Multi-criteria Decision-Making Analysis of Plastic Waste Gasification

Abstract

Polypropylene, low-density polyethylene, high-density polyethylene, polyvinyl chloride, flexible polyurethane foam, polyethylene terephthalate, and polystyrene are considered the most prevalent types of plastic waste. Here, air and the steam gasification processes of these plastic waste types are examined using multi-criteria decision-making analysis. The performances of the prevalent plastic waste types in air and steam gasification are studied and compared with respect to hydrogen to carbon monoxide ratio in the syngas, lower heating value of the syngas, cold gas efficiency, exergy efficiency, and normalized CO2 emission. In air gasification, high-density polyethylene has the best performance with respect to the H2/CO ratio, low-density polyethylene has the best performance with respect to the lower heating value of the syngas, polyethylene terephthalate has the best performance with respect to the cold gas and exergy efficiencies, and polystyrene has the best performance with respect to normalized CO2 emission. In steam gasification, polyvinyl chloride has the best performance with respect to H2/CO ratio, low-density polyethylene has the best performance with respect to lower heating value of the syngas and cold gas efficiency, polypropylene has the best performance with respect to exergy efficiency, and polystyrene has the best performance with respect to normalized CO2 emission. Therefore, selecting the best plastic waste for each gasification process requires a multi-criteria decision analysis and, in this regard, a technique for order preference by similarity to an ideal solution is utilized. The results for several scenarios show that low-density polyethylene is the best plastic waste for air gasification, and high-density polyethylene is the best plastic waste for steam gasification.