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Research Paper Future of Food: Journal on Food, Agriculture and Society
3 (1)-Summer 2015
Planning Urban Food Production into Today’s Cities
A. JENKINS
* 1
, G. KEEFFE
1
, N. HALL
1
1.School of Planning, Architecture and Civil Engineering, Queen’s University Belfast, United Kingdom
* Corresponding author’s contact details: E-Mail: ajenkins02@qub.ac.ukr: Tel.: +39-0117486
Data of the article
First received: 15 January 2015 | Last revision received: 10 May 2015
Accepted: 11 May 2015 | Published online: 15 May 2015
URN nbn:de:hebis:34-2014020344928
Key words
Urban Agriculture, Food
Production, Light Capture,
Facade, Roof, Urbanism
Abstract
If cities are to become more sustainable and resilient to change it is likely that they will have to
engage with food at increasingly localised levels, in order to reduce their dependency on glob-
al systems. With 87 percent of people in developed regions estimated to be living in cities by
2050 it can be assumed that the majority of this localised production will occur in and around
cities. As part of a 12 month engagement, Queen’s University Belfast designed and implement-
ed an elevated aquaponic food system spanning the top internal oor and exterior roof space
of a disused mill in Manchester, England. The experimental aquaponic system was developed
to explore the possibilities and diculties associated with integrating food production with ex-
isting buildings. This paper utilises empirical research regarding crop growth from the elevated
aquaponic system and extrapolates the ndings across a whole city. The resulting research
enables the agricultural productive capacity of today’s cities to be estimated and a framework
of implementation to be proposed.
Introduction
The future possible impacts of technological food
systems within todays cities are at present di-
cult to assess. The aim of this paper is to devise a
method of analysis in order to determine the ag-
ricultural productive capacity of a Northern Eu-
ropean city ratied through the use of real-world
data on technical food systems. This data was col-
lected from an operational elevated aquaponic
system in Manchester, England designed and con-
structed by Queens University Belfast. The paper
discusses the benets of integrating agriculture
within buildings and cities and analyses its im-
pact on total domestic food production; the envi-
ronmental benets associated with this; and the
resulting economic impact such activities could
have on buildings, neighbourhoods and cities.
The ecological context of food in the UK
Self-suciency and food
The UK, like many other developed regions, is de-
pendent upon food imports to sustain its popula-
tion. In 2006 the UK spent £6 billion on importing
fruit and vegetables alone and is reported to be
‘about 60 percent food sucient’ (The Cabinet Of-
ce, 2008), leaving a 40% food decit which has
to be import from other countries. Over the past
six years, the debt of the UK as a percentage of
GDP has doubled from 42.8 percent in 2007/2008
to 84.3 percent in 2013, which equates to a gross
debt of £1.387 trillion (Oce for National Statis-
tics (ONS), 2013). As a result, the food supply chain
upon which the UK depends on is economically
fragile, susceptible to change without warning, and
Citation (APA):
Jenkins, A., Keeffe, G., Hall. N.(2015). Planning Urban Food Production into Today’s Cities,
Future of Food: Journal on Food, Agriculture and Society
,
3(1), 35-47
35
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ill equipped to deal with shock. These gures, how-
ever, only take into account the economic strain
of supplying the UK with food. The feeding of the
UK population also has an environmental impact.
Taking into account nourishment, shelter, mobility,
goods and services the ecological footprint of the
UK is estimated to be three times its size, requiring
321,621,000 global hectares to sustain its popula-
tion (Stockholm Environment Institute (SEI), 2003).
This impact corresponds to 5.45 global hectares per
capita, which is in striking contrast to the fair land
share per capita of 1.8 global hectares (World Wide
Fund for Nature, 2012). This dictates that the UK’s
ecological footprint needs to decrease by at least
65 percent in order to live in equilibrium with the
replenishment of natural resources. Nourishment,
as a proportion of the overall ecological footprint,
accounts for 28 percent of the total impact of the
UK, requiring nearly 92 million global hectares (SEI,
2003). In 2008, the food industry accounted for 18
percent of the total CO2 equivalent production in
the UK, estimated at a total of 147 million tonnes
per annum (The Cabinet Oce, 2008). The transport
of food within the UK produces 19 million tonnes of
CO2 and burns 20.9 million tonnes of oil per year (The
Cabinet Oce, 2008). If every person on the earth
lived as one did in the UK, three earths would be
needed in order to supply the demand indenitely.
