In a critical review published in Case Studies in Construction Materials, researchers Hilal Khan, Zamil Bin Zahid, Fazal Hussain, Junaid Ahmad, and Rao Arsalan Khushnood explore a powerful solution to the construction industry’s massive carbon footprint. With cement production responsible for roughly 8% of global CO₂ emissions, the review focuses on biochar-based cementitious composites as a promising path toward carbon-negative construction. The authors highlight how a material derived from biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More, known as biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More, can not only sequester carbon but also drastically improve the mechanical and multifunctional properties of concrete. This extensive review synthesizes existing research to demonstrate biochar’s potential to transform cement-based materials into sustainable, high-performance building blocks for the future.

The incorporation of biochar fundamentally alters the structural integrity of cementitious composites, offering significant mechanical enhancements. The review finds that adding small amounts of biochar, specifically within a 5-10% replacement range, can increase compressive strength by up to 18.7%. This improvement is attributed to biochar’s ability to act as a micro-filler, densifying the cement matrix and creating a more compact structure. Beyond compressive strength, biochar additions have also been shown to improve flexural strength by 23.1% and fracture energy by 78%. These gains are a result of biochar particles acting as a toughening agent, deflecting crack paths and improving the material’s resistance to crack propagation. Furthermore, the review notes that microstructural analyses, using techniques such as SEM and XRD, confirm that biochar improves hydration kinetics and pore structure, leading to better durability against water, chloride, and sulfate ion penetration.

Beyond structural performance, biochar addresses the critical need for decarbonization in the construction sector. As a carbon-rich material produced from biomass, biochar itself is a carbon sink. The review emphasizes that using biochar allows for carbon sequestration through two primary mechanisms: direct immobilization of biogenic carbon and enhanced mineral carbonation within the concrete. The review presents a finding that these combined pathways can yield up to an 18.3% CO₂ uptake efficiency in accelerated curing regimes, a crucial step in mitigating the environmental impact of concrete production. The sustainability assessment of biochar-based concrete, encompassing a full life cycle analysis, demonstrates a significant reduction in global warming potential (GWP) of approximately 47%, positioning these materials as a promising solution for a circular economy.

The concept of “smart infrastructure” is also a core theme, with biochar enabling a suite of new functionalities in concrete. For instance, incorporating biochar into cementitious composites can significantly reduce thermal conductivity by up to 67%, improving the material’s insulation properties and contributing to greater energy efficiency in buildings. The material can also be made “self-sensing,” meaning it can monitor its own structural health. The review notes that hybrid systems using biochar and nano-carbon black achieved a 35.6% drop in resistivity, with a strong correlation (R2>0.95) between the change in resistance and the applied stress. This allows for real-time structural monitoring, enabling proactive maintenance and enhancing safety. In a forward-looking application, the review also highlights the potential for biochar-rich matrices to serve as structural electrodes for energy storage, delivering capacitance greater than 1.3 mF/cm² and supporting a dual role as both a structural component and an energy storage unit.

The economic viability of these composites is also a key takeaway. The review presents a techno-economic model showing that incorporating 30% biochar into concrete blocks yields an overall economic benefit of $34.1 USD/m³. This benefit further increases to $41.1 USD/m³ in hybrid systems that also use fly ashAsh is the non-combustible inorganic residue that remains after organic matter, like wood or biomass, is completely burned. It consists mainly of minerals and is different from biochar, which is produced through incomplete combustion.   Ash Ash is the residue that remains after the complete More. This economic gain is driven by factors such as avoided waste disposal fees and the acquisition of carbon credits. Stakeholder feedback, particularly from the business and research sectors, shows that over 80% of respondents identify these environmental and economic benefits as essential drivers for the large-scale adoption of biochar. To fully realize this potential, the authors suggest a need for further research, standardized guidelines, and supportive policy mechanisms to overcome scalability challenges and fully integrate this material into the mainstream construction industry.

SOURCE: Khan, H., Zahid, Z. B., Hussain, F., Ahmad, J., & Khushnood, R. A. (2025). Sustainable Multifunctional Biochar-Based Cementitious Composites for Carbon Sequestration, Energy Storage, and Smart Infrastructure Applications: A Review. Case Studies in Construction Materials, 25, e05117.