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Industrial-scale upcycling of waste polyethylene terephthalate (PET) plastic into porous carbon globally for CO2 capture was verified as a multifunctional alternative to conventional CO2 absorption and plastic waste management technologies.

Owing to the increasing demand for propylene, many propylene production pathways have been developed, such as naphtha catalytic cracking, olefin metathesis, propane dehydrogenation, and methanol to propylene (MTP) conversion. As environmental regulations become more stringent, green propylene should be explored to enhance sustainable production and reduce CO2 emissions. MTP conversion through CO2 hydrogenation (indirect MeOH synthesis) and CO2 electrolysis (direct MeOH synthesis) has been explored as a green propylene production pathway. To evaluate the possibility of green propylene production from technical, economic, and environmental perspectives, process simulation, economic analysis, and environmental assessment were performed for MTP conversion via indirect and direct methanol synthesis. Furthermore, the best alternative for green propylene production was determined via an analytic hierarchy process, considering technical, economic, and environmental aspects, at the same time, with different weighted values of each criterion, under uncertainty. Our results indicated that MTP via direct MeOH synthesis was superior in cases where the environmental impact is the most important, while MTP via indirect MeOH synthesis was the most appropriate alternative for green propylene production, with the technical and economic impacts being more critical than the environmental impacts.

In this work, a comprehensive study of CO2 methanation by coupling process simulation, economic analysis, and life cycle assessment (LCA) was conducted to find out the most practicable pathway for green methane production in terms of technical, economic, and environmental aspects. For this work, different renewable energy resources, such as hydropower, wind power, and solar power, and water electrolysis, like alkaline water electrolysis (AWE) and proton-exchange membrane water electrolysis (PWE), leading to 6 scenarios for H2 production were considered. From the economic analysis in terms of itemized cost estimation, the levelized cost of methane (LCOM) for scenarios 1 to 6 was obtained as 0.108, 0.118, 0.144, 0.121, 0.132, and 0.159 $ kWh−1, respectively. In addition, from LCA, the respective quantified environmental impacts (i.e., CO2 emission) were obtained as 0.347, 0.813, 2.33, 0.537, 0.842, and 2.52 kg CO2-eq kg H2−1 for scenarios 1 to 6, respectively. And then, the analytic hierarchy process (AHP) was carried out to decide on the most appropriate renewable energy and water electrolysis based on different criteria of renewable energy capacity with Technology readiness level (TRL) of water electrolysis, LCOM, and CO2 emission for technical, economic, and environmental criteria, respectively. From this work, H2 production from AWE with wind power (i.e., scenario 2) was selected to be the best pathway for green methane production owing to the narrow priority range of 0.130–0.191. Furthermore, scenario 5 (i.e., PWE with wind power) was determined to be the second pathway with the same reason.