Food waste and land use
In 2011, the world’s population surpassed 7 billion
people for the rst time in human history (Econom-
ic and Social Aairs division of the United Nations
(ESA), 2013). As a result, the availability of agricultural
land per capita is decreasing. In 1970, 0.38 hectares
of global agricultural land was available per person.
This value decreased to 0.23 hectares in 2000, and
is projected to decline to 0.15 hectares per capita
by 2050 (Food and Agriculture Organisation of the
United Nations (FAO), 2012). A single hectare of ag-
ricultural land will, by 2050, have to supply enough
food for 6.7 people annually, whereas the same
area of land in 1970 only had to produce enough
food for 2.6 people. It is a possibility, that by 2050,
this agricultural land may become exhausted and
be incapable of supporting the intensive agricul-
tural activities needed to feed the 10 billion world.
The availability of food, however, is only part of the
problem facing future populations; waste is also a
concern. The Food and Agricultural Organisation of
the United Nations reports that 28 percent of global
arable land is used annually for the production of
food that is either lost or wasted (FAO, 2013). With-
in the UK this food waste equates to approximately
16 million tonnes per year at a cost of £22 billion
per annum (Waste & Resources Action Programme,
2011). The UK is, in essence, paying to waste food,
waste energy, and damage the environment un-
necessarily through the intensive industrial ac-
tivities which are needed to feed its populations.
The wasting of food also has social and humanitar-
ian impacts. It is estimated that 12 percent of the
world’s population is undernourished at a gure
of approximately 842.3 million people (FAO, 2013).
Taking into account that 28 percent of all food pro-
duced is either lost or wasted, world hunger could
be solved twice over if a solution could be brokered.
The actions needed to prevent any further ecolog-
ical deterioration as a result of the intense industri-
al activities needed to feed the UK, as well as ad-
dress the issues surround food security, lay in the
ability to produce more food domestically, in ad-
dition to wasting less. However, these actions are
in no way simple. The Oce for National Statistics
notes that 69 percent of UK land is already utilised
for agriculture, with 11 percent of land developed,
11 percent as forest/woodland and the last 9 per-
cent left to other natural habitats (i.e. grassland,
mountains, moors, coastlines and marine environ-
ments) (Oce for National Statistics and East Anglia
University, 2010). The need to produce more food
when there is little to no additional land available
makes the goal of producing more food dicult.
By 2050 the urbanised population of the planet is
expected to reach 67.2 percent; accounting for 1.1
billion people in developed regions and 5.1 billion
people in less developed regions (ESA, 2013). If cit-
ies are to become more sustainable and resilient to
change it is likely that they will have to engage with
food at increasingly localised levels. With 87 percent
of developed regions estimated to be living in cities
by 2050 it can be assumed that the majority of this
localised production will occur in and around cit-
ies, and more specically, within or upon buildings.
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Soil-less growing technologies
Background to the technologies
Nearly all food today is grown in soil but within ur-
ban areas, and more importantly within or upon
buildings, soil-based agriculture may not be the best
method. This is due to the large proportion of con-
taminated land in many urban areas - a byproduct
of the industrial revolution - as well as its additional
weight, which adversely aects its ability to be ret-
rospectively added to buildings. Thus, localised food
production within cities depends upon alternatives
to soil based practices. One such alternative is to use
technical food systems. These hybridised systems,
utilising technical products such as glass, plastic, and
mechanical pumps, allow food to be grown direct-
ly in nutrient rich water at a fraction of the weight.
