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Ch7.Gould.final.2.3.12.text
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Handbook of Metropolitan Sustainability
Chapter 7: Urban Agriculture: Building-integrated Agricultural Systems
Danielle Gould and Ted Caplow, Ph.D.
7.1 Introduction
Every person physically consumes products made from biomass, meaning our livelihoods are inextricably tied
to the crisis facing global agricultural land and water supply. Faced with global urbanization and population
growth, along with the effects of resource scarcities and climate change, cities around the world have become
increasingly focused on improving their environmental, social, and economic sustainability. While strategies
have concentrated on the energy efficiencies of buildings and transportation, they have largely overlooked the
environmental footprint of producing and bringing food into the city.
The design of truly sustainable cities, therefore, must incorporate a more comprehensive assessment of energy,
water, and land consumed during food production, processing, storage, preparation, distribution, and disposal.
One such approach is Building-integrated Agriculture, where farming systems are located on and in buildings,
using renewable, local sources of energy and water. Integrating the farm into the built environment has the
potential to significantly reduce fossil fuel consumption, improve urban ecology, enhance food safety and
security, enrich the lives of city dwellers, and conserve building energy.
The past few years have seen a surge of interest in Building-integrated Agriculture around the world.
Demonstration projects and conceptual studies have run the gamut from ambitious high-rise “vertical farms”
aimed at changing mankind’s relationship to landscape, to greenhouse floating on barges in city centers, to
ecological mini-parks growing everything from fish to pumpkins where community-revitalization and job
growth are the primary objectives.
7.1.1 Global challenges regarding population,landscape, and agriculture.
Pressures related to population growth, the environment, and agriculture will challenge the sustainability of our
global food system and our ability to meet climate change goals. Globally, agriculture occupies 40% of the
world’s land surface, uses 60% of fresh water withdrawals worldwide, and causes between 17 and 32% of
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world greenhouse emissions (Bellarby et al, 2008). Agriculture is also the largest source of water pollution, a
role perhaps most obviously manifestedin the coastal “dead zones” that have become common around the
mouths of rivers that drain large agricultural watersheds, including the Mississippi River in the United States
and the Danube River in Europe.
Global population is expected to exceed 9 billion by 2050. 6.4 billion of those people are expected to be urban
dwellers; double the 3.3 billion in 2007(ESA, 2007).According to FAO estimates, in order to meet the
nutritional needs of this growing population, agricultural production will need to increase by a minimum of
70% (FAO, 2010). Experts also predict that by 2050, global warming will cause widespread shortages of food,
water, and arable land within a broad belt extending north and south of the equator and encompassing some of
the world’s most densely populated regions (Lobell, 2008) (Pollan, 2010).
As cities expand in both population and area, they will require increasingly extensive infrastructures for
transporting and distributing food into the city. Within the current system, food in the United States travels an
average of 1,500 miles to reach urban consumers, adding to traffic congestion, fossil fuel consumption, air
pollution, and carbon emissions (Pirog and Benjamin, 2003). As an example, the conventional production a
single kilogram of tomatoes in the United States requires 170 ml of diesel fuel, 1.3 mg of pesticide and no less
than 140 liters of fresh water. During this process between one half and one kilogram of carbon dioxide gas is
released into the atmosphere, according to New York Sun Works analysis (New York Sun Works, 2008).
At the same time, increasing urbanization and the global construction boom have underscored the importance
of efficiency in the built environment. In the United States, buildings account for 39% of energy use, 72% of
electricity consumption, 12% of water consumption, and 39% of carbon dioxide emissions (EPA, 2009).
Figures for Europe are similar (Balaras et al, 2007).Considered separately, agriculture and building both have
enormous ecological impacts; by integrating them the aggregate impact can be reduced. This potential for
impact reduction, and the parallel potential for economic savings that accompanies it, are the driving forces
motivating Building-integrating Agriculture.
7.1.2 Food System Overview
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A food system is comprised of all the processes involved in producing, processing, packaging, distributing,
marketing, consuming, and disposing of food. Approximately 80% of the energy consumed in the U.S. food
system is used for the processing, packaging, transporting, storing, and preparing of food (Hill,
2008).According to Lester Brown of the Earth Policy Institute, we consume two-thirds as much energy
transporting food as we use to grow it (Wilson, 2009).
