Waste plastic resource recovery from landfilled refuse: A novel waterless cleaning method and its cost-benefit analysis

The efficient classification and resource conversion of landfilled refuse can simultaneously realize the secondary pollution prevention and land replacement. This work aimed to investigate the waste plastic resource recovery from landfilled refuse via a novel waterless cleaning method. Composition analysis showed that the content of waste plastic from landfilled refuse had differences between different regions, and the specific weight content range was between 15-40%. Moreover, when the landfill time was less than 7 years, the high calorific value (>35 MJ/kg) and mechanical property (declining range <3%) of waste plastic were basically the same as those of the original waste plastic, indicating a high resource attribute. However, due to the high degree of pollution, it was difficult to directly make high-value utilization. Furthermore, a waterless device was designed for waste plastic cleaning, and 94% cleaning rate was obtained with the optimal conditions of the sand medium particle size of 4-14 mesh, stirring speed of 50 r/min, and the operation time of 45 min. The actual on-site pilot test was carried out under the best conditions, and the results showed that the cleaning rate of waste plastic could reach 90%. On the basis, cost-benefit analysis of different waste plastic recycling methods was carried out. Compared with the other four methods, direct extrusion molding after multi-effect cleaning had lower resource consumption (cost of 88.64 RMB), higher economic benefit (net income of 311.36 RMB), and was more in line with the characteristics of raw materials. This research can provide scientific basis and technical support for the cleaning and upgrading and resource utilization of plastic in refuse.