The number of people on our planet is growing rapidly. Food security is becoming increasingly difficult to achieve. The amount of arable land is limited, and increasingly threatened by climate change. Agronomists, engineers and architects are already working on ideas for the agriculture of tomorrow. Their scenarios show that agriculture is moving to the city - and going vertical.
Usually, it is people who live and work behind the walls of a high-rise building. Decorative houseplants are the only touch of green. In future, however, lettuces, tomatoes or rice plants will flourish behind the windows of skyscrapers. These city farms will reach for the sky as futuristic green high-rises alongside multi-story office buildings.
Architects are sketching visionary agricultural towers, with efficient greenhouses stacked up to a dizzying height, and have dubbed the system “vertical farming.”
The urban farms are equipped with environmentally friendly wind turbines and solar cells. The buildings are reminiscent of a sci-fi film: glass pyramids, towers flooded with light and the bulbous silhouettes of skyscrapers. The various floors have no internal partitions, but are entirely devoted to hydroculture: various types of fruit and vegetables will grow here, and rice and wheat seedlings will sprout.
There will even be room in these vertical farms for free-range hens and water tanks housing shrimp and fish. Some of them are designed to be installed on floating urban islands in coastal waters, which will be self-sufficient thanks to their integrated greenhouses.
Food for megacities
The city sketches and ideas for the agriculture of the future are merely imaginative designs at present. But if over 9 billion people are going to be living on the earth in 40 years’ time, we need innovative ideas today to ensure food security. The population of large cities, in particular, is growing rapidly: by 2025, the urban population, now standing at 3.5 billion, will grow to an estimated 4.5 billion, while the rural population will merely increase from 3.4 billion to around 3.5 billion.
The United Nations expects particularly strong growth in the megacities with over 10 million inhabitants. For example, 21 million people live in Delhi today, but in 2020 that figure is expected to grow by 5 million, according to the World Urbanization Prospects of the United Nations. Large cities such as Mumbai in India, Dhaka in Bangladesh, Kinshasa in the Democratic Republic of the Congo or Shanghai in China will also have considerably more people to feed.
More agricultural land is urgently needed. But there is hardly any more land on the planet to use. In fact, the available area of arable land per head has been shrinking for decades. According to United Nations figures, by 2050, there will be only around 0.19 hectares per head of suitable arable land – in 1950, the figure was almost three times as high at 0.52 hectares. More and more agricultural land is being lost owing to heat stress and drought.
“The losses in yield due to these abiotic stress factors are enormous, up to 80 percent in some cases,” says Dr. Alexander Klausener, head of research at Bayer CropScience. Current climate change trends could make the situation even worse, says the researcher. Urban agriculture could help to control the problems of the future.
Scientists like Professor Dickson Despommier see vertical farming approaches as the solution to a number of 21st century problems. The U.S. microbiologist from Columbia University in New York City is the original inventor of the high-rise farm. He sees the idea as much more than an important contribution to global food security.
Multi-story greenhouses could also save energy and transport costs. The expense currently involved in transporting our fruit and vegetables and emissions of environmentally damaging greenhouse gases could be considerably reduced, he says. Another advantage of the skyscraper farms is that land currently used for agriculture could be returned to nature - vital ecosystems such as forests, which store CO2, thereby removing it from the atmosphere, could be revived in this way.
Today, a city needs many times its own area in agricultural land if it is to feed its inhabitants. In future, says Professor Despommier, a 30-story building could supply around 50,000 people with fruit, vegetables, eggs, fish and chicken.
Efficient indoor farms
Life inside the visionary multi-story farms will be arranged as sustainably as possible: water circulates in closed systems, animal feed can be made from plant waste and fertilizers from animal manure or sewage. Plants will grow in soil-free material such as mineral wool or coconut fiber, since pests are less of a problem if there is no soil.
The modern greenhouses will form their own ecosystem inside the metropolis – shielded from fluctuations in water supply and climate. They will thus yield several harvests per year, and city dwellers will be able to buy fresh food from the high-rise farm around the corner whenever they wish.
