A study conducted by:
Kristin Anderson, Nicola Areshenko, Alan Brown, Jennifer Buskey, Amanda Colligan, Marisa Dahlman, Catherine Dell’Orto, Catherine Tuglus

Course Director: Dr. Dickson Despommier
Columbia University, Spring 2003

Introduction

The process of urbanization has occurred at the end of the twentieth century and is expected to continue well into this century with nearly half the world population living in urban areas now and increasing by two percent each year. (UNEP) With the enlarging global population and increasing urbanization, the demands on resources will contribute to further degradation of the environment. The implications of this rapid urban growth will make sustainability of the urban settlement a priority. The ideal urban settlement will reduce environmental degradation with the recycling of wastes for production of energy and food products for consumption.

The Vertical Farm is a concept that seeks to address the major concerns of the environmental degradation of the modern city by composting, recycling waste and farming in a standard tenement building. The "ecological footprint" of the city will be lessened and therefore the city will become a more sustainable setting. The reduction of wastes and the production of foods for consumption will in turn increase the quality of life for all those within the city and its surrounding area. The reduction in transportation of both wastes and of food products and the use of abandoned buildings will directly increase the quality of the urban settling.

The model of the urban Vertical Farm will be in New York City. The negative consequences of the established situation and the impacts of the urban Vertical Farm will be addressed.

Background

Figure 1: The process flow diagram concerning organic products for New York City before and after The Vertical Farm

Sustainable development is becoming more imperative. In the City mass amounts of land and resources are consumed on a daily basis only to result into their eventual burial in a landfill. The vertical farm will make use of what is now considered waste and use it to create energy and food.

A densely populated city such as New York City consumes the resources of the surrounding land at an alarming rate, utilizing over 266,000 acres of land for food alone (Appendix A – calc. 2a), and then land filling over 7 million tons of waste from this food (20). Vertical Farming, in which agricultural products are produced within the city limits, stems from a need to address these concerns. Urban agriculture not only decreases the amount of land used, but also eliminates the need for transportation of food to the city. This effectively decreases fuel consumption as well as the emission of green house gases associated with the food industry.

The goal of Urban Agriculture is not only more efficient land utilization, but also self-sustainability. As mentioned earlier, the current situation is one in which the city imports produce, and exports waste. Urban Agriculture strives to utilize waste and other resources within the city for crop production, thus closing the loop, and therefore creating a more self-sustained city (see figure 1 below). By utilizing these resources, Urban Agriculture should also be effective in lowering the cost of food. This is especially important for the poorer areas of the city, where food cost is a concern.

Available resources within the city limits for use in Urban Agriculture, such as the Vertical Farm, include wastewater, sewage sludge, post-consumer organic wastes, vacant lots, abandoned buildings, rooftops, and, of course, idle hands. There are many ways these resources can be utilized by various Urban Agricultural practices. This report seeks to explore the plausibility of the vertical farm specifically its impact on waste management practices, the ecology of the city, and other societal impacts.

Current Agriculture in the United States

Figure 2: A flow diagram of the vertical farm processes. It shows the internal cycles, and the external inputs. Things that are not shown include any excess water flow or flow values for streams. Quantities of flow are unobtainable at this time because the project is still in its infancy (8)

The primary agricultural system relies on rural farms to produce all agricultural for urban and rural consumption. In the U.S., 4.4 billion acres were used for cropland production in 2000, 70% of which were used solely for domestic production (23,15). While the population of the U.S. increases by an average by 5,000 each day, the amount of agricultural viable land decreases by 15,000 acres (20). This reduction is primarily due to erosion and encroachment of industry and the suburbs (roads, homes, etc).

Advances in crop management have increased crop yields per acre, however, these advancements generally require an increased use of pesticides and irrigation, resulting in an increase in polluted agricultural run-off. In 1998, it was recognized that one third of the sediment, two-fifths of the phosphorus, and one-half of the nitrogen in surface water was the result of agricultural run-off alone (15). Non-ecologically safe farming practices have also led to an average annual loss of 24 billion tons of topsoil (3). Additionally, liberal irrigation practices have led to major depletions in aquifer levels. The decrease in available fresh water and healthy land increases the sizes of the per capita US ecological footprint. The current “ecological footprint” for food consumption is estimated at 3.2 acres per capita and growing.

