In an effort to better understand the benefits provided by this green technology, Drs. Shivanthi Anandan and Jacob Russell from the Department of Biology teamed up with Dr. Michael Waring from Drexel’s Civil, Architectural and Environmental Engineering Department. Together, these three researchers have been studying how well the biowall works in removing airborne pollutants, or volatile organic compounds (VOCs), such as benzene, formaldehyde and toluene. They’re also looking at how the different plant types (and their root microbes) in the biowall vary in their abilities to purify the VOCs, and which of the root-associated microbes are involved in VOC degradation.
While the building was under construction, the group obtained permission to install sampling ports on each of the building’s five floors to measure the quality of the air before and after passing through the biowall. Measurements from each floor will reveal removal efficiency and any changes in air quality from floor to floor due to differences in temperature, light, humidity or plant types.
While data are not yet available to fully evaluate the wall’s efficiency in improving indoor air quality, the answers are coming soon, according to Drs. Waring and Russell. “What’s great is that the research being done here can very easily fit into our coursework,” Russell says. He and Waring both plan to have students continue the biowall research in their courses this spring and hope to have more definitive answers at the end of quarter. Waring plans to have students continue measurement of VOC removal and Russell’s class will work with the molecular data to identify, or “barcode,” the bacterial root communities.
In the meantime, the trio performed various experiments on VOC removal efficiency under controlled conditions in Waring’s lab, a project funded by a GRID grant awarded by the Commonwealth of Pennsylvania’s Department of Health in 2011. This experiment gave the researchers a more controlled environment in which to examine the plants’ microbes and how they respond to VOCs.
“The cool part about the biowall is that it’s really about the microbes,” Waring says. “The plants are just homes for the microbes; that’s all that they are there for. The microbes actually eat the VOCs as food.”
In his lab, Waring grew plants in aeroponic, or suspended, chambers, and exposed the plant roots to VOCs at known concentrations to observe how and if the microbial communities changed.
“We saw a shift in the microbes—what started off as one kind of community altered and changed after we hit it with VOCs over time. The communities changed in relative abundance—some types of microbes almost disappeared, others started to proliferate.”
What exactly does that mean? Studying the changes in microbial communities will allow an estimation of the plants’ (and microbes’) contribution to air purification. Russell and Anandan conducted a similar experiment on plants from the Dodge Foundation biowall in Morristown, NJ. They found diverse communities of bacteria and fungi that can be grown in culture, “so we can more easily study how specific species break down VOCs,” Russell says.
[The biowall] makes people excited for reasons they don’t really understand or care about, but everyone’s interested in it. - Dr. Michael Waring
In the long term, this work should help to identify plants and microbes that are efficient VOC degraders, which would inform the design of more efficient living walls, and even healthier indoor environments.
Outside of the plant and microbial community experiments, the researchers are all interested in continuing to use the biowall as an educational tool and for community outreach. It’s important to note, Anandan says, that the plants in the biowall may come as a surprise.
“The plants are normal household plants; nothing is exotic in the biowall,” she says. “The point is to show people that anyone can do this. These are all plants you can buy at Home Depot or Lowes.”
“One of the things I think is really great about the wall is it has its own life, it has its own gravity,” Waring says. “It makes people excited for reasons they don’t really understand or care about, but everyone’s interested in it. And it has a really big potential to excite students—there are always students in my classes that ask me about it and want to study it.”
In addition to the coursework planned for the spring quarter, research on the biowall has included—and will continue to include— participation from Drexel STAR Scholars and co-op students. Additional financial support for the research was provided by the Office of the Provost and the College of Arts and Sciences.
