Techno-economic analysis of process alternatives for the production of ethylene-propylene rubber from forest-based feedstocks

The ethylene-propylene rubber (EPR) manufacturing process includes gasification of the feedstock, conversion of the resulting synthesis gas into methanol followed by the production of olefins (ethylene and propyl-ene) by the methanol-to-olefins process, and polymerization of the monomers into EPR. A hypothetical northern bleached kraft pulp facility with a capacity of 1000 metric tons/day was considered as the biomass receiving site for the EPR production. Two scenarios were considered for the base case: (1) gasification of 100% of the black liquor produced by the kraft pulp mill (85 kt EPR/year) and (2) a 30% increase in pulp production and use of the corresponding extra black liquor obtained in the pulp process for the production of EPR (debottlenecking scenario, 27 kt EPR/year). The base case was compared with a process alternative in which black liquor was replaced by biomass (50-100 kt EPR/year) and also with another route based on the purchase of bioethanol and its subsequent dehydration to ethylene and propylene (85 kt EPR/year). Order-of-magnitude capital and operating costs were estimated, and internal rates of return (IRRs) were calculated relative to the level of risk of the different process pathways. Sensitivity analysis was conducted for key parameters. The variables with the most important effects on the economics of the gasification routes were capital investment and EPR price. In the case of the ethanol dehydration route, purchased ethanol price also had a significant importance. Of the gasification routes, the debottlenecking case presented the most promising economics, mainly due to a reasonable capital investment (237 million US dollars [USD]) with satisfactory IRR (26%) and payback time (3.3 years). The bioethanol-dehydration route showed the most attractive economic metrics (USD 220 million capital expenditure, 36% IRR, and 2.4-year payback time).