Impact assessment of a novel carbon utilization technology in the context of industrial symbiosis and circular economy

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The escalating climate crisis is increasingly affecting life on Earth, prompting societies worldwide to implement diverse solutions for the transformation of their energy and industrial systems. The primary goal is to stabilize or even reduce atmospheric carbon dioxide (CO2) levels. Given that carbon and hydrogen are fundamental elements on Earth, integral to modern products, the demand for these elements is currently met predominantly by fossil resources. To transition the chemicals and materials sector, alternative sources must be explored. Electrolysis offers a solution for hydrogen, while carbon capture and utilization (CCU) emerges as a candidate for carbon. Unlike carbon capture and storage or direct removal, CCU is suitable for maintaining carbon in a technical cycle, but not for long-term removal of CO2 from the atmosphere.

This thesis focuses on the CO2 potential from industrial point sources on a European scale, with particular emphasis on biogenic sources. The biogenic CO2 potential, estimated at 507 million tons annually, is relatively small compared to fossil point sources. Of this, 58 million tons are attributed to biogas combustion and upgrading, bioethanol production, and other fermentation processes. Bioethanol and biomethane upgrading stand out as “low-hanging-fruit” CO2 sources for CCU applications due to their relatively low capture costs and high CO2 quality. The study identifies 162 biomethane and 13 bioethanol sites in Europe with significant renewable power generation in close proximity, making them suitable for local, decentralized CCU applications.

Additionally, the thesis evaluates the techno-economic and environmental impacts of an electrochemical CCU pathway. The technology is anticipated to generate completely sustainable ethylene oxide (EO), a crucial bulk chemical in various downstream processes. Currently, EO is produced from fossil resources through the CO2-intensive ethylene oxidation process. Optimizing energy efficiency and utilizing by-products could enhance competitiveness economically. In the best-case scenario, the energy-driven production costs of 1,540 €/t approach the market price of the fossil benchmark, with a payback period of less than 10 years. However, conservative scenarios result in significantly higher production costs and a negative net present value, rendering the process economically infeasible.

Environmental assessments on a cradle-to-gate basis, focusing on the global warming potential (GWP) and primary energy demand (PED), reveal that the most efficient fully renewable scenario could achieve net-zero or slightly negative GWP. In contrast, grid-mix electricity scenarios result in a GWP of 3–6 kg CO2 equivalents per kg EO, two to four times higher than the fossil benchmark. PED across all scenarios is significantly higher than the fossil benchmark, primarily due to the high energy demand of CO2 conversion compared to a highly optimized benchmark system. Nevertheless, in renewable energy scenarios, PED is largely covered by renewable energy, making the novel process preferable environmentally when renewable energy is available. The impact of the CO2 source is comparatively less significant.

Given the immaturity of CCU technology, more detailed assessments should be conducted as additional data becomes available. Economically, there is a need for more incentives, such as subsidies for environmentally friendly alternative production processes and stricter treatment of fossil emissions through measures like carbon taxes and the European Emissions Trading System. In a circular (carbon) economy, accounting not only for CO2 emissions but also for CO2 as a commodity is essential to determine net CO2 emissions and track progress toward climate protection targets. Lastly, further investigations into social and environmental impacts are necessary to establish a comprehensive link between the negative and positive aspects of processes, connecting costs and benefits to promote truly sustainable CCU processes and a sustainable economic structure.