Limits to Paris compatibility of CO2 capture and utilization

Abstract

The Paris Agreement’s temperature goals require global CO2 emissions to halve by 2030 and reach net zero by 2050. CO2 capture and utilization (CCU) technologies are considered promising to achieve the temperature goals. This paper investigates which CCU technologies—using atmospheric, biogenic, or fossil CO2—are Paris compatible, based on life cycle emissions and technological maturity criteria. We systematically gathered and harmonized CCU technology information for both criteria and found that CCU with technology readiness levels (TRLs) of 6 or higher can be Paris compatible in 2030 for construction materials, enhanced oil recovery, horticulture industry, and some chemicals. For 2050, considering all TRLs, we showed that only products storing CO2 permanently or produced from only zero-emissions energy can be Paris compatible. Our findings imply that research and policy should focus on accelerating development of CCU technologies that may achieve (close to) zero net emissions, avoiding lock-in by CCU technologies with limited net emission reductions. The Paris Agreement’s temperature goals require global CO2 emissions to halve by 2030 and reach net zero by 2050. CO2 capture and utilization (CCU) technologies are considered promising to achieve the temperature goals. This paper investigates which CCU technologies—using atmospheric, biogenic, or fossil CO2—are Paris compatible, based on life cycle emissions and technological maturity criteria. We systematically gathered and harmonized CCU technology information for both criteria and found that CCU with technology readiness levels (TRLs) of 6 or higher can be Paris compatible in 2030 for construction materials, enhanced oil recovery, horticulture industry, and some chemicals. For 2050, considering all TRLs, we showed that only products storing CO2 permanently or produced from only zero-emissions energy can be Paris compatible. Our findings imply that research and policy should focus on accelerating development of CCU technologies that may achieve (close to) zero net emissions, avoiding lock-in by CCU technologies with limited net emission reductions. In the 2015 Paris Agreement, almost all of the world’s nations committed to collectively hold “the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels.”2UNFCCCDecision 1/CP.21: adoption of the Paris agreement.in: Report of the Conference of the Parties on its Twenty-First Session, Held in Paris From 30 November to 13 December 2015. Addendum: Part Two: Action Taken by the Conference of the Parties at Its Twenty-First Session FCCC/CP/2015/10/Add.1. 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An IPCC Special Report on the Impacts of Global Warming of 1.5°C Above Pre-Industrial Levels and Related Global Greenhouse Gas Emission Pathways, in the Context of Strengthening the Global Response to the Threat of Climate Change. 2018Google Scholar CCU appeals to policymakers and the general public because it is seen as part of the circular economy and a form of sustainable waste processing.15Styring P. Jansen D. de Coninck H. Reith H. Armstrong K. Carbon Capture and Utilisation in the Green Economy. The Centre for Low Carbon Futures 2011 and CO2Chem Publishing, 2011Google Scholar It also appeals to industry because CCU creates value from waste through CO2-based products16Cuéllar-Franca R.M. Azapagic A. Carbon capture, storage and utilisation technologies: a critical analysis and comparison of their life cycle environmental impacts.J. CO2 Util. 2015; 9: 82-102Crossref Scopus (720) Google Scholar,17IEATransforming Industry Through CCUS. International Energy Agency, 2019Google Scholar while avoiding the storage costs and concerns of geological storage of captured CO2, known as carbon (dioxide) capture and storage (CCS).18Lilliestam J. Bielicki J.M. Patt A.G. Comparing carbon capture and storage (CCS) with concentrating solar power (CSP): potentials, costs, risks, and barriers.Energy Policy. 2012; 47: 447-455Crossref Scopus (70) Google Scholar However, the relevance of CCU in climate change mitigation is questioned in the literature, based on several concerns: (1) CCU products may not always substantially reduce emissions compared with their conventional counterparts that do not require the energy-intensive CO2 capture and conversion steps;19Abanades J.C. Rubin E.S.S. Mazzotti M. Herzog H.J.J. On the climate change mitigation potential of CO2 conversion to fuels.Energy Environ. Sci. 2017; 10: 2491-2499Crossref Google Scholar, 20Garcia-Herrero I. Cuéllar-Franca R.M. Enríquez-Gutiérrez V.M. Alvarez-Guerra M. Irabien A. 