Membrane system for management and utilization of indoor CO₂

Human exposure to elevated CO₂ can have adverse health effects. As the proportion of indoor living expands, increases in atmospheric and indoor CO₂ concentrations could pose potential health impacts. A strategy to decrease indoor CO₂ levels depends heavily on ventilation, which brings outdoor air indoors, requiring alternative CO₂ removal technology. However, indoor CO₂ removal has been limited to sorption processes that require an additional step for desorption, which is challenging to adopt in urban buildings. This work applies membrane-based gas separation to remove CO₂ in the atmosphere, mainly designed for indoor air conditions. The requirements for an effective and practical membrane process are discussed through theoretical calculations and experiments using a commercial hollow fiber membrane module. The membrane system allows the application of CO₂-lean retentate gas to indoor air management for a healthy indoor environment (<1000 ppm). Besides, the CO₂-rich permeate gas is successfully utilized to promote indoor plant growth, suggesting it for future farming. These results demonstrate that the membrane system has the potential to provide the optimized CO₂ concentration for various applications in indoor spaces, which will guide the future development of membrane systems.