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Food and Agriculture

Farming in the Sky in Singapore

Workers harvesting vegetables from one of Sky Green’s vertical towers. Credit: Kalinga Seneviratne/IPS

SINGAPORE, Dec 8 2012 (IPS) - With a population of five million crammed on a landmass of just 715 square kilometres, the tiny republic of Singapore has been forced to expand upwards, building high-rise residential complexes to house the country’s many inhabitants.

Now, Singapore is applying the vertical model to urban agriculture, experimenting with rooftop gardens and vertical farms in order to feed its many residents.

Currently only seven percent of Singapore’s food is grown locally. The country imports most of its fresh vegetables and fruits daily from neighbouring countries such as Malaysia, Thailand and the Philippines, as well as from more distant trading partners like Australia, New Zealand, Israel and Chile.

An influx of immigrants has resulted in a rapid crowding of Singapore’s skyline, as more and more towering apartment buildings shoot up. And meanwhile, what little land was available for farming is disappearing fast.

The solution to the problem came in the form of a public-private partnership, with the launch of what has been hailed as the “world’s first low carbon, water-driven rotating vertical farm” for growing tropical vegetables in an urban environment.

The result of a collaborative agreement between the Agri-Food and Veterinary Authority of Singapore (AVA) and a local firm, Sky Green, this venture aims to popularise urban farming techniques that are also environmentally friendly.

With a robust economy that boasts a gross domestic product of 239.7 billion dollars, Singapore has plenty of money. “But money (is) worthless without food,” according to Sky Green Director Jack Ng.

“That’s why I wanted to use my engineering skills to help Singapore farmers to produce more food,” Ng told IPS.

A vertical vegetable tower using the hydraulic rotating system. Credit: Kalinga Seneviratne/IPS

An engineer by training, Ng created the vertical farming system, which he nicknamed ‘A Go-Grow’. It consists of a series of aluminium towers, some of them up to nine metres high, each containing 38 tiers equipped with troughs for the vegetables.

In keeping with Sky Green’s focus on environmental sustainability, the water used to power the rotating towers is recycled within the system and eventually used to water the vegetables. Each tower consumes only 60 watts of power daily – about the same amount as a single light bulb.

Ng knew that if the system was too expensive or complicated, urban farmers would not be able to survive. And given that he designed the project with retirees and other housebound farmers in mind, he tried to create a situation in which “the plant comes to you, rather than you going to the plant.”

The multi-layered vegetable tower rotates very slowly, taking some eight hours to complete a full circle. As the plant travels to the top it absorbs ample sunlight and when it comes back down it is watered from a tray that is fed by the hydraulic system that drives the rotation of the tower.

This closed cycle system is easy to maintain and doesn’t release any exhaust.

Ng says that such towers, if set up on roofs of the many multi-storey residential blocs that house most of Singapore’s population, could provide livelihoods for retirees and housewives, who would only need to spend a few hours up on the roof to attend to the system.

Sky Green towers currently produce three vegetables popular with locals – nai bai, xiao bai cai and Chinese cabbage, which can be harvested every 28 days.

They already supply NTUC FairPrice, Singapore’s largest grocery retailer that has a network of over 230 outlets and supermarkets. The urban-grown vegetables cost roughly 20 cents more per kilogramme than the imported varieties.

The group’s purchasing manager, Tng Ah Yiam, recently told a Straits Times reporter that these ‘sky farms’ are now able to offer their customers quality, locally-grown vegetables “that are fresher because they travel a shorter distance from farm to shelf”.

Sky Green plans to supply two tonnes a day to NTUC by the middle of next year when they expand their farm towers.

Coordinated efforts

A Sky Green farm tower. Credit: Kalinga Seneviratne/IPS

The Sky Green project feeds into a trend that has been underway in Singapore for several decades.

Since the urban expansion of the 1990s Singapore has attempted to respond to the scarcity of land available for traditional cultivation by promoting rooftop vegetable gardens.

A number of local institutions developed hydroponic and aeroponic cultivation systems but none ever took off. “There was always concern over whether or not the rooftops could take the weight of these structures,” Shih Yong Goh, former head of public affairs at AVA, told IPS.

Experts like Lee Sing Kong, director of the National Institute of Education and a long-time advocate of the use of ‘sky farms’, believe there is an urgent need for Singapore to become less dependent on food imports.

Given the increasing frequency of extreme weather events, including “natural disasters such as flooding, which could impact food production, it may be necessary for Singapore to look at producing some of its own vegetables from the food security point of view”, he told IPS.

Kong said that he is currently involved in the development of ‘vegetable factories’, whole buildings designed to grow fresh produce.

“We have (begun) developing a 6-tiered aeroponic system to grow vegetables with the help of LED lights,” he said, adding, “this is in the experimental stage. If the model proves to be successful, then the multi-tiered system can be installed within enclosed buildings for producing vegetables. This will certainly enhance the opportunities for urban agriculture.”

Since 2005, the government has shed some of its reservations about rooftop production. The National Parks Board recently converted the rooftop of a multi-storey residential building in the densely populated Upper Serangoon Road into an educational farm to promote urban agriculture among school children.

