5 Innovative Greenhouses

If you want to see what greenhouses are truly capable of, check out the Eden Project, the largest greenhouse in the world. Located in Cornwall, England, the Eden Project is a sprawling, multi-domed structure that replicates various climates from around the world.

Dubbed a "green theme park," Eden is home to more than 100,000 different plants and hosts at least 1 million visitors annually [source: Icons]. It was established to illustrate humanity's dependence on plants and to stress the importance of sustainable development and environmental research and education.

The facility strives to make as little negative impact on the environment as possible. Virtually all of Eden's water comes from recycled, filtered rainwater, but the site's commitment to sustainability doesn't stop there. In June 2009, plans were revealed for a new geothermal plant that would provide Eden with a virtually endless supply of natural, renewable energy.

Large greenhouses like the Eden Project are great, but they take up a lot of room. With humanity's population constantly expanding, it's entirely possible that we simply won't have the space for luxurious, sprawling buildings in a few decades -- greenhouses or not. We need to be smarter with our land, which is where vertical greenhouses come in.

Built like skyscrapers dozens of stories high, it's believed that vertical greenhouses' controlled environments could produce 400 to 600 percent more food than what's possible with similar acreage on traditional outdoor farms. Because the majority of the world's population lives in urban areas, the greenhouse-skyscrapers could be located in cities, allowing areas that are now almost completely dependent on imported goods to become self-sustaining. The pollution produced by transporting food would be radically decreased, and much of the land now used for agriculture could be freed for development or even returned to its natural state.

Deserts aren't exactly known for their agriculture. However, the designers behind the Sahara Forest Project believe they can use greenhouses to change sandy desert dunes into lush, life-giving forests.

The Sahara Forest Project works by combining two existing technologies: Seawater Greenhouses, which irrigate crops with evaporated, desalinated ocean water, and Concentrated Solar Power (CSP), which uses sunlight and mirrors to convert water into steam that powers turbines. The two technologies work well together because the greenhouses produce 500 percent more water than the plants need [source: Oppenheim]. Some of the extra water can be used to provide the CSP turbines with fuel and to clean the mirrors, making the Sahara Forest Project a closed system that produces food, energy and fresh water.

Additional, unused water generated by the greenhouses will initially be used to grow plants like jatropha for biofuel. However, the excess water, influx of new plants and local cooling effect of the greenhouses will eventually transform portions of the desert into forested land.

The greenhouse at the United States Antarctic Program's McMurdo Station holds perhaps the most important patch of vegetation on the continent. To anyone not living there, it probably wouldn't be all that impressive -- just 200 square meters of plants, fruits and vegetables, including lettuce, tomatoes and pansies [source: SpaceRef]. However, when you're living in the harshest environment on the planet, a roomful of plants and vegetables is an amazing thing, especially considering they all have to grow without any soil or access to natural light.

Because of the continent's prolonged periods of darkness and light, the McMurdo greenhouse forgoes a traditional glass ceiling. Instead, it resides in a warehouse that uses artificial light to replicate normal day and night cycles. To prevent any microbes from contaminating the Antarctic environment, all plants have to be grown hydroponically (without soil). Despite the limitations this harsh environment imposes, the McMurdo greenhouse is extremely successful. It can produce more than 300 pounds of food per month, including as many as 750 heads of lettuce, allowing the people stationed there to have a fresh salad several times a week -- a real luxury in Antarctica [source: SpaceRef].

Although Antarctica remains the most hostile environment on Earth, it's not the most inhospitable place we have established a greenhouse. Lada (named after the Russian goddess of spring) is a greenhouse that has been growing plants on the International Space Station since 2002.

The Lada greenhouse consists of three modules (one for control and two for vegetation) and was developed jointly by U.S. and Russian scientists. Although Lada uses controlled light and moisture, everything else -- air, gravity, humidity and temperature -- is dictated by the environment on the space station [source: NASA]. This allows scientists to see how plants cope in a radically different setting. It also enables them to monitor the effect of potential contaminants, such as radiation, that the astronauts, the spacecraft and, thus, the plants, are exposed to in space. By understanding how plants acclimate to the rigors of space travel, we can begin preparing for a future when astronauts can grow their own food in space and on other planets.