An assessment of carbon emissions reduction potential through zero waste activities in South African municipalities.
The inception of global warming has resulted in mitigation efforts across all relevant sectors. Waste management activities produce approximately 12% of methane emissions in South Africa. The current scope of waste management favours sustainable strategies targeting zero waste and waste diversion, however landfill disposal of municipal solid waste (MSW) is still the primary strategy employed by South African municipalities. This study evaluated the greenhouse gas (GHG) impacts of various waste management scenarios that included recycling, composting, anaerobic digestion, and landfill gas recovery through case studies of the eThekwini Municipality (Mariannhill landfill) and uMgungundlovu District Municipality (New England Road landfill) MSW streams. Each waste management strategy was assessed on the basis of GHG emissions, landfill space savings and economic feasibility. A waste stream analysis (WSA) was conducted to obtain both the qualitative and quantitative data required. The results of the WSA determined that the biogenic fraction of the MSW stream for typical South African municipalities varies between 32-40% while the recyclable fraction ranges between 38-44%. The Waste Resource Optimisation Scenario Evaluation (WROSE) model was developed for the quantification of GHG emissions and is based on the US EPA emissions factors for landfill disposal, landfill gas recovery, recycling and composting. An emissions factor was derived to include the GHG impacts of anaerobic digestion using a streamlined life cycle analysis approach. The results confirmed that recycling, anaerobic digestion and composting all produce GHG reductions, in comparison with the baseline scenario of landfill disposal, and a combination thereof through Mechanical Biological Treatment (MBT) produced the greatest net GHG reductions (between -63,338 to -71,522 MTCO2e/annum for the New England Road MSW stream, and -71,280 to -86,123/annum MTCO2e for the Mariannhill MSW stream). The results indicated that the implementation of MBT scenarios would produce landfill space savings of 94,375 to 103,302 m3 for the Mariannhill landfill, extending the landfill lifespan by 12-14 years, while savings of 73,399 – 74,100 m3 could be realised for the New England Road landfill, extending the landfill lifespan by 2-3 years. The study concluded that while the focus of waste management has changed and zero waste/waste diversion goals require alternative waste management methods to be implemented, the capital and operational costs of some technologies are the main barrier for implementation in developing countries, and that the environmental and social benefits should be evaluated further to truly gauge the costs/benefits involved.