There are two recognised methods in which food
can be grown within technical food systems. These
include hydroponics and aquaponics. These tech-
niques utilise similar equipment in order to grow
food, but the way in which they make nutrients
available to crops is very dierent. Hydroponic sys-
tems utilise nutrients that are added manually to
a recirculated water system, whereas aquaponics
aims to develop an ecosystem between sh and
crops. Aquaponic systems are dependent upon the
naturally occurring nitrogen cycle to make nutrients
available to crops. The system utilises waste ammo-
nia (NH3) - produced by the sh as a byproduct of
respiration - and through the natural colonisation of
nitrosomonas and nitrobacter bacterias within the
system, converts the waste ammonia primarily into
nitrite (NO3) and later into nitrate (NO2). This con-
version serves two functions. Ammonia is toxic to
sh it would poison them if allowed to accumulate
within the water supply. The second function of this
process is that nitrate is an available form of nitro-
gen - a plant’s largest nutrient requirement - which
crops can easily take up across the surface of their
roots. The sh, bacteria and crops live symbiotical-
ly, much as they would within a natural ecosystem.
In both hydroponics, and aquaponics, crop roots
are in direct contact with the nutrient rich water.
As such, the crops use little eort in acquiring nu-
trients and can instead, utilise a larger proportion
of their energy to grow. As a result, yields are sub-
stantially increased (in some cases up to four times)
and water use is reduced by a factor of up to ten
when compared to traditional agriculture (Bern-
stein, 2011). Through the growing of crops indoors
or under glass, a protective environment is creat-
ed which increases resilience to shock events such
as storms, prolonged rainy periods, temperature
drops or dry spells. Their reduced weight, through
the use of Nutrient Film Technique (NFT) - a grow-
ing channel utilising only a few centimetres of
water - allows such systems to be successfully ret-
rotted into or onto existing buildings without
compromising the building’s structural integrity.
The design of a novel roof-based aquaponic system
As part of the Manchester International Fes-
tival 2013, Queen’s University Belfast was ap-
proached to design and implement an elevated
aquaponic food system within a disused mill in
Figure 1: Aerial view of the elevated urban farm in Manchester, England (left) with rooftop
NFT system (right)
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Manchester, England (Fig. 1). The project itself
was a 12 month engagement and included the
design, construction and commissioning of one
of the very rst elevated farms within the UK.
The system was partially contained within the
building and partially upon the roof, where light
levels were highest. The more visually engaging
components of the system were contained on the
top internal oor of the building. This included sh
tanks, a ltration/mineralisation system, and deep
rooted crop bags placed in the south-facing win-
dows (Fig. 2). The roof space housed the NFT sys-
tem - located within a large polytunnel - capable
of growing 4,000 leaf crops at any one time. The
design team worked closely with structural en-
gineers throughout the course of the design and
construction of the systems to ensure it would not
compromise the existing structure of the mill. As a
result, the heaviest elements of the system (i.e. sh
tanks and polytunnel) sit upon primary beams in
order to safely distribute the load to the ground.
In total there are 12 sh tanks, which are fed with
ltered, clean, fresh water returning from the roof
as a result of bacterial and crop ltering actions. The
overow from the sh tanks collects in a sump, and
the water is pumped to the ltration/mineralisation
bank where it drains consecutively through a series
of siphonic containers comprising of expanded clay
balls and worms. The expanded clay balls provide
the large surface area needed upon which nitrify-
ing bacteria can colonise, with the worms helping
with the breakdown of solid waste. When the water
is nitrogen rich and free of solid waste it is pumped
toward the silicon bags hanging in the south facing
windows. These deeper grow bags cultivate plants
such as tomatoes and peppers, which require sig-
Figure 3: Facade Farm prototype
Figure 2: Internal view of the urban farm in Manchester, England.
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nicantly larger root systems in order to grow. The
water is lastly pumped up to the roof and into the
polytunnel where it ows down through 34 NFT
channels, each 14m in length, in order to grow leaf
crops (Fig 1). The clean ltered water ows back down
to the sh tanks, where the process can start again.
