Carbon-Negative Concrete Technology The Future of Environmentally Friendly Building Materials

Carbon-Negative Concrete Technology: The Future of Environmentally Friendly Building Materials

The construction industry is currently facing immense pressure to reduce carbon emissions, as concrete is not only one of the most widely used materials but also a major source of CO₂ due to its reliance on Portland cement. In response, Shimizu Corporation has conducted extensive research to develop sustainable material solutions aimed at achieving carbon neutrality. One of the most remarkable outcomes is carbon-negative concrete, which partially replaces cement and aggregates with biochar. This biochar is produced from sawdust through a carbonization process and has the unique ability to retain a significant amount of carbon that would otherwise be released into the atmosphere through natural decomposition or combustion. Thanks to this property, carbon-negative concrete not only maintains the necessary mechanical strength for construction but also directly contributes to reducing greenhouse gas emissions. This innovation is considered a promising step that opens new directions for the advancement of green construction in Japan and worldwide.

1. A Story from Japan: Shimizu Corporation and Carbon-Negative Concrete

1.1. Introduction to Shimizu Corporation

Carbon-Negative Concrete Technology The Future of Environmentally Friendly Building Materials

Shimizu Corporation (清水建設株式会社) is one of the largest and oldest construction groups in Japan, founded in 1804 by Kisuke Shimizu I. From its beginnings as a small carpentry workshop, Shimizu has grown into a global corporation with over 11,000 employees in Japan and around 21,000 worldwide. Headquartered in Kyobashi, Tokyo, the company operates across various fields, including industrial and civil construction, real estate development, design, infrastructure engineering, and building maintenance services. Shimizu is particularly renowned for its focus on sustainable development, exemplified by the “SHIMZ Beyond Zero 2050” strategy, which aims to achieve carbon neutrality, promote material recycling, and apply environmentally friendly construction technologies.

1.2. How They Developed the New Technology

Carbon-Negative Concrete Technology The Future of Environmentally Friendly Building Materials

In its pursuit of sustainable building materials, Shimizu has placed particular emphasis on reducing emissions from cement, the largest source of CO₂ in traditional concrete. Instead of relying solely on hydrated cement, the company developed carbon-negative concrete technology by incorporating biochar, a product of biomass carbonization. This biochar is processed into fine powder or coarse particles and added directly into the concrete mix as a special additive.

Carbon-Negative Concrete Technology The Future of Environmentally Friendly Building Materials

The primary raw material for biochar production is sawdust, a byproduct of wood processing. Typically, the carbon in sawdust would be released into the atmosphere as CO₂ through natural decomposition or combustion. However, through carbonization, most of the carbon in sawdust is transformed into a stable form that is resistant to decomposition and unlikely to emit CO₂ unless exposed to extremely high temperatures. Thanks to this process, the fixed carbon content of dried biochar can reach up to around 90%, enabling long-term storage of a significant amount of carbon within the material.

In experimental applications, Shimizu combined two forms of biochar: fine powder with particle sizes under 1 mm and coarse particles between 2–5 mm. The fine powder was used to replace part of the fine aggregate in the concrete, while the coarse particles were mixed to optimize mechanical properties, ensuring both carbon fixation capacity and structural durability.

1.3. Pilot Project in Fukuoka

Carbon-Negative Concrete Technology The Future of Environmentally Friendly Building Materials

Shimizu’s carbon-negative concrete technology, SUSMICS-C, developed through the use of biochar to capture and store carbon within concrete, has gone beyond the research stage and been applied in real-world projects in Japan. According to Shimizu, this eco-friendly concrete was first used in an actual construction project on February 21, 2023. During the project, biochar was incorporated in two forms: coarse particles of approximately 2–5 mm and fine powder smaller than 1 mm, which replaced part of the fine aggregate and enhanced carbon sequestration. The application of SUSMICS-C in this construction project marked a significant milestone, demonstrating the feasibility and commercial potential of carbon-negative concrete technology within the Japanese construction industry.

2. Principles and Production Process of Carbon-Negative Concrete

2.1. Raw Materials

Carbon-Negative Concrete Technology The Future of Environmentally Friendly Building Materials

In the SUSMICS-C technology, Shimizu employs biochar as the main component for carbon sequestration in concrete. Biochar is processed into two forms, each serving different functions in the concrete mixture: fine powder with a particle size of less than 1 mm, and coarse particles sized between 2 and 5 mm. Fine biochar powder is used to partially replace traditional fine aggregates, increasing the surface area for carbon fixation within the concrete mass, while coarse particles help maintain the structure, support mechanical strength, and ensure bond integrity.

In addition to biochar, the mixture includes blast furnace cement (type B) as the main binder, along with other additives to adjust workability, plasticity, impermeability, and stability of the concrete. With the appropriate dosage and proper mixing ratios of biochar, SUSMICS-C concrete achieves stable carbon sequestration while still meeting standards for strength and mechanical performance.

2.2. Processing Steps

Carbon-Negative Concrete Technology The Future of Environmentally Friendly Building Materials

The production of carbon-negative concrete using SUSMICS-C involves a sequence of scientifically controlled steps to ensure effective CO₂ fixation and long-term material sustainability. First, biomass materials such as sawdust and wood residues are carbonized under low-oxygen conditions to produce biochar. This process transforms the organic carbon in biomass into a stable form that is resistant to decomposition or CO₂ release.

The resulting biochar is then processed into two forms: fine powder (particle size 1 mm) and coarse particles (2–5 mm), optimizing both carbon storage and mechanical properties of the concrete. These components are then mixed with blast furnace cement, aggregates, and specialized admixtures to create a workable concrete mixture with proper plasticity. Throughout the mixing process, Shimizu applies strict quality control to ensure uniform distribution of biochar within the concrete mass, thereby maintaining the required compressive strength while maximizing carbon absorption and long-term storage efficiency.

3. References

[1] Shimizu Corporation, “Company Outline,” Shimizu Corporation. [Online]. Available: https://www.shimz.co.jp/company/about/outline/. [Accessed: Sept. 20, 2025].

[2] Shimizu Corporation, “技術・ソリューション SUSMICS-C バイオ炭コンクリート,” Shimizu Corporation. [Online]. Available: https://www.shimz.co.jp/solution/tech383/. [Accessed: Sept. 20, 2025].

[3] Shimizu Corporation, “News Release: Development of Carbon Negative Resin Concrete,” Shimizu Corporation, Jun. 21, 2023. [Online]. Available: https://www.shimz.co.jp/company/about/news-release/2023/2022061.html. [Accessed: Sept. 20, 2025].

[4] Shimizu Corporation, “News Release: Shimizu Develops Biochar Concrete,” Shimizu Corporation, 2022. [Online]. Available: https://www.shimz.co.jp/company/about/news-release/2022/2022017.html. [Accessed: Sept. 20, 2025].

[5] Shimizu Corporation, “News Release: Verification of Carbon Negative Concrete in Actual Construction,” Shimizu Corporation, 2024. [Online]. Available: https://www.shimz.co.jp/company/about/news-release/2024/2024044.html. [Accessed: Sept. 20, 2025].

[6] World Construction Today, “Shimizu Corporation develops carbon-negative resin concrete applied for the first time in Fukuoka City Road Project,” World Construction Today. [Online]. Available: https://www.worldconstructiontoday.com/news/shimizu-corporation-develops-carbon-negative-resin-concrete-applied-for-the-first-time-in-fukuoka-city-road-project/. [Accessed: Sept. 20, 2025].


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