While in 1940 every calorie of fossil-fuel energy produced 2.3 calories of food energy, we now invest 10
calories of fossil-fuel energy in the production of a single calorie of the food sold in supermarkets (Pollan,
2008).As ever more attention is directed at the environmental flaws in the existing agricultural industry, and as
global climate change and its implications place additional constraints on available resources of land, water,
and energy, the need for creative and adaptive methods of food production has become clear.
A small number of cities have begun incorporating food policy into the their larger environmental
sustainability initiatives. In 2008, Greater London Authority commissioned London's Food Sector Greenhouse
Gas Emissions, a report aimed at quantifying the GHG contributions of London's food sector. The study found
that London's food sector produces approximately 19 million tons of CO2 annually through production,
manufacturing, distribution, retail, and consumption (Brooklynhurdst, 2008).These food sector emissions
represented more than one fifth of the city’s total annual emissions of 90 million tons of CO2 (Greater London
Authority, 2010). The Swedish National Food Administration launched new food guidelines that reflect CO2
emissions on grocery items and restaurant menus, after a 2005 study found that food consumption was
responsible for one quarter of the nation's per capita emissions (Rosenthal, 2009).
7.1.3 Opportunity for Building Integrated Agriculture
With nearly half of the world’s population living in urban areas, the rationale for growing more food in the city,
close to the point of consumption is becoming increasingly clear to municipalities. Urban farming has enjoyed
a steady growth in popularity in recent years, as has consumer demand for local produce. In most major
metropolitan centers, however, city farms tend to be small, with only modest output, resulting from the high
cost of real estate.
Given the absence of land, a chance exists to produce significant quantities of food for urban populations,
leveraging underutilized rooftop space and building facades. The opportunity arises out of the adaptation of
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farming methods found in the greenhouse sector, especially hydroponic techniques, combined with energy-
saving innovations. If designed well, bringing agriculture into the built environment has the potential to
significantly reduce fossil fuel consumption, improve urban ecology, enhance food safety and security, enrich
the lives of city dwellers, and conserve building energy.
As a theoretical example, rooftop surveys of solar power potential indicated that New York City has sufficient
rooftop real estate to meet 100% of the fresh vegetable demand for the city's entire population. A 2006
Columbia University study on rooftop PV potential estimated that more than 5,000 ha of unshaded rooftop
space exist in the five boroughs of New York City (Ettenson et al,2006).Based on the modest commercial
hydroponic production yields reported on the Science Barge (Caplow and Nelkin, 2008) and the per capita
fresh vegetable consumption in the US (Rosenfeld, 2010), this unused rooftop space is capable of meeting the
entire fresh vegetable demand of over 30 million people. While a theoretical figure, it serves to illustrate the
enormous potential for year-round, local food production in NYC, even if only a small fraction of these
unshaded rooftops hosted high yielding hydroponicfacilities.
Most urban buildings, due to their size, dense occupancy, and internal power consumption, discharge
substantial amounts of heat through the building envelope all year round, whether deliberately or otherwise.
This heat is often difficult and expensive to recapture for building use, but is much easier to use as a source of
heat for plants. Among other advantages, plants welcome the high levels of carbon dioxide in the exhaust air
from building ventilation systems, the result of human respiration. Because hydroponic greenhouses are
relatively light, installation on rooftops does not normally require significant structural reinforcement to the
host building (Caplow and Nelkin, 2007).
7.2 Definition
Building Integrated Agriculture (BIA) is a new approach to food production based on the idea of locating high
performance hydroponic farming systems on and in buildings, using renewable, local sources of energy and
water (see Fig. 7.1).
Greenhouse hydroponics is a technique for growing plants, especially vegetables, in nutrient-rich water. The
water contains the essential mineral nutrients the plants need, removing the need for soil. Recirculating
hydroponics, the most modern and environmentally sustainable method, reuses the nutrient solution and water
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until it is depleted of useful elements. Hydroponics employs engineering to optimize crop production, quality,
and yield. (see Fig. 7.2)
7.2.1 System description
BIA systems are located on and in mixed-use buildings and are designed to exploit synergies between the built
environment and agriculture. Installations typically include features such as recirculating hydroponics, waste
heat captured from a building's heating-ventilation-air condition system (HVAC), solar photovoltaics or other
forms of renewable energy, rainwater catchment systems, and evaporative cooling. Whether horizontal
(rooftop) or vertical (facade), system components vary based on building size, structural capacity, local
climate, and light availability. (see Fig. 7.3)
7.3 Ecological Performance
BIA is an environmentally sustainable strategy for urban food production that reduces our environmental
footprint, cuts transportation costs, enhances food security / safety, cools buildings, and combats global
warming.
