Investigation on organic pollutants from a domestic heating system using various solid biofuels.

Various herbaceous biofuels (straw, whole plant cereals and set aside hay) and spruce wood were tested for their potential to form PCDD/F, PCPh, PCBz and PAH during combustion. The trials were conducted in an automatically charged multi-fuel furnace for domestic applications (50 kWth). Both, flue gas and the different ash fractions were analysed. CO-emission results show, that combustion conditions were relatively uniform (mean CO-level: 200 mg/m3 at 13% O2 in flue gas). Likewise, the TOC- and PAH-emissions in the fuel gas remained constantly on a relatively low level. However, for the PCDD/F, PCPh and PCBz increased emissions were detected when herbacious fuels were applied. This may be attributed to their higher chlorine concentration and the high ash content, which is responsible for increased dust emissions during combustion. Similar observations were also found for the PCDD/F-concentrations in the ashes. Combustion chamber ashes usually showed a drastically reduced contamination with highly toxical compounds, compared to the ash fraction from the heat exchanger ash or to chimney soot.

PCDD/F- and PAH-emission from house heating systems.

Combustion experiments were carried out in different house heating systems using various fuels. The emission samples and the chimney soot samples were analyzed for polychlorinated dibenzo-p-dioxins/furans (PCDD/F) and polycyclic-aromatic-hydrocarbons (PAH). The PCDD/F-concentrations in fluegases using untreated wood were in the range of 2-25 pg I-TE/m3. The combustion of paper, cartons, painted wood and wood with 2-5% PVC gave PCDD/F-concentrations from 38 to 952 pg I-TE/m3 and 380 to 2,240 ng I-TE/kg (chimney soot). The PAH-concentrations in flue gas were about 30 times higher using an old technology in relation to a new one.