(87e) Transforming the Chemicals and Materials Industry Toward Net-Zero Greenhouse Gas Emissions: Approach and Preliminary Results

Abiding by the Paris Agreement is essential to limit global average temperature rise to 1.5C. 70% of all GHG emissions are embodied within the end-products of materials industries, and 30% with those are from the chemicals and materials industry (CMI). ¹ Therefore, establishing a CMI that has net-zero greenhouse gas emissions is one of the cornerstones of limiting climate change.

Most corporations have pledged to achieve this goal within a few decades but the roadmap to transition to a sustainable and net-zero global CMI is still unclear. The blueprint of such a roadmap requires the ability to model the material, energy, and economic exchanges within the CMI under various production pathways, upper limits on resource availability (water, biomass, renewables), and dynamic predictions of C credits and renewable energy prices. To this end, we focus on designing the mass and energy flows through a net-zero CMI at steady state.

The chemical industry is one of the “harder to decarbonize” sectors due to its inherent dependence on fossils for their C content. The sequestration of C in end products like plastics, and foams, presents an environmental menace due to their stability and resilience to fragmentation. However, these qualities may also be leveraged to recover and recycle these products which in turn, could reduce the demand of virgin fossil resources and lower emissions over a time horizon. Current research in the direction of network optimization for net zero operation of the chemical industry, does not include all possible solutions like CCS, CCU, biomass, electrolytic hydrogen (both for direct heating and thermal energy), resistance heating, and materials recycling and utilizes the life cycle framework for model representation. ² We apply the sustainable circular economy framework (SCE) to our comprehensive superstructure model of the chemicals industry. ^3,4 We model the transformation of products of CMI from their feedstocks i.e., their complete value chains as a network. This network contains multiple alternatives at each node and therefore can map out multiple pathways. Such a network or “superstructure” in our case, includes the three broad classes of alternate production pathways i.e. upstream intervention like using biomass and captured C to replace fossil feedstocks, end-of-pipe solution like capturing and storing C in geological reservoirs, and utilizing ecosystem services like tree cover for C sequestration, and circularity to keep plastics and resins within the materials loop via mechanical and chemical recycling. Our data also encompasses a higher degree of granularity over existing literature. ^5,6

We use the LCA framework to exhaustively model value chain processes in the CMI at steady state. Products transformed by the processes, and emissions and resource use associated with these transformations, are captured as matrix entries in the technology and environmental intervention matrices respectively. Data for net-zero production are put together with our existing data for the conventional CMI. ⁷ The SCE framework is employed to model circular flows between the modules. ^3,4 We design the process network to gain insight into the trade-off between cost and net GHG emissions, as well as the global requirement for materials. Mass balance equations governing each process, and resource allocation according to C content in the valuable products, in case of multifunctional modules, serve as constraints in the optimization problem. Process data for the model has been collected from life-cycle inventories, ^8,9 the literature, government databases, ¹⁰ and GHG inventories ¹¹.

The solution of our optimization problem is represented as a Sankey diagram of C flows between Earth’s resources and the processes in the chemicals industry. Preliminary results indicate the importance of “circularity solutions” in reaching the goal of net zero emissions. The deployment of only end-of-pipe carbon capture and utilization still has finite emissions which can’t be offset unless materials are circularized within the value chains. We also confirm that net-zero goals cannot be reached unless the electricity sector is powered significantly by renewables.

These results represent detailed, industrially relevant, and useful solutions for companies and countries alike. Chemical manufacturers can select appropriate products from our compiled database to find the optimal path to C neutrality. Finally, this dataset and model as applied to the framework, are the stepping stones towards the design of a roadmap to a C neutral global CMI, when integrated with temporally specific economic models.

References

1. Circle Economy (2020) The circularity gap report
2. Kätelhön, A., Meys, R., Deutz, S., Suh, S., & Bardow, A. (2019). Climate change mitigation potential of carbon capture and utilization in the chemical industry. Proceedings of the National Academy of Sciences, 116(23), 11187-11194.
3. Thakker, V., & Bakshi, B. R. (2021). Toward sustainable circular economies: A computational framework for assessment and design. Journal of Cleaner Production, 295, 126353.
4. Thakker, V., & Bakshi, B. R. (2021). Designing Value Chains of Plastic and Paper Carrier Bags for a Sustainable and Circular Economy. ACS Sustainable Chemistry & Engineering, 9(49), 16687-16698.
5. Meys, R., Kätelhön, A., Bachmann, M., Winter, B., Zibunas, C., Suh, S., & Bardow, A. (2021). Achieving net-zero greenhouse gas emission plastics by a circular carbon economy. Science, 374(6563), 71-76.
6. Quarton, C. J., & Samsatli, S. (2021). How to incentivise hydrogen energy technologies for net zero: Whole-system value chain optimisation of policy scenarios. Sustainable Production and Consumption, 27, 1215-1238.
7. Sen, Amrita, George Stephanopoulos, and Bhavik Bakshi. "Mapping Anthropogenic Carbon Mobilization Through Chemical Process and Manufacturing Industries." PSE 2021+ Conference Proceedings (2022). https://pse2021.jp/
8. Ecoinvent version 3.8. https://www.ecoinvent.ch Accessed 3 March 2022
9. United States Life Cycle Inventory (USLCI) https://www.nrel.gov/lci/ Accessed 9 Sept. 2021
10. Flowcharts- Lawrence Livermore National Laboratory https://www.flowcharts.llnl.gov/ Accessed 11 Sept 2021
11. United States Environmental Protection Agency https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks Accessed 3 March 2022