In the United States, each hectare of rooftop vegetable farm could on average free up 20 hectares of rural land,
save 74,000 tonnes of fresh water each year and, if fully integrated with building heating systems and onsite
solar power, eliminate 1000 tonnes of CO2 emissions per year compared with a conventional greenhouse. A
well-designed system, adapted to work in the heart of the city, where both transport and heating costs have
been substantially reduced, results in a financially viable business.
[insert table 1 here]
7.3.1 Water
Agriculture is the largest consumer of fresh water, using around 70% of all freshwater withdrawals worldwide
(World Economic Forum, 2009). As global population grows, agriculture will increasingly compete with
domestic and industrial demand, which will inevitably increase the cost of the resource. For example, it can
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take as much as a tonne of water to produce the wheat in a single loaf of bread. Vegetables are not quite as
thirsty as grains, but it can still take hundreds of liters to produce a kilogram of fresh vegetables, using
conventional methods. According to estimates, by 2025, 1,800 million people will face absolute water scarcity,
which will only be intensified as rapid urbanization taxes surrounding water resources (FAO). Particularly in
desert environments, water conservation has become one of the fundamental building block of sustainable food
production.
Water management is a key feature of the BIA systems employing recirculating hydroponic technology,
harvesting rainwater, and using graywater from the host building. Hydroponic agriculture is the most water
efficient form of agriculture available in the world and consumes up to ten times less water than conventional
agriculture, while also eliminating pollution from chemical pesticides and fertilizer runoff (Brown JE, 1995).
Plants are grown without soil, with their roots in direct contact with a nutrient-enriched flow of irrigation
water. The plumbing is enclosed to reduce evaporation, and arranged in an endless loop so that all of the water
is eventually taken up by the crop.
Integrating the greenhouse with the host building, creates an opportunity to utilize Graywater (from sinks,
showers, food preparation, cosmetic water features, etc) either directlyin the case of certain crops, or after
passing through a vegetative “living machine” to improve water quality and remove impurities that might harm
the crop. Filtered graywater may also be used for evaporative cooling systems.
In extreme desert climates, where evaporative losses both from the plants and associated mechanical cooling
systems might at times be large due to high solar input, water efficiency can be further improved by recovering
exhaust air water. In this technique, as air is pushed out of the greenhouse, moisture is condensed into a colder
surface and returned to the irrigation or cooling systems.
7.3.2 Power
Crop quality and yield are largely functions of climate control within the greenhouse environment. Maintaining
constant temperature and humidity levels in a greenhouse allows year round crop production but also presents
an energy and efficiency challenge. In northern latitudes, winter-time heating accounts for the majority of
energy demand and CO2 emissions; nearly all of this heating need is met using fossil fuels.
When compared with a conventional, slab-mounted greenhouse, rooftop integration yield direct energy savings
by eliminating heating losses through the building roof and the greenhouse floor, and by capturing waste heat
from the building exhaust air. Special greenhouse design features, including double-glazing and a thermal
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blanket, can result in substantial additional reductions in heating demand. Locating the project in a dense urban
area, where temperatures are warmer due to the urban heat island effect, also plays an important role in
reducing heat demand. The remaining heating needs of the facility can be met using renewable fuels, such as
biodiesel or waste vegetable oil, virtually eliminating net CO2 emissions from heating.
In warmer climates, cooling loads present the energy challenge. A greenhouse placed on the roof of an urban
building provides a suitable space to implement a large evaporative cooling system for the combined structure.
Without the greenhouse, evaporative cooling systems would likely be unfeasible for the building due to
constraints of space, humidity, and/or cost(Caplow and Nelkin, 2007). Energy can also be saved in the
combined structure by the elimination of solar gain and thermal losses through the building roof, because this
surface now becomes the floor of the greenhouse, with approximately the same temperature above and below.
The electrical needs of a Building Integrated Agriculture facility can be met by on-site solar photovoltaics.
Solar photovoltaics are a particularly appropriate fit for Controlled Environment Agriculture as peak electrical
demand coincides with peak electrical supply: strong sunlight on a hot summer afternoon. Electrical load can
be minimized by using natural ventilation, evaporative cooling, and high-efficiency pumps and fans.
