System Analyses of High-Value Chemicals and Fuels from a Waste High-Density Polyethylene Refinery. Part 2: Carbon Footprint Analysis and Regional Electricity Effects

The growing generation of plastic waste (PW) is placing severe burdens in the terrestrial and marine environments due to its inappropriate management at end of life. Governments are aware of this situation and have proposed production bans or initiatives to minimize the amount of PW that is landfilled and encourage recycling or energy recovery. Circular economy is a strategy that reuses PW to produce new polymers while avoiding its disposal and displacing the use of virgin materials. This study reports on a refinery design that employs fast pyrolysis of waste high-density polyethylene and downstream separations to obtain monomers, aromatics, and hydrocarbon fuels. This study focuses on a life cycle carbon footprint analysis (CFA) and the effects of regional electricity grids on cradle-to-gate greenhouse gas emissions using process simulation for life cycle assessment inputs. The effects of heat integration on greenhouse gas (GHG) emissions were investigated in scenarios, as well as the investigation of parameter sensitivity and uncertainty. The CFA results show that the GHG emissions of ethylene, propylene, and aromatics mixture (1.08, 1.10, and 1.16 kg CO2 equiv/kg, respectively) are equal to or less than those of fossil products when heat integration is included assuming U.S. average electricity grid. The evaluation of regional electricity grids on GHG emissions for all products was conducted for 50 states in the U.S.