# E-Waste Plastics in the Environment: Assessment, Characterisation, and Bioprocessing
## 4 Advances in Biotechnology-Based E-Waste Plastic Processing
After the incubation of the e-waste plastics across the several experimental conditions, it was found that exposure to both the bacterial consortium and the selected _P. aeruginosa_ strain resulted in exacerbated chemical changes, decreases in thermal stability, and surface deterioration when compared to plastics incubated under control conditions. These changes were found to be more pronounced when incubated in the presence of the single microorganism rather than the bacterial consortium. Specifically, Fourier transform infrared analysis found changes over the incubation periods which were consistent with the degradation across all of the treatments, and generally more pronounced in the case of _P. aeruginosa_ exposure, such as the complete removal of peaks attributable to C=O and C-O, and the appearance of new peaks attributable to asymmetric C-O-C and N-H, as well as a shift towards higher wavenumbers of peaks attributable, for example, to OH, asymmetric C-H, and C=C. Such changes are potentially indicative of hydrolysis reactions, the degradation of the polymer backbone, and the breakdown of a variety of chemical groups present in polymeric materials. On the other hand, the thermal analysis revealed that e-waste plastics exposed to _P. aeruginosa_ demonstrated the lowest thermal stability overall after both 3 and 6 months of exposure (differential thermal analysis peaks of 409 \({}^{\circ}\)C and 401 \({}^{\circ}\)C, and rates of decomposition of 24.7 \(\times\) 10\({}^{-3}\) and 22.7 \(\times\) 10\({}^{-3}\) mg/\({}^{\circ}\)C, respectively) compared to both the other treatment (411 \({}^{\circ}\)C, 17.4 \(\times\) 10\({}^{-3}\) mg/\({}^{\circ}\)C and 412 \({}^{\circ}\)C, 18.5 \(\times\) 10\({}^{-3}\) mg/\({}^{\circ}\)C, respectively) and control conditions (419 \({}^{\circ}\)C, 15.8 \(\times\) 10\({}^{-3}\) mg/\({}^{\circ}\)C and 419 \({}^{\circ}\)C, 11.9 \(\times\) 10\({}^{-3}\) mg/\({}^{\circ}\)C, respectively). However, mass variation was not assessed in either experimental condition. Chemical changes and decreases in thermal stability were also observed in plastics from the control condition when compared to plastics that were not incubated, which could be attributed mainly to the presence of other biological agents due to the used soil not having been sterilised before the experiment. This lack of soil sterilisation constitutes the main vulnerability of the approach described in [PERSON] et al. [65]--although the purpose of the study was to attempt a simulation of in situ biodegradation, the uncontrolled presence of other biological agents in the soil may have impacted the activity of the used _P. aeruginosa_ and consortium formulations. Differences in the initial microbial loads in the different pits may also have contributed to different biodegradation rates. The authors did not specify minimisation strategies for these factors, such as the mixing of sampled toposil and subsequent distribution into the several treatment pits. Additionally, the justification for the source of the used soil, or the level of plastic/e-waste plastic contamination in said source before the experiment, remained unclear. On one hand, the use of soil from an e-waste plastic-free source could minimise the interference of native microorganisms in the experiment (given that the soil was used unsterilised) compared to microorganisms from e-waste-rich areas, which are more acclimated to its presence. On the other hand, the results obtained would fail to closely reflect the in situ biodegradation of e-waste plastic in areas where their presence is more prevalent, and where bioremediation efforts would be the most impactful (i.e., the surroundings of e-waste processing industries). Limitations, Challenges, and Opportunities in E-(Waste)-Plastic Biodegradation_  
The hydrophobic nature of plastics constitutes an inherent challenge to their biodegradation, hampering the attachment of biodegradation microorganisms. E-waste plastics, additionally, tend to have higher molecular weights and include toxic compounds in their formulation.