Experimental assessment of the CO2 phytoremediation efficiency of living walls in indoor environments

Living walls (LWs) may complement conventional ventilation by mitigating indoor carbon dioxide (CO2) accumulation. This study experimentally quantified the CO2 phytoremediation performance of two passive LWs installed in a 38 m3 full-scale climate chamber and composed of Spathiphyllum, Philodendron hederaceum, and Epipremnum aureum. Decay and pulse tests were performed at 20 and 24 under three lighting conditions: LED OFF, 50%, and 100% intensity. In the decay tests, illumination increased the measured decay constant from 0.00566 min−1 to 0.00816 min−1 at 20 and 0.01105 min−1 at 24 , reducing cumulative CO2 exposure by up to 44%. After subtraction of the OFF reference contribution, the net LW-equivalent CO2 removal airflow rate was 5.75 m3 h−1 at 20 and 12.39 m3 h−1 at 24 . A concentration-dependent net uptake relationship, , was also derived for use as a biological sink model. Pulse tests simulated the CO2 generation of approximately three school-aged children. After 60 min, the final concentration increase was reduced by 20–27% and 35–39% at 20 under 50% and 100% LED intensity, respectively, and by 26–27% and 33–37% at 24 . Under full illumination, the equivalent respiratory load decreased from 3.3 to 2.1 occupants. Overall, passive LWs provided a measurable but limited CO2 mitigation contribution and should be considered complementary biological sinks rather than substitutes for ventilation.