The Science Barge, a 120-square-meter hydroponic greenhouse constructed on the steel deck of a barge in New
York City, was operated as a prototype and research facility for environmentally sustainable urban food
production. The facility’s daily power demands, were met onsite by a 2.4 kW solar array, a 2 kW wind turbine
array, and a 5 kW generator running on biodiesel (Caplow and Nelkin, 2007).Data from a 24-square-meter
cucumber plot located in the greenhouse during the summer months were collected to evaluate potential for
rooftop integration. Weekly cucumber yields averaged 1.3 kilograms per square meter, using 1.4 kWh square-
meter of electricity. A ratio of approximately 3:1 between greenhouse floor area and solar panel area (or 40
peak watts per square meter of greenhouse) would allow 100% solar operation (Caplow and Nelkin, 2007).
7.3.3 Carbon
Carbon efficient energy supply options for BIA include solar photovoltaics, organic waste recovered onsite and
from the city at large, energy offset savings from shading and cooling of host buildings, and energy offset
savings from avoided imports of the fruits and vegetables produced onsite.
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Solar photovoltaics can be strategically integrated into the greenhouse structures themselves. In most
greenhouse geometries at most latitudes, including in the UAE, there are portions of the greenhouse roof that
can be shaded without reducing available light to the crop. There are also portions of the structure that cover
processing, access, and mechanical areas, where energy management and worker comfort will be enhanced by
overlying solar panels. Finally, there are vertical as well as horizontal surfaces on the building envelope to
consider for both crop and solar panel deployment. BIA Partners has extensive direct experience with building-
integrated photovoltaics (BIPV), and with solar panels deployed in conjunction with hydroponic greenhouses.
7.3.4 Materials
The majority of BIA implementations require a greenhouse. In contrast to the majority of extensive field
greenhouse systems, intensive BIA systems justify rigid, high-quality, and long-lasting materials. Greenhouse
structures may be made from aluminum or steel; in both cases the materials have a lifetime measured in
decades and can be recycled. Glazing systems are typically either single-pane glass, which lasts as long as the
structure itself, or multi-pane polycarbonate, which must be replaced every 5 to 10 years due to photo-
degradation.
The hydroponic growing systems within the greenhouses are dominated by PVC and HDPE parts, including
buckets, tubes, gutters, and hose. Although lightweight and ubiquitous throughout modern society, these
materials have a mixed ecological profile (due to emissions during manufacture, particularly with regard to
PVC, and disposal concerns with regard to most plastics) and represent an area for continued improvement in
BIA.
Consumable materials for advanced hydroponic systems are minimal. Plants are typically rooted in rockwool, a
mineral product, and often further supported by mineral media that can include expanded clay, perlite,
vermiculite, etc. New and promising products in this market include expanded recycled glass and other
“unmined” solutions. Plant nutrition is provided by mineral salts manufactured exclusively for the hydroponics
industry. In the fully recirculating nutrient flow systems that represent the mainstream of modern BIA, these
salts are almost entirely absorbed by the plants. Both initial application and any residual waste stream are both
very small in comparison to the food produced.
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A quantitative analysis of material flows in proposed large-scale BIA greenhouses for the states of Texas and
Massachusetts, USA, was completed at BrightFarm Systems in 2010. The modeling revealed that the embodied
energy in the greenhouse structure and its subsystems, when amortized over the expected lifetime of this
equipment, accounted for less than 10% of the aggregate emissions of carbon dioxide (and other potential
greenhouse gases) to the atmosphere from the BIA greenhouses. These aggregate BIA emissions, in turn, were
typically about one-third less than the total emissions in the conventional food supply chain that would be
replaced by the BIA system.
7.4 Community Impact
The need to transport perishable vegetables long distances from farm to table lies at the heart of problems
associated with food quality and nutritional profile. Long transportation means shelf life needs to be extended
by way of techniques that alter the quality of the vegetables. Tomatoes, for example, are mostly grown with
shelf life in mind, harvested before they are ripe and allowed to ripen during transportation or in ethylene
chambers (Yokotani et al, 2009) techniques often damage flavor and nutritional quality, while also having a
negative impact on the health of a community.
Minimizing the journey from farm to fork creates a plethora of benefits for communities including: improved
access, food security, nutritional profile, and educational opportunities(see Fig 7.4).
Access
Lengthy transportation, produce spoilage, and middlemen raise the price of perishable fruits and vegetables.
High retail prices for items such as lettuces, tomatoes, and cucumbers discourage many low-income
communities from buying, and supermarkets from stocking, these items. Yet perishable fruits and vegetables
are critical components of a healthy diet.
