Biohydropyrolysis of polymeric components of E-waste

Abstract

The rapid advance in information technology and the relentless desire of consumers for the “state of the art” products have led to an accelerated obsolescence of e-waste. The majority of technologies that are being developed to re-process e-waste have concentrated primarily on the recovery of the metallic fractions. This has resulted in a growing concern in the generation of a tertiary waste in the form of plastic components of e-wastes. Thermochemical conversion, by pyrolysis of these plastic components offers a favourable method of converting the waste to generate easily transportable oil and chars. The key challenges in direct pyrolysis of e-waste plastics are the presence of brominated flame retardants and the subsequent formation of dioxins. Lowering the temperature of pyrolysis could suppress the formation of dioxin. The additional advantage of this would be the lowering of the energy requirement for pyrolysis. Bioleaching offers a promising technology in extracting valuable metals from e-waste. Coupling this technology with pyrolysis based on our new technology, bio-hydropyrolysis, will offer a more complete solution to the management of e-waste. The microbial attack of plastics is known to induce chemical degradation as a result of bond cleavage. This study examined the potential of chemical/biodegradation of polymeric waste, achieved during the bioleaching process, to lower the temperature of pyrolysis. A series of experimental investigations was conducted using the six most common polymeric materials found in e-waste: High impact polystyrene (HIPS), Polypropylene (PP), Acrylonitrile butadiene styrene (ABS), Polyvinyl chloride (PVC), Polycarbonate (PC) and Flame Retardant Epoxy Resin (FR4). It is well known that these conventional plastics are not easily biodegraded under atmospheric conditions. Their biodegradability was therefore considered with the added use of heat and oxidizing reagents. The possibility of chemical depolymerisation was also considered.