The origin of potential precursors of secondary organic aerosols during combustion of biochar and softwood in residential heating

Abstract

Compounds that are potential precursors of secondary organic –aerosols account for up to 33.4 ± 7.1 mg/m3 in softwood combustion emissions, while biochar can be considered zero-emission fuel (0.18 ± 0.06 mg/m3). The characteristic feature of gaseous emissions from biochar combustion is the presence of n-alkanes (70.3 ± 6.6 µg/m3), which arise from the thermal degradation of waxes, cuticles, and plant lipids. In addition to alkanes, carboxylic acids (4.9 ± 0.2 µg/m3) are present in biochar emissions at significantly lower concentrations. In deposits from biochar combustion (6.1 ± 0.8 g/kg), the internal parts of the boiler capture 20% more organic compounds than in wood-burning deposits (4.84 ± 0.91 g/kg). The greater uptake of organic compounds in biochar combustion deposits (513.8 ± 6.2 g/kg) than in softwood (382.7 ± 27.3 g/kg) is related to the higher elemental carbon content in biochar. The organic compounds present in deposits from biochar are mainly methyl ketone, fatty acids such and alkanes. In deposits from softwood, the compounds of chemical groups of phenols, anhydrosaccharides and acetic acids are present. The novelty lies in identifying and determining the quantity of organic compounds that form precursors of the solid organic aerosols in the combustion of biochar.