The NFT system was capable of growing 26.66 crops/
m2, including the additional space taken up by ltra-
tion, sh tanks and walk ways between crops. Based
on a growing season of eight months, consisting of
four harvests, the system is capable of producing up
to 16,500 crops per annum. The sale of the crops in
the local shop as part of the project sold for between
£2 and £4 per crop dependant on size and species
of crop. Hence, the system could generate between
£33,000 and £66,000 per year. The material cost of
the system itself was approximately £30,000 with
an additional £30,000 spent on labour. The system
was designed to need only one person to operate it
on a day to day basis and a full operational manual
was produced by Queen’s University Belfast upon
the hand over of the system to the building tenants.
Although the aquaponic system and urban farm
was successful, it was clear upon completing the
project that it may not necessarily be good practice
or cost eective in future to locate these systems
within buildings. They not only take up space with-
in structures that could otherwise be utilised for
oce or residential purposes, generating income,
but they also create issues related to ooding and
water ingress from open water systems - i.e. a mix-
ture of pressurised and unpressurised plumbing.
Containing technical food systems within buildings
also greatly reduces the amount of light available
for crop growth. Deploying these systems on the
external skin of buildings - i.e. rooftops and fa-
cades - in the future would eradicate both of these
issues in addition to freeing up the oor plan of
buildings for commercial or residential activities.
Facade Farm Prototype
The benets associated with exterior systems led to
the development of the ‘facade farm’ prototype: a
twin walled glass facade, capable of growing crops
within its cavity. The vertical surfaces of architecture,
which generally experience too much glare or too
much heat gain, would be the perfect sites for the
growing of plants, which in turn would reduce both
glare through foliage and heat gain through transpi-
ration, decreasing building energy consumption and
creating economic return through the sale of crops.
The rst constructed facade prototype took all
the available research from the larger aquapon-
ic system, which occupied a whole building, and
miniaturised it into a space 3m high, 2.5m wide
and 35cm deep (Fig. 3). This space housed all the
components seen within the larger system, includ-
ing sh tanks, ltration/mineralisation unit, and
growing channels. The prototype of the facade
farm was capable of delivering 15 crops per me-
tre squared of vertical surface, taking into account
the space required for sh tanks and ltration. The
prototype cost approximately £7,500 minus la-
bour and using the sale value of the crops sold in
the adjacent shop, is cable of producing approxi-
mately 450 crops per year (60 crops/m2/annum).
Figure 4: A section of the three-dimensional model (left) with sample image of
shadow information (right)
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The Agricultural Capacity of Cities
Cities can reduce their ecological footprint and pos-
itively aect their impact on the earth through the
integration of urban agriculture upon their abun-
dant surface area. However, not all surfaces within
a city are capable of supporting the growth of crops
due to orientation and/or overshadowing. A virtual
modelling methodology - one that views cities as
illuminated surfaces - is necessary so that the pro-
ductive capacity of a city can be quantied, and the
impact on domestic food production be calculated.
The following analysis describes a methodology
where direct light falling upon a surface is captured
through the use of a three-dimensional model, and
the aggregated annual lighting data used to help
predict the total annual crop production of a city.
For the purposes of this paper, the city centre of
Manchester, England was used as a case study to
help derive and test the method of analysis. The
main reason for this choice is the close proximity
of the centre of the city to the elevated aquaponic
system used for productive assessment. The centre
of the city lies upon an area of land approximately
369 hectares in size, although its total surface area
is closer to 720 hectares. This implies that through
the building of structures the surface area of the
city has doubled in size. The following analysis
strives to determine to what extent this additional
surface area is capable of supporting crop growth
and hence, help inform a future framework of inte-
gration for urban agriculture within the city itself.
It should be noted that the research understands
that availability of light is only one aspect eect-
ing the integration of urban agriculture with-
in existing cities. Other issues include the access
to the right skills, ownership of urban surface,
as well as the inclination of inhabitants to grow
food. However, the point is taken that this meth-
od of analysis would be used at a city level, to dis-
cuss such possibilities with local authorities and
to identify which areas might be suitable for pilot
studies. Upon which, more detailed site analy-
sis regarding applicability can be taken forward.
Three-Dimensional Modelling
To make it possible to determine upon which sur-
faces of the city crops can be grown, the over-
shadowing of each horizontal and vertical surface
must rst be visualised and understood. This is
achieved by creating an accurate three-dimen-
sional model of a particular city within virtual
space onto which virtual light rays can be cast.
