WSA V Dissertation Oscar Rodriguez - Rooftop Agriculture · London Rooftop Agriculture: A Preliminary Estimate of Productive Potential 1 Contents 1.0 Abstract 04 1.1 Acknowledgements

London Rooftop Agriculture: A Preliminary Estimate of Productive Potential

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Contents

1.0 Abstract 04

1.1 Acknowledgements 05

1.2 Literature Review 06

1.3 Agriculture / Horticulture 08

2.0 The Global Food Economy 09

2.1 Brief History of Agriculture: from Agriculture to Agribusiness 10

2.2 Climate Change and the Fossil Fuel Market 16

2.2.1 Climate Change So Far 17

2.2.2 Climate Change Projections & Effect on Global Food Economy 19

2.2.3 Modern Agriculture’s Contribution to Climate Change 20

2.2.4 The Future of the Fossil Fuel Market 21

3.0 London’s: Roofscape & Food 23

3.1 London’s Roofscape 24

3.2 London’s Food Economy 28

3.3 Fruit and Vegetable Production Target Determination 29

3.4 The Case for Localised Food Production 30

4.0 Rooftop Agriculture and Architecture 33

4.1 Production Technique 35

4.3.1 Containerised 35

4.3.2 Intensive 37

4.3.3 Hydroponic 40

4.2 Other 43


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5.0 Estimate of London’s Available Flat Roof Area 44

5.1 Aim 45

5.2 Method 45

5.3 Sampling 47

5.3.1 Residential - High 48

5.3.2 Residential - Mid 49

5.3.3 Residential - Low 50

5.3.4 Commercial - High 51

5.3.5 Commercial - Mid 52

5.3.6 Commercial - Low 53

5.3.7 Coefficient Determination 54

5.4 Mapping 55

5.3.1 The Grid 56

5.3.2 Water 57

5.3.3 Green 58

5.3.4 Industry and Infrastructure 59

5.3.5 Residential 60

5.3.6 Commercial 61

5.3.7 Individual Buildings 62

5.3.8 Full Analysis 63

5.3.9 Mapping Comparative Evaluation 64

5.5 Results 69

5.6 Method Evaluation 70

6.0 Estimate of London’s Total Flat Roof Area 72

6.1 Aim 72

6.2 Method 72

6.3 Results 73

6.4 Evaluation 74


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7.0 Yield per Hectare Range Determination 76

7.1 Aim 76

7.2 Methodology 76

7.3 Open Air Containerised Production Coefficient 79

7.4 Greenhouse Hydroponic Production Coefficient 80

7.5 Mankiewicz Production Coefficient 81

7.6 Evaluation 82

8.0 Preliminary Estimate of London’s Productive Potential 83

8.1 Scenario 1 86

8.2 Scenario 2 87

8.3 Scenario 3 88

8.4 Scenario 4 89

8.5 Conclusion 90

8.6 Further Study 93

9.0 Appendix 94

9.1 Referenced Bibliography 94

9.2 Contributing Books 95

9.3 Reports 96

9.4 Articles 98

9.5 Audio/Video 99

9.6 Internet Sites 100

9.7 Image List 101

9.8 Appendix Source Material 103

9.9 Sample Tile Enlargements 112


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1.0 Abstract

This study will address what, in the author’s experience, has been a recurring side item to

many studies I have read about urban agriculture, a subject which has recently received a

marked increase in attention. Rooftop agriculture, specifically its quantitative study has, as

this study will attempt to illustrate, been tackled at best in a fragmented fashion. My interest is

born from what I perceive to be a possible confluence, particular to the current political

climate, which has seen concerns over food, energy and climate animate architectural

discourse to levels reminiscent of the mid to late 70s.

Rooftop food production holds a tenuous, idealistic stigma with limited perceived commercial

application and a myriad of insurmountable logistical obstacles. I firmly believe the inertia to

its serious consideration is of major concern as at the most basic theoretical level the activity

demonstrates the capacity for benefits well beyond the immediate material output. Thus, this

study is aimed at breaking through that inertia with what could best be described as a

preliminary estimate of potential.

As a native Londoner I have directed my attention to my home city whose food procurement

is heavily dependent on imports and sourcing from producers committed to conventional,

agro-chemical intensive production. My principle aim is to thread various fragmented pieces

of research on the subject while underpinning it with the combined results of three pieces of

fieldwork informing a series of hypothetical rooftop fruit and vegetable production scenarios. A

comprehensive study, with a thorough analysis of implementation through to distribution is

well beyond the remit of this dissertation and though these issues may be touched upon, it is

not my intention to elaborate on them.


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1.1 Acknowledgements

I would like to thank Ian Knight my dissertation tutor; Tara Garnett, Benjamin Linsley and

Keith Agoada for the chance to interview them; and my family and friends who patiently

listened to me rant about the subject for months.


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1.2 Literature Review

The following books and reports have contributed to my outline of the problems with modern

industrial agriculture and the case for localised production.

Data on climate change originates from the 2007 Intergovernmental panel on Climate Change

(IPCC) Fourth Assessment Report. The contributions of all four working groups have been

used along with the synthesis report. Speculative analysis of how the global food economy

may be affected by climate change is also provided which I have used in conjunction with

more rhetorical sources.

Edward Goldsmith’s essay entitled “Feeding People in an Age of Climate Change” in

“Surviving the Next Century”, edited by Herbert Girardet, offers a panoptic critique of the

global food economy which is largely supported by the more comprehensive critiques from

“The End of Food” by Paul Roberts and “The Global Food Economy: Battling for the future of

farming” by Tony Weis. Roberts’ book is largely US centric. Janine Benyus’s, “Biomimicry”

also contributes a historical evaluation of the American food economy in the context of her

advocacy for her particular branch of design science. The relationship between the fossil fuel

market and agriculture is covered by Richard Heinberg’s “The Party’s Over” and “Peak

Everything” which also introduce the case for localised food production.

