Techno-economic and environmental assessment of sustainable thermochemical pathways for olefins production promoting carbon circularity

This study investigates sustainable olefins production via thermochemical recycling of plastic and biomass wastes. The thermochemical processes include plasma or autothermal co-gasification that produces the syngas used in the methanol synthesis. The main product is the olefins that are synthesized via methanol-to-olefins process. The superstructure incorporates pre- and post-combustion CO2 capture, with CO2 management paths including geological injection, methanation, syngas synthesis through reversible water gas shift and solid oxide electrolyser cell technology for upgrading CO2 into valuable products. Chemical processes were modeled using Aspen Plus®, while CO2 abatement technologies, energy systems and utilities were integrated with an equation-oriented approach using Osmose Lua platform. This framework optimizes energy integration and determines operating conditions minimizing total costs and impact. As a result, CO2 capture and upgrading improve carbon efficiency from 55 % up to 97 % compared to steam naphtha cracking, whereas energy efficiency enhances from 56 % up to 72 %. Olefins yield increase by incorporating carbon into value-added products rather than emitting, phasing out fossil fuels and compensating fossil indirect emissions. Six configurations reduce fossil CO2 emissions more than 50 %, with two reaching carbon-neutrality. Seasonal CO2 storage extends economic benefits by providing feedstock for CO2 upgrading when renewable, low-cost electricity is available, paving the road to sustainable chemicals production with diversified energy vectors.