Environmental impact of carbon cross-media metabolism in waste management: A case study of municipal solid waste treatment systems in China.

Waste treatment is a metabolic process that incurs pollutants migration across environmental media (i.e., air, water, and soil) and involves various conversions of physicochemical forms of carbon. Multiple forms of carbon compounds, such as CO2, CH4, CO, VOCs, and other organic matter can contribute to a series of transboundary environmental problems. However, current strategies targeting pollution reduction in single medium may cause pollution transfer to other environmental media, leading to comparatively large difficulty in assessing the related environmental impact on integrated ecosystems. This paper develops an analysis framework of carbon cross-media metabolism in municipal solid waste (MSW) treatment systems that include landfilling, composting, incineration, and anaerobic digestion. Life cycle impact analysis and sensitivity analysis methods are used to recognize the essential technologies in promoting the carbon cross-media migration and decreasing the integrated environmental impacts. The framework is implemented in a case study of the MSW treatment systems of 2013 in China. Results show that 86%–98% of carbon pollutants generated through landfilling, composting, and incineration ended up in the natural environment, while anaerobic digestion achieved an 87% pollution removal rate. Co-generation technology applied in incineration flue gas treatment, biochemical + membrane treatment technology in wastewater treatment, and co-processing of sludge in cement kilns were identified as the essential technologies affecting carbon migration across the gas-liquid, liquid-solid, and solid-gas interface, respectively. The relatively high environmental impacts of landfilling and incineration can be decreased by optimizing their technological compositions and applications. This study can provide support to replace the traditional environmental practice aiming at pollution control in single environmental medium independently by a systematic management approach that considers carbon cross-media metabolism and integrated environmental impact.