Data on London’s food system has been sourced from work by Herbert Girardet, John Jopling

James Petts and Tara Garnett. Garnett’s “Cooking up a Storm” is a UK centric look at the

GHG contribution to and the susceptibility of food production to climate change with an

emphasis on strategies for reducing impact which include localisation. Her 1999 report “Urban

Agriculture: Rethinking London’s food economy” and James Petts’, 2001 World Health

Organisation series on urban food security case study on London, “Urban Agriculture in

London”, are London-specific studies.


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Herbert Girardet dedicates a full chapter to urban agriculture in “Cities People Planet”,

examining potential benefits and historical precedent. Nancy Jack and John Todd’s “From

Eco-cities to Living Machines” promotes rooftop agriculture within a general advocacy of work

conducted by the New Alchemy Institute in the seventies. Their suggestions are largely

conjectural but present direct theoretical precedence to my enquiry.

The various examples of rooftop food production models were largely sourced from the

internet in reports and articles that range from the anecdotal to the rhetorical. Steve Lerner’s

compilation of essays in “Eco-Pioneers” includes one on Paul Mankiewicz’s impressive

rooftop greenhouse production model. Few books exist, that tackle the issue directly and in

most cases I have had to interpret fragmented, secondary and incomplete information.


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1.3 Agriculture / Horticulture

It is important to note that the umbrella term for food production is generally recognised as

“agriculture”, which given its Latin derivative suggests food production over a field or large

area of land.

Agriculture : Latin : ager (a field) + cultūra (cultivation)

Horticulture may be a more appropriate term for this study given its urban context and the

reference to gardens rather than fields.

Horticulture : Latin : hortus (garden) + cultura (cultivation)

I would like to declare that my use of the term agriculture is with full awareness of the

distinction and that the panoptic nature of the study justifies its use over the latter.


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2.0 The Global Food Economy

This section includes the following.

• Brief, editorialised history of agriculture from the Neolithic, through to the Green

Revolution and a summarised critique of its contemporary form.

• Introduction of the IPCC’s latest data on climate change.

• Description of how the effects of climate change may affect the global food economy.

• Summary of modern industrial agriculture’s contribution to climate change.

• Summary of projected trends affecting the fossil fuel market.


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2.1 A brief history of Agriculture: from Agriculture to Agribusiness

Roughly 12,000 years ago, following the last Ice Age, the over hunting of mega-fauna on

which hunter-gatherer man had survived, led to a centuries-long food crisis from which

horticulture is believed to have begun, forcing the previously nomadic groups into sedentary

life patterns leading to the formation of the first settlements.1 Commonly referred to as the

Neolithic Revolution, man’s nutritional strategy began a gradual process of intensification; the

production of more food per unit of land, and displacement; the distancing of consumer from

producer which finds its most extreme expression in the modern food economy.

The plough sowed the seeds of “agriculture” by permitting farmers to till larger areas of land.

Units of land were arranged as monocultures allowing for iterative processes in their

management. Higher yields fed growing populations and the administration of harvests and

tradable surpluses presented the need for full-time managers, recorders and protectors which

marked the advent of complex societies. Standing armies defended settlements and secured

territorial expansion. Organised irrigation, animal domestication, food storage and

transportation added further layers of labour specialisation. Surpluses were fed into a trading

system which connected settlements and crystallised civilisations alongside ideologies

intrinsic to their conditions.2

The Sumerians are widely attributed with having “invented” agriculture in its operative

definition circa 55,000BC, but the Romans pushed the displacement trend of its development.

With an empire in control of an expanse of land with a range of crop accommodations,

production became region specific and thus primarily trade orientated within the limits of their

transport infrastructure.

1 Richard Heinberg, Peak Everything, (Clairview, 2007) p.51 2 Ibid, p51


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In Western Europe the degree to which farmers were bound to their land was formerly

legislated. Declining birth rates and population in late antiquity moved the Roman Empire to

enforce legislation that bound farmers or “coloni” to their land, culminating in the Laws of

Constantine I, in 325AD. Farmers underwent a decline in status towards “serfdom”, derived

from the Latin “servus” for slave, which would contractually bind them to land holding lords

who would grant protection in return for labour or payment in produce. Farmers thus became

intrinsically woven into the land they tended and formed the core of their respective

civilisation’s strategy for energy capture. As such, the integrity of these early complex

civilisations was secured as long as food production maintained positive energetic returns on

energy invested.3

Serfdom declined, eventually abolished in 14th century. In Britain, the open field system

became the most prevalent form of land administration.4 Land around settlements was

arranged into several large unfenced plots and divided into long strips to make best use of the

heavy ploughs required to cut through heavy clay soils powered by teams of oxen collectively

shared by participating families. Much of this land was legally designated “common” land,

which, while still owned, participants in its cultivation were granted certain rights in its

management and ownership of produce.5

By the early 18th century subsequent population growth called for greater intensification which

together with further advances in labour saving mechanisation, notably Jethro Tull’s seed drill

in 1731, the introduction of four field crop rotation replacing Roman three field crop rotation,

and selective breeding, required larger units of land to reap effective rewards.6 Dissolution of

farmers’ rights to common land accelerated with the series of “Enclosure Acts” from 1750 to

1850, allowing landowners to evict farmers and employ these new technologies to greater

3 Joseph Tainter, The Collapse of Complex Societies, (Cambridge University Press, 1990), general thesis 4 Otto Thomas Solbrig, So Shall You Reap, (Island Press, 1996), p.127 5 Vandana Shiva, Earth Democracy, (Zed Books, 2006) p.19 6 Mark Overton, Agricultural Revolution In England, (Cambridge University Press, 1996), p.121-122


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effect for their own profits.7 Allotments within urban boundaries were offered as compensation

for rural-urban migrants who had been expelled from common land.