To create the virtual model of Manchester more
than 2800 building plots were created in three-di-
mensional space, with each plot containing infor-
mation on building form and building height (Fig.
4). Both of these characteristics are crucial in deter-
mining the overshadowing, and therefore reduc-
tion in light capture, as a result of adjacent build-
ings. All building plots were modelled simply and
therefore were all represented as having at roofs.
In later analysis, all pitched roofs are identied and
omitted from the analysis due to the lack of data re-
garding the growing of crops on an inclined plane.
However, these surfaces may be utilised for solar
energy capture in the form of photovoltaics or so-
lar hot water which could help operate the techni-
cal food systems upon adjacent roofs and facades.
The data used to create the virtual model of Man-
chester was taken from Land Map (www.landmap.
ac.uk), which identied the height of each build-
ing plot above ground level. This data is referenced
by Land Map as originating from Cities Revealed
which is now part of the Geo-information Group.
Modelling Light Intensity and Assessing Shadow Data
Once the model of the city in question has been cre-
ated in three-dimensional space it is then capable
of accepting light rays in order to generate accurate
shadow maps.
To collect the shadow information, a physical sun
object was added to the scene, which is dependent
upon latitude, longitude, time of day and month of
year to calculate the sun’s position. The latitude and
longitude used for Manchester was 53°29’N 02°12’W.
Using this object, images were taken at half hourly
intervals from sunrise to sunset to represent a typical
day within each month. The 21st day of each month
was used to represent a ‘typical day’ within the study,
due to the winter and summer solstices occurring on
the 21st of December and 21st of June respectively.
To better represent the three-dimensional data as
two dimensional images, the analysis splits the infor-
mation into vertical and horizontal data sets. To col-
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lect these two data sets three views are utilised in or-
der to better represent the ndings. The light capture
of the horizontal surfaces - i.e. roof spaces - is viewed
from above in plan so as to clearly view each individ-
ual roof. In contrast, the vertical data - i.e. building
facades - is dicult to represent as a single image.
Therefore, two views with dierent vantage points
were utilised in order to fully understand the light
capture of the vertical surfaces. These views were
taken from the south-east and the south-west at an
elevation of 60 degrees and in parallel projection. For
the facade study, no data was captured from north
facing surfaces as it could be assumed that these
surfaces would be over-shadowed for the majority
of the day and would only receive diused radiation.
In total, over 250 images were taken to represent
each half hourly shadow across a single day within
each month of the year (Fig. 4)
Creating Shadow Maps
To create the shadow maps, the individual shadows
for each respective month were overlaid on top of
one another and a transparency applied to them
in order to create a gradient map. Where multiple
shadows coincided, darker patches would be seen,
and areas mostly out of shadow would be repre-
sented as lighter patches (Fig. 5). However, this ap-
Figure 6: Completed roof top shadow map for March (left ) and completed south-east
facade map for June (right)
Figure 5: Multiple shadows with the same transparencies (left) and with accurate transparencies
applied (right)
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proach does not accurately represent the impact
of a single shadow upon the daily solar capture of
a surface throughout the day. That is to say that
an area in shadow at midday would see a great-
er decrease in its overall daily light capture, than
an area only in shadow during sun rise or sunset.
In order to account for this the impact of each shad-
ow was individually calculated. This was achieved
by calculating the proportion of total daylight that
landed upon a surface within each half hourly pe-
riod against the total light capture of a known day.
Taking April as an example, the light falling upon a
surface between 13:00 and 13:29 accounts for 6.2
percent of its total daily light capture, whereas the
light falling upon a surface between 07:00 and 07:29
accounts for only 0.4 percent of its total light cap-
ture. Therefore, a surface in shadow between 13:00
and 13:29 would see a reduction in it total daily light
capture of 6.2 percent and a surface in shadow be-
tween 07:00 and 07:29 would only see a 0.4 percent
reduction in its daily solar capture. Hence, shadows
towards the middle of a day have a larger impact
on the overall light capture of a surface and should
be represented as darker than shadows towards the
extremities of the day. Once calculated, the trans-
parencies were amended to reect this, represent-
ing the data more accurately than before (Fig. 5).
