Published by City Farmer, Canada's Office of Urban Agriculture

Singapore's New Business Opportunity: Food from the Roof

By Geoff Wilson

Geoff Wilson is President of the Urban Agriculture Network - Western Pacific and a director of Nettworx Publishing Pty Ltd, based in Brisbane. Queensland, Australia. In 2000 the the Urban Agriculture Network - Western Pacific, presented Singapore's AeroGreen Technology Pte Ltd., with its annual Urban Agriculture Award. In mid 2004 the network presented this annual award jointly to Gregory Chow lecturer of Singapore's Ngee Ann Polytechnic and the Changi General Hospital1s rooftop farm project initiated by Gregory Chow.

The article above is from a talk by Geoff Wilson to the Singapore Society for Soilless Culture, on July 13, 2005.

Geoff Wilson can be contacted by email:

Singapore has a new business opportunity - food production from its residential and commercial rooftops.

Major keys to this opportunity lie in two words - aeroponics and aquaponics.

These two technology spinoffs from hydroponics and aquaculture could make Singapore a world leader in:

* Tourism and education focused on the two technologies.

The Agri-Food and Veterinary Authority of Singapore already has this opportunity within its easy reach for greater fresh food security for Singapore's three million or so citizens, especially if the AVA teams up in with Singapore's education and commercial entrepreneurs, both of which are already involved in innovative and successful hydroponics and aquaculture.

Singapore's is already a global leader in the aeroponic technology.

This is an offshoot of hydroponics, which is most successful for growing temperate-climate fresh vegetables (such as lettuce) in sub-tropical and tropical conditions.

In aeroponics, plant roots are contained in a light-proof box. Cooling of the nutrient water held at ground level, and subsequent misting of the nutrient in light-proof boxes, lowers the plant root zone temperature and increases root zone aeration.

However, to guarantee productivity of temperate-climate plant crops under Singaporean conditions, it has been found that expensive refrigeration-cooling of the nutrient was needed so that root zones were kept at around 10 degrees C lower than the day-time ambient temperature, which could "cook" the roots and cause wilting and plant loss.

Nevertheless, the economics of the Singapore market (where fresh, temperate-climate vegetables are air-freighted to the city daily from three continents) has meant that locally-produced lettuce via aeroponics would work. But the cooling of nutrient solutions has been expensive - around S$5/kg of lettuce grown.

This has been an economic limitation on the aroponic technology until 2004.

Thanks to Gregory Chow, lecturer at the Ngee Ann Polytechnic, Singapore now has Air-Dynaponics - a much less costly way of maintaining low root-zone temperatures for commercially-successful aeroponics. It costs only about one fifth to cool the nutrient solution.

It, and other low-cost cooling systems (such as the Boxsell Hydroponics cooling/aeration tower from Australia), could thus open up the aeroponic technology to many more countries in the tropics and sub-tropics to locally-produced, temperate-climate vegetable crops.

Air-Dynaponics and similar systems use the cooling principles of the latent heat of vaporization and the venturi effect in an air-powered operation that not only reduces the temperature of a nutrient solution, but also adds to its aeration (dissolved oxygen).

Plants need this dissolved oxygen - and so do fish.

The Air-Dynaponics and similar systems thus also open up wider commercial investment not only in the aeroponic technology, but also in the aquaponic technology in which fish provide organic hydroponic nutrient for plants.

Fish wastes from aquaculture (excreta, surplus feed and micro-organisms growing on both) provide the sole nutrients for organic vegetable growing in hydroponic channels or from aeroponic boxes.

However, in sub-tropical and tropical aquaponics there are two major advantages offered by Air-Dynaponics and similar systems, which are:

1. Temperature flexibility --- where a sub-tropical or tropical fish species may require tank water temperature around 28 or 29 degrees C for optimum production, the organic hydroponic or aeroponic element for temperate-climate vegetables may require temperatures around 21 degrees C. Air-Dynaponics and similar systems could cater for this without undue expense for energy.

2. Improved aeration (oxygenation) -- dissolving oxygen in water for fish or plants is easier in cooler water. An Air Dynaponics system in aquaponics would mean that the cooler nutrient solution for plant growth can be returned to the fish tank (a) stripped of its nutrients that lead to fish deaths if allowed to accumulatate (b) with a much higher dissolved oxygen content for improved fish health and higher stocking rates.

