A review on the pyrolytic conversion of plastic waste into fuels and chemicals

We reviewed 195 references discussing the pyrolysis of plastic waste, with the aim of analyzing the technical aspects (feedstocks, process parameters, reactors, products, catalysts, kinetics, and pollutants), the economic feasibility for the industrial implementation, and the environmental assessment through Life Cycle Analysis (LCA). In the last decade, the scientific community primarily studied individual virgin polymers (79% of the references) through batch lab-scale tests, mostly at temperatures around 500◦C (46% of the selected references). Depending on the polymer (PE, PP, PET, PS), reactor type and operating conditions the relative amounts of gas/ condensable/solid products varied, whereas PVC was considered undesirable due to the formation of corrosive gases. Liquid products are the most common targets, due to their application as fuels. Several technical issues (such as the impact of residence time and pressure, and low-cost catalysts) need further attention. Very few LCA studies explored plastic waste pyrolysis, with insufficient results for a thorough environmental assessment of the processes. Only seven references investigated the techno-economic feasibility of plastic waste pyrolysis at fullscale, achieving results that are interesting but too scarce for any conclusive evaluation. This represents the most significant knowledge gap identified in the review, as the techno-economic sustainability is a fundamental factor for the technological transfer. Pyrolysis has been proven to be a viable technology to convert plastic waste into high value-added products that can be utilized as fuels, chemicals and/or building blocks. This review provides guidance for further research and aims at stimulating the interest of the industrial world regarding the possible implementation of this technology.