Transportation of the crops into cities is another major source of pollution. Currently, agricultural products are produced far from the major areas of consumption- the cities that currently house half of the world’s population (17). It is estimated that, on average, food travels 2000 km before reaching the final consumer (3), resulting in greenhouse gas emissions of approximately 1 kg per 8 kg of food transported (Appendix A – calc. 1b). If the average amount of consumed agricultural produce is taken to be 322 kg per capita, then the average annual release of green house gas per person is approximately 40 kg (12). Food production also uses a large amount of energy for machinery. It is estimated that to produce 1 BTU of food approximately 20 BTU’s of fuel are needed (3).

Current yields of vegetable production in the U.S. produced by conventional horticultural and open field methods in 2001 are, on average, 26,759 Kg/Ha, totaling 35,512,780 metric tons (23). It is estimated though that nearly 3,110,000 tons are left in the field (20) (Appendix A – calc la). This loss, combined with loss during transportation and in the market indicates that over 20% of all food produced in America is wasted (28).

New York City: The Current State of the Agriculturally Unsustainable City

New York City has a population of approximately 9 million people in all five boroughs, plus the visitor influx. The average per capita annual use of agricultural produce is approximately 711 pounds (12). The combined per capita consumption of the entire population of New York City is nearly 3 million tons, which translates into over 108,000 Ha or 266,000 acres of cropland needed solely for growing produce for New York City (Appendix A-calc.2a). The total ecological footprint of food consumption alone for New York City, as a whole, is over 28.8 million acres (Appendix A-calc.2b). This is 1.2% of the total U.S. land area (Appendix A-calc.2c). Food production for New York City requires an estimated 1.4E15 BTU of fuel energy, equivalent to 9.9 billion gallons of diesel fuel annually. In addition, transportation of produce to New York City results in 24 million tons of greenhouse gas emission (Appendix A-calc.2d).

Flow Inventory

Table 1: Flow inventory for the vertical farm. Includes probable flows during start-up, steady state, and shutdown. Input, output, and major internal flows are included

Advantages and Disadvantages of Vertical Farming

The Vertical Farm Layout

References for the above picture: (building) http://www.umassmed.edu/research/building/buildingsection.cfm (fish) http://ag.arizona.edu/azaqua/minitapi.gif (worms) http://www.cityfarmer.org/wormcomp61.html (food waste) http://aggie-horticulture.tamu.edu/earthknd/compost/slide9a.1.gif (produce) http://www.thepetprofessor.com/pictures/vegetable-pictures.html (farmmarket) http://www.experiencewashington.com/images/state/10056.jpg

Resources of the City

The resources sought after for The Vertical Farm are the common outputs or excess from the city’s normal processes. Resources being considered as inputs for the farm include; wastewater, post-consumer organic wastes from grocery stores and restaurants, unutilized space, including abandoned buildings and lots, and idle hands.

Wastewater

Wastewater in NYC is a combined stream of greywater, blackwater (along with sludge), and street run-off. “Grey water” is water from showering, dish washing, and clothes washing. “Blackwater” is the water from toilets, and septic tanks, and street run-off is water entering from sewage drains on street level due to rainfall street washing etc. The used water is piped to wastewater facilities in various parts of the city, where it is treated. New York generates wastewater at a rate of 1.4 billion gallons each day (10). There are various ways this resource stream can be used within The Vertical Farm. With water supplies becoming more of a concern, harnessing this resource is very important creating a more sustainable city. This study will concentrate on using greywater and blackwater in vertical farming.

Greywater

Figure 2: Anaerobic-aerobic greywater treatment system consisting of a two stage (three stages can also be used) septic tank, a sand filter, and a planter bed (27).

Small-scale systems are discussed in this study; we could feasibly redirect streams of greywater directly from their sources for use. Of the wastewater produced in New York City, 60% is greywater. Greywater consists of 7 mg/l nitrogen, 13.7 mg/l phosphorous, and 79.4 mg/l suspended solids along with grease, fatty oils and sodium, calcium, fluorine, and various metals and minerals with a BOD5 of 150 mg/l, although the true composition depends on the personal habits of the community (27). There are various biological treatment methods as well as chemical methods already described for greywater use in irrigation or hydroponics, most of which are easily integrated into a small scale Vertical Farm (27).