It could be argued that enclosure gave birth to modern agri-business as it represented a

complete emancipation from the communitarian value-laden identity of land and its demotion

to mere resource. This transition is more commonly referred to as the British Agricultural

Revolution. Labour substitution and population growth availed the incumbent Industrial

Revolution of the labour and demand that incentivised it by the late 18th century.

Coal powered the first steam engines which both revolutionised transport and supplied the

torque which spun the wheels, cams and drive belts of the cottage industries of the early 19th

century. Steam ships and trains hiked global mobility in an age of burgeoning globalisation to

ever greater levels. Then along came petroleum.

Petroleum began as an illumination fuel substitute for whale oil in the late 19th century.

Gradually substituting hands and feet, it now drives the engines of the fleets of land, sea and

air borne vehicles responsible for tilling land, harvesting, spraying inputs and distributing

produce within a market of international scale.8 Tractors and combine harvesters changed the

modern agricultural landscape by encouraging the planting of expansive monocultures that

automated tools could manage at ever greater rates of efficiency. Such efficiency gains

changed the structure of the market gradually driving out uncompetitive small landholders

who would sell their lands to larger producers.

The Green Revolution of the 50s is attributed with consolidating the use of agrochemicals with

mechanisation and selective breeding into the model of production prevalent to this day.

Containerisation, refrigeration, development of preservatives and packaging materials further

extended the distances food could travel and supported an abundance of cheap food

available wherever it was demanded, if it could be afforded.

7 Otto Thomas Solbrig, So Shall You Reap, (Island Press, 1996), p.138 8 Paul Roberts, The End of Food, (Bloomsbury, 2008) p.218


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Monocultures left crops at the mercy of pests and parasitic plants. Petroleum-based synthetic

pesticides and herbicides were developed to replace the natural defences otherwise present

in complex, diverse ecosystems. Most common brands are based on organophosphates,

which the German military are believed to have tested as a nerve agent in the 1920s.9 Neural,

endocrine and respiratory disruption, are the headlines of an extensive set of side effects

through direct use.

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Indirect exposure through contamination of produce and drinking water has been linked to

cancer and miscarriages among many other effects. Organisms beneficial to the welfare of

the ecosystem where such chemicals are applied are also affected, impairing its long term

productivity. The effects of pesticides are also cyclically compromised as pests develop

resistance and wider ecological shifts respond.

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Synthetic fertilisers were a product of the Haber Bosch process, developed in Germany

before WW1 for ammonia production primarily for use in explosives. Replacing time honoured

natural nutrient cycling; industrial agriculture is crucially dependent on them for the yields that

have sustained the exponential population growth characteristic of the post war era. Currently

40% of global population survives on the extra calories attributable to them with projections

that this will rise to 60% within this century.12

9 Paul Roberts, The End of Food, (Bloomsbury, 2008) p.218 10 Tony Weis, The Global Food Economy, (Zed Books, 2007) p.31 11 Edward Goldsmith, Surviving the Next Century, (Earthscan, 2007) p.63 12 Paul Roberts, The End of Food, (Bloomsbury, 2008) p.215

“In the early 1990s the WHO reported that 3 million people suffer acute pesticide poisoning

every year, causing 220,000 deaths (including those caused by pesticide-induced suicides).”

“As many as 500 species of insects have already developed genetic resistance to

pesticides, as have 150 plant diseases, 133 kinds of weed and 70 species of fungus”


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Localised diminishing returns have already been identified despite growing application.

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Nature’s adaptive measures are frequently countered with more varied and powerful

application of these chemicals, exacerbating soil degradation and productive potential. This

agrochemical treadmill, along with excessive mechanisation and deforestation-induced

erosion has done near irreparable damage to topsoil.

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Accumulation of the spectrum of agrochemicals in our soils is enacting a heavy price on their

long term productivity and other connected systems. Their presence in the water cycle has

disrupted aquatic ecosystems, accelerating the growth of aquatic vegetation beyond natural

equilibrium. Its subsequent death triggers eutrophication, rendering these bodies of water

dead zones to marine life. The UN Environmental Program estimated the number of

worldwide dead zones at 150 in a 2003 report.15

Despite its claims, the Green Revolution far from solved world hunger. While the volume of

food has easily outstripped requirement by one and a half times according to the UN World

Food Programme,16 the problem of access persists. Entitlement to food has by most accounts

decreased as governments of the developing world restructure their agricultural economies

for export on lands previously occupied by subsistence farmers in order to qualify for World

Bank and IMF credit.

13 Edward Goldsmith, Surviving the Next Century, (Earthscan, 2007) p.63 14 Paul Roberts, The End of Food, (Bloomsbury, 2008) p.214 15 Ibid, p.217 16 Tony Weis, The Global Food Economy, (Zed Books, 2007) p.11

“By one FAO estimate, the soil of nearly a third of all arable

land is so acid that it can’t support high-yielding crops”

“…FAO admitted in 1997 that wheat yields in both

Mexico and the US had shown no increase in 13 years”


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“There are now 842 million people suffering from under-nourishment in a world

that already grows more than enough food to feed the global population.” 17

On the other side, 1.6 billion overweight and 400 million obese were estimated by the World

Health Organisation in 2005.18

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The UN’s 2006 World Population Prospects report projects global population to exceed 9

billion between now and 2050.20 Genetically modified foods have been touted since the early

90s as the next mechanism to secure production in the face of rising demand. While side

effects are downplayed by an active biotech lobby, questions still arise as to their capacity to

achieve the volume necessary. With freshwater depletion at rates beyond replenishment,

declining soil fertility, rising input costs, climate instability and the falling proportion of skilled

farmers to population, biotech rhetoric fails to enthuse the confidence it targets.

