Emission characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans from industrial combustion of biomass fuels

Although biomass fuel has always been regarded as a source of sustainable energy, it potentially emits polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This study investigated PCDD/F emissions from industrial boilers fired with three types of biomass fuel (i.e., bagasse, coffee residue, and biomass pellets) via stack sampling and laboratory analysis. The measured mass concentrations of PCDD/Fs varied among the boilers from 0.0491 to 12.7 ng Nm−3 (11% O2), with the calculated average international toxic equivalent quantity (I-TEQ) from 0.00195 to 1.71 ng I-TEQ Nm−3 (11% O2). Some of them were beyond the limit value for municipal waste incineration. 2,3,4,7,8-PeCDF could be used as a good indicator of dioxin-induced toxicity of stack flue gases from biomass-fired boilers. The PCDFs/PCDDs ratios were more than 1, likely indicating the formation of dioxins in the boilers favored by de novo synthesis. The emission factor (EF) of total PCDD/Fs averaged 5.35 ng I-TEQ kg−1 air-dry biomass (equivalent to 39.0 ng kg−1 air-dry biomass). Specifically, the mean EF was 6.94 ng I-TEQ kg−1 (52.6 ng kg−1) for biomass-pellet-fired boiler, 11.8 ng I-TEQ kg−1 (74.6 ng kg−1) for coffee-residue -fired boiler, and 0.0277 ng I-TEQ kg−1 (0.489 ng kg−1) for bagasse-fired boilers. The annual PCDD/F emission was estimated to be 208 g I-TEQ in 2020 in China, accounting for approximately 2% of the total national annual emission of PCDD/Fs. The results can be used to develop PCDD/Fs emission inventories and offer valuable insights to authorities regarding utilizing biomass in industry in the future. [Display omitted] •PCDD/Fs emissions from biomass-fired boilers were characterized.•PCDD/F EFs for pelletized biomass were calculated for the first time.•2,3,4,7,8-PeCDF well predicts dioxin toxicity related to biomass-fired boilers.•Biomass-fired boilers in China emitted 208 g I-TEQ PCDD/Fs in 2020.