Biochar-treated cement strengthens buildings while storing carbon

Biochar-treated cement strengthens buildings while storing carbon
by Riko Seibo
Tokyo, Japan (SPX) Oct 22, 2025
A joint research team from Hefei University of Technology, Zhejiang University, and South China University of Technology has developed a new approach to make cement both stronger and more sustainable by integrating specially treated biochar. This carbon-rich additive, derived from plant waste, enhances cement's ability to absorb and store carbon dioxide, offering a path toward low-carbon construction materials.

Cement production remains one of the largest industrial contributors to global CO2 emissions. Seeking to mitigate this impact, the researchers explored how modifying biochar's structure could help cement capture more carbon. Biochar samples were produced by heating corn straw at various temperatures and then separating their sedimented components. Both the original and separated biochars were treated with an alkali solution to improve their porosity and surface activity before being tested for CO2 adsorption and mechanical performance in cement mixtures.

Results showed that sedimented biochar particles exhibited superior CO2 trapping ability compared with untreated samples. Alkali treatment further refined the micro-pore structure, enhancing gas adsorption capacity. Among all tested conditions, biochar produced at 500 oC achieved the best overall performance, combining strong CO2 uptake with improved cement strength and density.

When incorporated into cement, the CO2-loaded modified biochar increased the material's density and compressive strength, particularly at a one-percent replacement ratio. The team also found that carbon dioxide was primarily captured through physical adsorption - a rapid and efficient process under ambient conditions.

Beyond mechanical benefits, biochar inclusion substantially reduced the net carbon footprint of the cement composites. The researchers emphasized that optimizing biochar's preparation and dosage can transform conventional cement into an active carbon-storage medium without sacrificing durability.

"This work provides new insight into using biochar as a sustainable additive that supports carbon neutrality in the construction sector," said lead author Binglin Guo. "By improving both strength and carbon sequestration, biochar-modified cement offers a practical step toward greener building materials."

Research Report:Investigation of the CO2 adsorption behavior of alkali-modified biochar components in cement composites