Paul Roberts concludes…

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17 Jean Ziegler, Special Rapporteur of the UN Commission on Human Rights, 2004, cited in Weis, 2007, p.11 18 BBC, 2nd January, 2008, http://news.bbc.co.uk/1/hi/health/7151813.stm (accessed December 2008) 19 Paul Roberts, The End of Food, (Bloomsbury, 2008) p.208 20 Tara Garnett, Cooking Up A Storm, (Food Climate Research Network, Sept 2008), p.77 21 Paul Roberts, The End of Food, (Bloomsbury, 2008) p.208

“But even optimists acknowledge that if these predicted breakthroughs fail

to materialize, or don’t come soon enough, the entire food economy could

gradually slip into a state of demographic disequilibrium where productivity

is once again in a race with population growth and where the most heavily

populated countries compete for access to large surpluses of grain and

soybeans, just as the big industrialised nations now compete for oil”

“A system so focused on cost reduction and rising volume that it makes a billion of us fat, lets

another billion go hungry, and all but invites food-borne pathogens to become global epidemics...”


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2.2 Climate Change and the Fossil Fuel Market

Modern agriculture is not only a major contributor, but a highly susceptible industry to the

effects of climate change. Predictable weather is a cornerstone of agriculture from theoretical

conception and as Paul Roberts argues, most optimistic projections of the future of our food

supply are fatally built on the assumption of climatic stability and a placebo-like confidence in

technological advances.22

22 Paul Roberts, The End of Food, (Bloomsbury, 2008) p.208


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2.2.1 Climate Change – the story so far

The IPCC’s 2007 report begins with the following statement

“Warming of the climate system is unequivocal, as is now evident from observations of

increases in global average air and ocean temperatures, widespread melting of snow and ice

and rising global average sea level.” 23

Below is an extract from the IPCC’s fourth assessment report on climate change displaying

observed and recorded changes in global temperature, sea level and northern hemisphere

snow cover.

23 IPCC, Climate Change 2007: Synthesis Report, (Cambridge University Press, 2007) p.31

Figure 1


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Atmospheric concentrations of three of the four principle GHGs are stated to have increased

as follows in parts per million (ppm) and parts per billion (ppb) values.

• Carbon Dioxide (CO2) pre-industrial value of 280ppm to 379ppm in 2005

• Methane (CH4) pre-industrial value of 715ppb to 1774ppb in 2005

• Nitrous Oxide (N2O) pre-industrial value of 270ppb to 319ppb in 2005 24

Halocarbons are stated to have increased from a near-zero pre-industrial level by no

assigned value. The average 0.74°C rise recorded over the last 100 years should illustrate

the severity of our actions when viewed in light of the absolute stability of atmospheric GHGs

in the 10,000 years before the industrial revolution as the following extract suggests.

“The combined radiative forcing due to increases in CO2, CH4 and N2O is +2.3 [+2.1 to +2.5]

W/m2 and its rate of increase during the industrial era is very likely to have been

unprecedented in more than 10,000 years” 25

Eleven of the twelve years between 1995 and 2006 are declared as having been the warmest

since records began in 1850.26 Global sea levels are stated (with pronounced caveats) as

having risen by an average rate of 1.8mm per year over the period 1961 to 2003, then rising

to an average of 3.1mm per year from 1993 to 2003.27 Stronger language describes the

extent to which satellite imagery from 1978 has demonstrated an average 2.7% rate of

constriction per decade, with rates increasing to 7.4% during summer months.28 The increase

in size and number of glacial lakes, ground instability in permafrost regions and frequency of

rock avalanches are all said to be supported by a high level of confidence.

24 Ibid, p.30-33 25 Ibid 26 Ibid 27 Ibid 28 Ibid


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2.2.2 Climate Change Projections – general effects on Global Food Economy

In the summary of the IPCC’s, Climate Change 2007: Impacts, Adaptation and Vulnerability,

temperature rise projections for 2090 to 2099 range from a 1.1 to a 6.4°C increase depending

on scenario. A rise of 3°C within a range of 2 to 4.5°C is attributed to its business-as-usual

scenario. Higher frequency of extreme weather events, further rising sea levels, disruption of

water cycle and terrestrial biological systems, particularly pest vectors, are often cited as the

most pronounced immediate concerns, though effects will vary in region and by crop.29

Productivity is expected to increase in the short term for certain crops in currently cold

temperature areas in the northern hemisphere before decreasing once mean temperatures

rise beyond 3°C. In tropical latitudes, productivity is expected to fall within a more immediate

change in mean temperature. Developing countries with poor water and transport

infrastructure will be most affected, limiting access to food and exacerbating hunger.30

Physical effects are largely speculative. A sea level rise projection of 88cm by 2100 would

directly affect 30% of global agricultural land through flooding, increased soil salinity and

wider ecological shifts.31 Heavy precipitation, surface runoff and increased glacial runoff could

potentially contribute to further soil erosion and greater frequency of mud and landslides,

directly affecting productive land.

While uncertainty prevails given the infinite variables involved, an inconsistent supply of food

and extreme weather induced possibility of direct disruption to our production, transport,

storage and distribution infrastructure will inevitably translate to price volatility and subsequent

social unrest if not addressed in an anticipatory fashion.

29 IPCC, Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment

Report of the Intergovernmental Panel on Climate Change; Chapter 8 Agriculture,

(Cambridge University Press, 2007), p.297-298 30 Ibid 31 Edward Goldsmith, Surviving the Next Century, (Earthscan, 2007) p.63


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2.2.3 Modern agriculture and its contribution to climate change

Modern agriculture and its global distribution network are major contributors to greenhouse

gas emissions. In 2005, global agriculture contributed net GHG emissions of between 5.1 -

6.1 GtCO2-eq/yr. 3.3 GtCO2-eq/yr were attributed to methane, primarily from livestock related

production and the decomposition of organic material in oxygen deprived conditions. 2.8

GtCO2-eq/yr were attributed to nitrogen oxide primarily from microbial transformation of soil

based nitrogen exacerbated by the application of excessive fertiliser beyond plant needs.

