New insights into the green cement composites with low carbon footprint: The role of biochar as cement additive/alternative

The cement industry is a major contributor to global carbon emissions. The production of limestone is a major source of carbon emissions, accounting for 55–70% of the entire production process. Therefore, seeking alternative to replace raw materials is an effective way to reduce carbon emission in cement industry. Biochar (BC), a zero-carbon material produced from biomass, is a promising alternative due to its unique physicochemical properties. BC can significantly reduce the carbon footprint of cement products and enhance their hydration properties and durability as a cement additive/alternative. This paper summarizes the benefits and strengthening effects of BC in cement preparation, examines the factors that affect the preparation and characteristics of BC, as well as the selection of molding conditions for BC-cement composites (BCCCMs) to highlights its customizability. Additionally, systematically analyzes the performances and various applications (e.g. thermal and acoustic insulation, electromagnetic shielding, ecologically pervious concrete, ultra-high-performance concrete and carbon sequestration) of BCCCMs. Further, the cost and environmental impacts of BCCCMs are briefly discussed to assess its potential in carbon emission reduction and contribution to the circular economy. Overall, this paper highlights the potential of BC as a sustainable and environmentally friendly alternative to reduce carbon emissions in the cement industry.