Polycyclic aromatic hydrocarbons on particulate matter emitted during the co-generation of bioenergy and biochar from rice husk

The aim of this study was to evaluate the emissions of polycyclic aromatic hydrocarbons (PAHs) bound to the particulate matter (PM) during the combustion of raw pyrolysis volatiles (bio-oil and pyrogas mixture) generated from the pyrolysis of rice husk. Five different raw pyrolysis volatiles were produced at varying pyrolysis temperatures (400-800 degrees C) and subsequently combusted in a laboratory-scale, continuous pyrolysis-combustion facility at 850 degrees C. 15 priority pollutant PAH levels in the resulting biochar, bio-oil, and PM were evaluated. Results showed that combustion of the raw pyrolysis volatiles produced at elevated pyrolysis temperatures resulted in greater concentrations of PM-bound PAHs (119% increase between 400 and 800 degrees C) due to the increased PAH and oxy-aromatic content of the bio-oil fraction. Significantly increased benzo(a) pyrene (BaP) equivalent toxicity of the biochar and PM was observed at elevated pyrolysis temperatures.