Cement production is one of the most carbon-intensive industrial processes worldwide, responsible for about 8% of global CO₂ emissions. Researchers from Hefei University of Technology, Zhejiang University, and South China University of Technology have developed a promising solution: an alkali-modified biochar additive that allows cement to both absorb and store carbon dioxide while becoming stronger and denser.

Biochar is a porous, carbon-rich substance made by heating agricultural waste, such as corn straw, in low-oxygen conditions. When modified with an alkali solution, its surface structure becomes more refined, creating tiny pores that can trap CO₂. The researchers found that biochar produced at 500°C performed best, particularly when added at just 1% by weight of cement.

Strength and sustainability combined

The study demonstrated that CO₂-saturated, alkali-treated biochar significantly increased the compressive strength of cement composites. The trapped carbon remained stable within the hardened matrix, contributing to long-term carbon storage. Importantly, the CO₂ adsorption occurs through physical mechanisms, meaning the process is fast and efficient under normal conditions without requiring extra energy inputs.

By partially replacing conventional cement with treated biochar, the material’s overall carbon footprint was reduced. This approach presents a feasible pathway toward carbon-neutral construction materials that maintain, or even improve, structural performance.

Towards circular, carbon-negative building materials

Biochar-modified cement represents a growing area of innovation in biobased and circular construction materials. It not only valorises agricultural residues but also helps close the carbon cycle by locking atmospheric CO₂ into long-lasting infrastructure. For architects and designers seeking to lower the environmental impact of buildings, such biochar composites offer a practical, scalable route to climate-conscious construction.

Source: EurekAlert!
Photo: Pixabay