# E-Waste Plastics in the Environment: Assessment, Characterisation, and Bioprocessing
## 4 Advances in Biotechnology-Based E-Waste Plastic Processing  
The escalating generation of e-waste, coupled with the limitations and environmental impacts of current processing methods, urges the development of sustainable strategies for handling e-waste plastics. Traditional approaches, such as mechanical dismantling followed by pyrolysis or melt extrusion, are often energy-intensive and can contribute to pollution [57]. Biotechnology offers a promising alternative, with the potential to transform e-waste plastics into valuable resources (e.g., valuable monomers or other building blocks) while minimising their environmental impacts. Microorganisms, mainly bacteria and fungi, have demonstrated abilities to degrade a wide range of plastics [58]. Given the capacity to use the polymer backbone as carbon sources and effectively break them down into simpler molecules, these microorganisms can act as biorefineries for the revalorisation of various urban wastes, including e-waste [59]. We identified only six previous studies addressing the role of fungi or bacteria in treating e-waste plastics (Table 4). For example, the fungus _Aspergillus niger_ has been shown to effectively colonise and deteriorate e-plastics in waste printed circuit boards (wPCBs) during 45 days of incubation (assessment via SEM and Fourier transform infrared (FTIR) spectroscopy) and post-21 days of metal bioleaching ([PERSON] et al., [60]). As the exposure of the wPCBs to _A. niger_ increased, the time expended for the degradation of the thermosetting plastics through a subsequent incineration process was also found to decrease. These findings highlight the capacity of this fungal species to treat the plastic components of wPCBs (and bioleach metals alike), potentially contributing towards a cheaper, less energetically intensive, and less environmentally hazardous e-waste processing solution. Another study using fungi to assess the biodegradation of e-waste-sourced polymers is [PERSON] et al. [61]. Similarly, a filamentous fungus (_Penicillium bevacizumab_) was found to have the potential for removing the epoxy-based polymeric fraction of a printed circuit board over 28 days of incubation in liquid culture medium. This was demonstrated by mass loss (up to 75% removal within 28 days of exposure), changes in the particle number and brittleness, and chemical changes assessed through FTIR-ATR which were consistent with chain scission and oxidation events. The assessment of the metal solubilisation remained outside of this study's scope, unlike the exploration detailed in [PERSON] et al. [60]. Thus, further explorations building upon this approach could attempt a more integrated approach for treating non-plastic constituents together with these e-waste plastics. Similarly, bacterial consortia have been shown to colonise and deteriorate the surface of e-waste plastics [62; 63]. In [PERSON] et al. [63], a study mainly dedicated to the bioleaching of metals from waste mobile phone printed circuit boards, a previously acclimised heterotrophic acidophilic bacterial community, non-specified by the authors, was used for this purpose in liquid culture media over 15 days. Although the focus of the study was on metal bioleaching (with the microorganisms not demonstrating much potential for this purpose), the surface morphology, analysed through scanning electron microscopy, revealed increased brittleness. Furthermore, the observed mass variation could be attributed not only to the low-yield metal bioleaching process, but also, to some extent, of the plastic matrix's biodegradation. Since plastic biodegradation was not in this study's scope, the decrease in mass of the plastic component, specifically, and any chemical changes have not been assessed. However, considering the capacity of a variety of microorganisms to biodegrade several types of plastics, future studies using e-waste, even those focusing primarily on metal bioleaching, could also consider how the process affects the plastic component of the used waste.