Recent advances in the gasification of waste plastics. A critical overview

The current review provides an assessment of the main waste plastics valorization routes to produce syngas and H2, thus covering different gasification strategies and other novel alternative processes, such as pyrolysis and in-line catalytic steam reforming. The studies dealing with plastics gasification are in general scarce. However, due to the knowledge acquired on biomass and coal gasification, the state of development of plastic gasification technologies is considerable and, in fact, several gasification studies have been performed at pilot scale units. Air gasification is the most studied and developed strategy and pursues the production of a syngas for energy purposes. In spite of the higher H2 content and heating value of the gas produced by steam gasification, this alternative faces significant challenges, such as the energy requirements of the process and the tar content in the syngas. Moreover, the co-gasification of plastics with coal and biomass appears to be a promising valorization route due to the positive impact on process performance and greater process flexibility. Other promising alternative is the pyrolysis and in-line reforming, which allows producing a syngas with high hydrogen content and totally free of tar.