Two basic systems for greywater pre-treatment are the aerobic and the anaerobic-aerobic system. The aerobic system uses a filtration system before passing the water through a planter bed for biological removal of chemicals. The anaerobic-aerobic system uses a three-stage septic tank to remove sludge and grease followed by a sand-bed system, allowing the water to transition from anaerobic to aerobic conditions before passing it to the planter bed. The latter is generally used when food wastes are present in the greywater. Water exiting the planter bed is of almost potable quality (27). Figure 2 is a schematic of the anaerobic-aerobic system, which is the preferred system in this study.

Blackwater/Sludge

Figure 3: Basic flow schematic of blackwater treatment. Blackwater is passed into an anaerobic digester, which reduces the BOD of the blackwater and breaks down nutrients into more plant usable forms, while producing methane and carbon dioxide. The methane is combusted, producing energy. The effluent from the reactor is then passed through a micropore filter to prepare it for UV radiation/Ozone treatment that removes any remaining pathogens (14, 19, 25, 30).

Blackwater is traditionally the liquid water associated with sewage derived from toilets and septic systems. In NYC, blackwater is separated from the sludge during the “dewatering” process of the combined wastewater stream, which occurs at the Wards Island treatment plant. The sewage is moved there by barge from various other treatment facilities (10). After dewatering, the biosolids are palletized and recycled into fertilizers of various sorts sold to rural areas for utilization. These biosolids could be treated and used within the city limits, although there are some concerns with the current treatment methods (6). There has also been health complaints associated with NYC sludge pellets (18). Due to these complaints, the use of the city treated sludge will not be considered as a possible input for this study. Although the sludge is nutrient loaded, there are other alternative fertilizers that would provide the same service, but without the health concerns (i.e. compost). Blackwater, or the water removed from the dewatering process will, however, be considered. Water is a very valuable resource, and nutrient loaded water is even more valuable to The Vertical Farm. This water, though still contaminated, is in a form that could be further treated by both biological and chemical means, and then utilized. This resource can very valuable especially to hydroponics systems, and can be transported directly from Wards Island by an existing transportation infrastructure (10). The basic characteristics of blackwater are the following: 0.16 g/l BOD5, 0.23 g/l suspended solids, 0.007 g/l phosphate, and 0.51 g/l nitrogen (27).

There are both aerobic and anaerobic methods for blackwater treatment. Aerobic systems include both anaerobic and aerobic components (planter beds), and are used in many places to treat municipal sewage (sludge and blackwater - which is not considered in this study due to lack of community support). A common methodology is known as the “Living Machine” which is in practice in various locations, including one in South Burlington, Vermont, which treats 80,000 gallons of municipal sewage per day (16).

For the purposes of primary treated blackwater, and to utilize all possible resources derived from blackwater, a simpler anaerobic method will be used, which allows for energy production through biogas combustion. Below is a basic schematic of a possible blackwater treatment method.

The initial biogas anaerobic reactor will produce 1 m3 of about 55% methane, 45% CO2 gas for every cubic meter of digester volume (14). The resulting effluent will have an acceptable BOD5, but will conserve a large amount of nutrients not conserved in other aerobic digestion methods. It will not, however, remove all pathogens; therefore a follows the reactor, which will prepare the effluent for UV radiation/Ozone treatment to thoroughly disinfect the effluent of pathogens (19). Because anaerobic processes often emit strong, obnoxious odors, lime treatment may also be used to increase the pH and eliminate odors if necessary (30). Activated carbon control may also be utilized for odor treatment.

