Low emissions from wood burning in an ecolabelled residential boiler

Artikel i vetenskaplig tidskrift, 2006

Emissions of organic compounds from wood burning in a modern ecolabelled residential boiler (30 kW) were studied. Smoke was collected in the chimney outlet at different times during the burning cycle for subsequent analysis by gas chromatography. The studied ecolabelled wood boiler had high combustion efficiency, and the flaming phase emissions were very low. The greenhouse gas methane (CH4) was determined in low concentrations of about a few mg m−3 and was the major volatile hydrocarbon emitted. The CH4 emission factor was calculated to 0.04 g kg−1 dry fuel. Benzene, in the range 0.1-1 mg m−3, was the predominant aromatic compound emitted. Other major aromatic compounds were methylbenzene, dimethylbenzenes and ethenylbenzene. The concentrations of the studied polycyclic aromatic compounds were generally low, except for naphthalene, which was the third most prominent aromatic compound. However, the total emissions of these health and environmentally hazardous compounds were low. The already low emissions of most of the organic compounds decreased further towards the end of the burning cycle, although the concentration of carbon monoxide (CO) increased. This indicates that large CO emissions are not necessarily linked to large emissions of organic compounds. Relative to benzene, the concentrations of many of the aromatic compounds studied were higher in the glowing combustion phase, than in the flaming combustion phase. The total environmental and health impact of the studied emissions from the ecolabelled boiler is considered to be low. This wood boiler can be recommended as an environmentally sound residential heating alternative.