eg magazine sustainability, resource efficiency & climate change

Agriculture is responsible for 15 percent of global greenhouse gas emissions. More than two-thirds of the world’s fresh water is used for agriculture. And around the world, farmers are losing the battle for water for their crops as scarce water resources are increasingly being diverted to expanding cities. As climate change brings warmer temperatures and more droughts, the water crisis will worsen.

To feed the growing and increasingly urban global population of 9 billion expected by 2050, we need to boost food production by 70 percent through higher crop yields and expanded cultivation.

In 1999, while exploring the negative impacts of agriculture, Despommier, a professor of environmental health sciences at Columbia University’s Mailman School of Public Health, and 105 graduate students came up with the concept of the vertical farm—a multi-story building growing layers of crops on each floor.

At present, lettuce, leafy greens, herbs, strawberries and cucumbers are the most commonly grown crops in vertical farms, but in theory, corn and wheat could be grown, as well as biofuel crops and plants used to make drugs. Hydroponics use 70 percent less water than conventional agriculture; aeroponics use even less; and all water and nutrients not taken up by the plants are recycled.

Climate controls and LED lights programmed to deliver the wavelengths of light that plants prefer create optimum growing conditions. Methane generated from restaurant or crop waste can supply energy and heat for vertical farms.

As a balanced mini-ecosystem, the vertical farm has many advantages. A vertically farmed acre can produce the equivalent of 4 to 6 soil-based acres, depending on the crop (for strawberries, 1 vertical farm acre produces the same amount as 30 outdoor acres). Plants can be grown year-round, unaffected by weather conditions such as droughts, floods or pests. Vertically farmed food is safe from contamination (for example, from e-coli or radiation), and is grown sustainably and organically without the use of fertilizer, pesticides or herbicides.

Some skeptics have said that the amount of electricity that would be needed to replace sunlight in vertical farms would be prohibitively expensive and unachievable. But Despommier counters that the cost of LED lighting is offset by savings from the elimination of fossil fuel use in fertilizer, transport, storage and distribution, as well as from less spoilage and waste. This, however, remains to be proven, since no one has yet done a life cycle cost comparison between vertical farm-grown crops and those produced conventionally.

For the full article see: 21Ventures newsletter

http://dl.dropbox.com/u/1570121/21V_Newletter_Q42011.pdf