Vegetables for space – greenhouse created for the South Pole
07 November 2016
By the end of next year, the EDEN ISS greenhouse will supply the German Neumayer III polar station with fresh fruit and vegetables.
It will also test how fresh plant-based food could be cultivated on the International Space Station ISS and during future missions to the Moon and Mars. The not quite so everyday Antarctic container has arrived at the German Aerospace Centre (DLR) site in Bremen and its conversion into a self-sufficient biotope for salad, herbs, cucumbers and maybe even strawberries. DLR researcher Paul Zabel is already preparing for his extraordinary mission to the End of the World.
Defying the Arctic winter
A great deal of state-of-the-art technology is required to cultivate plants at the South Pole. "First of all, we need to provide the basic needs of the plants in the polar greenhouse, which cannot be taken for granted in the Antarctic," says Zabel, of the DLR Institute of Space Systems. "Pipes to supply sufficient water, lamps to provide the right light and even filters and nozzles for a growth-promoting air mixture must first be laid and installed." During the Antarctic winter, the environment is extreme and hostile to life. Temperatures drop to -30°C and no sunlight breaks the darkness of the polar night for months. The greenhouse has particularly effective insulation, as from December 2017 onwards it must defy Antarctic conditions.
Plant cultivation without soil
An essential factor for horticulture in extreme conditions is having the right water supply. Large water tanks are therefore installed in the floor of the greenhouse container. In the eternal ice, these are then filled with previously melted, filtered and purified water from the Neumayer III Antarctic station operated by the Alfred Wegener Institute (AWI). "The water is not fed directly to the plants but is rather computer-controlled to add a special nutrient solution," explains Zabel. "Every five to 10 minutes, the plants are sprayed automatically with the water-nutrient mixture so that they can be cultivated completely without using soil." The process, called aeroponics, basically saves the transportation of large quantities of soil.
Sterile air with increased carbon dioxide content
The air in the greenhouse will be adapted as much as possible to the needs of the plants. For this purpose, bottles of carbon dioxide will accompany the container to the Antarctic to enrich the carbon dioxide content in the greenhouse air. "It will be crucial to keep the air free of harmful germs and fungal spores," says EDEN ISS Project Coordinator Daniel Schubert from the DLR Institute of Space Systems. "To do this, we are installing various air filters as well as a system for air sterilisation using UV radiation." Like a space station, the greenhouse will have a completely closed air circuit, including an airlock through which Zabel will enter the greenhouse every day. The closed circuit also allows all the water that the plants release into the air to be recovered and fed back to them. "I will, so to speak, only take the water that I harvest out of the greenhouse with the ripe fruit. The rest will be reused," adds Zabel.
Special light for every plant
To survive in the polar night, the plants, in addition to air, need a nutrient-water mixture and a blue and red light cocktail, which makes vials and plants glow violet. "In order to grow each plant species individually, we are building water-cooled LED systems in which each LED can be individually controlled via a computer," explains Schubert. The plants will be illuminated for 16 hours in an implied day-night rhythm and will have eight hours of nightly rest without light. Engineer Zabel also needs the right light in Antarctic darkness: "In addition to the dim LED light, there will be a white light for me, so that I can hopefully work well in the greenhouse."
The installation of basic supplies will be completed around Christmas, followed by the working area, the changing room and the computer technology required for Zabel's stay by spring. After that, a trial will start at the DLR site in Bremen, before it is shipped en route to Antarctica in October 2017.
Preparations for the dress rehearsal on ice
Since 2011, the DLR Institute of Space Systems has been researching the artificial conditions under which salads or cucumbers flourish and taste best in the established EDEN laboratory. The Antarctic will be the field test for whether plant cultivation in total isolation is successful. For DLR researcher Zabel, it will be a very personal challenge to hold out for a year in the eternal ice. He is currently intensively studying the art of plant cultivation at Wageningen University in the Netherlands, one of the project‘s partners. In the summer of 2017, there will also be a first trial cohabitation for the entire overwintering crew in Bremerhaven and then a challenging survival training course in the Alps.