Polycyclic aromatic hydrocarbons emissions from biomass-fueled boilers in China

Biomass serves as a sustainable energy source; however, the environmental risks associated with polycyclic aromatic hydrocarbons (PAHs) emitted from industrial biomass-fueled boilers are not well understood. This study analyzed 16 priority PAHs in both particulate and gaseous phases from 13 representative real-world industrial biomass-fueled boilers. Flue gas samples were collected from the stacks and analyzed using advanced techniques. Total PAHs concentrations ranged from 1.36 to 8870 μg m^-3 (9 % O₂ v/v), with benzo[a]pyrene emissions from certain boilers exceeding the allowable emissions standards for the coking chemical and petroleum refining industries in China. PAHs were predominantly found in the gaseous phase, with both gas and particle phases exhibiting similar toxicity. The average emission factor (EF_mass) was 9.23 mg kg^-1, while the toxicity-equivalent emission factors (EF_CEQ, EF_MEQ, and EF_TEQ) were 1.96 × 10^-2, 1.39 × 10^-2 and 7.61 × 10^-4 mg kg^-1, respectively. It is estimated that annual PAH emissions from 2020 to 2050 will significantly decrease if biomass is used as industrial fuel in boilers (0.61 to 1.32 Gg y^-1) instead of being openly burned in the field (3.39 to 7.21 Gg y^-1). Overall, this study provides a comprehensive evaluation of PAH emissions from industrial biomass combustion, offering valuable data for future research and policy-making.