Green wall technology for the phytoremediation of indoor air: a system for the reduction of high CO₂ concentrations

Abstract

Along with the growing requirement to reduce building carbon emissions, a need has arisen to find energy efficient means of improving the quality of indoor air. Indoor plants have been shown to be capable of reducing most air pollutants; however, practical numbers of potted plants will not have the capacity to control many forms of air pollution, especially CO₂. Green walls are space-efficient means of increasing the density of indoor plants. We assessed an active green wall for its potential to reduce CO₂ in chambers and a test room. Chlorophytum comosum and Epipremnum aureum were both effective cultivars for CO₂ removal at light densities greater than 50 μmol m⁻² s⁻¹. Substrate ventilation increased the rate of CO₂ draw down from chambers, possibly due to increased leaf gas exchange rates. Green walls were then tested in a 15.65-m³ sealed simulation room, allowing the calculation of clean air delivery rate (CADR) and air changes per hour (ACH) equivalents based on CO₂ draw down. Rates of CO₂ draw down were modest under typical brightly lit indoor conditions (50 μmol m⁻² s⁻¹); however, when light intensity was increased to relatively bright levels, similar to indoor conditions next to a window or with the addition of supplementary lighting (250 μmol m⁻² s⁻¹), a 1-m² green wall was capable of significant quantifiable reductions of high CO₂ concentrations within a sealed room environment. Extrapolating these findings indicates that a 5-m² green wall containing C. comosum could balance the respiratory emissions of a full-time occupant.