https://doi.org/10.1177/0734242X19895321 Waste Management & Research 1–13 © The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0734242X19895321 journals.sagepub.com/home/wmr Introduction Population growth and technological innovation not only pro- moted new electronic products generation, but also increased the volume of waste electrical and electronic equipment (WEEE) as a municipal solid wastes part in the last decades. The WEEE (also called E-waste(s)) includes both large and small items, ranging from refrigerators, televisions, and washing machines, to smaller ones like laptops and personal computers, mobile phones, CD/ DVD players, radios, modems, and cameras (Awasthi et al., 2016). Environmental Protection Agency of United States (EPA) esti- mates that the electrical and electronical waste volume is increas- ing three times faster than the other municipal solid waste types, like food leftover, paper and cardboard, plastics, wood, glass, household waste, and miscellaneous (Ilyas and Lee, 2014; Karwowska et al., 2014; Zheng et al., 2013). With respect to the last EPA report, annually about 50 million tonnes of WEEE are generated all over the world, and just 18% of this amount is going to be recycled, and the rest of them will be were treated by incin- eration or land fill processes (Liu et al., 2016). WEEE usually con- tains toxic materials, including haloids and metals (Table 1), and these substances spread in the environment could result in unfa- vourable environmental effects, and also threaten human health in the case that they are not properly managed. WEEE disposal meth- ods like landfilling and incineration may transport toxic substances into groundwater or the atmosphere, where the release of heavy metals and polyhalogenated organics, such as polychlorinated biphenyls and polybrominated diphenyl ethers, from WEEE has been reported in literature (Arshadi and Mousavi, 2015a; Kiddee et al., 2013; Qu et al., 2007). In addition, several investigations indicated the presence of these substances in significant concentra- tions in blood, serum, hair, human milk, and urine from people who lived in the neighbourhood of WEEE disposal areas (Eguchi et al., 2012; Robinson, 2009; Zheng et al., 2013). Strategies to overcome the WEEE disposal problems considerably differ among countries. For instance, African countries mainly reuse disposed electronic products, whereas Asian countries use rather unsafe pro- cedures, namely landfilling and incineration (Wong et al., 2007). In some Asian countries like China and India, the management laws for WEEE disposal have been recently amended, and the manufac- tures must dispose of WEEE using advanced technology (Kiddee et al., 2013). The analysis of E-waste indicates that high electrical conduc- tive metals, like silver, palladium, copper, and iron, exist in it, however, the gold and copper contents are significantly higher than other metals (Table 2). Some statistics demonstrated that the level of gold and copper in E-waste are about 35–50 and 13–26 Biohydrometallurgy as an environmentally friendly approach in metals recovery from electrical waste: A review Alireza Habibi , Shatav Shamshiri Kourdestani and Malihe Hadadi Abstract Nowadays, large amount of municipal solid waste is because of electrical scraps (i.e. waste electrical and electronic equipment) that contain large quantities of electrical conductive metals like copper and gold. Recovery of these metals decreases the environmental effects of waste electrical and electronic equipment (also called E-waste) disposal, and as a result, the extracted metals can be used for future industrial purposes. Several studies reported in this review, demonstrated that the biohydrometallurgical processes were successful in efficient extraction of metals from electrical and electronic wastes. The main advantages of biohydrometallurgy are lower operation cost, less energy input, skilled labour, and also less environmental effect in comparison with pyro-metallurgical and hydrometallurgical processes. This study concentrated on fundamentals and technical aspects of biohydrometallurgy. Some points of drawbacks and research directions to develop the process in the future are highlighted in brief. Keywords Bioleaching, waste electrical and electronic equipment, E-waste, cyanogenic bacteria, lithotrophic bacteria, operational consideration, process parameters Received 31st May 2019, accepted 21st November 2019 by Associate Editor Rodrigo Navia. Faculty of Petroleum and Chemical Engineering, Razi University, Kermanshah, Iran Corresponding author: Alireza Habibi, Faculty of Petroleum and Chemical Engineering, Razi University, Kermanshah, Iran. Email: a.habibi@razi.ac.ir 895321WMR 0 0 10.1177/0734242X19895321Waste Management & ResearchHabibi et al. review-article 2020 Review Article