by Kathryn Flehmer
For many people in the Midwest, the word “farm” brings to mind acres of corn, fields of wheat, and barns that house cows and chickens in the sprawling countryside. However, how much longer can this image remain true? Throughout the world, over 80% of the land suitable for farming is in use. The human population is set to increase by an estimated three billion by the year 2050. This means about 109 hectares of new land will be needed to grow enough food, if the traditional farming practices continue. With these estimates, is it possible that this system of farming can persist? Some people don’t think so. Dickson Despommier, a 67-year old microbiologist at Columbia University, believes that the only way we can subsist is by drastically changing the way we farm. Instead of sprawling farms, Despommier envisions 30-story high sky scrapers that could provide enough food and water for 50,000 people a year.
Called vertical farms, these structures would be home to various kinds of fruits, vegetables, and small animals. Despommier told Popular Science magazine that the idea of the vertical farm was the brainchild of Despommier and his students. Students were assigned a project on urban sustainability. They first proposed the production for 13 acres of farmable land on commercial rooftops of Manhattan. They figured, however, that this would feed just 2 percent of the city. Despommier then suggested that they take the 1,723 abandoned buildings in Manhattan and retrofit them to house hydroponics. Hydroponics is the practice of growing plants using mineral nutrient solutions instead of soil.
According to Despommier’s website, www.verticalfarm.com, 60% of the human population now lives in city buildings. As we are all protected against the elements, Despommier writes, why not extend that coverage to our food-bearing plants as well?
He thinks irrigation plants in these buildings can produce not only enough food, but water for 50,000 people as well, through evapotranspiration. Condensation would come from the leaves of plants, Despommier said. Irrigation would come from the sewage (which would first be de-sludged). Then it is filtered through non-edible barrier plants, and then again through zebra mussels, one of nature’s best filterers. Despommier says that more than 100 strawberries, blueberries, and even miniature banana plants will inhabit these buildings.
Based on a compilation of extensive research, the vertical farm website lists many advantages of vertical farming, including:
- Year-round crop production
- No weather-related crop failure
- Organic food with no herbicide, pesticides, or fertilizers
- Eliminates agricultural runoff by recycling black water
- Returns farmland to nature, restoring ecosystem functions and services
CNNMoney.com reported that the construction of a 21-story vertical farm would cost about $84 million to build, $5 million in operating costs each year, and revenue $18 million a year.
A 30-story tower, set in the middle of the city, is a bit hard to imagine. So let’s take a verbal tour of this futuristic farm. The building itself will be circular, using space more efficiently and allowing maximum light into the center. Floors are stacked like “poker chips” for flexibility.
Most of the vertical farm’s energy will be supplied by a pellet system. However, there will also be a rotating solar panel that will follow the sun throughout the day, which ensures the most efficient use of solar energy.
In conjunction with the solar panel, there will be a wind spire. This wind spire uses small blades to turn air upwards, instead of conventional windmills, which are too big for cities. The building is coated with titanium oxide-glass panels that collect pollutants and let rain slide down the glass instead of beading; this allows for better light filtration and pollutant cleansing.
The entire vertical farm is regulated from the control room, which allows for year-round, 24-hour agriculture. The crops in the farm could include fruits, vegetables, grains, fish, poultry, and pigs.
How Does It All Work?
According to New York Magazine, the vertical farm also generates its own power from waste and cleans sewage water. Inside the ceiling of each floor, pipes collect moisture through an evapotranspiration recovery system. The pipes work much like a bottle of Coke that sweats on a hot day. Super-cool fluid inside pipes attracts plant water vapors. The moisture, which comes from plants, can then be bottled and sold. Despommier estimates that one vertical farm could recover 60 million gallons of water a year through this method.
Wastewater from the city’s sewage system is treated through filters and is sterilized, resulting in gray water. This water is not drinkable, but can be used for irrigation.
Working on the “Field”
A crop picker monitors fruits and vegetables with an electronic eye, checking for ripeness, temperature, etc. Because maximization of space is a priority, there are two layers of crops on each floor. If small crops are planted, there could be up to ten layers per floor, as well as crops that could hang from the ceiling. Runoff from irrigation is collected at the Pool and is piped into a filtration system. A Feeder directs programmed amounts of water and light to individual crops.
Pellet Power System
The pellet power system is another source of power for the vertical farms. It turns non-edible plant matter (e.g. corn husks) into fuel. It could also process waste from restaurant kitchens. Plant waste is processed into a powder, condensed into clean-burning fuel pellets and becomes steam power.
While it may take a few years for this idea to literally get off the ground, the concept of vertical-farms has caught the attention of many. Vertical-farms use current technologies and all that is needed for this plan to continue, Despommier said, is money.
(Description information courtesy of New York Magazine.)