Final Report: Biowall’s Impact on Indoor Air Quality and Energy

EPA Grant Number: SU835505
Title: Biowall’s Impact on Indoor Air Quality and Energy
Investigators: Hutzel, William J , Bouley, Michelle , Dana, Michael N , Drummond, Adam , Huang, Linhan , Martin, Andrew , Newkirk, Daniel , Nola, Olivia , Qu, Ming , Xue, Yu , Yearwood, Moriah
Institution: Purdue University
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: August 15, 2013 through August 14, 2014
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2013) RFA Text |  Recipients Lists
Research Category: P3 Challenge Area - Built Environment , P3 Challenge Area - Energy , Pollution Prevention/Sustainable Development , P3 Awards , Sustainability


The average American spends more than 90% of his or her time indoors where the air is 2-5 times more polluted than outdoors. A principal cause of indoor pollution and its associated health concerns are volatile organic compounds (VOCs), which are emitted by a wide array of household products. Taken as a whole, poor indoor air quality (IAQ) is estimated to cost the United States at least $40 billion annually due to related illness and lost productivity. The elderly and the young are especially at risk to illness due to lifestyle habits and weaker immune systems.

Energy efficient buildings typically seal the leakage paths for outside air infiltration but this can lead to poor IAQ as an unintended side effect. The Biowall is a new concept for maintaining high levels of indoor air quality and has the potential to reduce HVAC energy use by reducing outside air requirements for buildings. The device consists of a living plant filter that is integrated into the heating and cooling system of a residence or a small commercial building. This technology leverages the natural ability of plants to reduce CO2 and remove VOCs.

To evaluate this concept, a living plant filter was designed and grown in a simulated building environment. The plant filter was integrated with a heating and cooling system and fully instrumented so precise measurements of air temperature, air humidity, air quality, and component-level energy consumption could be made. Various growth media, plant varieties, and watering strategies were evaluated to investigate options for improving a Biowall’s performance. The experimental work involved introducing toluene, a common VOC in buildings, into a test chamber where precise measurements of the VOC decay rate could be made. Comparisons were made with the toluene removal rate, both with and without the Biowall.

Summary/Accomplishments (Outputs/Outcomes):

The graph below shows the generation and decay of Toluene as a function of time in a test chamber. Two scenarios, with and without a Biowall, were investigated. The graph shows that the Biowall test improved the indoor air quality three times faster. The results were statistically significant and validated over multiple tests.

The results of the IAQ experiments were used to calibrate a thermodynamic model showing the Biowall’s performance in a small energy-efficient and air tight home. The analysis specifically evaluated the potential for annual energy savings from varying the amount of outside ventilation air because the Biowall can maintain reasonable IAQ with less outside air. The thermodynamic modelling for the EPA P3 project compared:

  • Different energy saving technologies (Biowall and Energy Recovery Ventilator)
  • Energy performance in three different climates (hot, moderate, and cold)

The results are shown in the graph below. The overall magnitude of annual energy for heating and cooling varied significantly by geographic location. That was not really a surprise. However, the energy modelling did show that a combination of a Biowall and an Energy Recovery Ventilator used the least amount of energy for heating and cooling in all three climate zones. The Biowall by itself saved energy as opposed to a house with no energy conservation strategies.


In this EPA P3 research project the Biowall was shown to reduce VOCs in ventilation air. This was accomplished by direct measurements of a Biowall’s performance in a laboratory setting. An energy model put these finding into context by estimating a Biowall’s impact in a home over a calendar year. The results encourage us to continue this research with commercialization as an end goal.

Beyond energy savings, we are enthusiastic about the positive impact that a Biowall could have on a homeowner’s physical and mental health. By bringing a living organism into a dwelling, a Biowall can improve the aesthetic value of a space and the life of the homeowner. That impact of a “green lifestyle” was not evaluated in this Phase I research, but literature is increasingly showing that this could become another important selling point.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Other project views: All 5 publications 1 publications in selected types All 1 journal articles
Type Citation Project Document Sources
Journal Article Cho J, Mansfield J, Krockenberger K. Using plants to reduce energy. Journal of Purdue Undergraduate Research 2013;3(Fall):24-31. SU835505 (Final)
  • Full-text: Purdue - Full Text PDF
  • Supplemental Keywords:

    plant cultivation, phytoremediation, carbon activated filter

    Relevant Websites:

    Biowall: Planting a Healthy Home Exit
    Purdue Applied Energy Laboratory Exit
    YouTube Video: The Biowall Project in 3MT Competition Final Round @ 2013 ESE Summit Exit

    P3 Phase II:

    Biowall’s Impact on Indoor Air Quality and Energy