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Carbon capture, storage and utilisation technologies: a critical analysis and comparison of their life cycle environmental impacts.J. CO2 Util. 2015; 9: 82-102Crossref Scopus (720) Google Scholar,19Abanades J.C. Rubin E.S.S. Mazzotti M. Herzog H.J.J. On the climate change mitigation potential of CO2 conversion to fuels.Energy Environ. Sci. 2017; 10: 2491-2499Crossref Google Scholar (3) CCU may not be economically feasible because of the high financial costs associated with the energy-intensive CO2 capture and conversion steps;19Abanades J.C. Rubin E.S.S. Mazzotti M. Herzog H.J.J. On the climate change mitigation potential of CO2 conversion to fuels.Energy Environ. Sci. 2017; 10: 2491-2499Crossref Google Scholar,23Fernández-Dacosta C. Shen L. Schakel W. Ramirez A. Kramer G.J. Potential and challenges of low-carbon energy options: comparative assessment of alternative fuels for the transport sector.Appl. Energy. 2019; 236: 590-606Crossref Scopus (54) Google Scholar and (4) CCU may form a political distraction from reducing CO2 emissions, in particular when replacing CCS, because the scale at which CO2 could be utilized is limited compared with the scale at which CO2 could be stored geologically.21Mac Dowell N. Fennell P.S. Shah N. Maitland G.C. The role of CO2 capture and utilization in mitigating climate change.Nat. Clim. Chang. 2017; 7: 243-249Crossref Scopus (394) Google Scholar The goal of this review is to provide conceptual clarity on what CCU is and what can be expected from different CCU technological routes, in particular in reaching the Paris Agreement’s LTTG. We first describe the different process steps and varieties of CCU technologies. Next, we present a framework to assess “Paris compatibility” in the context of CCU, using criteria based on technological maturity and greenhouse gas emissions reductions. We then show the results of a systematic review of the CCU literature following this framework. Last, we discuss our findings and provide a research and policy outlook for climate change mitigation through CCU. For an overview of acronyms used, see Note S1. In line with our definition of CCU, we defined six key characteristics of CCU (Figure 1):(A)Sources of CO2. CO2 can originate from fossil fuel or biomass combustion in power plants or industrial plants, from industrial processes such as the calcination reaction in cement production or biomass fermentation, or from the atmosphere directly using direct air capture (DAC).(B)Capture of CO2. CO2 is captured technologically on an industrial scale by separating CO2 from a bulk gas stream or the atmosphere using a solvent or sorbent, a membrane, cryogenics, or industrially cultivated organisms, such as microalgae, to photosynthesize CO2 into biomass.(C)Utilization of CO2. CO2 is used directly or indirectly by converting CO2 into a range of products, often requiring electricity, heat, and/or catalysts.(D)CCU categories. The resulting CCU products can be categorized as direct uses, enhanced hydrocarbon recovery (EHR), mineral carbonates and construction materials, and fuels and chemicals.(E)Substitute. A CCU product is assumed to replace a product in the conventional economy with the same chemical structure, composition, or characteristics, typically produced from fossil fuels and referred to as the substitute.24Zimmermann A.W. Wunderlich J. Müller L. Buchner G.A. Marxen A. Michailos S. Armstrong K. Naims H. McCord S. Styring P. et al.Techno-economic assessment guidelines for CO2 utilization.Front. Energy Res. 2020; 8: 5Crossref Scopus (0) Google Scholar(F)CCU lifetime. CO2 is, depending on the CCU product, stored permanently or released into the atmosphere after a certain period of time, called its lifetime, ranging from days to centuries. For example, for fuels, the utilized CO2 is emitted into the air upon combustion. For the purpose of this paper, we define storage as reaching permanency when it has a duration consistent with geological timescales: centuries or longer. Because we consider CCU for climate change mitigation, we exclude the use of CO2 from natural reservoirs because this source of CO2 does not reduce atmospheric CO2 concentrations.25NETLCarbon Dioxide Enhanced Oil Recovery - Untapped Domestic Energy Supply and Long Term Carbon Storage Solution. National Energy Technology Laboratory. U.S. Department of Energy, 2010Google Scholar Our definition of CCU constrains CCU to processes that “technologically capture CO2,” including industrial and engineered biological processes such as CO2 capture from flue gases by microalgae, and excluding land-based CO2 sequestration in biomass (in contrast to, for example, Detz and van der Zwaan13Detz R.J. van der Zwaan B. Transitioning towards negative CO2 emissions.Energy Policy. 2019; 133: 110938Crossref Scopus (18) Google Scholar and Hepburn et al.11Hepburn C. Adlen E. Beddington J. Carter E.A. Fuss S. Mac Dowell N. Minx J.C. Smith P. Williams C.K. The technological and economic prospects for CO2 utilization and removal.Nature. 2019; 575: 87-97Crossref PubMed Scopus (326) Google Scholar). Use of biomass for energy and materials is therefore also not in the scope of this review. CCU is sometimes connected to CDR. CDR is a necessity to limit warming to 1.5°C3Rogelj J. Shindell D. Jiang K. Fifita S. Forster P. Ginzburg V. Handa C. Kheshgi H. Kobayashi S. Kriegler E. et al.Mitigation pathways compatible with 1.5°C in the context of sustainable development.in: Global Warming of 1.5°C. 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