Wastewater Summary

Post-Consumer Organic Wastes and Treatment

Post-Consumer Organic Wastes consist of food waste that may be composted as a potential fertilizer source. It is estimated that NYC landfills over 7 million tons of compostable organic wastes each day, which emit approximately 1.8 million tons of greenhouse gas (20). If composted properly, this waste could create nearly 16.1 million tons of rich fertilizer, which could be utilized as a supplemental effluent to processed greywater or blackwater. The basic nutrient content of mixed organic waste compost according to FoodFen study is 6.6 kg N, 3 kg P2O5, 5.4 kg K2O, 1.08 kg Mg, and 0.96 kg S per ton (24). Currently in the U.S. only 6% of organic wastes produced are composted (4).

In some systems unneeded organic waste may be digested to produce energy through biogas production using an anaerobic biogas reactor similar to the blackwater anaerobic treatment schematic. With the help of an anaerobic reactor to add nutrients to a solution, compost can also be used for use in hydroponics (7).

Any organic material can be used for composting, however, the addition of materials that might compete with or destroy fungus or bacteria should be avoided. The ideal pile for composting is 3 cubic feet, which will lead to 1.75 cubic feet when the composting process is complete, i.e. after anaerobic digestion.

Worms will be used to aerate the compost. Full Circle is currently conducting a vermiculture waste management project that uses 100,000 pounds of earthworms to process about 200 cubic yards a day of waste from horse stables at the Louisiana Downs racetrack into compost and worm castings. Not only does this process save the track thousands of dollars in annual avoided feces disposal, the castings are then sold as a soil amendment product, marketed under the Growers Pride label. Earthworms can be expected to convert at least half of their body weight per day into rich worm castings. For the purpose of the vertical farm, the worms would be used to speed the composting process, and would then be fed to omnivorous fish grown within the farm.

The primary purposes of an anaerobic digester are twofold. First, it is an efficient method for breaking down and recycling nutrients from treated blackwater, organic material shipped into the vertical farm, and wastes produced by the vertical farm, in order to nourish both the agricultural and aquacultural operations of the farm. Second, it is an excellent mechanism for generating energy for the vertical farm by producing methane, which can be burned to produce electricity and heat. Additional functions of the digester are to eliminate pathogenic organisms, to provide carbon dioxide for photosynthesis, heat, and adjustment of pH of the nutrient solution (1).

Anaerobic digestion is not a new concept. The first anaerobic digester was built in India in 1859. In 1985, energy from anaerobic digestion fueled street lamps in England. In 1998, it is estimated that 600 farm-based digesters were in use, only 31 of which were in operation in the USA (1).

Components

A diagram of the anaerobic digester is provided in Figure 1 (2). The digester will be of sufficient size to hold 70 L of organic waste and water, and will be located adjacent to the vertical farm. The main components of the anaerobic digester are: 1) an insulated vessel to hold and process the blackwater, organic materials, and wastes (insulation is used to reduce heating costs and maintain a homogeneous temperature within the digester); 2) a hardwood pallet (or base); 3) effluent inlet and outlet pipes to bring in treated blackwater and macerated wastes; 4) an effluent retention sump; 5) a solids outlet to recycle sludge; 6) a gas outlet to collect methane and carbon dioxide generated by the digestion process; 7) a gas collection overflow tube to prevent excess gas pressure from building up in the vessel; and 8) a gas agitation jet, to rotate the mixture in the digester vessel.

Process

Composted material and other organic wastes, which have been macerated and shredded, are mixed with treated blackwater and added to the digester vessel through the effluent intake pipe. The influent total solids concentration will range from 5-8%, of which approximately 55-65% will be organic matter (3).

The digestion process occurs in two steps. First, “acid-forming stage,” volatile solids in organic waste are broken down to fatty acids. This step is carried out by a group of bacteria called “acid formers.” In the second step, another specialized group of bacteria called “methane formers” are responsible for conversion of the acids to methane gas and carbon dioxide (4).

The digester is continuously rotated for several reasons. First, rotation prevents scum buildup on the sides of the vessel by a gas agitation jet and to homogenize the mixture. Second, mixing facilitates digestion by continuous contact of bacteria with the waste material. Third, rotation distributes the heat generated more uniformly (4).

Gases, methane and carbon dioxide, are emitted and are collected via the gas collection pipe at the top of the vessel. The typical proportion of methane and carbon dioxide produced by the decomposition of organic matter in an anaerobic digester is 60%, and 40%, respectively. A trace amount of hydrogen sulfide is also produced (1).

