13. Growing plants without soil

“Vertical farms offer the promise of a truly sustainable urban life”

Dickson Despommier

In my first post I stated that without soil we would simply starve… well this may not be strictly true. Plants require water, light, aeration, nutrients and support; they do not explicitly require soil… this is just a medium that happens to bring all of these factors together.

Hydroponics:

Plants can be grown in nutrient-rich water, held in place by manmade support structures. Modern hydroponic systems were developed in the 1930s but evidence suggests that the Hanging Gardens of Babylon, which date back to ~600 B.C., depended on hydroponic culture. Clearly, it’s not a new concept. Plants grown hydroponically absorb nutrients more efficiently, thus increasing yield.

Aeroponics:

In the 1980s, scientists took this one step further and began growing plants in air! They found that 'misting' water vapour and nutrients to the plant made it easier to aerate the root structure. 

Fig. 1 Diagram outlining typical ‘aeroponic’ setup (Source: www.soilless.org) 

Vertical farms:

If we used these approaches to grow food indoors, stacked up in city skyscrapers, we could eliminate the need for agricultural expansion and could protect ourselves against the limitations of agricultural intensification (soil degradation and climate change). We could also prevent fertilizer runoff, use less water and reduce the need for transport from distant rural farms, which adds cost, consumes fossil fuels and causes significant spoilage. In 1999, Dickson Despommier proposed a ‘vertical farm’ design, which he claimed could produce 2,400 acres worth of food in one 30-story high, five acre plot, using no soil and running entirely off renewable energy. He argued that although upfront costs may be high, once operational these farms would be able to produce food that is cheaper than current supermarket prices. Nevertheless, vertical farms are unlikely to be able to supply our entire global food demand alone. Therefore, in my opinion soil is still essential. 

Fig. 2 The front cover of the most recent edition of Dickson Despommier’s book called ‘The Vertical Farm’. (Source: Amazon)