Applying a life cycle perspective to research on metal recovery from electronic waste using bioleaching

Applying a life cycle perspective to research on metal recovery from electronic waste using bioleaching

Villares, M.

Guinée, J.B. (mentor)
Offerman, S.E. (mentor)

Delft University of Technology

Industrial Ecology

Industrial Ecology

2015-08-31

The Master’s programme Industrial Ecology is jointly organised by Leiden University and Delft University of Technology. Waste electronics and electrical equipment (WEEE) constitute a growing waste stream which is becoming more problematic in its management. Unsafe disposal contributes to environmental pollution and threatens human health as well as wasting secondary resources. A biologically mediated natural process, termed bioleaching, applied to the recovery metals from electronic waste, may become a promising emerging technology contributing to secondary resource recovery. Improved resource efficiency is highly relevant in the context of a transition to a more environmentally benign circular economy. Initial experimental bioleaching results using bacteria show efficient yields. 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 micro organisms can work at close to ambient temperatures and directly generate few contaminants. This thesis reports on the environmental assessment of the novel bioleaching process. LCA methodology was applied at the early research stage to the process to embed it in a life cycle context, linking it to upstream and downstream flows. Then LCA was combined with an elaborate conjectural scenario to gauge its application in a potential future context and compare it to an established metal recovery process. The implications for LCA methodology were then discussed. Using primary data from the lab research, a product system was defined at laboratory scale to which LCA was applied. Data for elemental copper recovery was not available so this was estimated. After gathering ample contextual information on the direction of research, regulations, technological precedents and existing similar technologies a short term future scaling up scenario was defined. A second LCA was performed on this estimated scaled up product system. Environmental profiles were obtained for the lab product system, the scaled up system and optimised versions of the scaled up system. The latter were compared to the environmental performance of an existing technology, which aligned with the scaled up scenario in terms of scope and comparability. In the first two LCAs potential hotspots were identified in the energy and material inputs for the bioleaching process and solvents for copper recovery. However, the comparison with the existing technology returned a far inferior environmental profile, even after further optimisation. These results could not be considered robust given the precociousness of application, yet valuable information was generated. The uncertainties also prompted further enquiry about the system boundary and comparability of product systems. Despite the amount of uncertainty and conjecture involved, the whole exercise can nonetheless be considered a valid, informative mock-up of a plausible future. The tandem application of ex ante LCA and exploratory scenario brings a degree of systematic rigour and discipline to an ambiguous situation. It provides a medium for stimulating attitudes of critical examination and discovery in the very early in development can allow it to have a significant influence in broadening the research context. It is recommended that, for the bioleaching research, the LCA be built upon and refined in subsequent development stages with appropriate data gathering. In general, the approach should be applied again, possibly even earlier and for other technologies, to test it and establish its validity as an environmental screening tool in these anticipatory circumstances. As estimations are key for its application, this component should be targeted by dedicated simulation software and databases also adapted for this purpose. The promotion of the systems approach perspective of the methodology can also be disseminated by using it as an exercise as part of the training of designers, researchers and engineers. If it can be sufficiently validated after application to other research and concepts then it may be expanded to incorporate economic & social aspects.

LCA
bioleaching
WEEE
scenario
metal recovery
e-waste

http://resolver.tudelft.nl/uuid:ad116c32-ea7c-40eb-955a-ba96d62ac5c8

Student theses

master thesis

(c) 2015 Villares, M.