Chemical recycling of PET waste is a promising approach for the recovery of high-quality monomers that aims at improving the circularity of plastic production. Solvolysis technologies are being developed and include hydrolysis with acid/base catalysts or enzymes to promote depolymerization reactions into PET constituent monomers, terephthalic acid (TPA) and ethylene glycol (EG). However, the use of electricity, steam and organic solvents/chemicals has been identified as main factor affecting the economic and environmental performance of these technologies. This paper studies an alternative neutral hydrothermal process (nHTP), which involves hydrolysis at high temperatures and pressures without the use of catalysts, looking into the impact of water recycling and EG recovery in terms of costs and GHG emissions. The results reveal that recovering EG pays off the higher CAPEX and OPEX and yields a significant reduction in wastewater treatment costs, resulting in a TPA production cost of 1–1.4 EUR/kg and a carbon footprint of 1–1.7 kg CO₂e/kg TPA. Although the process demands less electricity and steam compared to other hydrolysis technologies, fuel requirements for high temperature heat might limit its potential in the absence of sustainable heat options. Future studies are recommended to assess the utilization of lower-cost feedstocks (mixed waste and textiles), valorization of the solid by-product, and system integration possibilities to identify synergies between technologies in a broader chemical recycling context. ... Read more

This study evaluates the introduction of Carbon Capture and Utilization (CCU) process in two Colombian refineries, focusing on their potential to reduce CO2 emissions and their associated impacts under a scenario aligned with the Net Zero Emissions by 2050 Scenario defined in the 2023 IEA report. The work uses a MILP programming tool (Linny-R) to model the operational processes of refinery sites, incorporating a net total cost calculation to optimize process perfor-mance over five-year intervals. This optimization was constrained by the maximum allowable CO2 emissions. The methodology includes the calculation of surplus refinery off-gas availability, the selection of products and CCU technologies, and the systematic collection of data from re-finery operations, as well as scientific and industrial publications. The results indicate that inte-grating surplus refinery fuel gas (originally used for combustion processes) and HTL bio-crude off-gas (as a source of biogenic CO2) can significantly lower scope 1 and 2 CO2 emissions, align-ing with long-term decarbonization goals. However, these advantages carry additional costs due to significant increases in utility demands. In the high-complexity refinery, electricity consumption increases by a factor of 16, steam demand by a factor of 2.5, and water usage by a factor of 3. Similarly, in the medium-complexity refinery, electricity consumption rises by a factor of 19, steam demand by a factor of 7, and water usage by a factor of 4. These increases are primarily driven by the renewable energy requirements for water electrolyzers and CO2 capture units. Fur-thermore, despite achieving CO2 neutrality in scope 1 and 2 emissions by 2050, scope 3 emis-sions increase due to additional CO2-based methanol production.

Economic analyses highlight profit opportunities in the long term, as the production costs of CO2-based methanol is lower than forecasted fossil-based cost of production , enhancing their economic viability in the long term. The study emphasizes the critical influence of refinery complexity levels on the scale and timeline for implementing these technologies to achieve short- and long-term CO2 reduction targets. However, further evaluation is necessary to align these results with national electrical grid ca-pacity, water supply availability, and expansion plans.
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