For the first time, scientists from the University of Tokyo have unveiled a groundbreaking technique to precisely quantify the amount of carbon dioxide (CO2) absorbed by concrete through various sources, including both natural atmospheric CO2 and industrial emissions. This advance is poised to revolutionize carbon accounting and trading mechanisms by providing an unprecedented level of accuracy in tracing the origins of sequestered carbon in cementitious materials. The innovation stems from harnessing the subtle distinctions within carbon isotopes, which act as molecular fingerprints, and has the potential to be adapted for monitoring other greenhouse gases as well, marking an important milestone in climate change mitigation research.
Concrete production has long been recognized as one of the largest contributors to global CO2 emissions, responsible for approximately 8% of anthropogenic emissions worldwide. Traditionally viewed as a linear carbon emitter, the industry has recently witnessed promising developments where concrete can be engineered to actively capture and store CO2 during certain phases of its lifecycle. However, a fundamental challenge has been the inability to distinguish the origin of CO2 absorbed by concrete—whether it stems from combusted fossil fuels or from naturally occurring atmospheric sources. Professor Ippei Maruyama and his team at the Building Material Engineering Laboratory set out to solve this puzzle, aiming to enhance the transparency and credibility of carbon reduction claims linked to concrete technologies.
Central to their approach is the use of isotopic ratio analysis, which exploits the unique signatures of carbon atoms differing in neutron number. Carbon predominantly exists as the isotope carbon-12 (^12C), but a minority exists as carbon-13 (^13C) and carbon-14 (^14C). While ^14C decays over thousands of years and is virtually absent in fossil-derived CO2, atmospheric CO2 contains a measurable level of this isotope. Conventionally, radiocarbon dating focuses on ^14C abundance to estimate the age of materials. However, environmental mixing of gases during the CO2 fixation process in concrete complicates simple isotope interpretation, requiring more nuanced analytical frameworks that the research team has now developed.
The innovation in this study revolves around a novel correction model designed to accurately account for isotope fractionation effects, which occur when different isotopes separate or concentrate unevenly during physical or chemical processes. Traditional correction methods, inherited from radiocarbon dating protocols, fall short when applied to environments where atmospheric air mixes with industrial exhaust gases during concrete carbonation. Such mixing skews the isotope ratios, introducing significant errors into source attribution calculations. Recognizing this gap, Maruyama’s group devised a mathematical framework that rigorously adjusts isotope ratio readings, thereby dramatically enhancing the precision of distinguishing between fossil-derived and atmospheric CO2 embedded in concrete.
To empirically validate their methodology, the team subjected concrete samples to controlled laboratory environments containing varying proportions of industrial exhaust gases and atmospheric CO2. By pulverizing the cementitious materials and analyzing the embedded carbon isotopes with mass spectrometry techniques, they demonstrated that under ideal laboratory conditions, the integration of fossil-derived CO2 into concrete can be extremely efficient, often exceeding expectations. Yet, the real-world application remains complex due to environmental variability—such as fluctuations in humidity, temperature, and ambient CO2 concentration—which influence the carbonation dynamics and associated isotope ratios. Their analytical model is designed to be robust enough to accommodate these variables as the research progresses.
The implications of this work extend beyond academic interest: industries adopting carbon capture in concrete manufacturing now have a scientifically validated means to quantify the true source of sequestered CO2. This differentiation is crucial from a regulatory and economic standpoint because atmospheric CO2 absorption does not equate to a net reduction in emissions, while capturing fossil-derived CO2 from industrial exhaust represents a true mitigation benefit. Accurate carbon accounting informed by isotope analysis could thus reshape emission inventories, inform policy development, enhance carbon credit systems, and incentivize technologies that genuinely reduce carbon footprints.
Further exploration of this isotope-based approach could also spur innovations in monitoring other industrial gases with complex origins, such as methane or nitrogen oxides, where source attribution remains a challenge. The methodology highlights the power of stable and radioactive isotope tracing as a versatile investigative tool in environmental science and industrial process evaluation. By extending the scope beyond carbon in concrete, similar isotope fingerprinting techniques might be customized to achieve high-resolution tracking of various atmospheric pollutants and greenhouse gases, supporting broader climate action efforts.