Carbon dioxide emissions were reported as relatively balanced discounting emissions from

transport, storage, refrigeration and general supply side management. Together these

accounted for 10-12% of total anthropogenic GHG emissions. 32

32 IPCC, Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment

Report of the Intergovernmental Panel on Climate Change; Chapter 8 Agriculture, (Cambridge University

Press, 2007), p.499-501


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2.2.4 The Future of the Fossil Fuel Market

Modern, large scale commercial food production is heavily dependent upon the fossil fuel

market at every phase of production to such a level that Richard Heinberg describes the

modern agricultural system as a

“method of using soil to turn petroleum and natural gas into food” 33

Oil fuels the machinery, the global distribution network and is the chemical feedstock of the

pesticide end of the agrochemical industry. Natural gas is heavily consumed by the Haber-

Bosch process in synthetic nitrogen fertiliser production. Along with coal, they are also

sources of electrical generation which power the remaining processes.

The level of energy intensity becomes immediately apparent when you consider the 33,000

cubic feet of natural gas required to produce one ton of conventional nitrogen fertiliser which

could generate the 9,671 kilowatt electricity requirement for 10 and a half months of an

average American home.34 Furthermore, on average, for every calorie of food energy

produced, ten calories of hydrocarbon energy are required to produce it in the entirety of its

process.35

Such dependence on a complementary market exposes the global food system to its volatility

which is further compounded by climatic and political variables. Cheap mobility has built the

complex globalised economy we identify today. The ability to displace market from supply at

the distances our produce travels today has only been viable because the cost of transport

has not outweighed the productive comparative advantage of sourcing from great distances.

33 Richard Heinberg, Peak Everything, (Clairview, 2007) p.48 34 Paul Roberts, The End of Food, (Bloomsbury, 2008) p.215 35 Richard Heinberg, Peak Everything, (Clairview, 2007) p.48


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This year, the oil market demonstrated its appetite for short term volatility reaching a record

$150 a barrel in July.36 Perhaps, most concerning is the projection by the International Energy

Agency; on whose advice governments structure their energy strategies that the global peak

in oil extraction could occur in 2020.37 Such official confirmation in the “peak oil” theory first

proposed by M. King Hubbert, a petroleum geologist working for Shell Oil, who in 1956

predicted US oil extraction to peak in 1970 using a model linking rates of extraction to

discovery, could signify a pertinent end to long term optimism.38

The misplaced optimism in biofuels as a plug-in substitute for fossil fuels took a crippling hit

when their effect on the food market, with which they compete for land and inputs, led to this

year’s headline grabbing food price rises. Furthermore, remaining natural gas reserves are

cornered by Russia and Iran, potentially exacerbating supply inconsistency because of

geopolitical circumstance.39

Structural change in the fossil fuel market should now be considered as unequivocal as

climate change. Its effects on the next century, in particular our food system are projected to

be epoch defining.

36 BBC News Online, The Price of Oil

http://news.bbc.co.uk/1/hi/in_depth/business/2008/oil_/default.stm 37 Guardian Online, George Monbiot meets Fatih Birol, citing World Energy Outlook 2008 report,

http://www.guardian.co.uk/environment/video/2008/dec/15/fatih-birol-george-monbiot 38 Richard Heinberg, The Party’s Over, 2003, (Clairview Books) 39 Paul Roberts, The End of Food, (Bloomsbury, 2008) p.215


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3.0 London: Roofscape and Food


• Brief description of London’s roofscape.

• Outline of London’s food system.

• Outlined case for localised production in London.

• Calculation for a production target based on latest consumption figures.


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3.1 London’s Roofscape

London is overwhelmingly a low lying city of pitched roofs. Its rain soaked stigma is widely

acknowledged and its roofscape is arguably primarily a practical response. Timber framed,

slate and tile clad roofing constitute the prevalent form of construction of its mainly Georgian,

Victorian and post-war detached and semi-detached suburban housing stock. Homes built

between and after the war years vary in form and construction as modernist construction

technology granted the possibility of effective, water and snow shedding flat roofs. These

entailed an initial construction and maintenance premium as the first generations of

waterproof membranes failed to be as effective as conventional pitched roof construction. Flat

roofs generally continue to bear this premium to this day.

I have found very little commentary on London’s roofscape and introduce the following types

as a highly generalised, personal interpretation of what is typical. Each type is assigned a

description of opportunities and obstacles.

Figure 2


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Residential Types

Victorian Terraces

• Main building covered by pitched roof.

• Back extensions offer small patch of

accessible flat roof typically of between 20 to

40sqm in size.

• Access to sunlight uncompromised by main

pitched roof.

• Consistent repetition in general.

• Central and West London mainly

Georgian Terraces

• Main building covered by typical double

pitched roof though flat roof types evident.

• Small back extensions generally shaded by

taller main building.

• Access to flat roof types a major obstacle

though possible.

• Varied flat roof density.

• Inner shell in and around Central London

Figure 3 : Maida Hill, West London

Figure 4 : Ladbroke Grove, West London

Figure 5 : Typical Double-pitched roof Georgian Terrace


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Residential Types

Post War Suburban Detached and Semi Detached

• Pitched roofs invariably dominant.

• Small back extensions with varied access to

direct sunlight.

• Access to extension flat roof types a major

obstacle though possible.

• Very low flat roof density.

• Outer shell of London.

Modernist Housing Estates

• Flat roof density varies. Large blocks generally

flat roofed though variants exist.

• Optimal access to sunlight.

• Dedicated access to roof generally available.


• Spread over entire city.

Figure 6 : Sitwell Grove, Harrow, NW London

Figure 7 : Carlton Vale Estate : West London


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Commercial Types

Classical Commercial

• Flat roof density varies though large expansive

units of area are available.

• Production would compete for space with

mechanical plant requirements.

