The next profit
frontier for green roof companies is
FOOD FROM THE ROOF
By Geoff Wilson, President of the
Urban Agriculture Network Western Pacific, and Convenor of Green Roofs for
Healthy Australian Cities
All Photos Courtesy Geoff
has a new business opportunity food production from its residential and
commercial rooftops. It is an opportunity likely to open up to every city in
Who better to embrace the opportunity as it spreads globally than the green
roof companies already operating strongly in 16 countries?
A survey of the food-from-the-roof opportunity in Singapore, a thriving
Asian city-state with miniscule farmland resources, has shown it may be able
to devote up to 1,000 hectares of its urban rooftops to fresh vegetable
production now mostly imported (at a considerable fossil fuel energy cost).
Singapore is an
island on which only about 1,500 hectares of farm land remains,
most of Singapore Island being taken up with urban apartment
blocks, commercial buildings, industrial areas, plus parks and
nature reserves. This picture shows the commercial buildings,
but extensive dormitory suburbs of high rise housing can be seen
in the background.
It is the latter buildings, with flat roofs and extensive
balconies, that "sky farm" bridges for growing food have been
When that happens it will
influence myriad cities elsewhere.
Add to this rooftop opportunity the considerable food production potential
in Singapore of:
Vertical farming on the sun-facing walls of buildings;
Sky farms on bridges between buildings;
Intensive aquaculture in basements and at ground level.
This begins to outline a bold new opportunity for the global green roof
industry currently developing strongly (and very reasonably) along non-food
For what Singapore has in prospect today in food from the roof, the rest of
the world will be offered tomorrow.
Left: The front
facade of the Raffles City complex of three hotels and a
shopping centre. No green roof development is visible from the
street - but look down from the 40th floor....Right: Two
green roof projects are seen from the Swisshotel The Stamford.
The first, in the foreground above the main Raffles City
entrance, is a flower and garnishing "farm" for the complex.
Just visible in the background is a smaller hotel with a rooftop
garden, seen below.
from the 40th floor of the 70-floor Swisshotel The Stamford
shows a rooftop garden on a small hotel in Singapore. It is
becoming much more popular -- and likely to be meshed with the
growing movement in Singapore for rooftop food as well as
recreation. Intensive fish farming on rooftops or at ground
level can be the drive of aquaponics - in which fish wastes
become the plant food for vegetables, food and flowers.
Major keys to this opportunity lie in food production technologies still
developing, such as hydroponics, aeroponics and aquaponics all of which
better utilise fresh water.
Technology spin-offs from hydroponics and aquaculture are now expected to
make Singapore, and my home town of Brisbane, in Australia, the two most
likely world leaders in:
Ground-level production of urban fin fish, crustaceans and mollusks in
specially-designed containers, raceways or floating tanks using roof water
Rooftop production of fresh vegetables, flowers and fruit from the wastes
of such aquaculture in a system named aquaponics;
Tourism and education focused on the two technologies.
I predict that contributions in these fields in the two southern hemisphere
cities will become as important as the admirable leadership in green roof
development that Toronto, Canada, is now well showing in such things as
building insulation, better handling of roof water runoff and aesthetics.
Both green roof streams are new business opportunities well worth grasping
as climate change factors require the urgent attention of all of us even
if its on the principle of doing something just in case.
Lets look at what is in prospect in Singapore to see how the future of our
own cities on most parts of the planet can be glimpsed as if in a crystal
A survey by Ngee Ann Polytechnic students supervised by their hydroponics
lecturer Gregory Chow, found that four suburban areas of northern Singapore
-- about one tenth of the total built environment -- had about 212 hectares
of apartment and commercial rooftops to grow fresh vegetables, using
Extrapolation of this across the whole of Singapore reveals that that around
1,000 hectares of rooftop space could be available (relatively easily) for
urban food production in Singapore.
Gregory Chow calculated that about 39,000 tonnes of vegetables a year could
be produced from the 212 hectares he and his students studied. If these
vegetables were sold for around $2/kg the value of produce would be around
S$40 million a year - approximately U.S. $ 23.5 million a year.
