Carbon capture and storage potential of biochar-enriched cementitious systems

A promising solution to nullify the net embodied greenhouse gas emissions of civil infrastructure is the use of carbon-negative materials for concrete manufacturing. Carbon-neutral coal ash and agriculture/forestry byproducts, such as biochar, exhibit a high carbon dioxide (CO2) uptake potential. The aim of the study is to explore the viability of using biochar as a carbon sink and to develop carbon-neutral concrete with improved performance. Experimental findings suggest that the optimal amount of biochar (1%) slightly improves hydration and mechanical properties, but the combination with mineral additives significantly enhances the performance. Thermogravimetric analysis (TGA) revealed that compared to OPC, the addition of 1% biochar contributes to a 42% increase in CO2 uptake, while the combination of biochar with 10% class C fly ash further increases CO2 capture capacity of the mix by 92%. Under accelerated carbonation conditions, the biochar-enriched mortars exhibit a 20% higher modulus of elasticity indicating an effectively increased stiffness over the reference carbonated OPC. The carbonated biochar mortars also exhibit up to 64% increased toughness indices indicating the material's great resistance to crack coalescence and propagation at the strain softening stage. Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy (SEM-EDS) results validated our prediction that the porous morphology of biochar promoted enhanced CO2 absorption and in-situ mineralization of calcium carbonate, resulting in a denser and stronger cement matrix.

Automated summary

The use of carbon-negative materials, such as biochar, in concrete manufacturing shows promise in nullifying the net embodied greenhouse gas emissions of civil infrastructure. Experimental findings suggest that adding 1% biochar slightly improves hydration and mechanical properties, while combining it with mineral additives significantly enhances performance. The combination of biochar and fly ash increases the CO2 capture capacity of the mix by 92%.