Experimental evaluation of green algae growth rates on carbon sequestration efficiency for sustainable landscape architectural applications

Abstract

Urban environments contribute nearly 70% of global emissions, necessitating high-efficiency biological mitigation strategies. Microalgae, as an eco-friendly and renewable resource, have the potential to address environmental challenges such as rising urban temperatures and high carbon emissions. However, optimising algal growth conditions for maximum efficiency in both carbon sequestration and pigment recovery remains underexplored. The methodology employed involved culturing the three species (Scenedesmus sp., Chlamydomonas sp., and Coelastrum astroideum) in BBM and BG-11 media at various pH levels (5.0, 6.8, 9.0) and photoperiods (24:0, 18:6, 12:12). Growth performance was monitored by measuring optical density and biomass, while chlorophyll content was assessed via Metler-Toledo UV7 Spectrophotometer. Carbon sequestration rates (CSR) were calculated based on biomass production, and chromaticity analysis was conducted to determine pigment variations across the treatments. This study identifies Coelastrum astroideum as a superior biological candidate for urban integration, achieving a maximum Carbon Sequestration Rate (CSR) of 2.56 g/L and a peak biomass of 1.63 g/L. Through experimental evaluation of Scenedesmus sp., Chlamydomonas sp., and C. astroideum, research demonstrated that performance is optimized using Bold’s Basal Medium (BBM) under slightly alkaline conditions (pH 6.8–9.0) with balanced light-dark cycles (18:6). The analysis established a near-perfect correlation (r≈0.999) between biomass accumulation and CSR, supporting the literature's assertion that microalgae fix carbon up to five times more efficiently than terrestrial plants. For practical landscape architectural applications, these findings support the development of bio-reactive facades and "living skins" (e.g. Greenwall) as high-performance urban infrastructure. Furthermore, the strong correlation between chlorophyll content and green chromaticity (a*) provides a framework for non-destructive visual monitoring, allowing designers to assess system health and sequestration status in real-time without laboratory extraction. This research is significant as it contributes valuable insights into the optimisation of algae-based systems for sustainable applications in the built environment.