Olefins productin through sustainable pathways: techno-economic and environmental assessment

Olefins are the building blocks of polymers. Today the production of olefins is highly based on fossil-based inputs both in terms of feedstock and energy requirements. The traditional process for the production of olefins is steam naphtha cracking and it is considered one of the highest CO2 emitting processes. Plastic waste is rich in carbon content, but this potential is yet to be utilized. Currently, the majority of plastic waste within the EU is used for energy recovery by incineration of plastics which emits direct fossil CO2. In pursuit of a carbon-neutral and sustainable future, discovery of new strategies for handling plastic waste are essential. Such carbon-rich compounds can be used for producing high-value chemicals, especially olefins. From the co-gasification of plastic and biomass waste, syngas can be obtained for producing first methanol through Fischer-Tropsch synthesis and after olefins with the methanol-to-olefins process. For preventing direct CO2 emissions, capture, storage, and different utilization technologies (CO2 injection, methanator, rWGS, and co-electrolysis) are integrated into the main process. In addition, two different gasifier modes, plasma and autothermal can be used in the waste gasification step. All the chemical processes used are modeled and simulated in Aspen Plus v11 and technologies are modeled in the OSMOSE Lua platform. The minimum energy requirement identification and heat integration problems are handled by OSMOSE as well. A total of 8 different configurations are evaluated by OSMOSE solving the total cost optimization problem for periods with varying electricity costs depending on source of generation. As a result, 7 out of 8 configurations showed no direct CO2 emissions with carbon efficiencies around 99%. The need for fos- sil fuel consumption was eliminated. The amount of feedstock required decreased by 40-50% for delivering the same capacity of production. The specific energy consumption for the integrated systems was determined to be in between 11-12.5 kWh/kgproducts. In addition, autothermal gasification showed less energy consumption and enhanced energy efficiency with less feedstock consumption compared to plasma gasification. In terms of economic performance, all configurations showed positive net plant revenue with autothermal gasification configurations generating more than plasma mode. These results provided that an alternative solution for plastic waste management and non-fossil-based olefins production without emitting direct CO2 is possible at the expense of higher electricity consumption, which soon could be fully handled with the renewable energy systems.