How did Wolverton expose potted plant roots to air?

1. BioHome botanical air filter

In the BioHome experiment, according to a diagram in Wolverton’s article, “Plant Based Air Filters for Formaldehyde Remediation in FEMA Trailers,” the plant pictured is set in soil with activated carbon, with an air space below the soil. There is a tube by which water drains into a receptacle for “excess water.” It appears that the plant is top-watered, and has a bottom-mounted fan for air circulation.

Wolverton described that setup as:

A working model equaled the VOC removal capacity of 15 regularly grown interior plants. (See Fig. 2 in the above article).

2. FEMA botanical air filter: the EcoPlanter

By the time Wolverton was called upon to perform phytoremediation (plant remediation) of formaldehyde in FEMA trailers, he had developed a more effective system, replacing the use of soil with the soil-less “hydroculture” in which pebbles or porous media could hold the plant roots.

He stated the advantage was that “studies show that hydroculture plants are more effective in removing VOCs,” because “air can pass more easily down to the root zone through pebbles than through soil. “

He described the new system thusly:

The first (WES) plant-based air filter did not use soil but a substrate consisting of expanded shale or clay, activated carbon and zeolite. (See Fig. 7 in the above-referenced article.)

These soil-free filters employed a mechanical fan to pull air down through the highly adsorptive substrate (activated charcoal and possibly absorbant pebbles) in which an interior plant was grown. The substrate traps any airborne contaminants where naturally occurring microbes, living on and around the plant’s root system, biologically break down the trapped chemicals. The plant and microbes use these end products as a source of food and energy.

Actually, Figure 8 is more informative than Figure 7, as it shows the placement of the two-speed fan in the bottom of the system.

This was the system utilized in the FEMA trailers to remove formaldehyde. The system claimed to have the gas removal capacity of 100 plants. It was made commercially available only in Japan.

3. 2012-2013 botanical air filter: the Plant Air Purifier

The most recent iteration of this system holds a larger plant, and more water, than the EcoPlanter, and is sold in the United States by Wolverton Environmental Services under the name of Plant Air Purifier (Trademark).

The Plant Air Purifier’s price tag of $229 (as of 2015) must be seen from the perspective of its equivalency to 50-100 plants, in air purification capability, and the difficulty of the average person’s engineering a convenient plant fan to improve the effectiveness of the filtering capability.

Click next page to see what may be involved in creating a nearly equivalent plant filter that is home-made.