Millions of city dwellers worldwide live in areas with limited opportunities to obtain fresh produce, also
referred to as Food Deserts (Bitler and Haider, 2009). These areas tend have the highest levels of diet-related
diseases; obesity and diabetes in developed countries; and anemia, scurvy, and rickets in developing world.
Rooftop greenhouse production can provide more fresh, nutritious, and affordable produce directly to
neighborhoods where conventional supermarket chains choose not to sell.
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Food Security
The dramatic fluctuation in food prices is a result of our food system’s dependence upon scarce resources,
particularly fossil fuels. Food price fluctuations disproportionally affect low-income populations who spend a
higher proportion of their income on food. Growing food in the city reduces reliance upon fossil fuels and
enhances food security for those who need it most, especially given the trend to biofuels from food crops
(Brown L, 2007).
Nutrition & Quality
The need to transport perishable vegetables long distances significantly hampers food quality and its nutritional
profile. Long transportation requires the shelf life of vegetables to be extended, which is accomplished through
a variety of unsustainable techniques or by being harvested before they are ready to allow for transport.These
techniques often damage flavor and nutritional quality, while also having a negative impact on the health of a
community.
The prevalence of food borne illness have significantly increased in recent years. The controlled environment
of the greenhouse helps to reduce or eliminate the risk of pathogens. Food produced in the city, for local
residents, needn’t travel more than a few kilometers, reducing the handling. This proximity to the end-user
ensures not only a fresher, more nutritious product but also greater control over the food delivery chain. (see
Fig 7.5)
Education
As climate change threatens their future, and rates of childhood obesity and diabetes continue to rise, it is
critical that children learn about the food they eat, where it comes from, and how it is grown. The lack of
transparency and traceability in major supermarkets and fast food restaurants has effectively silenced children’s
questions about how their food is made. This is especially true of city kids.
Rooftop sustainable greenhouses provide a unique, hands-on location for teaching about environmental
sustainability, food production, and nutrition. In the greenhouse, students benefit from access to living plants
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and natural biological processes. Soil and hydroponic growing areas, aquaponic systems, and worm
composting stations provide hands-on opportunities to engage with nature. “Green” learning environments
have also been demonstrated to improve student focus and performance and increase student learning and
content retention.
7.5 Other Forms of Urban Agriculture
Building-integrated agriculture represents a balanced and practical approach to urban agriculture, combining
technically and commercially proven farming practices with fairly straightforward building integration
practices not unlike those required for green roofs, solar panels, passive ventilation, and daylighting systems.
There are various other forms of urban agriculture ranging from the technically mundane but popular and
effective open-air market gardens and backyard plots, all the way to unproven concepts such as Vertical
Farming, which refers to food cultivation on multiple interior levels of high-rise buildings.
The growing popularity of all forms of urban agriculture is striking. Although not a new idea in a historical
sense, urban farming appears to have begun accelerating since the latter half of the 20thcentury largely in
response to unprecedented growth in the size and relative popularity of cities. Urban agriculture is not
exclusive to either wealthy or poor nations, but can be found in one form or another at all social and economic
levels, ranging from urban market gardens in sub-Saharan Africa largely irrigated by wastewater to high-tech
greenhouse schemes to provide onsite food for the newest and wealthiest cities of the Middle East and China.
7.6 Case Studies
A selection of projects from BrightFarm Systems illustrates the range of applications, but is not intended as a
comprehensive summary of the many BIA projects blooming around the world. All of these projects are either
built, under construction, or engaged in a formal feasibility study.
7.6.1 The Sun Works Center for Environmental Studies
The Manhattan School for Children, a publicly funded state school, hasdevelopeda new 150 m2 greenhouse
classroom on a rooftop four stories above ground. Opened to students and teachers in 2011, the greenhouse
includes seating for 35 students, hydroponic systems to grow lettuces, tomatoes, peppers, cucumbers,
aubergine, and squash for the school cafeteria; an aquaponics module with tilapia, catfish, and mollusks; a
composting and vermiculture operation; solar panels; rainwater capture; and a web-based interface for data
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logging and display. This second-generation pedagogical system supports classes in biology, chemistry,
physics, ecology, and nutrition, and is serving as a pilot project for adaptation to hundreds of other public
schools in New York City. Projects built around this model in New York City schools are expected to range in
scale from modular classroom systems to full-scale rooftop greenhouse implementations.