The nal stage of producing the shadow maps was
to combine the shadow information with accurate
lighting data. The data, kindly provided by SolarGIS,
captured information on both direct irradiation (i.e.
direct sunlight) and diused irradiation (i.e. diused
light from the sky). An area in continual shadow
would only ever receive diused irradiation from
the sky, whereas an area in constant sunlight would
always be exposed to the total direct irradiation val-
ue. Taking the lighting data for March as an exam-
ple, it can be seen that the total direct irradiation is
2.18 kW/m2/day and the total indirect illumination
is 1.40kW/m2/day. Therefore, it can be assumed that
all areas that are a solid black within the shadow
map (i.e. always in shadow) would have a light cap-
ture of 1.40kW/m2/day whereas the areas without
any shading would achieve a light capture of 2.18
kW/m2/day. The resulting images clearly represent
which roofs and facades are susceptible to overshad-
owing, and how much energy each surface receives
throughout the day within each month (Fig. 6).
Upon the completion of the shadow maps it was
important to identify pitched roofs and eliminate
them from the research. If Manchester was to be
comprised entirely of at roofs, it would have a
total roof area of 136.3 hectares. However, 44.2
percent of the buildings have pitched roofs leav-
ing the remaining at roof area at 76 hectares.
Figure 7: Annual roof top shadow map
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Average Annual Light Capture
To determine the overall capacity of the horizontal
and vertical surfaces to produce food, the average
annual light capture would also be required. In or-
der to combine all the overshadowing data into
an annual shadow analysis, the yearly impact on
light capture for each shadow had to be calculat-
ed. This was achieved by calculating the proportion
of total daylight that landed upon a surface with-
in each half hourly period of a specic day, against
the total light capture of a total year. Thus, provid-
ing a percentage contribution of each half-hourly
section to the total yearly light capture of the city.
For example; the light capture of a surface in shad-
ow between 10:00 and 10:29 of a typical December
day is reduced across the year by 0.1 percent. If a
surface is in shadow between 12:00 and 12:29 in
June, its light capture is decreased by 0.9 percent
across the year. When all 258 shadows are laid upon
one another, and the yearly transparencies of each
shadow applied, an annual lighting map emerges.
A stepped gradient was added in order to reduce
the number of colour shades within the image and
to allow a clearer dierentiation to be drawn be-
tween well lit and poorly lit areas (Fig. 7). The annual
shadow map covers a much larger range of values
than previous monthly lighting information and, as
such, is divided into nine 0.5kWh/m2/day energy
levels. The annual results were processed in blue to
help dierentiate the data from the monthly data.
In order to determine what relevance this data
has on annual crop growth, the energy needed
by a plant for photosynthesis to occur must be
included in the research. As a working average
some plant species require a minimum of 1MJ/m2/
day (0.28 kWh/m2/day) of light energy to survive.
To obtain maximum growth rates, however, they
require 3MJ/m2/day (0.83kWh/m2/day) (Badg-
ery-Parker, 1999). In order to maximise the inte-
gration of technological food systems, the satura-
tion point of photosynthesis (i.e. 0.83kWh/m2/day)
will be taken as the baseline from which crops can
be grown in a city to achieve the highest yields.
Predicted productivity
If every at roof of the total 76 Hectares was capable
of growing crops, Manchester could grow approxi-
mately 20.2 million crops at any one time based
on 26.66 crops/m2 as found in the elevated aqua-
ponic system. Extrapolating this throughout the
year, based on a two month growing cycle for eight
months of the year, Manchester would be capable
of growing close to 81 million crops per annum.
Based on a sale price of between £2 and £4 (as per
the sale values achieved from the food shop adja-
cent to the elevated aquaponic system), the result-
ing crop could be worth between £162 million and
£324 million per annum. Using the annual lighting
data above, all areas indicating a yearly average
light capture of 0.9kWh/m2/day or above would
be considered perfect sites on which to grow food.
