I find the concept of green roofs and green walls fascinating. Each month, I eagerly await Kevin Songer’s contributionon green roofs. That is why I was happy to learn about a living wall not far from my home in the Philadelphia suburbs and decided to pay it a visit. Drexel University inaugurated its indoor green wall last September. It will serve the purposes of purifying the air and beautifying the location; but, most of all, it will be used to study the functioning and benefits of living walls. This research project is being carried out by a team which includes biologists and an environmental engineer. It also gives students the opportunity of a hands-on learning experience.
Drexel University boasts the largest North American indoor living wall or Biowall, as they prefer to call it. The five-story high living wall stands in the lobby of a new building, the Papadakis Integrated Sciences Building, in the heart of Philadelphia. About 12 species of tropical plants have been selected for this wall. Sorry, no native plants here! Those that grow through the cold winters of southeastern Pennsylvania (hardiness zone 7a) would not survive the constant indoor temperatures. Dr. Shivanthi Anandan explains that plants were bought in local nurseries “chosen for their robust growth, and also to illustrate the fact that these plants can be bought by the general public”.
Still, the ecological value of an indoor living wall makes it worthy of this discussion. Accumulated pollutants are a serious problem of enclosed buildings. This indoors pollution has earned the name of “sick building syndrome” (EPA Fact sheet). It is caused primarily by volatile organic compounds (VOCs for short). There are a few ways to combat the accumulation of such undesirable aerial compounds. Increased air circulation is helpful but requires a larger consumption of fossil fuels used for cooling and heating the building. Air filters are beneficial but they must be replaced constantly. A properly designed living wall would circulate air through it trapping pollutants; a more effective and elegant solution to the problem of “sick building syndrome”.
An important aspect of Drexel University’s Biowall is its role as a living laboratory to study the function of this air filter. More important than the plants themselves are many microorganisms that live on or around the roots. A rich community of bacteria and fungi works hard to capture and destroy some of the volatile compounds mentioned. It turns them into food for themselves and for the plants they live on in a remarkable feat of biochemistry. For instance there are some bacteria that break down benzene and toluene. The team of Drexel researchers plans to learn about these microorganisms, how they work, how beneficial they are.
They will be studying the chemical composition of air before and after it goes through the biowall. Some previous studies show a significant reduction of some pollutants. There will also be more detailed studies at the microscopic level performed in the lab. It is hoped that the results will serve to create improved and more efficient walls.
In the meantime, I will settle for a very modest version of a living wall. A local nursery carries “living wall planters” which can be hung indoor or under a roof outdoors. They are large pockets made of a thick felt. I am happy to know that the felt is 100% recycled plastics. The waterproof lining is Army tested. Still, I would think carefully about where to place them. The back porch may be a good place. This will be the perfect Christmas present for a plant lover friend of mine. My unsuspecting “victim” will receive a couple of native ferns along with it. I hope that she gets the message about the value of native plants.
All photos by Beatriz Moisset
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