• Optimal access to sunlight as overshadowing

is not prevalent as may be the case in taller

cities like New York.



• Central London

Contemporary Commercial

• Flat roofs are prevalent in new commercial

developments. Increasing prevalence in

number of green roofs indicative of possibility.

• Production would compete for space with

mechanical plant requirements.

• Optimal access to sunlight as overshadowing

is not prevalent as may be the case in taller

cities like New York.



• City of London

Figure 8 : Embankment, Central London

Figure 9 : Spitalfields Development, City of London


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3.2 London’s food economy

In 2000, Londoners consumed 6.9 million tonnes of food 81% of this was imported and over

half a million tonnes was disposed of as waste.40 Its transport contributed accounted for

3,558,650,000 tonne-km of road freight. Fruit and vegetable (including potatoes) consumption

accounted for just over 1.3 million tonnes with an ecological footprint of just under

600,000gha (3% London’s total food related footprint).41 In 2001, the value of London’s fresh

fruit and vegetable market was estimated at almost £2 billion, attributing a value of almost £2

per kilogram of produce.42 In total, London’s food system accounted for 41% of the city’s

entire ecological footprint, which was calculated to be 42 times its biocapacity, 293 times its

geographical area; equivalent to twice the size of the UK.43 The source of this data is now

over 8 years old. In its long term projections, trends were categorically positive in nature

suggesting higher consumption and related effects.

A small proportion of London’s food is home grown. According to DEFRA’s 2002 census,

London has 12,064 hectares of farmland divided into 472 registered holdings with 1,310 farm

employees contributing £32million to its economy.44 397 hectares are committed to fruit and

vegetable production accounting for 17.5% of the total number of holdings. Approximately

30,000 allotments cover a further 831 ha of land.45 Greenhouses in the Lower Lea Valley

covered 300 acres in 2001 producing, among other vegetables and flowers, a third of the

UK’s cucumber output in energy and chemically intensive automated commercial hydroponic

systems.46 No figures exist for domestic or recreational production in back gardens and

rooftops. One study calculated the combined area of London’s 2.8 million back gardens at

30,455 hectares, almost 20% of the city’s total area.47

40 Best Foot Forward, City Limits, (CIWM, 2001) p.12 41 Ibid, extrapolated from 600,000gha divided by 20,685,000gha (London total), p.25 42 Ibid, p.37 43 Ibid, summary p.VI 44 Mel Barrett & Dan Keech, Capital Eats, (Sustain, 2004), p.3-4 45 Tara Garnett, Urban Agriculture in London : Rethinking Out Food Economy, (Growing Cities, Growing

Food, 1999), p481-3 46 James Petts, Urban Agriculture in London, (WHO Regional office for Europe, 2001), p.5 47 Ibid, p.8


29

3.3 Determining a Production Target for London’s Fruit and Vegetables

DEFRA’s 2006 Family Food report outlined the results of a UK food consumer survey. Weekly

fruit and vegetable intakes were tabulated from 2003 to 2006. Below is the relevant extract. I

have highlighted the line of interest to this study which claims the average consumer intake of

fruit and vegetables (including processed products) stood at 2,454g/week in 2006. An 8.2%

intake increase for that period is evident.

For the sake of this study, I assert that a viable production target to meet the fresh fruit and

vegetable consumption of the average Londoner stands at 3kg a week. This figure has been

rounded up to the nearest full kilogram for ease of calculation and encompasses an

assumption that a greater level of health conscious consumer behaviour will justify the

inflation as the DEFRA study supports.

Fruit and Vegetable Production Target

• Population of London 7.2 million people • Average UK consumer fruit and vegetable intake 2,454g/week

(DEFRA 2006) o Figure inflated to 3,000g/week

• 3kg x 52 weeks 156kg/annum • 7,200,000 x 156 / 1000

1,123,200t/annum

Figure 10


30

3.4 The Case for Localised Production and Rooftop Agriculture in London

If it can be agreed that London’s food economy is beyond any reasonable measure of

sustainability, localising production within urban boundaries could be considered a worthy

start towards a better system.

Urban agriculture is far from a new phenomenon; Victory Gardens during the WW2 are the

most vivid recent example of localisation driven by crisis. Girardet cites the example of the

marais in Paris at the turn of the 20th century. 100,000 tons of high value out-of-season

vegetables were grown on 1,400 hectares of peri-urban land using horse manure as fertiliser.

A proportion of output was even exported to the UK.48 Singapore, Dar-Es Salaam and

Moscow are highly lauded examples of cities achieving significant nutritional autonomy.49

Cuba was forced to carry out a comprehensive transition from a model of Soviet, mechanised

agrochemical-intensive agriculture to agro-ecological urban organic farming following the

collapse of the Soviet Bloc in 1989. Oil availability dropped to below half, pesticide and

fertiliser imports fell by 60% and 70% respectively50 and the 57% caloric dependence on

agrochemical inputs drove daily intake levels down from over 3,000 to under 2,000 between

1989 to 1993.51 Cuban scientists, together with a team of Australian permaculture expert, led

an effort to convert all available land within urban boundaries to production. Licenses were

granted to citizens intent on growing food in parks, gardens, vacant plots, rooftops and public

spaces with a condition that a proportion of their output be sold to the state for rationed

distribution. Surpluses were then sold at markets to supplement farmer’s incomes. It is

estimated that Havana now supplies 50% of its own vegetable requirements in a system Paul

Roberts describes as the only comprehensive transition to this date.52

48 Herbert Girardet, Creating Sustainable Cities, (Green Books, 1999), p.53 49 Herbert Girardet, Cities People Planet, (Green Books, 1999), p.239 50 Peter Rosset, The Greening of the Revolution, (Ocean, 1994), p.3-4 51 Paul Roberts, The End of Food, (Bloomsbury, 2008) p.305 52 Ibid p.305


31

Reducing food transport is the most obvious opportunity urban agriculture can offer as the

displacement of supply and demand is constricted. Availability of arable land within urban

boundaries is its primary limiting factor for which this study seeks to propose alleviation.