Therefore, Gregory Chow of Ngee Ann Polytechnic and other workers in low-cost cooling and aeration of hydroponic nutrient, are developing a technology of great significance to the execution of a plan by the Singapore Government to increase food production from local farms - both at ground level and on appropriate urban rooftops.

Consequences of refinement of the Air-Dynaponics and similar technologies (particularly to produce the best-flavoured produce) can allow them to be capable of:

In my view Singapore currently provides some of the world's best hydroponic education. But it could be made even superior through extrapolation of the Air-Dynaponic (and associated) technology from the existing inorganic hydroponic education -- into organic hydroponics and aquaponics as well.

There is scope for special urban agriculture education in certificate, diploma, graduate and post-graduate studies that focus on the higher technologies of urban hydroponics and aquaculture for the tropics and sub-tropics.

Reinforcement of this possibility comes from the innovative ideas of Professor Lee Sing Kong, Dean, Graduate Programmes and Research, National Institute of Education, of Singapore's Nanyang Techological University. For some time now Professor Lee has been advocating "sky farms" that use the aeroponic technology so well pioneered by Singapore's AeroGreen Technology Pte Ltd., initiated by the Sime Derby company. Professor Lee1s "sky farm" concept is another Singaporean idea whose time has come for the whole world's innovative approaches to urban agriculture that meshes with enlightened architectural design and urban planning.

It focuses on sunlit bridges between high-rise apartment buildings or even office towers. They could be retro-fitted as single or double units at first or second-floor levels, or part of a tier of vertical structures servicing the food (and organic waste management needs) of multiple stories.

Aeroponic vegetable production on the bridges would use nutrient solutions stored and cooled at ground level, then piped to light-proof boxes above. The "sky farm" bridges can thus be relatively light structures.

The significant saving with this system is the cost of farm and transport energy (mostly diesel fuel) and consequent air pollution with diesel particulates that are known to cause asthma, emphysema and even cancer - particularly in the very young and the elderly.

Tenants of the buildings would be able to harvest the temperate-climate vegetables themselves, perhaps in co-operatives similar to the one already operating a rooftop hydroponic unit at Singapore's Tanjong Pagar apartment complex.

Gregory Chow has also foreseen what Singapore could become in leading the world towards practical and economic ways to grow food on urban rooftops.

A survey by Ngee Ann Polytechnic students that he supervised, found that four suburban areas of northern Singapore (about one fifth of the total) had about 212 hectares of apartment and commercial rooftops to grow fresh vegetables, using inorganic hydroponics.

About 39,000 tonnes of vegetables a year could be produced from the 212 hectares. If these vegetables were sold for around $2/kg - the value of produce would be around S$40 million a year.

Given that the Singapore Government's objective is to displace around 20% of the annual consumption of 380,000 tonnes of fresh vegetable consumed each year with local production (currently at only 5% pa of the total), this Ngee Ann Polytechnic study is significant justification for an analysis of what Air-Dynaponics could do to increase rooftop production of fresh vegetables across the whole of Singapore.

Gregory Chow has demonstrated already, what can be done in rooftop farming with his award-winning project on the atrium of the 800-bed Changi General Hospital. His pioneering is well deserving of further support by Changi General Hospital in the public interest - both locally and globally. I hope that Dr Mallick Fazalur Rahman, Managing Director of Hydroponics & Plant Care Ltd., will be able to now expand on Gregory Chow1s work at CGH, with an innovative aquaponic unit that will trigger global publicity for the hospital.

The Ngee Ann innovations also highlight the great need for a similar economic study of the potential of Professor Lee1s "sky farm" concept, which would blend in well with both the food-producing potential of Singapore's rooftop spaces, plus the potential of "vertical farming" down the sunlit faces of apartment buildings.

It is my contention that Singapore could produce, most economically, at least a third of its future fresh vegetables from rooftops and "sky farms".

If Air Dynaponics and other offshoots of aeroponic technology can be better harnessed, the fish production potential of Singapore's apartment buildings could skyrocket also.

In so doing it would provide the world with an important demonstration of how urban agriculture, designed into buildings, could greatly enhance the food security of many cities in the tropics and sub-tropics.

At the same time, Singapore could further develop its tourism and its educational opportunities for both its own citizens and for those of its neighbours -- and perhaps develop a higher-technology export industry focused on supplying kit-form equipment of various kinds for both rooftop applications and for "sky farms".

I commend Singapore's consideration of these ideas before others act first.