However, once these sites are identied further re-
search would be needed to conclude the viability
of urban agriculture dependant on access, struc-
tural integrity and the inclination of the building
owner to partake in such activities to name a few.
In the case of Manchester, 99.4 percent of avail-
able at roof surface is capable of supporting
crop growth and therefore, the total growing ca-
pacity of city centre roofs in Manchester is 80.4
million crops (based on four harvests per an-
num) indicating a total worth of between £160.8
million and £321.6 million per annum based
on a sale value of between £2 and £4 per unit.
In total, the area of vertical facade accounts for 310.6
hectares of the total surface area of the city. Based
on the information collected from the facade proto-
type - that facades can produce up 15 crops per me-
tre squared of vertical surface - the vertical surfaces
of Manchester are capable of growing 46.5 million
crops at any one time. However, approximately 20
percent of the entire facade area is incapable of
supporting crop growth due to close proximity of
other buildings (i.e down tight streets or alley ways)
with a further 35 percent of the facade area facing
between North-East and North-West, never receiv-
ing any direct sunlight as a consequence. Although
capable of supporting plant life during the bright-
er and warmer months, for the purposes of this re-
search, the north facing facades would be collec-
tively titled ‘additional growing space’ due to their
orientation. The east, south and west facades would
be more eective at growing crops. Therefore the
overall productive area of vertical surfaces is 167.7
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hectares, not including the 86.9 hectares of north
facing facades. Using this area to grow crops in dou-
ble skinned facade farms would enable a total of
25 million crops to be grown at anyone time. Based
on four harvests per year, 100 million crops could
be grown on the vertical surfaces of Manchester
worth between £200 million and £400 million per
year based on a sale value between £2 and £4.
In total, between both vertical and horizon-
tal surfaces, the city centre of Manchester is ca-
pable of growing an estimated 180.4 million
crops per year, achieving a maximum sale val-
ue of approximately £721.6 million per annum.
Framework of Integration
Light capture
Light capture is one of the key requirements for
the successful integration of urban agriculture
alongside access, demand and structural integrity.
Manchester performs well in this respect with 99.4
percent of roof space and 45 percent of vertical sur-
face providing suitable to excellent light capture.
An aspect of the annual light study which has not
been alluded to until this point, is the information it
provides for the integration of urban agriculture. It
would make little sense to roll out urban agriculture
across all productive surfaces before rst exploring
and testing what systems are best suited to this scale
of agriculture within the context of Manchester. Ad-
ditional parameters to consider will also be how well
a system performs against expected production,
how the systems within the the city are run, who
operates them, and where the produce is sold. The
areas which receive the highest light levels would
be the best sites for further analysis when testing
the above. Beyond this, areas which receive less
light can also be sought, in order to test a systems
ability to perform in less than perfect conditions.
Prioritisation of implementation
The research collected to date on the operational el-
evated aquaponic system in Manchester, along side
the facade farm prototype, shows that horizontal
systems are easier to implement and to maintain.
Although the ability of double skinned facades to
grow crops is apparent, their integration is more dis-
ruptive and far more complex. At the outset of inte-
grating urban agricultural systems, the route of least
resistance should rst be taken in order to reduce
expenditure, gain support and increase revenue
streams. Therefore, roof space should be considered
primarily as sites on which food can be grown with
facade integration occurring at a later date. Initially,
this might manifest itself as a succession of simple
greenhouses or polytunnels upon roof tops (as per
the polytunnel used in the elevated urban farm) to
kick start urban food production, which future urban
systems can build from and improve upon; most im-
portantly owing into newly created supply chains.
The majority of north facing facades should only be
considered for vertical systems in the event that all
other growing opportunities have been explored.