Given that the Singapore Governments objective is to displace around 20% of
the annual consumption of 380,000 tonnes of fresh vegetables consumed each
year with local production (currently at only 5% pa of the total), this Ngee
Ann Polytechnic study is significant justification for more serious analysis
of rooftop production of fresh vegetables across the whole of Singapore.
It is reduction of so-called food miles writ large!
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
farm on the atrium of the 800-bed Changi General Hospital in
Singapore. The bare concrete of the atrium roof was a problem in
that it diverted sunlight into nearby wards - to cause
objectionable glare and heating. The rooftop hydroponics,
growing cherry tomatoes and herbs, solved the problem and
created a rooftop farm that now supplies patients with healthy
fresh food. Another Singapore hospital is about to go even
further in food from the roof.
picture shows the traditional idea in Asia of family washing
being swung out on poles, there's also potential for swing-out
wall gardens from balconies on sunlit walls. I have a friend who
is designing such a unit using patented oval-pipe technology and
clip-together units. A vertical vegetable patch is the objective
- linking with rooftop aquaponics.
The Ngee Ann findings and the Changi Hospital example highlight the great
need for a similar economic study of the potential of another Singaporean
innovation the sky farm concept, which would blend in well with both the
food-producing potential of Singapores rooftop spaces, plus the potential
of vertical farming down the sunlit faces of apartment buildings.
Professor Lee Sing Kong, Dean, Graduate Programmes and Research, National
Institute of Education, of Singapores Nanyang Technological University, has
been advocating sky farms that use the aeroponic technology so well
pioneered by Singapores AeroGreen Technology Pte Ltd., initiated by the
Sime Derby company.
Aeroponics is where a hydroponic nutrient solution is sprayed onto plant
roots dangling in light-proof boxes. It allows temperate-climate fresh
vegetables to be produced economically in tropical and sub-tropical
Professor Lees good idea is 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
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 or
tropical-climate vegetables themselves, perhaps in co-operatives similar to
the one already operating a rooftop hydroponic unit at Singapores Tanjong
Pagar apartment complex, see below.
of high-rise apartment owners in Singapore operates these two
rooftop hydroponic units to grow bok choy they share. It
is an idea that is expanding among other high-rise apartment
It is my contention that Singapore could produce, most economically, at
least a third of its future fresh vegetables from rooftops and sky farms.
It may choose never to replace all imports, on either practical (e.g.
potatoes) or cost grounds.
But in well utilising its rooftop resources 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 and provide stimulus for further
food-from-the-roof technology to be developed in other climates.
Besides taking up the good ideas of their own citizens, Singaporeans also
need 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
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 (e.g. excess worms or insect larvae) being fed
to fish, crustaceans or molluscs growing in tanks or containers.
3. Has organic hydroponic growing of food plants on nearby rooftops (via
piped nutrient solutions of fish wastes and worm liquors, refined via
4. Has water being recycled to fish and crustacean tanks minus the plant
food, and with superior aeration.
Hydroponic Farm in Brisbane, Australia
The photo at left shows a
sub-tropical hydroponic farm growing bok choy in Brisbane, Australia using
clip-together oval channel equipment under hail netting. It is the kind of
food-from-the-roof technology likely to be adopted for Singapore rooftops -
with the hail netting serving as a worker safety net, plus a barrier to
rooftop debris flying away with wind gusts. An acre of this kind of
hydroponics is more productive than six acres of good soil -- using less
than a 10th of the water.
So Singapore's 1,000 hectares
(2,500 acres) could be equivalent to more around 6.000 hectares (15,000
acres) of soil horticulture. What's more, the roof-grown fresh food is close
to where it is needed above apartment blocks or restaurants -- thus saving
substantial transport energy costs.
Singaporeans also need to look at the innovations in aquaponics now well
confirmed in their great good sense in Canada and the United States where
rooftop growing of food is observable, but has yet to be given the
technology thrust it needs.
