Abstract

This study examines corn stalk biochar (CSB)-enhanced mortar as an innovative material for carbon capture and CO<inf>2</inf> 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 CO<inf>2</inf> 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. CO<inf>2</inf> 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. CO<inf>2</inf> absorption also improved with biochar. Mortars with 75% CSB achieved an 86% CO<inf>2</inf> 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 CO<inf>2</inf> absorption stabilization, reaching saturation by day 8 at 75% CSB. Scenedesmus sp. showed slightly higher CO<inf>2</inf> absorption efficiency than Chlorella sp., reaching peak absorption earlier and maintaining greater efficiency. Higher CSB concentrations accelerated CO<inf>2</inf> absorption, indicating that biochar–mortar mixtures, particularly when combined with algae, provide a promising solution for enhancing carbon capture and sequestration in green infrastructure.