Also, I commend Singaporeans to look closely at the new equipment from Australia that is being developed for sub-tropical and tropical hydroponics, aquaculture, aquaponics and vermiculture.

This equipment is capable of being meshed into urban agriculture that:

1. Has urban organic wastes changed into organic plant nutrients or organic fish feed in basements and at ground levels.
2. Has the waste by-products (eg. Excess worms or insect larvae) being fed to fish, crustaceans or molluscs growing in tanks of containers.
3. Has organic hydroponic growing of food plants on nearby rooftops (via piped nutrient solutions refined via microbial action).
4. Has water being recycled to fish and crustacean tanks minus the plant food, and with superior aeration.

Significant urban agriculture equipment that is complementary to the Singapore innovations is now available from:

Other Australian and North American companies involved in aquaponics will also have interesting options to offer Singapore, in both fresh-water and salt-water systems that combine the growing of fish and other aquatic food animals, with the growing of food plants that can utilize their wastes on rooftop farming and gardening, or on sunlit sides of buildings. If Singapore chooses to go down the exciting food technology road now being built for urban agriculture integrated into buildings, I believe it will be very pleasantly surprised at the number of people from around the world who will wish to visit it as techno-tourists for study tours, conferences, technical demonstrations and short-course education.

In addition, Singapore could well position itself in an important response the world must now make to both the rising cost of oil energy through increasing demand, and the increasing likelihood of disruptions to oil energy supplies as a result of terrorism or shortages to some nations as others buy up the managed production of OPEC.

The best urban agriculture response must include the adoption of food production systems that are less dependent on oil or coal for farming or transport energy.

It is a response in which organic hydroponics and aquaponics will have a big future in Singapore's urban-based agriculture on rooftops, sky-farms and use of vertical faces of city structures that can harvest the world's cheapest energy source - sunlight.


Singapore conferences on urban agriculture aquaponics and food from the roof

Two conferences are being held in Singapore's on urban agriculture, hydroponics aquaponics, food from the roof and associated technology.

The first is the International Conference and Exhibition on Soilless Culture, from September 5 to 8. It will cover hydroponics, aquaponics and urban agriculture. Contact the organiser Dr Mallick Fazalur Rahman M, Managing Director of Hydoponics & Plant Care Pte Ltd., Phone +65 6291 8153; Fax: +65 6298 7978. Mobile: +65 9678 5297, Email:

The second is "UrbanAg 2006", in late September, 2006. It will cover the urban agriculture and urban greenery of Singapore (some of the most advanced in the world), and producing food from the roofs of commercial buildings and private homes. Contact the organiser: Geoff Wilson, President of the Urban Agriculture Network-Western Pacific, Phone: +61 7 3411 4524; Mobile: +61 o412 622 779. Email:

Background on Geoff Wilson:

Geoff Wilson has been a food and agriculture journalist and communicator since graduating from agricultural college in 1958. He has written for most rural newspapers and magazines in Australia and New Zealand since then, and for newspapers and magazines in Asia, Europe and the United States. He currently writes on aquaculture, aquaponics, hydroponics, aeroponics, probiotics, urban agriculture and microfarming for "Aquaponics Journal" (US) and "Fish Farming International" (UK). Wilson is now launching "UrbanAg Online" with colleages in the United States, Canada and Singapore. It will be an urban agriculture news service to about 2,000 editors and journalsists around the world.

For 10 years to the late 1980s Wilson was agribusiness contributing columnist for "The Age" daily newspaper in Melbourne. He was managing editor of "Australian Dairy Foods" magazine for 12 years and "Caseus" the cheese magazine for 2 years; managed and edited "Australian Forest Grower" magazine for 8 years, and "Riverlander" magazine for two years (these being concurrent activities in freelance journalism and publishing during the 1970s and 1980s). He also worked in South East Asian countries on food industry and forest industry magazines such as "Asia Pacific Forest Industries" and "Asia Pacific Food Industries" (living in Singapore). He is President of the Urban Agriculture Network Inc - Western Pacific. The parent organization was established under the auspices of the United Nations Development Programme (UNDP) in 1996, and operates as an NGO from Washington DC. Wilson is now Australia's representatinve on a group of 16 national organisations moving to set up an international Green Roofs organisation, and is convening both the establishment of Green Roofs for Health Australian Cities and Aquaponics Association Australia for urban enthusiasts. Wilson is a committee member of the Aquaculture Association of Queensland.

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August 3, 2005

Published by City Farmer
Canada's Office of Urban Agriculture