Chinese researchers find adding biochar to cement can improve its CCS properties

In China, a research team from Hefei University of Technology, Zhejiang University, and South China University of Technology has discovered that adding specially treated biochar to cement can significantly improve its ability to capture and store carbon dioxide while strengthening the material itself.

Cement production is one of the world’s largest sources of CO₂ emissions. Finding cost-effective ways to store carbon directly in building materials could help reduce the industry’s environmental footprint. In the new study, scientists explored how modifying biochar, a porous carbon-rich material made from plant waste, can make cement more sustainable.

The researchers produced biochar by heating corn straw at different temperatures and separated its main component, called sedimented particles. Both the original and separated biochar samples were treated with an alkali solution to enhance their structure and tested for CO₂ adsorption. The team then mixed these biochars into cement at various proportions to evaluate their effects on strength and carbon capture.

The results revealed that the sedimented particles had a greater ability to trap CO₂ than untreated biochar, and that alkali modification further improved this capacity by refining the material’s microscopic pore structure. Biochar produced at 500 °C performed the best overall, combining strong adsorption ability with improved cement performance.

When added to cement, the CO₂-saturated modified biochar made the material denser and stronger, particularly at a one percent replacement level. The study also showed that the biochar captures CO₂ primarily through physical adsorption, which occurs quickly and efficiently under normal conditions.

In addition to enhancing mechanical strength, incorporating biochar reduced the total carbon footprint of the cement mixtures. The researchers concluded that the right combination of biochar type, treatment, and dosage can help transform ordinary cement into a carbon-storing material without compromising performance.