This NASA technical paper (1989) describes a two year study of plant phytoremediation to clean air from harmful substances. The motivation behind designing the Model Z was to find a promising approach to reduce trace levels of air pollutants.
In this study, the leaves, roots, soil, and associated microorganisms of the plants species in the Model Z were evaluated as possible means of reducing indoor air pollutants. Additionally, a novel approach of using living wall system was designed, where large amounts of contaminated air was moved through plant roots and their associated microorganisms then destroy the bacteria and the organic chemicals, converting them into new plant tissue.
The results of the study were consistent with well known NASA technical paper and mutually supportive plants, soil-micro-organism interactions, for cleaning VOC-contaminated air. Potted plant microcosm has a capacity to contribute greatly to healthier indoor air, and should be used as a tool to improve indoor air quality up to 85.8%.
Chemicals used in the plant tests were benzene, trichloroethylene (TCE), and formaldehyde, and 12 different species of common houseplants. Tests were done in sealed chambers with one of the selected species or soil controls without plants present, where one of the three chemicals were injected. Samples were collected immediately after chemical introduction, 6hrs after, and 24 hrs after.
Low-light-requiring houseplants have a potential for improving indoor air quality by removing trace organic pollutants from the air in energy-efficient buildings. Model Z living wall system is one of the most promising means of alleviating the sick building syndrome associated with many new, energy efficient buildings.
Different plant species removed chemicals during a 24 hr exposure:
Benzene 21.4 % – 67.7 %
TCE 10.0 % – 41.2 %
Formaldehyde 47.4 % – 70 %
When the same plants and potting soil are constantly exposed to chemicals, their capacity to continuously clean the air improves: i.e. Chinese evergreen improved benzene removal from 47.6 % to 85.8 % during a six week period. Living wall system with hundreds of air purifying plants can be an effective solution for removing VOCs.