Techno-economic analysis and life cycle assessment for catalytic fast pyrolysis of mixed plastic waste

Abstract

Pyrolysis of waste plastics has gained interest as a candidate chemical recycling technology. To examine the potential of this approach, we conducted a techno-economic analysis (TEA) and life cycle assessment (LCA) of a conceptual catalytic fast pyrolysis (CFP) facility that converts 240 metric tons/day of mixed plastic waste. The modeled base case predicts the minimum selling price (MSP) of a benzene, toluene, and xylenes (BTX) mixture at $1.07 per kg when co-products are sold at their average market prices. We predict that the aromatic product stream can be cost-competitive with virgin BTX mixtures ($0.68/kg) if the mixed waste plastics are available for less than $0.10/kg or if crude oil prices exceed $60/barrel. Moreover, we estimate that CFP-based conversion of waste plastics can reduce the total supply chain energy use by 24% but with a 2.4-fold increase in greenhouse gas (GHG) emissions per kilogram of BTX, relative to incumbent manufacturing process. Sensitivity analysis highlights that feedstock cost, co-product selling prices, capital cost for product separations, and operating costs are key cost drivers. Further, we examine three additional CFP processes that differ in product composition, namely naphtha, and a case where the products are rich in either C₂–C₄ olefins or BTX aromatic hydrocarbons. Whereas the MSP of naphtha ($2.18/kg) is ∼4-fold higher than virgin naphtha, both the olefin-rich and aromatics-rich product cases exhibit a potential reduction in MSP up to 40%, with a 21%–45% reduction in total supply chain energy and 2.2–3.8-fold increase in GHG emissions relative to incumbent manufacturing processes. LCA predicts that the CFP process exhibits lower fossil fuel depletion than virgin manufacturing across all cases as well as lower acidification, ozone depletion, and smog formation for select cases, but high utility and feedstock preparation requirements result in poorer performance across other metrics. Overall, this study highlights important process parameters for improving CFP of mixed waste plastics from economic and environmental perspectives.