Potential of Pyrolysis for the Recovery of Heavy Metals and Bioenergy from Contaminated Broussonetia papyrifera Biomass

Heavy metal contaminated biomass is a severe environmental problem. Presently, the disposal of heavy metal contaminated biomass tends to seek the recovery of both heavy metals and bioenergy. In this study, pyrolysis technology was employed to pyrolyze contaminated biomass to elucidate the influence and fate of the heavy metals and the potential for recovering bioenergy. The results showed that heavy metals in biomass reduced the reaction energy in the main decomposition stage by approximately 10%, while 25% of the biomass decomposed to solid products. Moreover, 63.2% to 68.2% of the Cd and 69.0% to 77.9% of the Cu were retained in the solid, and the metals in the residues existed as metal elements that can be recovered by general smelting. The majority of the biomass (75%) generated volatile products and was only slightly influenced by heavy metals. Compared with the uncontaminated biomass, the component of bioenergy was reduced only slightly, which suggests strong potential for recovering bioenergy. The finding of this paper can be a theoretical foundation to support the responsible disposal, through pyrolysis, of biomass contaminated by heavy metals.