Methane is an excellent fuel source, producing about 900 BTU/ft3 . We shall use a standard engine generator set (not described) to produce electricity. This set has about 20-40% efficiency in converting BTU’s of methane to electricity (1). For every pound of volatile solids, approximately 0.4 ft3/day of methane is produced (1). Assuming 500 pounds of volatile solids from food waste, fish waste, and blackwater sludge are processed per day, we expect to produce 200 ft3/day of methane, or a total of 180,000 BTU electricity per day.

Carbon dioxide is essential for photosynthesis of the hydroponic crops, to maintain temperature (acting as a greenhouse gas) in the digester and the agriculture space, and to adjust the pH of the solution in the digester (3).
An enriched nutrient solution flows out of the vessel through an outlet pipe, which feeds into the effluent retention sump. Based on measurements conducted on a system at Berea College in Kentucky which composted cafeteria food waste, expected measurements from sludge, and a ratio of 75% compost to 25% blackwater, we estimate that the nutrient composition of finished compost will be approximately 2.1-2.8% nitrogen, 0.60-0.68% phosphorous, 0.98-1.25% potassium, 0.35-0.51% sulfur, 0.41-0.51% magnesium, and 3.40-3.75% calcium (5). This solution will be used for feeding the crops and fish.

This device provides a reserve that will suck liquid into the digester rather than air in the event of a vacuum. Solid waste flows out of the bottom of the vessel through the solids outlet. A re-circulating sludge pump will be used to recycle the sludge to the next batch of composted material (2).

The average length time required for anaerobic digestion of each batch of compost and treated blackwater will be approximately 15-18 days (1).

Maintenance of environment in digester

In order to optimize the anaerobic digestion process, we will keep the carbon-to nitrogen (C:N) ratio in the reactor in a proportion of 30:1 by weight (3). Temperature will be maintained at 40-55 degrees C (3). This will be accomplished by insulating the vessel, and through the production of carbon dioxide, and expected heat to be generated from the composting and digestion process. pH will be maintained between 6.8-7.4, the optimal pH for methane forming bacteria (1). Testing for carbon/nitrogen levels, a thermostat, and a pH monitor device will continuously monitor these parameters.

Safety

The main safety concerns include the possibility of an explosion due to the flammability of methane. To prevent combustion, temperature will be closely regulated, air kept out of the methane lines, and any possible ignition sources will be removed from the proximity of the digester (1). A second safety issue is the possibility of an excess buildup of pressure due to overproduction of methane gas (1, 2). A pressure relief valve will be used to ameliorate potential problems caused by pressure build up.

Benefits

As should be readily apparent, anaerobic digestion is beneficial to the Vertical Farm, and to the environment as a whole. In addition to the recycling of nutrients and production of energy, this system results in substantial pathogen control, because pathogens such as E. coli, Salmonella, and Cryptosporidium cannot survive the high temperature of the digester. Moreover, anaerobic digestion destroys more organic compounds and produces more gas than aerobic digestion does. Processing bacteria in the digester leads to a significant reduction in odor-causing compounds, and fly eggs are killed during anaerobic digestion. With regard to the environment in general, the digester represents an efficient and renewable process for disposal of and utilization of organic waste. Furthermore, the conversion of methane to energy translates into the reduction of release of methane to the atmosphere, which is far more potent than carbon dioxide in causing global warming.

Land Use

Vacant Lots

Currently, over 9,000 acres of city owned and over 7,500 acres of non-city owned vacant land within NYC remains vacant (11). These vacant lands have the advantage of requiring little demolition, but have already been deemed unsuitable for other development use. This land is particularly useful for urban farming, which can utilize odd shaped plots of land for production, such as those along rail tracks or streets (1). These vacant lots, if properly shaped can be used for the construction of a vertical hydroponics farm.

Abandoned Buildings

Generally speaking, abandoned buildings must be demolished before use in any Vertical Farm scenarios. This adds to the start up cost of the project though the cost can generally be recouped. Currently, over 23,000 abandoned buildings including 150 acres of city-owned and approximately 200 acres of non-city owned abandoned buildings exist, which could either be converted, or demolished (11).

