sugars produced. This project seeks to map out the correlation between pretreatment conditions and the production of products derived from the degradation of the carbohydrate, lignin and extractive fractions of the biomass.

The first objective of this study is to apply recently developed HPLC-UV and HPLC-MS/MS protocols for determination of the variety of compounds present in pretreated biomass hydrolysates (e.g., organic acids, aldehydes, and phenols). The second objective is to characterize accumulation trends of degradation reactions occurring during biomass pretreatment by mapping the degradation product concentrations versus pretreatment conditions, particularly temperature, reaction time, pH, combinations of these parameters as defined by the severity and combined severity functions, and the flow regime (batch or flow-through).

Development of Process Models for Near-term Commercial Production

A highly detailed technical and economic model has been developed by the DOE National Renewable Energy Laboratory (NREL) for production of ethanol from biomass. This model is relatively futuristic: it assumes very large scales, huge capital investments and well-defined feedstock. This task will consist of simplifying and adapting the NREL model to suit smaller scale operations, which are more typical of current biofuel commercialization efforts. Parallel programs will also be developed to model other process configurations, such as anaerobic digestion or biodiesel. The goal of this work is to produce a suite of models running on process modeling software and MS-Excel tailored for small scale, commercial and near-commercial biofuel production.

Integration of Bioprocessing into Kraft Pulp Mill Operation

Current practice in the pulp and paper industry is to produce paper and energy as the primary products of a pulp and paper operation. Recent advances in pulping procedures and bioconversion technology are enabling the diversification of pulp production to include value-added chemicals and fuels as well. The focus of this research project is to identify, characterize and optimize bioconversion processes that can upgrade waste and low-value streams in a pulping operation into products of higher value. Approaches include the use of genetically modified organisms capable of fermenting a variety of sugars to fuels and chemicals, and acidogenic digestion of mixed sugar and acid streams to produce purified organic acids and other organic molecules.

Selected Publications

Selected Papers

Shou-Feng Chen, Richard Mowery, C. Kevin Chambliss, G. Peter van Walsum. “Pseudo Reaction Kinetics of Organic Degradation Products in Dilute-Acid-Catalyzed Corn Stover Pretreatment Hydrolysates.” In press with Biotechnology and Bioengineering, June 2007.

G. Peter van Walsum, Maurilio Garcia-Gil, Shou-Feng Chen, Kevin Chambliss., 2007. “Effect of Dissolved Carbon Dioxide on Accumulation of Organic Acids in Liquid Hot Water Pretreated Biomass Hydrolysates,” Applied Biochemistry and Biotechnology, 136-140:301-311.

Chen, S.-F.; Mowery, R. A.; Castleberry, V. A.; van Walsum, G. P.; Chambliss, C. K., 2006. “High performance liquid chromatography method for simultaneous determination of aliphatic acid, aromatic acid and neutral degradation products in biomass pretreatment hydrolysates,” J. Chrom. A., 1104: 54-61.

A. Coté, W. A. Brown, D, Cameron, G. P. van Walsum, 2004. “Hydrolysis of lactose in whey permeate for subsequent fermentation to ethanol,” Journal of Dairy Science, 87: 6, 1608-1620.

Kemantha Jayawardhana, G. Peter van Walsum. 2004. “Modeling of Carbonic Acid Pretreatment Process Using ASPEN-Plus,” Applied Biochemistry and Biotechnology, 115(1-3) 1087-1102.

Damon Yourchisin, G. Peter van Walsum, 2004. “Comparison of the Microbial Inhibition and Enzymatic Hydrolysis Rates of Liquid and Solid Hydrolysates Produced from Pretreatment of Biomass with Carbonic Acid and Liquid Hot Water,” Applied Biochemistry and Biotechnology, 115(1-3) 1073-1086.

G. Peter van Walsum, Helen Shi, 2004. “Carbonic Acid Enhancement of Hydrolysis in Aqueous Pretreatment of Corn Stover,” Bioresource Technology, 93:3, 217-226.

Z. Fan, C. South, K. Lyford, J. Munsie, P. van Walsum, and L.R. Lynd, 2003. “Conversion of paper sludge to ethanol in a semincontinous solids-fed bioreactor,” Bioprocess and Biosystems Engineering, 26:(2) 93-101.

Robert C. McWilliams, G. Peter van Walsum, 2002. “Comparison of Aspen Wood Hydrolysates Produced by Pretreatment with Liquid Hot Water and Carbonic Acid,” Applied Biochemistry and Biotechnology, 98-100:109-121.

G. Peter van Walsum, 2001. “Severity Function Describing the Hydrolysis of Xylan using Carbonic Acid,” Applied Biochemistry and Biotechnology, 91-93:317-329.

Lee R. Lynd, Kimberly Lyford, Colin R. South, G. Peter van Walsum, Keith Levenson, 2001. “Evaluation of paper sludges for amenability to enzymatic hydrolysis and conversion to ethanol,” TAPPI J., 84:2, 50.

G. Peter van Walsum, Lee R. Lynd, 1998. “Allocation of ATP to Synthesis of Cells and Hydrolytic Enzymes in Cellulosic Fermentative Microorganisms: Bioenergetics, Kinetics, and Bioprocessing,” Biotechnology and Bioengineering, 58:2-3, 316-320.

G. Peter van Walsum, Stephen. G. Allen, Mark. S. Laser, Mark. J. Spencer, Michael. J. Antal Jr., Lee. R. Lynd, 1996. “Conversion of Lignocellulosics Pretreated with Hot Compressed Liquid Water to Ethanol,” Applied Biochemistry and Biotechnology, 57/58:157-170.

G. Peter van Walsum, David G. Cooper 1993. “Self-Cycling Fermentation (SCF) in a Stirred Tank Reactor,” Biotechnology and Bioengineering, 42:1175-1180.