(100a) Framework and Results for Roadmapping to a Global Net-Zero Chemical Economy in an Uncertain Climate Future

The global transition to a net-zero carbon economy necessitates the transition of the chemicals and materials industry (CMI) as well. Products of the CMI, while hard to decarbonize, embody 70% of global greenhouse gas emissions.¹ Naturally, companies, policymakers and institutions worldwide have pledged and committed to enabling this solution.² The realization of such pledges, however, remains rife with uncertainty, unless a roadmap to carbon neutral chemicals is uncovered via systematic research.

Many low carbon (C) and net-negative C technologies are promising candidates to supplement or replace current methods of chemical production.³ Recent studies show a combination of recycling, bio-based manufacturing, and carbon capture and utilization as the optimal means to a GHG emission free CMI.^4,5 However, in many cases, these technologies are in their nascency, and the associated research, development, commissioning, and operational costs are prohibitively high. Our preliminary results indicate possible “win-win” solutions that improve both value and abatement. Net-zero, however, demands higher operational costs under current policies. Therefore, strategic investments into and development of these technologies, in keeping with regional climate policy stipulations and government incentives, is critical.

The existing literature in the area designs net-zero value chains for the plastics industry and the required capital investments.^4,6 However, technologies with lower readiness levels are not considered in these analyses and the uncertainty associated with their development is not accounted for. Moreover, these studies do not connect with cross-sectoral decarbonization goals such as those imposed by sectors likely to consume chemical energy carriers, the effect of a changing climate, or the uncertainty in costs.

To bridge this gap, we devise a formulation to design a robust cost-optimal roadmap towards a net-zero chemical industry, accounting for the evolution of technologies as well as connections with integrated assessment models (IAMs). The problem is framed as a stochastic multi-period optimization that incurs the minimum costs and is constrained to reach net-zero by 2050 while satisfying the growing need for chemicals.

We utilize our open-access model of the chemicals and materials industry (CMI) as the background dataset.⁷ This model provides an inventory of process data for conventional technologies that make up the CMI. Value-chain alternatives are added to this matrix to form a superstructure network of technologies. These alternatives include renewable energy driven process electrification, bio-based chemicals and plastics, point source carbon capture and utilization to value added chemicals, on-demand transformation technologies, mechanical and chemical recycling of polymers, pyrolysis and incineration of plastic wastes to produce primary chemicals and energy. The models used to accommodate circular flows and variable emission factors are adopted from earlier work.^{8, 9, 10, 11} The costs for these technologies are estimated from techno-economic analyses of the same in literature and the distribution of costs is estimated from roadmapping literature in other sectors. The network incurs operational costs as well as those associated with research and development of emerging technologies. The formulation only allows fully evolved technologies to be deployed and models this evolution as sigmoidal curves. These sigmoidal models parametrically estimate the adoption of a technology and can thus incorporate qualitative expert knowledge about the adoption. The availabilities of biomass, renewable energy, and carbon capture are modelled according to scenarios from IAMs. The solution yields the investment decisions along the time horizon and the evolving value chain of processes and associated resource use and emissions.

Preliminary results indicate the need to invest in CCU technologies early on. This fulfills the downstream demand for olefins and aromatics via on-demand conversion reactions. Mechanical and chemical recycling scale up as soon as they reach the point of adoption. Around the milestone years, bio-based production and pyrolysis scale up to incur net negative emissions via a combination of carbon sequestration and product displacement. The remaining demands are met by electrification technologies powered by renewable energy. We find that the year of adoption of electrification is determined by the IAM scenario under consideration. Sensitivity analyses reveal the dependence of CCU technologies to steep adoption parameters. When these parameters are below threshold values, they are bypassed in lieu of direct electrification.

Our results help us identify the technologies which are robust to the climate policy, evolution parameters, climate evolution and cost parameters. We find the material circularity options are particularly robust and form a part of the solution in most cases. The use of a network model of the industry also inherently allows for the adoption of only those technologies which reduce emissions across the portfolio of products. This study is the first to combine realistic, comprehensive technology models, adoption models and the insight from IAMs, to roadmap to a sustainable and circular future for chemicals in a global context. The general framework and can be used for any subset of the global chemical product system such as a company’s product portfolio.

References

1. Circle Economy (2020) The circularity gap report
2. Van Coppenolle, H., Blondeel, M., & Van de Graaf, T. (2023). Reframing the climate debate: The origins and diffusion of net zero pledges. Global Policy, 14(1), 48-60.
3. Gabrielli, P., Gazzani, M., & Mazzotti, M. (2020). The role of carbon capture and utilization, carbon capture and storage, and biomass to enable a net-zero-CO2 emissions chemical industry. Industrial & Engineering Chemistry Research, 59(15), 7033-7045.
4. 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.
5. Sen, A., Thakker, V., Stephanopoulos, G., & Bakshi, B. R. (2023). Designing roadmaps for transitioning to value chains with net-zero emissions: Case of the chemical industry. In Computer Aided Chemical Engineering (Vol. 52, pp. 2483-2488). Elsevier.
6. Zibunas, C., Meys, R., Kätelhön, A., & Bardow, A. (2022). Cost-optimal pathways towards net-zero chemicals and plastics based on a circular carbon economy. Computers & Chemical Engineering, 162, 107798.
7. Sen, A., Stephanopoulos, G., & Bakshi, B. R. (2022). Mapping Anthropogenic Carbon Mobilization Through Chemical Process and Manufacturing Industries. In Computer Aided Chemical Engineering (Vol. 49, pp. 553-558). Elsevier.
8. Thakker, V., & Bakshi, B. R. (2021). Toward sustainable circular economies: A computational framework for assessment and design. Journal of Cleaner Production, 295, 126353.
9. 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.
10. Thakker, V., & Bakshi, B. R. (2023). Ranking Eco-Innovations to Enable a Sustainable Circular Economy with Net-Zero Emissions. ACS Sustainable Chemistry & Engineering.
11. Thakker, V., & Bakshi, B. R. (2023). Mapping the path to a net‐zero chemicals industry by long‐term planning with changes in technologies and climate. AIChE Journal, e18381.