Enhancing CO2 Sequestration Through Corn Stalk Biochar-Enhanced Mortar: A Synergistic Approach with Algal Growth for Carbon Capture Applications

This study examines corn stalk biochar (CSB)-enhanced mortar as an innovative material for carbon capture and CO2 sequestration. CSB, a renewable agricultural byproduct, was incorporated into cement mortar at varying concentrations (2.5% to 75%), and its effects on the mortar’s physicochemical properties, its ability to support algal growth, and the CO2 absorption capacity of the algae were analyzed. Characterization of CSB showed a high carbon content (62.3%), significant porosity, and a large surface area (680.3 m2 g−1), making it ideal for gas capture. At low concentrations (2.5%), CSB slightly improved the mortar’s compressive strength and density. However, higher CSB levels (5% to 75%) led to significant reductions (p < 0.05) in strength and density, while water absorption increased. CO2 sequestration monitored from algal growth studies revealed that both Chlorella sp. (TISTR 8262) and Scenedesmus sp. (TISTR 9384) thrived on CSB-enhanced mortars. At a 75% CSB concentration, Scenedesmus sp. achieved a 24.2-fold increase in biomass by day 12, outperforming Chlorella sp., which showed a 26.6-fold increase. CO2 absorption also improved with biochar. Mortars with 75% CSB achieved an 86% CO2 absorption ratio without algae, while adding algae boosted this to nearly 100%, highlighting the synergistic effect of biochar and algal photosynthesis. Higher CSB levels accelerated CO2 absorption stabilization, reaching saturation by day 8 at 75% CSB. Scenedesmus sp. showed slightly higher CO2 absorption efficiency than Chlorella sp., reaching peak absorption earlier and maintaining greater efficiency. Higher CSB concentrations accelerated CO2 absorption, indicating that biochar–mortar mixtures, particularly when combined with algae, provide a promising solution for enhancing carbon capture and sequestration in green infrastructure.