Effect of\nBiomass/Sludge Blending on the Emission\nBehavior of Heavy Metals during Coal Combustion: A Global Meta-analysis

Co-combustion of coal and carbon-containing fuels, especially\nbiomass\nand sludge, is thought to be a good choice for the goal of carbon\nneutrality. Regardless of tremendous studies on the co-combustion\ncharacteristics, the effects of biomass/sludge blending on the emission\nbehavior of toxic heavy metals are still not so clear due to the differences\nin volatility of heavy metals, the wide variety of raw blended materials,\nthe changeable operating conditions, and the huge difference in experimental\nscale. To reach broad generalizations across larger numbers of study\noutcomes, a global meta-analysis was conducted in this work to comprehensively\nevaluate the impacts of various parameters on the emission of three\ntypical heavy metals (As, Pb, and Cr). Results showed that co-firing\nwith biomass/sludge would accelerate the emission of As and Pb while\nreducing Cr emission, mainly contributed by sludge rather than biomass.\nIn comparison to other types of sludge, the promotion and inhibition\neffects of sewage sludge were more significant. The combustion temperature\nand blending ratio were the key factors affecting heavy metal emission,\nfollowed by the oxygen concentration and carbonization temperature\nof biomass. Besides, no remarkable difference was found among bench-\nand large-scale testing results. The findings are expected to give\nnew insight into the clean co-combustion of coal and various kinds\nof solid wastes.