Wood Fuel Properties and Fuel Products from Woods

The fuel properties of wood can be summarized by ultimate and proximate analysis and determination of the high heating value. It is not valid to list these values for species since a species has not been adequately sampled and tested. Enough is known, however, to say that softwoods have a high heating value of about 9,000 Btu per pound; whereas hardwoods have a value of about 8,600 Btu per pound. These values are probably within about ±5 percent of a value expected for a specific sample. The ultimate analysis for wood is about 50 percent carbon, 6 percent hydrogen, and 44 percent oxygen on a moisture and ashfree basis. The ash content of wood is about 0.6 percent and 3 percent for bark, but the ash content of wood fuel can be higher due to dirt associated with harvesting. The sulfur and nitrogen content of wood and bark is usally less than 0.1 percent for each, but some bark may contain as much as 0.3 percent nitrogen. The proximate analysis of wood is about 75 to 80 percent volatile and 20 to 25 percent fixed