Forest-Based Biomass Basic Computations - Mathematics and Statistics for the Environment - page 327

TABLE 13.1
Lower and Higher Heating Values of Solid Fuels

Lower Heating Value (LHV) Higher Heating Value (HHV)

Fuel Btu/ton Btu/lb MJ/kg Btu/ton Btu/lb MJ/kg

Farmed trees 16,811,000 8406 19,551 17,703,170 8852 20,589

Forest residue 13,243,490 6622 15,402 14,164,160 7082 16,473

Source: Transportation Fuel Cycle Analysis Model , GREET 1.8b, Argonne National
Laboratory, Argonne, IL, 2008.

values of solid forest-based biomass fuels are listed in Table 13.1, and Table 13.2 illustrates the
variation in reported heat content values (on a dry weight basis) in the U.S. and European literature
based on values in the ECN Phyllis database (http://www.ecn.nl/phyllis/), the U.S. Department of
Energy Biomass Feedstock Composition and Property database (http://www1.eere.energy.gov/bio-
mass/feedstock_databases.html), and selected literature sources.

13.3.2 e FFeCt oF F uel m oisture on W ood h eat C ontent
Because recently harvested wood fuels usually contain 30 to 55% water, it is useful to understand the
effect of moisture content on the heating value of wood fuels. Table 13.3 shows the effect of percent
moisture content (MC) on the higher heating value as-fired (HHV-AF) of a wood sample starting at
8500 Btu/lb (oven-dry). Fuel moisture content is usually reported as the wet weight basis moisture
content. Moisture content expressed on a wet weight basis (also called “green” or “as-fired” moisture
content) is the decimal fraction of the fuel that consists of water; for example, a pound of wet wood
fuel at 50% moisture content contains 0.50 pound of water and 0.50 pound of wood. Note that the

TABLE 13.2
Heat Content Ranges for Forest Biomass Fuels (Dry Weight Basis)
English

Metric

Higher Heating Value Higher Heating Value Lower Heating Value

Fuel Btu/lb MBtu/ton kJ/kg MJ/kg kJ/kg MJ/kg

Woody crops
Black locust 8409-8582 16.8-17.2 19,547-19,948 19.5-19.9 18,464 18.5

Eucalyptus 8174-8432 16.3-16.9 19,000-19,599 19.0-19.6 17,963 18.0

Hybrid poplar 8183-8491 16.4-17.0 19,022-19,737 19.0-19.7 17,700 17.7

Willow 7983-8497 16.0-17.0 18,556-19,750 18.6-19.7 16,734-18,419 16.7-18.4

Forest residues
Hardwood wood 8017-8920 16.0-17.5 18,635-20,734 18.6-20.7 — —

Softwood wood 8000-9120 16.0-18.24 18,595-21,119 18.6-21.1 17,514-20,768 17.5-20.8

Sources: http://www1.eere.energy.gov/biomass/feedstock_databases.html; Bushnell, D., Biomass Fuel Characterization:
Testing and Evaluating the Combustion Characteristics of Selected Biomass Fuels , Bonneville Power
Administration, Portland, OR, 1989; Jenkins, B., Properties of Biomass, Appendix to Biomass Energy
Fundamentals , EPRI Report TR-102107, Electric Power Research Institute, Palo Alto, CA, 1993; Jenkins, B.L.
et al., Fuel Processing Technology , 54, 17-46, 1998; Tillman, D., Wood as an Energy Resource , Academic
Press, New York, 1978.