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Modeling of Biomass to Determine Proximate Compositions. Gavin George Dr. Larry Baxter Dept. of Chemical Engineering, Brigham Young University, Provo, Utah. Abstract:

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Modeling of Biomass to Determine

Proximate Compositions

Gavin George Dr. Larry Baxter

Dept. of Chemical Engineering, Brigham Young University, Provo, Utah

  • Abstract:

  • Estimated percentages of cellulose, hemi-cellulose, lignin, and other minor proximate components in biomass materials.

  • Analyzed by elemental ratios and experimental heating values.

  • Analysis:

  • Visual basic program to calculate the percentages of cellulose, lignin, protein, and other extractives.

  • Biobank database3 of elementary analysis supplied the needed elemental data.

  • Cellulose and lignin percentages were determined using the areas formed on the hydrogen/carbon vs. oxygen/carbon graph by lines drawn from the biomass to the points for cellulose, lignin, and a third compound.

  • Third compound was taken as a lipid or protein because a large portion of the unknown extractives were expected to have a similar composition.



  • Previous research limited to lengthy laboratory techniques.

  • A simpler approach; using heating values and molecular group contributions.

  • Basis for the computer code is a geometric relationship of elemental ratios plotted graphically.

  • Gross calorific values checked the validity of the findings by multiplying heats of combustion by mass percentages.

  • Predicted GCVs were then compared with experimentally determined gross calorific values.

  • The user interface of the program:

  • Majority of biomass material falls in the area between the lignin and cellulose points.

  • Deviation from the line connecting lignin and cellulose results from other compounds in the sample.

  • Different structures of lignin exist, represented by the cluster of three lignin points on the graph.

  • Used the relative amounts of hetero atoms in a sample to estimate the percentage of certain more complex components.

  • Percentage protein was determined by the established formula:

  • Mass% Nitrogen * 6.25 = Mass% Protein1

  • Conclusions:

  • The type of analysis provides more accurate estimates for those biomass materials with smaller amounts of exotic compounds and those with limited degradation of proximate compounds.

  • This program could prove to be an effective method to screen large numbers of biomass materials for a desired proximate composition. This could be followed by a more exact laboratory analysis.

  • Hemicellulose and cellulose concentrations differentiated by the following estimates:

  • Hardwood/Grasses: 63% Cellulose, 37% Hemicellulose4

  • Softwood : 53% Cellulose, 47% Hemicellulose4

  • Basic components such as cellulose, hemi-cellulose and lignin have distinct heating values, which determined a total heating value.

  • Hf Cellulose: 976 kJ/kmol2 Hf Lignin: 1593 kJ/kmol2

  • Hf Hemi-Cellulose: 762 kJ/kmol2

  • Acknowledgements:

  • US DOE/EE Biopower Program

  • National Renewable Energy Laboratory

1 - U.S Department of Energy, Office of Transportation Technologies, Biofuels,

2 - Development of an ASPEN Plus Physical Properties Data base for Biofuels Components, Robert J. Wooley Victoria Putsche,

National Renewable Energy Laboratory,

3 - BioBank version 2.4, BIOS consulting, Graz, Austria

4 - Emissions of Rural Wood-Burning Cooking Devices, Grant Ballard-Tremeer, Appendix D Wood combustion,

1.   5 - “Bioenergy Feedstock Characteristics”, Jonathan Scurlock, Oak Ridge National Laboratory, Bioenergy Feedstock Development Programs,