Hydroponics

The word hydroponics was derived from the Greek words “hydro” meaning water and “ponos” meaning labor (49). Essentially hydroponics implies the raising of plants without soil. It was fist developed by German scientists looking to quantify the necessary nutrients required for plant growth. Through many years of research, knowledge of hydroponics has been developed and refined. Recent interest in the growing method has been sparked by concern over increasing deleterious effects of soil based commercial agriculture land use.

Crops selected for The Vertical Farm are: tomatoes, cucumbers, lettuce, sweet potatoes and strawberries. These were chosen in part because of well-established commercial growing methods for each crop as well as their marketability in a large urban grocery. In the future we hope to provide foods suited to all cultures and economic groups, but for now we will focus on those with high market value.

Strawberry growers worldwide must fumigate soil with methyl bromide before planting to control soil-borne insects, diseases and weeds. Without methyl bromide, the fruit yield would be much smaller and of a lower, less readily marketable quality. (2) However, methyl bromide, like its chlorinated relative, is a source of ozone layer depletion. The Environmental Protection Agency has mandated that production and use of methyl bromide be phased out by the year 2005 because of its harmful effects. (3) We see this as another excellent reason to raise the plant in a commercial hydroponics setting.

For building constraints, we assumed we would be working with a space approximately the size of a turn of the century tenement building typical in New York City: six floors tall with a ceiling height of 9 feet and an average of 1500 square feet per floor. Given this size, we expect to grow two rows of crops per floor on the top five floors of the building thereby doubling our yield capacity. Calculations for crop yield are based on 3000 square feet.
Based on the calculated square footage, our expected yield is:

Lettuce: 688 lb.’s/100/square feet, 20,640 lbs/3000 square feet (42)
Cucumbers: 932 lb.’s/100 square feet, 27,960 lbs/3000 square feet (43)
Tomatoes: 835 lb.’s/100 square feet, 25,050 lbs/3000 square feet (44)
Sweet potatoes: 1,200 lbs/100 square feet, 36, 000/3000 square feet (45)
Strawberries: 333 lbs/100 square feet, 10,004 lbs/3000 square feet (46)

The growing media chosen for the crops is perlite. Perlite is a processed mineral that allows a constant concentration of water and nutrients (47). If maintained properly, perlite 8can withstand many years of use without degrading (48). Two concerns with using perlite are its poor pH buffering capacity and propensity to encourage algal growth (49). However, with proper inspection and maintenance of the growing equipment, we will avoid any of these potential drawbacks. Figure 1 details the nutrients as well as certain other environmental conditions required for proper growth of each crop. All nutrients will be drawn from the composting and black water, both detailed elsewhere in the paper. We will not need to rely on outside sources of fertilizer. This self-reliant closed system serves to greatly reduce the amount of pollution related to transportation, fertilizer, pesticide and herbicide production. Manual pollination performed by employees will be used for those plants requiring it.

Aquaculture

The Vertical Farm will harvest fish grown in aquaculture systems. The species of fish will be a hardy, subtropical, finfish such as Tilapia (Oreochromis niloticus). The advantages of raising tilapia on a commercial basis include the large density of fish per cubic foot of water and the tolerance of these fish to wide variations in temperature and water quality (57). The worms from composting and lettuce grown at higher levels of the farm will be utilized as food substrates for the fish. We anticipate that demand for the fish will be fair: currently, New York is one of the primary markets for live tilapia.

In any commercial aquaculture venture, food safety is an issue. Despite these concerns the World Health Organization considers the industry to be of low risk to human health (31). The report on tilapia aquaculture discussed potential pathogenic microbes including parasites, bacteria and viral pathogens. Despite the prevalence of parasites in fish harvested from natural sources, cultured fish should not come into contact with any source of such infection. Even in areas in which such parasitic infections are endemic, human infections are only a problem when the fish are improperly prepared before consumption. These are not generally issues of concern in the United States, and the closed nature of the aquaculture system is an additional barrier to contamination of the stock. Another concern is the concentration of toxic metals in the fish. The risk of unsafe metals is low due to the vertebrate fish’s ability to regulate the concentrations of inorganic metal concentrations. Mercury may be a problem with fish caught in the wild, but should not be an issue in farm-raised fish, as the feedstuff should not be contaminated and the water will be treated to remove heavy metals.

