Second air-exposure component: dedicated root-to-air space
Wolverton’s planting methods have avoided drenching the roots and insured VOC-containing air could circulate in the root zone. He accomplished this in three different ways:
1. BioHome soil/fan/charcoal system
The initial experiment in the BioHome, according to the Figure 2 picture, appears to have utilized soil separated by possibly a cloth from an airspace under the soil, with a means of collecting excess water, presumably from top-watering, below the air space.
Root air exposure was increased by incorporating activated charcoal into the soil and adding a fan set-up, shown in Figure 2.
2. Sub-irrigation systems
Hydroculture, now adopted by Wolverton, is a form of sub-irrigation, or watering from the bottom, the difference being that sub-irrigation is practiced with a plant potted in soil, whereas hydroculture is practiced with pebbles (hopefully porous ones) replacing the soil.
To make a sub-irrigated plant air filter using soil, activated charcoal should be added to keep soil aerated and to provide a repository for gases entering the root zone from the air. An optional external fan could be positioned to move air downwards from the top of the planter.
3. Hydroculture
Hydroculture is a passive form of hydroponics. Unlike hydroponics, which leaves no air space between roots and foliage and pumps air into the water, hydroculture leaves much space between the top of the root and the water reservoir. Hydroculture requires no pumping of water, and its roots travel through an aerated environment of. Hydroculture plants develop water roots capable of taking nutrients solely from water.
The main component of a hydroculture plant air filter is the substrate of porous rock and activated charcoal in which volatile organic gases are stored for later use; and, of course, the reservoir of water into which water roots grow.
To boost effectiveness as a filter, a very desirable component, if possible, is an added mechanical fan circulating air to the roots.
Click next page to see the third air-to-root component: a fan.