“Up to now, designs for vertical farms were mostly based on futuristic architecture,” says Professor Joachim Sauerborn, an agronomist at the University of Hohenheim. “The cultivation technology required in the building has received less attention. The emphasis has also been on high-value crops such as fruit and vegetables, sometimes in combination with fish and animal production.”
In contrast, the skyfarming concept developed by the University of Hohenheim is based on the needs of plants. “Our idea is comparable to housing design: first you identify the residents’ needs and then you plan a building with the necessary facilities,” says Professor Sauerborn, explaining his strategy. Plants, like people, have differing needs – lettuce grows differently from cereals.
Rice by conveyor belt
The test crop chosen by Sauerborn’s scientists is an important and environmentally significant staple food: rice. Rice is grown over an area of 157 million hectares worldwide, or 22 percent of the global cereal production area. Rice growing requires large quantities of water – up to 30 percent of the world's fresh water resources. Also, fermentation in flooded rice paddies produces methane gas, which is far more harmful to the environment than CO2.
“It is estimated that up to 20 percent of global methane emissions are attributable to rice-growing,” says the professor of agronomy. It was not only agronomists who attended an initial expert workshop on the skyfarming project in early July 2010. Engineers, architects, logistics experts and economists also gathered to discuss the vision of the “high-rise paddy field.”
The scientists see the rice seedlings growing not in static fields on each floor, but on indoor terraces which are constantly in motion. The individual rice seedlings will move in stages on a conveyor belt and go on a 120-day tour of the building while they gradually ripen into plants mature enough for harvesting. The growing seedlings will obtain nutrients through their roots: they will be constantly sprayed with a fine mist containing an optimum mix of nutrients. In this “aeroponic” system, the plant roots literally dangle in mid-air in special plastic bags. At the end of their conveyor-belt trip, after approximately four months, the rice plants can be harvested and the empty spaces filled with new seedlings ready to begin their journey.
According to Professor Sauerborn, this greenhouse can produce up to three harvests per year. The researchers are also expecting significantly greater harvests: the aeroponic system is easy to keep free of pests and germs. And in perfect growing conditions, the plants have a higher yield. Professor Sauerborn estimates that rice has a potential yield of 14 tons per hectare – in optimum conditions. In contrast, the yield in a normal rice paddy falls to around 4 tons per hectare because of climatic stress, pests and disease.
Using the skyfarming concept, one hectare of indoor growing space is due to a better use equivalent to between five and seven hectares out in the field. The rice plants also require significantly less water: “Around one liter of water is required to produce one kilogram of rice. Current rice-growing methods use around 600-900 liters of water per kilogram,” says the agronomist.
Fitness training for crops
It will be at least 15-20 years until rice crops can be planted in greenhouses, says Professor Sauerborn. In order to feed the growing world population until then, the main priority is to get the crops in shape to withstand changing climatic conditions.
At the Bayer CropScience Innovation Centre in Ghent, Belgium, Dr. Michael Metzlaff and his colleagues are working to make crops more resistant to climatic stress. “We want to make the plants able to produce consistently high yields in the long term despite fluctuations in environmental conditions,” says Metzlaff.
Crops have various defensive mechanisms to respond to short-term stress, but these require a lot of energy, which is then not available for growth. The result is enormous losses in yield, particularly following drought and persistent hot weather. With the help of modern genome research, the Bayer researchers can look deep into the genetic material of the crops, explain stress mechanisms and target them more precisely.
“One trick is to impede the action of the gene which governs the proteins involved in combating stress, by just the right amount,” says Metzlaff.
There is a great deal to do if we are to equip agriculture to meet future challenges and make it sustainable – although many of the technologies already exist. They need to be redesigned and optimized for the vertical farming system, using stable plastics for the greenhouse walls and the LED lighting which produces the correct light for plant photosynthesis. Ideas for water treatment and management and plant feeding are also on the agronomists’ wish-list.
Links to follow up:
Futuristic architecture for high-rise agriculture and vertical farms can be found at the following Web sites:
The Web site http://bigthink.com/dicksondespommier features interviews with Professor Dickson Despommier on the challenges of urban agriculture.
A cornfield in a high-rise - Video with Dickson Despommier
You Tube - Eco-Tower
You Tube - Vertical Farming/Vertical Gardens
High-rise as farmyard