Modeling of Biomass to Determine
Gavin George Dr. Larry Baxter
Dept. of Chemical Engineering, Brigham Young University, Provo, Utah
- Estimated percentages of cellulose, hemi-cellulose, lignin, and other minor proximate components in biomass materials.
- Analyzed by elemental ratios and experimental heating values.
- 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
- 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/kmol2Hf Lignin: 1593 kJ/kmol2
- Hf Hemi-Cellulose: 762 kJ/kmol2
- US DOE/EE Biopower Program
- National Renewable Energy Laboratory
1 - U.S Department of Energy, Office of Transportation Technologies, Biofuels, http://www.ott.doe.gov/biofuels/glossary.html#P
2 - Development of an ASPEN Plus Physical Properties Data base for Biofuels Components, Robert J. Wooley Victoria Putsche,
National Renewable Energy Laboratory, http://www.afdc.doe.gov/pdfs/3955.pdf
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, http://bioenergy.ornl.gov/papers/misc/biochar_factsheet.htmlz