Measurement and Modeling of Air Toxins from Smoldering Combustion of Biomass

Methane and low-molecular-weight hydrocarbons have been detected and quantified in smoke from biomass burning. The oxygenated organic emissions from 29 bench-scale fires of various types were investigated using individual components derived from ponderosa pine. Three replicates each of needles, litter, duff, and humus were allowed to smolder for 40 min, and two bark fires were allowed to smolder for 45 min. The condensible and noncondensible compounds were analyzed by gas chromatography/mass spectrometry. The major condensible compound emitted from all the fires, except the humus fires, was acetic acid. The smoldering needle fires gave the highest yield, while the flaming wood and smoldering humus fires emitted the least acetic acid. Methanol was the second most abundant compound. 2-Furaldehyde was also a major emission in all of the fires, along with acetol, vinyl acetate, formic acid, phenol, 5-methyl-2-furaldehyde, and 2-cyclopenten-1-one. For the noncondensible gases, the self-sustained duff fires and the smoldering humus fires produced the most carbon dioxide. All of the emissions, except for CO sub(2), were negatively correlated linearly with the combustion efficiency. The emissions were primarily dependent on fuel chemistry.