Interface with food networks
The nal factor considered within this study is the
ability to sell food once it has been harvested from
urban agricultural systems. Demand for the food
grown is a key requirement for the successful inte-
Figure 8: Location of 54 supermarkets including a 250m catchment area (left) and gradient map of demand (right)
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and Society, 3 (1)
gration of urban agriculture. Without demand for
food there would be no sale of crops, and there-
fore no economic model. Growing food where
it is needed - i.e. where it can be easily sold - will
increase the ability of these technical food sys-
tems to sell crops closer to the rate of production,
removing the possibility of surplus produce and
ensuring a resilient economic model. The ability to
sell food locally will also have the biggest impact
on food transport, as changing from food miles
to food steps will drastically reduce the distance
food travels. The adjacency of food production and
food sale will allow the continuous trade of fresh-
ly harvested organic fruit and veg, with higher
nutrient content, and little need for packaging or
refrigeration. As a consequence, CO2 production
would decrease and urban diets would improve.
In total, there are 54 supermarkets in Manches-
ter and, based on a 250m catchment area, the de-
mand for available roof space would initially be 74
percent (Fig. 8). As a result of this, food would nev-
er travel further than 250m to its point of sale. The
resulting gradient map based on these locations
identies the places that are in highest demand
and where food might be initially grown (Fig. 8).
Framework of integration into the city
The framework of integration proposed within this
research focuses on the availability of light and
the ndings discussed within the paper integrat-
ed with existing food networks and points of sale.
(Fig. 9). This map is the culmination of the research
as it identies areas from most to least desirable
for urban agricultural activities. This information
shows both the areas of high light capture and
high food demand in white, and the areas of low
light capture and low food demand in dark green.
The black areas are the areas identied previously
as not being able to support plant life (i.e. having
an average daily light capture throughout the year
of less than 0.90 kW/m2/day) . The resulting infor-
mation represents simply that the white areas be
developed rst, working through to the dark green
areas as the role of food production within the city
takes on a larger and more integrated role. This map
is the resulting framework of integration and will
hopefully lead to a city no longer comprised solely
of manmade surfaces, but a city integrated with a
natural metabolism, intrinsic to its future prosperity.
Conclusions and Future Considerations
The ndings of this paper show that cities are ca-
pable of producing large quantities of food and
wealth but currently only includes for such crops
as iceberg lettuce, rocket lettuce, Thai basil and
cabbages - as per the crops grown in the elevat-
ed aquaponic system - but it is the future ambi-
tion of the research to develop the light study
to include energy data of other crops and pro-
pose a city wide production map as to which
crops are best suited to which light energy levels.
Taking the total surface area of Manchester into ac-
count - including roads, paths etc. - 33 percent is ca-
pable of growing food. Within the UK, 11 percent of
the country has been developed. Applying the nd-
Figure 9: Roof top framework of integration based on light capture and demand.
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ings of Manchester, where the growing area was 1.5
times that of its footprint, it can be assumed for the
purposes of this research, that 16.5 percent of the
total land area of the UK could grow additional food.
As a model, urban agriculture is capable of pro-
ducing vast amounts of food and wealth, but can-
not solve the issues of globalised food produc-
tion and transport alone. Instead, it sits amongst
a range of options that need to be implement-
ed in order to reduce the impact humans have
on the natural landscape, and is a part of a series
of interventions that include a reduction in meat
consumption, the adoption of clean renewable
energy, the reduction of waste streams and the in-
tegration of closed loop urbanism, to name a few.
One thing is clear however, urban agriculture can
be integrated within today’s cities and produce vast
quantities of food without the need for purpose
built food producing sky scrapers that are depend-
ent on articial lighting to grow crops. Instead, the
retrotting of simplied food producing facades
and roof-based systems based on virtual lighting
data can make a real dierence (Fig. 10). Urban agri-
culture is the start of a city revolution that connects
the urban with the natural, improving the physi-
cal environments of cities forever and improving
the wellbeing of its inhabitants for years to come.
Acknowledgements
The writers wishes to thank the peer reviewers for
their helpful comments and to thank the
Association of European Schools of Planning for
the inclusion of this research within the AESOP 6:
Finding Spaces Conference as well as Rob
Roggema for his help throughout this process.
We would also like the thank SolarGIS for the
information they kindly shared regarding the solar
capture of Manchester, England.
Conict of Interests
The authors hereby declare that there is no conict
of interests.
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