A review of sustainable metal recovery from e-waste via bioleaching: Current status and strategies for improvement

Abstract

Metals are indispensable resources for forging infrastructures of modern society. Given the substantial environmental burdens associated with traditional mining practices, the recycling of metals from electrical and electronic devices has emerged as a strategic and sustainable alternative for metal sourcing. The conventional metallurgical methods, such as pyrometallurgy and hydrometallurgy, are commercially available. However, their low sustainability poses challenges to the pursuit of environmentally responsible metal recycling from waste electrical and electronic equipment (e-waste). This review critically examines strategies to recover metals from e-waste through bioleaching. The specific mechanisms of bioleaching are discussed, and recent studies (published in 2020 onwards) on e-waste bioleaching are summarised with respect to the bacterial and fungal species employed. Although bioleaching has the potential for sustainable metal recovery from e-waste, further process improvements are necessary for its commercial implementation. To enhance bioleaching efficiency, this review introduces two strategic approaches. In particular, it discusses the manipulation of microbial strains through adaptive laboratory evolution (ALE) and genetic engineering. Another approach involves optimising bioleaching operational conditions, which is discussed through the application of machine learning-based bioleaching optimisation and cell immobilisation using supporting materials. By highlighting these methodologies, this review aims to establish a sustainable and energy-saving metal supply through e-waste recycling.