Portable botanical biofilters to address internal combustion engine exhaust exposure

Abstract

Previous research has identified the capacity of active botanical biofiltration to provide significant benefits for indoor air quality, however existing systems are large and require integration into the building. Thus, a “Portable Botanical Biofilter” (PBB) has been developed, however, its pollutant filtration capacity is unknown and may be constrained due to the limited dimensions of practical portable systems. This study thus aimed to quantify a PBB's removal efficiency under controlled conditions for CO2, PM (Total Suspended Particles (TSP) along with particle size distribution) and total volatile organic compounds (TVOCs). Testing was conducted in a purpose-built 15.6 m3 chamber at two light intensities, regular lighting (79.4 μmol∙m−2 s−1) as commercially supplied to the system and with elevated supplementary lighting (167 μmol∙m−2 s−1). CO2 removal testing was conducted with the plant species Peperomia obtusifolia, Gibasis pellucida, and a no plant control. TVOC and PM removal testing was conducted with systems containing the known pollutant removing plants: Gibasis pellucida, Spathiphyllum wallisii and mixed modules containing Peperomia obtusifolia and Nematanthus glabra at the two lighting levels. All treatments removed CO2 significantly faster than the control, with supplementary lighting allowing CO2 removal at a significantly faster rate than regular lighting (0.232–0.673 g h−1). However, CO2 net removal rates were likely to be insufficient to have valuable effects in a realistically sized room. TSP removal differed significantly between treatments for plant species, but not between light levels. The system removed particles of all sizes, with promising results for the smallest particle size (PM0.3), with highly effective reduction in comparison to the control (up to ∼72%). We conclude that in its delivered, prototype state, the PBB was unlikely to be an effective air purifying device for the removal of indoor CO2, however promising results for the removal of TVOCs and PM were recorded. To improve both CO2 and other pollutant removal, further improvements to lighting, system sealing, and module design are required, along with further testing to allow comparison with other systems.