Concrete’s ability to sequester CO2 stems from its chemistry. The mineralization of CO2 during hydration reactions leads to the formation of carbonate compounds within the cement matrix, effectively locking carbon in a stable solid phase for extended periods. Understanding the subtle differences in isotope composition within these carbonate minerals offers a direct window into the carbon source history—whether it was atmospheric, recently emitted fossil fuel carbon, or even recycled industrial CO2. This level of insight was previously unattainable but is now accessible thanks to the analytical advancements demonstrated by the University of Tokyo team.
Moreover, one of the challenges addressed by this research is the “contamination” of fossil CO2 measurements by the presence of atmospheric CO2, which naturally infiltrates exhaust streams and ambient air in practical scenarios. Without precise separation of these sources, carbon quantification efforts could overestimate or underestimate true emissions reductions. The researchers’ success in developing a correction model for isotope fractionation enables confident distinction of mixed sources—a vital step for validating carbon capture technologies in the infrastructure sector.
Going forward, the team intends to expand the scope of their investigations by applying their methodology in industrial-scale settings, where conditions differ markedly from controlled laboratories. Such field validation is essential to confirm robustness and reliability before commercialization and regulatory acceptance. They also plan to refine their isotope measurement protocols and modeling algorithms to increase sensitivity and reduce uncertainties. This will facilitate seamless integration into carbon trading frameworks and environmental reporting systems, ultimately empowering stakeholders to make informed, scientifically-backed decisions.
This pioneering work is funded by Japan’s New Energy and Industrial Technology Development Organization (NEDO) under project JPNP21023, underscoring the strategic national priority placed on sustainable materials science and decarbonization technologies. It was published in the June 2026 issue of Cement and Concrete Research, highlighting the intersection of chemistry, materials engineering, and climate science in tackling one of the most pressing global challenges. Professor Maruyama and his colleagues demonstrate how fundamental isotopic science can be harnessed to deliver practical solutions with significant environmental and economic impacts.
The discovery not only advances our understanding of carbon cycling within industrial materials but also contributes to the larger dialogue on how technological innovation can facilitate the transition to a carbon-neutral future. By precisely tracing how and where CO2 is captured, accounted for, and stored within concrete structures, researchers are laying the scientific foundation for more effective climate policies, responsible corporate action, and sustainable infrastructure development. This innovation in isotope analysis represents an important step forward in harnessing advanced analytical techniques for environmental stewardship.
In summary, the University of Tokyo’s research stands as a landmark achievement in the quantification and verification of CO2 sequestration within concrete. Through meticulous isotope measurements and the creation of new correction paradigms, the researchers successfully discern fossil-fuel derived carbon from atmospheric sources embedded in cementitious materials. The potential applications, ranging from improving carbon accounting standards to supporting carbon markets, mark this work as both timely and transformational in the ongoing battle against climate change.
Subject of Research: Not applicable
Article Title: Quantification of sequestered fossil-derived CO₂ in cementitious materials and its atmospheric contamination using carbon isotope measurements
News Publication Date: 2-Jun-2026
Web References:
References:
Ippei Maruyama, Ryusei Igami, Ryo Kurihara, Masayo Minami, Hiroshi A. Takahashi, Abudushalamu Aili. “Quantification of sequestered fossil-derived CO₂ in cementitious materials and its atmospheric contamination using carbon isotope measurements,” Cement and Concrete Research, 2026. DOI: 10.1016/j.cemconres.2026.108290
Image Credits:
©2026 Maruyama et al. CC-BY-ND
Keywords
Carbon dioxide sequestration, concrete carbonation, isotope ratio analysis, carbon-13, carbon-14, fossil carbon detection, carbon accounting, climate change mitigation, isotope fractionation correction, cement chemistry, industrial CO2 capture, carbon trading
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