Membrane system for management and utilization of indoor CO2

Abstract

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.