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How to Figure the Btu Rating for Biomass

Biomass is defined as organic matter that includes plants, forest residue, animal waste and the organic components of municipal waste. Organic matter has bio-energy value that has been effectively stored from solar energy. When biomass is burned, it releases the proportional amount of carbon stored in its mass. The heating value of biomass is measured in British Thermal Units (Btu). Different types of biomass have different heating values. Empirical data (proximate analysis) reveals a close correlation between the elements contained in biomass and the actual energy value. The elements in biomass are carbohydrates and lignin/extractables. The lignin is the chemical glue that holds the carbohydrates together and the extractables are miscellaneous components such as sulfur and arsenic.

Instructions

- 1
  Determine the biomass type with which to compute the Btu rating for energy value. For instance, assume a biomass sample has the carbohydrate molecular formula C9H15O4 and a lignin/extractables formula of C12H28O2 - A2S4N4. Therefore, the entire sample will have 21 carbon atoms, 43 hydrogen atoms, six oxygen atoms, two arsenic atoms, four sulfur atoms and four nitrogen atoms.
- 2
  Calculate the heating value/energy content of the biomass sample by using the following empirical formula (proximate analysis):
  HV (in kJ/g) = 0.3491C + 1.1783 H - 0.1034 O - 0.0211 A + 0.1005 S -0.0151 N, where each variable represents the number of atoms in the sample.
  ̶0;C̶1; means carbon, ̶0;H̶1; means hydrogen, ̶0;O̶1; means oxygen, ̶0;A̶1; is arsenic, ̶0;S̶1; is sulfur and ̶0;N̶1; is nitrogen.
  The formula is:
  0.3491x21 + 1.1783x43 - 0.1034x6 - 0.0211x2 + 0.1005x4 - 0.0151x4.
  This equals 57.68 kJ/g.
- 3
  Convert the heating value of the biomass from kJ/g into Btu/lb. One kJ is equal to 0.9478 Btu and there are 454 grams per pound. Therefore, the Btu rating of biomass is 57.68 kJ x 0.9478 Btu x 454 grams/pound. This equates to 24,820 Btu/pound. Therefore, for each pound of biomass, the calculated Btu value is 24,820.

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