Comparative assessment of life cycle impacts of various plastic waste management scenarios in Johannesburg, South Africa

PurposeLandfilling can result in a loss in revenue that would otherwise have been accrued from recycling plastic waste, loss in potential jobs, and groundwater contamination. Plastics in landfills may also eventually find their way into marine environments, where they can be damaging to animals. This work aims to establish the environmental sustainability of current plastic waste management practices in South Africa using the City of Johannesburg (CoJ) as a case study.MethodologyFive scenarios encompassing combinations of landfilling, mechanical recycling, incineration with energy recovery, gasification, and use of plastic waste in a cement kiln were assessed through an environmental Life Cycle Assessment (e-LCA). Scenarios were developed based on an extensive literature review, current practices in South Africa and Europe, and the country's National Waste Management strategy, which aims to achieve "zero waste to landfill". SimaPro 9.1.1 software and the Ecoinvent Database were used to assess the life cycle impacts of each scenario over seven impact categories. The ReCiPe endpoint method, Egalitarian version, was employed in determining the impact potentials. A sensitivity analysis was also carried out to evaluate the model's robustness.Results and discussionOverall, the impact assessment results, including damage assessments and single score results, revealed that moving away from landfilling and combining mechanical recycling, incineration, gasification, and use of plastic waste (PW) as solid refuse fuel in a cement kiln is the least environmentally impactful scenario when managing plastic waste. Landfilling alone was the worst-performing scenario, resulting in adverse effects on human health, ecosystems, and resource depletion. This agrees with the waste hierarchy. On sensitivity analysis, the increase in transportation distances and reduction in market substitution factor in mechanical recycling did not change the ranking of scenarios despite reducing the net benefits to the environment. Including open dumping as an end-of-life scenario significantly increased the negative impact of the current plastic waste management scenario being practised in South Africa, while assuming a 100% mechanical recycling rate had the least environmental impact when compared to the other modelled scenarios.ConclusionsThe current plastic waste management practices in South Africa were found to be environmentally unsustainable based on the modelled scenarios, and a move away from landfilling is encouraged. The outcomes of this study will assist policymakers and other stakeholders in making informed decisions based on scientific evidence when formulating sustainability-related waste management policies.