7.6.2 The Science Barge
Built in 2006, the Science Barge (see Fig. 7.6) is a prototype sustainable urban farm on a mobile platform,
including a 120-square-meter recirculating hydroponic greenhouse. It is climate-controlled by passive
ventilation, evaporative cooling, and a vegetable oil furnace. The facility is self-sufficient, with all irrigation
via rainwater capture, and all electricity provided by solar panels, wind turbines, and a biodiesel
generatorrunning on commercially-obtained 100% plant-derived fuel). The farm grows tomatoes, cucumbers,
squash, bell peppers, lettuce, and herbs, with zero net carbon emissions, zero chemical pesticides, and zero
runoff. The Science Barge is a powerful environmental educator. Since opening to the public in May 2007, the
facility has hosted over 20,000 visitors, including students from over 200 local schools, and journalists from 45
countries.Produce yields for most of the barge crops were around 50 kg per m2,(Caplow and Nelkin, 2007) and
much of this produce found its way into school lunches or local farmers markets.
7.6.3 Forest Houses
The Blue Sea Development Corporation's new state of the art affordable housing complex, planned for the
South Bronx, will feature a 10,000 square foot fully integrated hydroponic rooftop farm, designed by
BrightFarm Systems.Like many inner city, low-income communities, the South Bronx suffers from food
deserts, where residents lack access to fresh vegetables at affordable prices. The rooftop farm will be able to
supply enough produce to meet the annual fresh vegetable needs of up to 450 people. It will also be capable of
capturing 750,000 liters of stormwater, and mitigating 80 tons of CO2 each year. Like many inner city, low-
income communities, the South Bronx suffers from food deserts, where residents lack access to fresh
vegetables at affordable prices. If an optional grid-tied solar photovoltaic system is installed, the net electrical
footprint will be zero.
7.6.4 Gotham Greens
Gotham Green's 12,000 square foot is New York City's first commercial-scale rooftop farm. An annual yield of
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30 tons per year of premium-quality fruit and vegetables has a wholesale value of approximately $500,000.
Over a 20 year design life, this greenhouse will save up to 4,000 barrels of oil compared to a conventional
greenhouse, and conserve 80,000 tonnes of fresh water.
On a per unit basis, CO2 emissions at this farm are modeledto be around 0.26 kg of CO2 per kg of vegetables,
including supplemental heating, grid electricity, and the embedded energy costs of the steel and polycarbonate
greenhouse structure. Net project emissions will be somewhat higher if supplemental lighting is used to boost
winter crop yields. Water demand of 19 liters per kg issubstantially provided by rainfall.
7.6.5 BrightFarms LLC
BrightFarms finances, builds and operates the hydroponic greenhouse farms on supermarket, distribution
center, and other commercial buildings (see Fig. 7.7). Since acquiring rooftop greenhouse design consultancy
BrightFarm Systems in December 2010, ten supermarket chains have agreed to work with BrightFarms,
including five of the top fifty national chains. Their first three commercial greenhouses will open in early 2012.
A single acre Brighfarms greenhouse will yield 500,000 lbs of produce per year, generating $1 to $1.5 million
in revenue and creating 8 to 16 new jobs. Based on estimates for a 1 acre greenhouse located in Chicago,
Illinois, the greenhouse will grow produce with 14 times less land and up to 9 times less water than
conventionally grown produce, which has been trucked in to a Chicago-based supermarket. According to
company estimates, the farm will mitigate approximately 740 tons CO2 and 430 lbs of pesticides annually.
Rainwater capture features will result in 5 million gallons of water saved per year.
7.7 Sustainability challenges and future trends
The development of a widespread, commercially viable BIA sector faces a number of barriers including
identifying appropriate sites, navigating zoning, building and permitting regulations, and managing efficient
productdistribution. A number of technical challenges must also be addressed, primarily related to replicable
energy saving, more sustainable lighting options and waste-heat capturing innovations.
While the cost of building BIA facilities renders their application less feasible for small residential buildings or
buildings with pitched roofs, there are a significant number of appropriately sized and structurally sound, flat
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roofs on supermarkets, warehouse roofs, school and hospital roofs, or shopping centers. Cities such as New
York City, Boston, and Vancouver are all investing resources to understand the benefits of and opportunities for
encouraging BIA. In the future, much more research is needed to quantify absolute energy benefits, carbon
sequestration, and potential for workforce development. Additionally, more comprehensive and precise
information about the energy consumption and emissions from conventional agriculture and distribution is
needed to fully measure the benefits of BIA.
