Particulate matter emissions, and metals and toxic elements in airborne particulates emitted from biomass combustion: The importance of biomass type and combustion conditions.

The aim of this study was to investigate the impact of biomass combustion with respect to burning conditions and fuel types on particulate matter emissions (PM) and their metals as well as toxic elements content. For this purpose, different lab scale burning conditions were tested (20 and 13% O in the exhaust gas which simulate an incomplete and complete combustion respectively). Furthermore, two pellet stoves (8.5 and 10 kW) and one open fireplace were also tested. In all cases, 8 fuel types of biomass produced in Greece were used. Average PM emissions ranged at laboratory-scale combustions from about 65 to 170 mg/m with flow oxygen at 13% in the exhaust gas and from 85 to 220 mg/m at 20% O. At pellet stoves the emissions were found lower (35 -85 mg/m) than the open fireplace (105-195 mg/m). The maximum permitted particle emission limit is 150 mg/m. Metals on the PM filters were determined by several spectrometric techniques after appropriate digestion or acid leaching of the filters, and the results obtained by these two methods were compared. The concentration of PM as well as the total concentration of the metals on the filters after the digestion procedure appeared higher at laboratory-scale combustions with flow oxygen at 20% in the exhaust gas and even higher at fireplace in comparison to laboratory-scale combustions with 13% O and pellet stoves. Modern combustion appliances and appropriate types of biomass emit lower PM emissions and lower concentration of metals than the traditional devices where incomplete combustion conditions are observed. Finally, a comparison with other studies was conducted resulting in similar results.