In a recent thesis submitted to Mississippi State University, Benjamin Shannon examined the practical application of biochar as a sustainable partial replacement for cement in concrete production. As the construction industry seeks to lower its massive carbon footprint, biochar offers a dual benefit by sequestering carbon and reducing the volume of energy-intensive cement required for building materials. This study specifically focused on how the absorption capacity of different biochars affects the final strength of the concrete, comparing wood-derived biochar with poultry litter-derived versions. The findings suggest that with the right preparation, biochar can transition from a waste product to a high-value building component.

The primary results indicated that wood-chip biochar is a far more effective construction additive than poultry litter biochar. When wood biochar replaced seven percent of the cement by weight, the concrete achieved a compressive strength of approximately 4,200 pounds per square inch after twenty-eight days of curing. In contrast, poultry litter biochar caused a significant drop in strength, making it unsuitable for structural applications. This difference is largely due to the higher carbon content and more stable physical structure of wood-based materials, which integrate more cleanly into the cement matrix without causing chemical interference.

A critical finding of the research was the importance of moisture management during the mixing process. The study showed that adding biochar in a dry state often led to internal cracking because the porous biochar particles sucked water away from the surrounding cement. By pre-soaking the biochar in water before mixing—a process known as pre-saturation—the researchers ensured that the cement had enough hydration to reach its full strength. This technical adjustment allowed the biochar to act as an internal water reservoir, slowly releasing moisture as the concrete dried, which actually helped the material cure more evenly over time.

Quantitatively, the environmental impact of this substitution is substantial for the construction sector. By integrating biochar, the study calculated a fifteen percent reduction in the total carbon emissions associated with a standard concrete mix. Because the production of Portland cement is responsible for a large portion of global industrial carbon dioxide, even a single-digit percentage replacement can result in millions of tons of avoided emissions if adopted on a wide scale. Furthermore, the carbon stored within the biochar itself remains locked inside the concrete for the life of the structure, effectively turning buildings into carbon sinks.

The study also evaluated how biochar affects the workability and density of the wet concrete. While the addition of biochar makes the mixture lighter, which can be an advantage for certain architectural designs, it also requires more careful handling to ensure the material remains easy to pour. The researchers found that at the seven percent replacement level, the concrete remained within the standard operational limits used by professional contractors. This suggests that the transition to biochar-enriched concrete would not require major changes to existing construction equipment or labor practices, facilitating easier adoption by the industry.

Beyond strength and carbon savings, the research touched on the long-term durability of these new composites. The biochar-doped concrete showed a slight increase in porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More, yet it maintained a solid enough structure to resist the typical weathering and pressure found in common infrastructure projects. This balance of sustainability and performance provides a clear roadmap for engineers looking to meet new green building standards without compromising the safety or longevity of their projects. As the demand for net-zero construction grows, using wood-waste biochar as a cement substitute appears to be one of the most viable paths forward.

Source: Shannon, B. (2025). Quantifying benefits of biochar with variable absorption capacity as a partial cement replacement in concrete (Master’s thesis). Mississippi State University.