A plastic waste to ethylene (PtE) process through steam-oxygen gasification, methanation and oxidative coupling of methane was investigated. Gasification was modelled using a stochastic reactor model, while the downstream process was modelled using Aspen Plus. This study investigated two cases, one with venting of captured CO2 and one with CO2 compression and transport. In addition, two alternative feedstocks and their effect on the process were explored.
The model was evaluated from a technical, economic, and ecological perspective. For the ecological evaluation, the investigated plastic recycling process was compared to naphtha steam cracking, and it was found that 5.7-18.4 kgCO2eq/kg ethylene can be avoided. The minimum ethylene sales price was found using a discounted cashflow calculation and is between 4.9-5.4 €/kg. This leads to costs of CO2 avoided between 230-666 €/tCO2eq. Moreover, a sensitivity analysis on costs of CO2 avoided using 20,000 random parameter values was conducted.