NASA Spinoff

Originating Technology/NASA Contribution

In order for NASA astronauts to explore the solar system, they will need to travel not just as pioneers but as settlers, learning to live off the land. Current mission needs have NASA scientists exploring ways to extract oxygen from the lunar soil and potable water from human wastes. One of the basic goals, however, will be for pioneering space travelers to learn to grow and manage their own crops. This requires the development of space-age greenhouses where astronaut farmers can experiment with harvesting large-scale food crops.

Dr. Weijia Zhou (left), director of the Wisconsin Center for SpaceAutomation and Robotics at the University of Wisconsin-Madison,inspects soybeans grown in the plant growth unit aboard theInternational Space Station (ISS). Coating technology used inside theminiature plant greenhouse removes ethylene, a chemical produced byplant leaves that can cause plants to mature too quickly.
In the 1990s, researchers at the Wisconsin Center for Space Automation and Robotics, a NASA research partnership center at the University of Wisconsin in Madison, sponsored by Marshall Space Flight Center’s Space Product Development program, produced an ethylene reduction device for a plant growth unit. Ethylene is a naturally occurring, odorless, colorless gas given off by plants that hastens the ripening of fruits and the aging of flowers, encouraging decay. Comprised of carbon and hydrogen, in closed growing environments, like on a spacecraft or in a terrestrial greenhouse, ethylene builds up quickly and plants mature too fast. Removing ethylene, therefore, is important to preserving crops not just in space, but also on Earth, where grocers and florists have an interest in reducing the gas that ultimately shortens the shelf life of their products.

The ethylene reduction device, also called the ethylene “scrubber,” draws air through tubes coated in thin layers of titanium dioxide (TiO2). The insides of the tubes are exposed to ultraviolet light, which creates a simple chemical reaction, converting the ethylene (C22H4) into trace amounts of water (H2O) and carbon dioxide (CO2), both of which are actually good for plants.

The ethylene scrubber first launched aboard Space Shuttle Columbia mission STS-73 in 1995, where onboard the spacecraft the device was used successfully to preserve a crop of potato seedlings. Subsequent evolutions of the technology were flown aboard numerous International Space Station (ISS) expeditions.


KES Science & Technology Inc., a Kennesaw, Georgia-based company specializing in sustaining perishable foods, licensed the ethylene scrubbing technology from the University of Wisconsin (Spinoff 2001 and 2002). KES partnered with Akida Holdings, of Jacksonville, Florida, which now markets the NASA-developed technology as AiroCide. According to the company, it is the only air purifier that completely destroys airborne bacteria, mold, fungi, mycotoxins, viruses, volatile organic compounds (like ethylene), and odors. What’s more, the device has no filters that need changing and produce no harmful byproducts, such as the ozone created by some filtration systems.

Now in widespread use, the device is still helping preserve fresh foods, but has also seen applications in the medical and dental fields as well as in killing airborne pathogens, including anthrax and dust mites. One of the most recent applications of this NASA technology now available is in a new line of home refrigerators. Other companies have begun looking at using the device for treating whole house systems.

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