Comparison of Emissions from Wood Combustion. Part 2: Impact of Combustion Conditions on Emission Factors and Characteristics of Particle-Bound Organic Species and Polycyclic Aromatic Hydrocarbon (PAH)-Related Toxicological Potential

The impact of combustion conditions on emission factors and characteristics of log wood combustion was investigated. Two different kinds of log woods (spruce and beech) and one kind of briquette (spruce sawdust) were used to study differences in emission behavior depending upon the wood type. Beech wood was used to examine additionally the impact of different moisture contents and maloperation on emissions of fine particulate matter (PM). Therefore, wood logs with three different levels of moisture content were used. Maloperation was simulated by an overload scenario and an air deficiency scenario. Toxicity equivalent (TEQ) values were calculated for the different combustion conditions. It was found that PM mass varies only by a factor of 8 at a maximum, whereas TEQ values can vary more than a factor of 80 (regular beech wood combustion, 6 mu g MJ(-1); beech wood combustion in an overloaded combustion chamber, 500 mu g MJ(-1)). In particular, wood with a higher moisture content (19%) released high amounts of intermediate products from lignin and cellulose degradation. The PM emissions in this case were the highest among the tested operation conditions, especially during the initial (cold start) inflaming (660 mu g MJ(-1)), but were not in correspondence with the toxicity potential. The TEQ(37 mu g MJ(-1)) in that case was much lower than during maloperation.