Carbon dioxide capture and use in photobioreactors: The role of the carbon dioxide loads in the carbon footprint

Abstract

This research evaluated the carbon dioxide capture and use by Scenedesmus obliquus in a photobioreactor under different CO₂ loads. Performance indicators, carbon and energy balances, sustainability indicators, and carbon credits on the photobioreactor were assessed. The results expressed that the CO₂ loads of 384.9 kg/m³/d (15% CO₂) provide the best trade-off for the process. For this condition, maximum biomass productivities of 0.36 kg/m³/d, carbon dioxide conversion rates of 0.44 kgCO₂/m³/d, and oxygen release rates of 0.33 kgO₂/m³/d were observed, reaching maximum CO₂ removal efficiencies of 30.76%. Volatile organic compounds were the major products generated (>80%). However, only <3% was fixed in biomass. From the environmental and economic point of view, the net energy ratio was 3.44, while the potential carbon credit was of 0.04 USD per m³ of culture. Finally, the use of adequate CO₂ loads was also proven to be determinant to improve the global performance of the system.

Keywords: Algae/chlorophyceae; Bioconversion routes; Carbon credits; Carbon loads; Life cycle assessment; Mass balance.