Meanwhile, Sky Green has signed an MOU with Singapore’s Temasek Polytechnic technical college. Dr. Lee Chee Wee, director of the School of Applied Science, believes that partnering with Sky Green will expose his students to how technology is used in vegetable farming and make “modern farming so much more attractive as a career choice for our graduates”.


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  • $12472

    While the idea does have merit and they recognize that not producing their own food represents a huge liability they seem to be ignoring the root problem.

    They need to lower their population, in fact many countries need to lower their populations to sustainable levels.

    Many, perhaps most of the world’s ills are directly related to too many people competing for too few resources. And even if resources were not a problem excessive numbers of people create another risk, a pandemic. More hosts represent more opportunity for deadly mutations and a more rapid spread of a pathogen.

    It is simple, either humanity controls our own numbers or nature will take care of the problem the problem in an especially brutal manner which has not been seen since the black plague.

  • Dan_Vasey

    So instead of importing vegetables from bordering Malaysia, or from other nearby countries in the event of disruptions in the normal supply, Singapore would use energy-intensive materials in building vertical gardens and run gas-generated electricity to LED lights and hydroponic pumps, emitting carbon in the process.

    Have you done a life-cycle energy analysis? When I ran analyses on other vertical farming schemes, I found the results appalling.

    Please do not reply the LED lights could run on solar-generated power, as some advocates of vertical farming have suggested. That would mean turning sunlight into electricity and electricity back into light, with an overall efficiency of about five percent. Even granting that LED light improves photosynthetic efficiency, that would be an astonishingly complex alternative to using sunlight directly in market gardens some kilometers beyond Singapore’s borders.

    For a developed economy, Singapore does well on per capita carbon emissions, though a tropical climate and the lack of long-distance transport within the country help. This proposal looks like a costly retrograde step.

  • otropogo

    Insurance is always expensive. Singapore’s wealth won’t help it if its regular food suppliers will not or cannot supply the food it needs. Since it lacks the military resources of the larger nations, it won’t be able to invade its neighbours’ territory and take what it wants. Its people will starve.

    While Singapore’s democratic and libertarian credentials are shaky, it has always been noted for its pragmatism. So if it takes a 95% energy loss to convert sunlight to led light, and Singapore buys into it, my guess is there isn’t a more economical way. And if it requires oodles of carbon emissions to effect all this leafy food, well, better black than dead.

    Drastically lowering the population is not working out so well for China, where the outlook for the elderly is increasingly dismal. If any developed country could do this by fiat, Singapore would certainly be the most likely candidate. I suspect they’ve looked at the long-term effects and realized it wouldn’t work.

  • Alain


    I saw a documentary where I live (in Belgium), where they are doing exactly the same research, for exactly the same reasons. They concluded that it will become economically competitive in a future world of 9 billion people with crude oil at $100 the barrel looking dirt cheap, making by 2025 one kilogram of such grown vegetable cheaper by 20 cents compared to the same imported from 1000km away who was grown on an open field, according to their estimates. Why ? Because the LED’s are specially designed to supply only selected UV and infrared wavelengths, do this 24/7/365, instead of the 6 months a year growing season with 9 hours a day of real sunshine in the field in Europe. The electricity was generated in a basement small fuel cell, fed by a methane source, methane generated by recuperated vegetable city wastes that were composted in a closed tank, bottom of that tank supplying compost that could be used to grow other vegetables in that closed system, and top of that tank generating methane turned in the fuel cell into electricity, building heat, water vapor and CO2 for the plants to absorb during the cold winter period. They said that now in 2012, it was still marginally more expensive than vegetables grown naturally in the field a 1000km away, but that the gap was narrowing fast. With their experimental data, they calculated that a 1 million people city like Brussels, could be fed using a few dedicated 100m x 100m buildings having each 10 stories, using that 24/7/365 system to provide each one of the million people with 0.2 kg of fresh vegetables a day, enough to cover each persons needs. That was on TV, I do not know if the statements are correct, just saying what I saw.

  • zlop

    To generate power — build it high enough and exploit lapse differences.
    For example, X-Seed 4000 design is 4 km tall.
    In 4 km — Argon lapses 75.4°K — Hydrogen lapses 2.7°K — Krypton lapses 156.8°K

  • zlop

    Bill Windows is funding population reduction.
    Mosquito delivered vaccinations, preventing pregnancy, are not yet developed.

  • zlop

    “Drastically lowering the population is not working out so well for China”
    More forced abortions and execution vans are needed.

  • zlop

    How efficient can a LED be ?
    “Thermoelectrically Pumped Light-Emitting Diodes Operating above Unity Efficiency”

    “In their experiments, the researchers reduced the LED’s input power to just
    30 picowatts and measured an output of 69 picowatts of light – an efficiency of 230%”

  • Nabin Kumbhakar

    The modern concept of farming is too awsome/Can I see the design drawings of the farm if you mail me at I too doing a thesis project on it so just for study purpose wanting to have a look at it

  • Tom Youngjohn

    Well God bless Singapore and the inventor!

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