Vacant rooftops are a short-sighted opportunity cost in this regard. The term

“disintermediation”, coined by environmentalist Paul Hawken is the most appropriate umbrella

term for this theme referring to the reduction of the number of processes involved in the

production and distribution of goods.53

Optimal lighting conditions and direct access to rainwater are also major opportunities from

rooftop production, particularly in low lying cities like London. Supplemented by existing water

infrastructure, an intelligently designed system could minimise overheads. Labour is also

hypothetically immediately available, limiting the need as is apparent with allotments, for

farmers to drive to their plots. High winds at elevated altitudes are also a matter of design and

can be countered or harnessed in microgeneration.

Girardet argues that contemporary planning policy does not welcome urban agriculture as it

carries with it a messy, incompatible stigma.54 While I agree that livestock may be worthy of

such a stigma, I would argue that compatibility is a question of design. Production of fruit and

vegetables need not be the source of unpleasant odours and contamination if carried out in

controlled circumstances using safe inputs. Conventional agrochemicals are categorically

unsafe and can be substituted with ecologically sensitive alternatives and directed design.

Rooftops in this regard could hypothetically protect production from surface pests, theft and

vandalism with appropriate access design and accommodate integrated pest management

(IPM) strategies that are pesticide free.

53 Nancy Jack Todd & John Todd, From Eco Cities to Living Machines, (North Atlantic Books, 1994), p.116 54 Herbert Girardet, Cities People Planet, (Green Books, 1999), p.252


32

Perhaps the most exciting opportunity, in the author’s estimation, lies in rooftop agriculture’s

compatibility with other metabolic processes within buildings. There is wide precedence in the

circulation of composted organic waste as examples in the following section illustrate.

Girardet cites a 1992 Energy Savings Trust report entitled “Meeting the Challenge to

Safeguard Our Future” which outlines UK schemes combining the waste products from CHP;

hot water and CO2 with greenhouse cultivation.55 Synergy with waste water, stormwater and

ventilation strategies may hypothetically be possible with intelligently designed interfaces that

sensitively integrate with other building functions.

Though speculative, such synergy is attracting increasing attention as the following examples

illustrate.

55 Herbert Girardet, The Sustainable Urban Development Reader, (Routledge, 2004),p.163


33

4.0 Rooftop Agriculture and Architecture


• Presentation of precedence in food production and architecture.

• Introduction to other forms of production

Figure 11 : Roof Top Farm Concept Sketch, Nancy Jack Todd & John Todd


34

Rooftop agriculture has no specific, traceable origin and is known to have been practiced

ever since mankind built roofs capable of carrying dynamic loads, whether it be in simple

plant pots forming part of an ornamental garden or out of necessity as is presently the case in

much of the developing world. The Hanging Gardens of Babylon are an oft-quoted example

of ancient hydroponics though its is not clear if food production was its primary purpose.

Nancy Jack Todd and John Todd were enthusiastic advocates of rooftop agriculture, extolling

their virtues in “From Eco-Cities to Living Machines.

The following extract perfectly captures the spirit of their work and the ideal to which rooftop

agriculture aspires.

56

56 Nancy Jack Todd & John Todd, From Eco-Cities to Living Machines, (North Atlantic Books, 1994), p.115

Figure 12

“The blending of architecture, solar, wind, biological and electronic technologies with

housing, food production and waste utilisation within an ecological and cultural context

will be the basis of creating a new design science for the post-petroleum era”


35

4.1 Production Technique

There are three conventional forms of rooftop food production; Containerised, Intensive and

Hydroponic.

4.1.1 Containerised production

This simply refers to the use of plant pots, soil bags

and any form of container into which soil is layered

and seeds are sown. Soil depths relate to the plants

to be grown in them and there is great scope for

improvisation. As the least capital intensive form of

production it is the most readily implemented,

requiring no more than the assurance the roof can

take the added loading. Containers can be

continually moved and rearranged according to

production schedules and, depending on the size

and weight, can be easily managed by limited labour.

More elaborate schemes use specifically designed

container systems.

Examples are widespread, particularly in the developing world where nutritional poverty

commands the need for such schemes. In 2002, the residents of the Pulkovskaya 9/2

apartment block in the Moskovsky district of St Petersburg formed a cooperative led by Alla

Sokol, and at minimal cost and limited resources planted crops in recycled containers on the

building’s 18,300sqft flat roof (above). Two thirds of the block’s residents were pensioners

who supplied the labour on the roof and in basement composting facilities that supplied

nutrient rich, vermiculture processed organic compost from residents’ waste streams. 57

57 Earth Pledge, Green Roofs, (Schiffer, 2005), p.54-55

Figure 13


36

At the other extreme, Canadian community group Action Comuniterre built a productive

garden on the roof of the Queen Elizabeth Health Centre in Montreal, using 60 specially

designed “Biotop” containers, connected in series to a common irrigation system. A range of

produce was grown prompting the system’s developer, Marc-Andre Valiquette, to estimate a

2,000sqft flat roof could produce a ton of fresh fruit and vegetable in a year (see appendix C).

Containerised production offers the opportunity for immediate and flexible implementation at

virtually any cost. Access and the roof’s ability to take on the extra loading are the only

limiting factors.

Figure 14


37

Cartwright Pickard’s 2007 Homes of the Future Competition entry, Lifehouse, also features a

small greenhouse and the suggestion of containerised production. Proposals like these

illustrate a growing awareness in practice as well as academia. 58

58 http://www.bdonline.co.uk/story.asp?sectioncode=725&storycode=3085832&navcode=2481

Figure 15


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4.1.2 Intensive production

Intensive rooftop food production expands on the many benefits attributed to intensive green

roofs which are classified as having a layer of soil 25-100cm deep above layered root and

water barriers. The depth can be designed to accommodate shrubs, perennials, trees and vines

and would be costly to retrofit onto an existing building given the need to reinforce roof

structure to take the extra loading. Effective integration is more easily designed in from

conception, costs permitting.