Herbicides and pesticides are of concern if the composting process results in the concentration of these chemicals in the redworms or earthworms. Presumably not all of the produce collected from restaurants and grocery stores will be organically grown, so there may be pesticide residues on the organic waste we plan to compost (vegetable/fruit peels, etc). Insecticides and herbicides can contaminate fish in agricultural run-off situations. It is unclear whether there is a risk posed by the secondary consumption of worms by fish and second passage of herbicide/pesticide (31).

In order to achieve adequate surveillance of the aquaculture products of the Vertical Farm the following are recommended:
1) Chemical hazards are assessed in the quality of water and substrate of the fish food
2) Strongly recommend to consumers that all fish be cooked and properly handled prior to consumption
3) Identify and evaluate the potential hazards associated with each step of the aquaculture system
4) Identify Critical Control Points- a step where a control can be applied and a safety hazard identified or reduced to an acceptable level
5) Identify the possible hazards and severity of the health effects (31)

The biological threat of the aquaculture system proposed by the Vertical Farm project is very low. The water will be clean and the containment of the fish should completely eliminate the possibility of biological hazards. The fish will be handled and consumed by an educated public who will be made aware that it is not to be consumed raw or undercooked. Control of chemical hazards associated with this system of aquaculture would rely on a quality control program and surveillance of the critical control points as outlined above. The mission of the Vertical Farm includes the goal of protection of the environment and of the consumer. It is of the utmost importance to ensure the success of the Vertical Farm to harvest and distribute the finest and safest of products to the public.

Conclusion

In summary, we have laid the groundwork for a feasible vertical farm pilot project. The implementation of this design will bring urban settings one step closer to self-sustainability and an enclosed energy feedback system of recycled outputs. This project will change the traditional conception of “waste,” demonstrating its value as a source of energy for food production. Furthermore we have shown that the ecological footprint left by the Vertical Farm will be minimal in comparison with traditional farming methods. Future considerations must include social considerations of community, land use, and a smooth integration into neighborhoods with available vacant land space, as well as employment opportunities made available by the Vertical Farm.

References

Appendix A – Calculations

1. Calculations for the U.S.
   1. Tonnage of food left in fields
      

      60 million/137 million tons of wasted food (of the 20% of food which is produced) in the U.S. is left in the fields (ref. 27) U.S. crop yield (ref. 22) = 26,759 kg/Ha Total food production = (179,000,000 Ha)(26,759 kg/Ha) = 35,512,780 tons Amt left in fields = (60/137)(.2)(35,512,780) = 3,110,000 tons

2. Calculations for NYC
   1. Land use for actual food production
      

      Average produce intake (ref. 11)= 322kg/person 9 million people (322 kg/person)(1 Ha/26,759kg) =108,000 Ha

   2. Ecological footprint
      

      Ecological footprint per person (ref. 3)= 3.2 acres 9 million people (3.2 acres/person) = 28.8 million acres

   3. Land area of U.S. required for NYC food
      

      Total U.S. land area (ref. 22) = 962,909,000 Ha Total NYC land required for food = 28.8 million acres = 1.165E7 Ha Percent = (1.165E7/962,909,000)*100 = 1.2%

   4. Annual diesel fuel usage and greenhouse gas emissions
      1. Diesel fuel: 77,400 BTU/0.55 gal of gas (ref. 5)
         

         Net energy of Vegetable Food (ref. 9)= 3.74 kcal/g = 22,600 BTU/kg Conversion (ref. 3): 1 BTU food/20 BTU fuel 3E9kg food (22,600 BTU/kg)(20 BTU fuel/1 BTU food)=1.4E15 BTU fuel (1.4E15 BTU fuel)(0.55 gal /77,400 BTU fuel)=9.9 billion gallons of fuel

      2. Greenhouse Gases (1kg food = 1 kg GHG (ref. 3))
         

         3E9 kg food for NYC (8kg GHG/1 kg food) =2.4E10 kg GHG

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