One of the more exciting innovations currently under research is the patented Vertically Integrated Greenhouse
(VIG), a highly productive, lightweight, modular, climatically responsive system for growing vegetables on a
vertical curtain wall façade that was designed by an interdisciplinary team led by New York-based BrightFarm
Systems, with contributions from the fields of ecological engineering, plant science, architecture, and HVAC
engineering (Caplow et al 2008).
In the building sector, the double skin facade (DSF) is an innovation thatcan reduce the energy used for space
conditioning in modern high rise buildings by up to 30%. A double skin facade consists of a vertically
continuous void space enclosed by a second curtain of glazing over the entire facade. A double skin provides
solar heat in winter, buoyancy driven cooling flows in summer, and allows opening windows year round.
Despite these advantages, double skin facade applications remain limited due to economic concerns and the
need to install a large shading system within the cavity to realize the full benefits.
The Vertically Integrated Greenhouse combines a double skin façade with a novel system of hydroponic food
production, for installation on new high-rise buildings and as a potential retrofit on existing buildings (see Fig.
7.8 and 7.9). In this design, crops are cultivated behind a glazed curtain wall on the southern facade of a
building, on an array of horizontal trays suspended on two vertical cables. The cables are looped around
pulleys, driven by a computerized motor on the farming level. The VIG is structured in modules that are 40 m
high. Shallow trays of plants, 2.0 m long, are suspended between the cables by swiveling clamps at each end.
Seeds are germinated in flat, 2.0 meter long trays at the bottom level, and planted into the bottom tray. Then,
trays rise up the front of the facade, pass over the pulley, and down the back, returning to the bottom for
harvest. The vertical alignment of the front and back trays can be controlled by a slight turn of the pulleys,
similar to adjusting a Venetian blind. This feature allows the VIG to track solar elevation in real time
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throughout the day and year, optimizing light capture. Occupants can see out of the building through the ‘slats’
formed by the dual row of plant trays (Caplow et al, 2008).
The Vertically Integrated Greenhouse functions alternatively as an adaptive solar energy capture device and a
biological shading system, in winter and summer respectively. Hence, in addition to producing food, the
installed plants, in effect, reduce building maintenance costs by providing shade, air treatment, and evaporative
cooling to building occupants.
7.7.1 Technical
For successful, year-round vegetable production, a greenhouse must maintainconstant temperature and
humidity levels, which is accomplished by use of a computerized controller.
First stage cooling, such as the use of a passive roof and side vents that escalates to forced ventilation when
required, is used to minimize energy demand. Ventilation, however, is only effective as long as the outdoor
temperature remains acceptable for plant growth. In the summer months, when outdoor temperatures climb
above acceptable levels, evaporative cooling is used in place of ventilation. Evaporative cooling involves
drawing air through a large evaporative pad wall composed of special corrugated cardboard sheets that
captures and re-circulates excess water within the pad wall. The Greenhouse air is then exhausted by fans.
When the greenhouse temperature is too cold, a ductless forced air heating system is employed.
In warmer climates, multi-stage cooling systems are necessary to minimize energy demand. Beginning with
passive ventilation, subsequent stages of cooling could include a combination of retractable mechanical
shading, forced draft, and evaporative cooling options. For maximum cooling, some form of ultra-high
efficiency heat pump must be considered.
7.7.1.1 Technical example: Vertically Integrated Greenhouse
Perhaps one of the more fully envisioned applications of Building-integrated agriculture is the “Vertically
Integrated Greenhouse”, or VIG, first proposed by a consortium of engineers and architects in 2008 (Caplow et
al, 2008).
The VIG can be deployed in many configurations, but its application to a double skin façade, a
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well‑established architectural technique in both new build and retrofit scenarios, best illustrates its versatility
in providing both cost-saving building services and potential crop revenue. (As of this writing, the VIG had
been physically deployed in a half dozen demonstration systems but not yet in a true double skin façade;
however, the design has been introduced in a variety of proposals around the world and the features and
benefits have been analyzed). (see Fig. 7.10)
In a typical VIG design, a glazed curtain wall (a “double skin”) is located 1.5 m outside the southern façade.
The void space behind this curtain wall is the VIG, containing stacked rows of hydroponic vegetable crops.
• The VIG is structured in modules that are up to 40 m high. Crops are cultivated in innovative plant
cable lift (PCL) systems, composed of two wire cables looped around pulleys, driven by a
computerized motor on the farming level. Shallow trays of plants, 2.0 m long, are suspended between
the cables by swiveling clamps at each end.
