Applying an ex-ante life cycle perspective to metal recovery from e-waste using bioleaching

Abstract Discarded electrical and electronic equipment is a growing waste stream becoming more problematic in its management. Unsafe disposal contributes to environmental pollution and threatens human health as well as wasting secondary resources. The recovery of valuable metals from electronic waste can be achieved by bioleaching, a biologically mediated natural chemical process. The bioleaching process may become a promising emerging technology contributing to secondary resource recovery relevant in the context of a transition to a more environmentally friendly circular economy. Initial experimental bioleaching results show efficient yields (98.4% copper removed). Claims of benign environmental performance in the research literature are only based on process centric suppositions. Compared to metal recovery using smelting at high temperatures, the bioleaching microorganisms can work at near ambient temperatures and generate few direct contaminants. Life cycle assessment was applied at an early stage to the novel bioleaching process on printed circuit boards to embed it in a life cycle context. Then LCA was combined with an elaborate conjectural scenario to steer its application in a potential future context, where it was compared to a current industrial pyrometallurgical technique. This is a relatively new application of LCA. Potential hotspots were identified related to energy and material inputs for the bioleaching process and solvents for copper recovery of the LCAs of the laboratory and scaled up systems. The comparison with an existing technology returned an inferior environmental performance, even after the simulation of further future optimisation. The tandem application of ex-ante LCA and exploratory scenario brought a systematic rigour and discipline to an ambiguous situation at the start of development of a novel technology. The approach displays potential hot-spots of a product system, in spite of the conjecture and uncertainties. It also broadened the research scope bringing a systems approach, long term view, environmental aspects, and alternative perspectives on the novel technology to the research domain. The foresight of the practitioner(s) was increased at a timely moment so the approach is of great service as a developmental design tool. Though imprecise with much conjecture involved, the whole exercise can be considered a valid mock-up of a plausible future providing useful provisional insights to be built upon.