Testing the single-pass VOC removal efficiency of an active green wall using methyl ethyl ketone (MEK)

Abstract

In recent years, research into the efficacy of indoor air biofiltration mechanisms, notably living green walls, has become more prevalent. Whilst green walls are often utilised within the built environment for their biophilic effects, there is little evidence demonstrating the efficacy of active green wall biofiltration for the removal of volatile organic compounds (VOCs) at concentrations found within an interior environment. The current work describes a novel approach to quantifying the VOC removal effectiveness by an active living green wall, which uses a mechanical system to force air through the substrate and plant foliage. After developing a single-pass efficiency protocol to understand the immediate effects of the system, the active green wall was installed into a 30-m3 chamber representative of a single room and presented with the contaminant 2-butanone (methyl ethyl ketone; MEK), a VOC commonly found in interior environments through its use in textile and plastic manufacture. Chamber inlet levels of MEK remained steady at 33.91 ± 0.541 ppbv. Utilising a forced-air system to draw the contaminated air through a green wall based on a soil-less growing medium containing activated carbon, the combined effects of substrate media and botanical component within the biofiltration system showed statistically significant VOC reduction, averaging 57% single-pass removal efficiency over multiple test procedures. These results indicate a high level of VOC removal efficiency for the active green wall biofilter tested and provide evidence that active biofiltration may aid in reducing exposure to VOCs in the indoor environment.

Biofiltration of airborne VOCs with green wall systems-Microbial and chemical dynamics

“…With the exception of 2‐ethylhexanol in experiment 2, the concentrations applied in the large chamber experiments were unrealistically high compared to VOC concentrations in normal office air, which are typically at the ppb‐level . Such exaggerated concentrations were used to stress the chemical/absorptive potential of the system and to see differences more clearly; the functionality of the actual commercial active green wall at low input of a single VOC has been reported earlier . More and more evidence is being accumulated on the potential of soil and plant‐associated microbes to utilize extremely low atmospheric concentrations of substrates such as H 2 .…”

“…Plants were maintained in their original potting soil or transferred to soilless growing medium, one plant per pot, after thorough washing of the root system with potable tap water, by Naava Ltd, Jyväskylä, Finland. The soilless growth medium used was Naava growth mix (Nmix) used in the commercial Naava Smart Green Walls, consisting of activated carbon and other granular constituents . Each pot (height 14.5 cm, width 13.5 × 13.5 cm) was a green wall prototype with its own fan (Figures , S1).…”

“…For comparison, the rhizosphere bacterial phylogenetic diversity was on average 45 in both VOC-fumigated and non-fumigated chambers, and showed no temporal trend in either (data not shown) the actual commercial active green wall at low input of a single VOC has been reported earlier. 24 More and more evidence is being accumulated on the potential of soil and plant-associated microbes to utilize extremely low atmospheric concentrations of substrates such as H 2 . 18,35 In fact, uptake of gaseous compounds is not necessary, as long as concentrations in the irrigation water remain low (by microbial degradation and/or sorption) to support VOC partitioning to the aqueous phase as air is circulated through moist Nmix.…”

An Assessment of the Suitability of Active Green Walls for NO2 Reduction in Green Buildings Using a Closed-Loop Flow Reactor

“…Whilst pollutant reduction by potted plants has been well described, for in situ use, such systems will be severely limited in their efficacy [29]. Several recent studies have reported that green wall systems, in particular active green walls, have a high capacity to phytoremediate several air pollutants including particulate matter (PM) [30,31] and VOCs [32,33]. Regarding green wall VOC removal, biodegradation of VOCs by the rhizospheric bacteria along with substrate adsorption are considered as the primary sinks for VOC removal [24,34], however, plant-associated effects also play a role in VOC removal [35].…”

Particulate Matter and CO₂ Improvement Effects by Vegetation-based Bio-filters and the Indoor Comfort Index Analysis

“…한편으로 공기정화식물의 실내공기질 개선효과를 최적화 하기 위해 공조설비와 연계한 바이오필터 연구도 보고되고 있다 (Llewellyn et al, 2008;Irga et al, 2017). 해당 유형 의 시스템은 주로 벽면녹화의 형태를 지니며, PPs에 비해 높 은 식물밀도, 수직배열 및 체적 확보가 가능한 식물생육환경 을 제공할 수 있다 (Torpy et al, 2018)…”