• The PCL design is based on a well-established hydroponic method called nutrient film technique
(NFT). A thin film of water runs along the bottom of each tray, delivering nutrients to the roots of
leafy plants, before flowing down to the next tray. The solution is recovered at the farming level for
reuse. Transpiration is limited to 10% of the flow rate by design.
• Seeds are germinated in flat trays on the bottom level, and planted into the bottom tray. The trays rise
up the front of the facade, pass over the pulley, and down the back, returning to the bottom for
harvest. The entire trip takes approximately 30 days.
• The vertical alignment of the front and back trays can be controlled by a slight turn of the pulleys,
similar to adjusting a Venetian blind. This feature allows the VIG to track solar elevation in real time
throughout the day and year, optimizing light capture. Occupants can see out of the building through
the ‘slats’ formed by the dual row of plant trays.
• Vertical spacing between trays on the cable can also be varied. Rows will be more tightly spaced in
winter, when the sun is lower, resulting in steady yields year-round.
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• In winter, the VIG is an effective solar capture device, warming and insulating the glazed façade of
the building. On winter nights, exhaust air from the building can be ducted to the VIG to maintain
plant temperatures.
• In summer, the VIG shades the interior of the building, and provides a source of fresh air to occupants
with opening windows. The VIG reduces solar heat gain by absorbing energy as latent heat, through
transpiration. The VIG mitigates the urban heat island effect like a green roof, but over a much larger
area.
7.7.2 Economic model
Integrating a farm into a building offers all of the building performance benefits of a more conventional green
roof, and results in a lower combined energy bill than if the components were separate. These systems are
achievable with extant technology. Projects such as Gotham Greens 10,000-square-foot (930 m2) greenhouse
cost approximately $1.4 million to build.
The economics of BIA were the subject of a 2011 article in the New York Times business section (Rifkin,
2011). Lufa Farms sells their produce directly to consumers through a Community Supported Agriculture
model. Consumers subscribe for either 12 or 24 weeks of a weekly vegetable basket that they pick up at
designated drop-off locations. BrightFarmsenters into 10-year purchase agreements with credit-rated grocery
retailers, requiring the retailer to purchase 100% of the BrightFarm’s output at fixed prices. BrightFarms
simultaneously contracts with third party growers (experienced local farmers) to guarantee the volume and
quality of output. According to CEO Paul Lightfoot, they are able to build a one-acre farm for approximately
$2 million and generate $1 to $1.5 million in annual revenue.
7.7.3 Urban planning
Increased attention towards sustainability in urban planning has largely focused on issues concerning
residential and commercial buildings, transportation, waste management, energy and water consumption, and
the economy; the food system has been absent in the discourse and planning.
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BIA is highly compatible with bioclimatic design principles, advanced by architects and environmental
designers, such as Ken Yeang(Yeang K and Richard, 1994), for the past few decades. Food crops grown on,
and in, buildings can provide heating, cooling, and ventilation, services for the building that decrease energy
use while improving the microclimate around buildings. In addition to thermal comfort and energy savings,
food crops can enrich the aesthetics and the psychological comfort of building inhabitants. Studies have
indicated that a ‘green’ work environment raises worker productivity by 1.0 to 1.5% (Kats, 2003).
In addition to existing cities, BIA has a strong role to play in new, planned urban developments, such as
Masdar in the UAE andDogtan in China. These cities are designed to minimize fossil fuel and water
consumption, as well as the external outputs of sewage, garbage, heat, pollution, and CO2. Integrated,
ecologically sound food production systems would form a central feature of truly renewable ecocities of the
future.
Over the past few years, designers, architects, urban gardeners, and artists have embraced the application of
green roofs and green walls owing to their economical, environmental, and aesthetic impact. Rooftop farms
create an equally aesthetically appealing and more productive opportunity to make use of underutilized space
that also provides new ways of growing meaningful amounts of food for local populations.
7.8 Sources of Further Information
BrightFarms: www.brightfarmsystems.com
Controlled Environment Agriculture Center (CEAC): http://ag.arizona.edu/ceac/
Lufa Farms: https://lufa.com/
Sky Vegetables: http://www.skyvegetables.com/
Gotham Greens: http://gothamgreens.com/
The Vertical Farm Project: http://www.verticalfarm.com/
Biog Box Farms: http://www.bigboxfarms.com/
Valcent: http://www.valcent.eu/
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