Non-agricultural roofs already carry value in their ability to retain stormwater and control its

emission into local infrastructure. Deep soil also acts as an effective form of insulation,

potentially countering urban heat island effects and reducing heating and cooling overheads.

Ecologically, an intensive green roof improves air quality, provides habitat for indigenous fauna

and lends clear aesthetic benefits to roofscapes. Agricultural green roofs add material output to

that list and like containerised production, set up an opportunity to integrate composted organic

waste management into a circular resource cycle.

To my knowledge, the most ambitious examples are McDonough and Partners’ proposals for

the Chinese city of Liuzhou (above), a former agricultural centre in southern China.

Responding to a surging population, the strain placed on available arable land drove the

proposal to raise rice and soy bean production to the interconnected roofs of a series of new

buildings.59

59 http://www.greenroofs.com/projects/pview.php?id=524

Figure 16


39

Below is Mithun Architects’ proposal for the Seattle based “Centre for Urban Agriculture”,

which won “best of show” at the Living Building Challenge in 2007.

Occupying a footprint of 0.72 acres its 23 stories of residential units accommodate over an

acre’s worth of productive area said to be able to meet the requirements of 450 people a year

with a range of vegetables and perennials. An organic café at ground level is also supplied by

food grown above it. 34,000sqft of solar panels claim to meet its residents’ full electrical

requirement.60

Mithun’s proposal also highlights the potential to exploit both lateral and vertical exposure to

sunlight, a principle underpinning another movement in the building integrated agriculture

discourse, namely vertical farming.61

60 http://www.treehugger.com/files/2007/09/mithun_architec.php 61 http://www.verticalfarm.com/

Figure 18 Figure 17


40

The Vinegar Factory at 431 East 91st street in New York is in my view the most complete

example of the possibilities. Comprising a bakery, offices, workshops, ground level retail and

half an acre of covered intensive raised bed organic production on the roof over three levels,

its owner, Eli Zabar, phased its expansion over many years, assimilating and converting

adjoining properties.62

Such examples illustrate the potential for a degree of vertical integration in food distribution.

62 http://vision4ourcities.wordpress.com/2008/08/22/eli-zabars-rooftop-greenhouse/#more-279

Figure 19 Figure 20


41

4.1.3 Hydroponic production is a well established growing technique with origins in the

work of German botanists, Julius von Sachs and Wilhelm Knop in the mid 19th century, who

developed the technique of suspending plants over a nutrient solution protected from

sunlight, using a structural matrix or piled inert material.63

The inclusion of soil or compost varies depending on the type of hydroponic system; with pure

systems excluding it altogether and “simplified hydroponics” using it in both nutrient delivery

and as a structural matrix. Conventional off the shelf systems are typically trays or channels

connected in series through which a carefully regulated nutrient solution is circulated using an

electrical pump. Simplified hydroponics could potentially incorporate local organic waste,

though such systems are typically of lower yield.

Nursery plants are fixed into slots in the tray or channel cover and their roots submerged into

the solution which is absorbed through capillary action. The solution is typically circulated in a

continuous, electrical pump driven loop to ensure all plants are provided for. Direct delivery of

nutrients permits plants to divert energy away from the growth of roots into the development

of leaves and fruit, thus raising productivity at 10 to 40 times that of conventional open field

production, particularly when accommodated within climatically controlled greenhouses.64

Systems are also lightweight, thus potentially avoiding the need for roof reinforcement.

63 James S. Douglas, Hydroponics. (5th ed. Bombay: Oxford UP, 1975). 1-3. 64 Red highlight appendix B

Figure 21 Figure 22


42

In 1998, Changi General Hospital (below), in Singapore, equipped their 2,000 sqft atrium roof

with 1,300 plants grown on a conventional channel based inorganic hydroponic system, both

to supplement their food supply and in a bid to reduce their energy and waste overheads.

The bare concrete roof had been diverting sunlight into nearby wards, raising cooling loads

and creating nuisance glare. The plants intercepted solar radiation which would have

otherwise been absorbed by the roof, thereby reducing utility bills.65

65 http://www.greenroofs.com/archives/gf_nov-dec05.htm

Figure 23


43

Commercial hydroponic systems are typically housed in expansive greenhouses with fully

automated water, nutrient delivery, and light and temperature control systems. These are

highly energy intensive and the inputs are generally industrial chemical products, though

organic substitutes are available on the market. Climatic stability and artificial lighting

maximise the number of growth cycles a plant can carry out, thus ensuring year round

production and maximising yields.

Commercial potential is best illustrated by the services of a recent California start-up

company called Sky Vegetables founded in 2008 by business graduate, Keith Agoada.

Supermarkets in flat roofed buildings seeking to exact value from them are guided through

the construction of a viable greenhouse hydroponic vegetable production model by Agoada

and his team. Renewable energy sources, rainwater harvesting and vermiculture composting

facilities further reduce overhead costs in the provision of food that avoids the need for

refrigeration and transport as it is carried down from roof to shelf.66

66 www.skyvegetables.com

Figure 24


44

4.2 Other Production Techniques

Other proven techniques include combining the principles behind hydroponics with large fish

tanks where fish excrement serves as fertiliser in aquaponics, believed to deliver comparable

productivity as hydroponics with less dependence on chemical nutrient products. Aeroponics

involves spraying plant roots with a nutrient rich mist permitting better oxygen delivery to roots

than liquid substrates.

Documents

WSA V Dissertation Oscar Rodriguez - Rooftop Agriculture · London Rooftop Agriculture: A Preliminary Estimate of Productive Potential 1 Contents 1.0 Abstract 04 1.1 Acknowledgements