Life cycle assessment of a bio-hydrometallurgical treatment of spent Zn-Mn batteries

As one of the most widely used battery categories, spent Zn-Mn batteries are becoming a significant environmental and health threat. Various technologies have been developed to address spent Zn-Mn batteries; these include pyrometallurgical and hydrometallurgical methods, as well as newly developed bio-hydrometallurgical methods. Bio-hydrometallurgical technologies use two strains of bacteria to leach Zn and Mn from spent batteries, after which soft magnetic ferrite is precipitated. However, the environmental performance of the bio-hydrometallurgical method is unclear. In this study, we conducted a Life Cycle Assessment (LCA) to estimate the environmental impact of a novel bio-hydrometallurgical method of recycling spent Zn-Mn batteries in a small pilot experiment. Our results showed that the dominant environmental impact categories were human toxicity and marine ecotoxicity, with values of 62.7 kg 1, 4-DB eq and 0.46 kg 1, 4-DB eq, respectively. The process of cutting and crushing spent batteries contributed the greatest environmental impact. Therefore, we suggest that the cutting and crushing process should be redesigned to decrease direct metal emissions. Substituting other energy sources for electricity and fully using the solid residues from bioleaching could also help lessen the environmental impact. Metal recovery in bio-hydrometallurgical treatment of spent Zn-Mn batteries could significantly reduce the overall impact, which calls for collection and recycling of spent Zn-Mn batteries.