Reducing Indoor Air Pollutants Through Biotechnology

Abstract

Indoor environmental quality is a growing concern, as populations become more urbanised and people spend a greater proportion of their lives indoors. Volatile organic compounds outgassing from synthetic materials and carbon dioxide from human respiration have been major indoor air quality concerns. The growing use of energy-efficient recirculating ventilation solutions has led to greater accumulation of these pollutants indoors. A range of physiochemical methods have been developed to remove contaminants from indoor air, but all methods have high maintenance costs and none reduce CO 2 , which some biological systems can achieve effectively with the additional benefit of the selfsustaining capacity of biological material. Bacteria are the major organisms involved in bioremediation of VOCs, although green plants may help sustain the bacterial community and add the capacity for CO 2 reduction to a system. The main problems faced by indoor air bioremediation systems is the extremely low concentrations of VOCs present indoors and the possibility of microbial release. Simple, passive biofiltration with potted green plants may be the simplest and most effective system for indoor air cleaning, but further research into substrate types, ventilation, and the microbiology of biodegradation processes is required to reveal their ultimate potential. Purely microbial systems have potential for the bioamelioration of high concentrations of toxic gases, but not without significant maintenance costs. Despite many years of study and substantial market demand, a proven formula for indoor air bioremediation for all applications is yet to be developed.

Characterisation of Nature-Based Solutions for the Built Environment

“…However plants can also produce pollen and biogenic volatile organic compounds that can be a source of ozone and fine particles which represent a risk for health [79]. Studies indicate that through appropriate lighting and spatial arrangement of plants (plantscape), the CO 2 and other pollution mitigation properties of plants can be optimized for improvement indoor air quality [46,80].…”

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

“…Green walls (also known as plant walls, plant‐based biowalls, botanical biofilters) are vertical structures in which one or several houseplant species are grown on soil or a soilless support fabric or growth medium. In active green walls, the volume of indoor air exposed to the system is increased by actively drawing air through the support, which together with the roots embedded in it is kept moist by regular or constant drippling irrigation . Supplementary lighting may also be provided.…”

“…Supplementary lighting may also be provided. Besides the reported positive effects of indoor plants on staff wellbeing, productivity and job satisfaction, such hydroculture‐based systems can effectively reduce indoor air CO 2 concentration and increase humidity …”

“…Much of the research on house plants and green walls has focused on their potential to remove harmful indoor air contaminants, especially volatile organic compounds (VOCs) . VOCs are chemically diverse and detectable in indoor air as a mixture of tens to hundreds of different compounds . VOCs in indoor air are often associated with sick building syndrome and are typically released from petrochemical‐derived materials such as furnishings, paints, solvents, and textiles .…”

“…Plants have been used to inoculate and support diverse bacterial degrader communities for the clean‐up of soil (rhizoremediation) or water (phyto/rhizofiltration) . Purely microbiological systems, or biofilters, have also been developed and operated to purify contaminated air even at an industrial scale, but the science of plant‐assisted remediation systems for air is newer and less developed . For hydroculture‐based biofilters, the proposed working mechanism for air VOC removal depends on the partitioning of pollutants from the gaseous to the aqueous phase, driven by concentration difference as microbes constantly consume pollutants from the water .…”