Australian and North American companies involved in various forms of
aquaponics via floating tanks or raceways 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, in rooftop farming and gardening,
or on sunlit sides of buildings.
clip-together Australian oval pipe system that provides
lightweight hydroponics for rooftops and balconies in Singapore.
If Singapore chooses to go down this 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.
growers have proved that papayas in hydroponics, like this one,
can be grown to production of fruit in little more than half the
time of soil-grown "Trees." The hydroponically-grown fruit is
claimed to be tastier. The tropical papaya is predicted to
become a favoured fruit to be produced from rooftops under hail
netting in Singapore, and could form a most attractive bank of
foliage for rooftop restaurants that also picks and serve the
ripe fruit chilled, juiced or in fruit salads.
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 regional shortages that may
My home-city of Brisbane in the Australian state of Queensland has the same
opportunity available to it, but is not as advanced technologically as
Singapore either in urban agriculture or urban aquaculture, nor in rooftop
greening. The lush ground-level garden of Singapore, plus the city-states
growing adoption of green roofs, has few equals elsewhere. Its municipal
greenery is a delight to visitor and resident alike.
But the best urban agriculture response must include the adoption of food
production systems that are less dependent on oil or coal for farming or
It is a response in which organic hydroponics and aquaponics, driven by
sensible waste recycling, will have a big future in urban-based agriculture
on rooftops, sky-farms and use of vertical faces of city structures that can
harvest the worlds cheapest energy source sunlight.
I believe that the worlds rapidly-advancing green roof industry that has
been cradled and nurtured in Europe, and now brought to a lusty infant form
in North America, must look to Asia and Oceania for some new directions for
profitable expansion of myriad services.
In its turn, the Southern hemisphere will be the great beneficiary of
northern hemisphere green roof science and technology, and practice.
It will make for an interesting blend of collaborative projects and
information exchanges between the 16 countries now forging an international
alliance for broad spectrum green roof development at a most opportune
moment in the history of human endeavour.
The Chinese have a curse: May you live in exciting times. I regard it as a
benediction when I look at all the possibilities for green roofs.
Geoff Wilson is President of the Urban Agriculture Network Western
Pacific, and a director of Nettworx Publishing Pty Ltd, based in Brisbane.
Queensland, Australia. Geoff has been a food and agriculture
journalist and communicator since graduating from agricultural college in
1957. He has written for most rural newspapers and magazines in
Australia and New Zealand since then, and for a number in Asia, Europe and
the United States. He currently writes on urban agriculture,
aquaculture, aquaponics, and hydroponics, particularly for Aquaponics
Journal in the United States.
Geoff is Convenor of both
the Aquaponics Association Australia, and the new Green Roofs for Healthy
The North American
Green Roofs for Healthy
includes professionals in urban planning, architecture, built environment
academia and development, suppliers of specialised materials and
consultancy, specialised builders and horticulturalists and professional and
trade press servicing these groups. In Europe there are now national green
roof organisations in Germany, Austria, Switzerland, Holland, United
Kingdom, France, Italy, Spain, Hungary and Sweden. Others are in
Japan, Singapore and Mexico.
Green Roofs for Healthy Australian Cities is currently recruiting members.
Membership promotion events for this Australian entity will be one-day
seminars on green roof technology and practice, in mid-2006. It is
hoped the seminars can be run in Brisbane, Sydney, Canberra and Melbourne
over two weeks in June 2006.
1. To provide opportunities for members to learn about green roof science,
technology, practice, economics and environmental and social benefits.
2. To promote Australian education in green roofs, particularly in
university and TAFE college courses that provide skills for the green roof
industry that can be expected to develop, and careers for the students of
3. To promote Australian research in sound green roof development.
4. To provide networking opportunities for Australians wishing to study
green roofs in Australia and overseas.
5. To publicise the environmental advantages of green roofs.
Geoff Wilson can be contacted by email:
Geoff@nettworx.info, or phone +61 7 3411 4524.