Abstract The production and demand for plastic products is set to only increase in the near future, despite efforts to curtail this demand. This increased demand and production comes with an increase in plastic waste, which already sees millions of tonnes discarded into landfills every year. Growing concern over the effects of this waste on the world's ecosystems has led to urgent interest in technologies for chemically converting waste plastic into other products. This manuscript uses process synthesis techniques to analyse and compare the relative performance of two commonly used chemical conversion processes: polyethylene pyrolysis and polyethylene gasification. This analysis technique is unique in that energy forms the basis of the analysis but also allows environmental and economic concerns to be considered simultaneously. It was found that pyrolysis processes are more in line with the goal of a cyclic economy for waste plastic, but that gasification processes can offer higher revenue through the production of alternate chemical products. The potential profits generated from these waste plastic processing strategies was found to be between 50 and 360 USD/ton of polyethylene, demonstrating a high economic value on what is, at present, a waste product.