Quantifying material flow of oily sludge in China and its implications

Oily sludge is classified as hazardous waste. If not treated properly, it can cause negative impacts on human health and the ecological environment. However, the current lack of macro and micro scientific understanding of the treatment of oily sludge hinders its sound management. In this study, at the microlevel, we selected two of the most common treatment processes of oily sludge and establish a database through data collection and estimation. Material flow analysis was adopted to reveal the generation, pretreatment, recycling, and disposal processes of mechanical separation and incineration. At the macrolevel, this article predicted the material flow of China's whole process management of oily sludge and analyzed the typical flow characteristics of valuable resources in the whole process to guide the formulation of relevant policies in the future. The annual generation of oily sludge in China was between 4.45 and 6.22 Tg, and the average comprehensive utilization rate was approximately 36%. We are still far away from a sound management system despite new legislative revisions. Close supervision and technical processes should be further enhanced shortly.