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Project Carbon – A Joint Effort of National Foliage Foundation and Green Plants for Green Buildings

Posted by Southern Botanical, Inc. in Dallas-Fort Worth-Arlington, TX on Apr 20, 2010

Project Carbon is a joint effort of National Foliage Foundation and Green Plants for Green Buildings (GPGB) that has been in focus for some time.

This is the beginning of an article posted on the Green Plants for Green Buildings website.

Southern Botanical, Inc.

Proposal Submitted to the National Foliage Foundation

Quantification of Carbon Assimilation in Interiorscape Plants In Simulated and In Situ Environments

Bodie V. Pennisi, Associate Professor with University of Georgia, Department of Horticulture, Griffin, GA 30233 and Marc van Iersel, Professor with University of Georgia, Department of Horticulture, Athens, GA 30602-7273

INTRODUCTION
The word “sustainable” is exemplified by mainstream ‘green’ movements such as the Leadership in Energy and Environmental Design (LEED) certification.

LEED promotes a wholebuilding approach to sustainability by recognizing performance in five key areas of human and environmental health: sustainable site development, water savings, energy efficiency, materials selection and indoor environmental quality. LEED has become an important element in the building industry but it lacks an agricultural connection to indoor plants and their role in promoting human health by improving indoor air quality (IAQ).

Since the 1970s, a multitude of research has shown the positive direct (by removing air pollutants) and indirect impact (by reducing patient recovery time in hospitals) of plants on buildings. The University of Georgia and other leading academic institutions around the world (e.g. in Japan, Australia, Germany, Korea) have more recently engaged in expanding the scientific knowledge with regard to species, types of harmful indoor air pollutants, efficiency and mechanisms via which plants are able to neutralize such pollutants.

We have documented the efficiency of volatile formaldehyde removal by indoor plants and found that the root zone is a major contributor to the removal process (Kim et al, 2008). We have completed our screening of the efficiency of volatile organics removal by various indoor species, and submitted a manuscript to the Journal of American Society for Horticultural Sciences (p. 8, Appendix). Of the 28 species tested, Hemigraphis alternata, Hedera helix, Hoya carnosa, and Asparagus densiflorous had the highest removal efficiencies for all pollutants; Tradescantia pallida displayed superior removal efficiency for 4 of the 5 VOCs (i.e., benzene, toluene, TCE, and á-pinene). The five species ranged in their removal efficiency from 26.08 to 44.04 ìg·m-3·m-2 ·h-1 of the total VOCs. Fittonia argyroneura effectively removed benzene, toluene, and TCE; Ficus benjamina, octane and á-pinene; Polyscias fruticosa, octane.

The variation in removal efficiency among species indicates that for maximum improvement of indoor air quality multiple species are needed and the number and type of plants tailored to the type of VOCs present and their rates of emanation at a specific indoor location. Based on this and other studies, it is clear that plants have the potential to significantly improve the quality of indoor air with respect to harmful volatile organic compounds such as 2 benzene, toluene, octane, trichloroethylene (TCE), and á-pinene. Sustainable certification programs, therefore, could implement phytoremediation as part of a program for IAQ improvement.

One aspect of indoor air quality has received minimal attention to-date: the impact of plants on removal of carbon dioxide from indoor environments. Light in the presence of water and carbon dioxide triggers internal mechanisms in chloroplasts (photosynthesis) that convert carbon dioxide and water into sugars and oxygen. The photoassimilates (sugars) are then used for new growth and maintenance of existing tissues and organs. As light is the driving force behind photosynthesis, generally, the higher the light level, the more sugars are produced. Indoors the most limiting factor for photosynthesis is light. The light levels in typical commercial interiorscape installations range from more than 250 foot-candles (fc) (rated as “good” level by interiorscapers), 200 – 150 fc (“medium” light), or 125 – 75 fc (“low” light).

Under such conditions, plants sustain variable photosynthetic rates, mainly depending on the ambient light levels. It is important to note that temperature also has a significant impact on the production of photoassimilates, mainly due to its effect on respiration. In contrast to photosynthesis, respiration breaks down sugars (providing building blocks for plant growth and maintenance respiration) and releases carbon dioxide. Generally, indoor air temperatures (21 °C day/18 °C night) are not conducive to excessive respiration rates and thus carbon dioxide release from the plant. Thus, the amount of carbon uptake and fixation in building interiors is directly related to light level, temperature and existing stored photosynthetic reserves (which in turn depend on production environment, level of acclimatization, etc).

While we have a plethora of data on photosynthetic performance of plants under various light regimes in simulated interior environments, we lack reliable knowledge of such performance in situ that is in a real-world interiorscape situation. Nor has there been a documented effort to systematically record photosynthetic rates of a number of plant species, at various canopy levels. Such quantitative data, correlated with data obtained under simulated environment, may enable us to extrapolate the amount of carbon dioxide assimilated under typical interiorscape conditions. 3 Lastly, we hope to be able to address the question: “If an interiorscape of certain size and plant species is implemented under typical light levels, how much carbon would be removed from the air over given period?”

Southern Botanical is a member of Green Plants for Green Buildings and supports their programs.