Contribution of waste burning to ambient PM2.5: A case study of Sharpeville, South Africa

Abstract

Insufficient waste management is becoming a significant environmental problem in South Africa, with 12.7 million tonnes of waste not being collected. Due to poor waste management services, informal waste disposal and burning have become the alternative methods. However, this poses significant environmental and health challenges, especially in low-income settlements like Sharpeville, where there is limited data to quantify waste burning emissions and assess their contribution to ambient air quality. South Africa does not have sufficient emission inventories for local sources such as informal waste burning. To address this issue, a study was conducted to estimate PM2.5 emissions from informal waste burning in Sharpeville and assess the contribution to ambient air quality. The study used a comprehensive methodology to estimate the contribution of each waste type by focusing on waste composition data collected in Sharpeville and combustible percentages from the literature. A Monte Carlo simulation was developed to account for uncertainties in waste burning calculations, providing variability in PM2.5 emissions ranging from 154g to 711g of the total waste sampled collected. The study found that organic waste was the dominant contributor to PM2.5 emissions. The results of the Monte Carlo simulation revealed a wide range of values for the amount of waste burned, with an average of 6 kg/day. The simulated emissions factor was used to estimate the total PM2.5 emissions, which ranged from 1318g/day to 34622g/day. AERMOD modelling was used to assess the distribution of PM2.5 concentration across Sharpeville, providing insights into spatial variability and potential exposure risk. The modelling applied different emission rates, ranging from 1.52x10-5- to 400x10-5 g.s-1, and compared the predicted results with measured PM2.5 concentrations from Sharpeville's AQMS. The Model runs illustrated notable variability, with the hourly highest concentration ranging from 9.38- to 2441μg/m3 and 0.5- to 400μg/m3 for the daily highest concentration. Despite limitations from data and modelling assumptions, the results offer valuable insights into the dynamics of PM2.5 emissions from informal waste burning. The study highlights the complex variations between waste generation, the population that burns waste, and the amount of waste that burns. Waste burning is a significant problem in informal settlements in South Africa, and the contribution to ambient air quality is unclear. However, the findings emphasise the importance of incorporating uncertainty considerations in modelling, establishing target mitigation strategies, and refining policy interventions to address this growing environmental issue.