The Pennsylvania State University
The Graduate School
College of Agricultural Sciences
GREENTOWERS: PRODUCTION AND FINANCIAL ANALYSES
OF URBAN AGRICULTURAL SYSTEMS
A Thesis in
Horticulture
by
Jonathan Gumble
2015 Jonathan Gumble
Submitted in Partial Fulfillment of the Requirements for the Degree of
Master of Science
August 2015
The thesis of Jonathan Gumble was reviewed and approved* by the following:
Robert D. Berghage Associate Professor of Horticulture Thesis Co-Advisor
Dan T. Stearns J. Franklin Styer Professor Thesis Co-Advisor
Mark A. Gagnon Harbaugh Entrpreneurship Scholar & Entrepreneur Coordinator
Andrew Lau Associate Professor of Engineering
Rich Marini Professor of Horticulture Head of the Department of Horticulture
*Signatures are on file in the Graduate School
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Abstract
By the year 2050, the population of planet Earth is expected to reach over nine billion people. In the next 35 years, we will have the task of supporting an additional two billion lives on a planet that is already struggling to provide a stable and acceptable food supply as well as an effective means of food distribution. Estimates show that of the seven billion people living on planet Earth, 870 million suffer from hunger.
The fight against world hunger is a complex, challenging, and multi-faceted issue that can only be fought through innovative solutions that address the multiple aspects comprising it. One of these aspects is simply limited access to food in urban neighborhoods and rural towns which are referred to as “food deserts”. These are prevalent throughout the United States and have resulted in food-insecure households.
Solutions to limited access do exist today in the form of innovative growing on developed land. The use of controlled agricultural environments through the means of greenhouse structures, LED lights, hydroponics, aquaponics, and aeroponics have made this possible. Multiple companies have come into existence and have built their businesses out of providing these innovative growing systems or growing food through their utilization.
Although these techniques and systems do exist, there is limited information and data on production yields both from the companies themselves as well as from existing scientific literature.
GreenTowers, LLC is an Urban Agricultural Design Company that came into existence in the past three years as a result of Penn State University’s College of Agricultural Science’s 2012 Ag Springboard Competition. The four co-founders; Dustin Betz, Jared Yarnall-Schane, Michael Zaengle, and Jonathan Gumble have transformed GreenTowers from a student competition team, to a full-time business. GreenTowers’ mission is “to reconnect individuals with nature and with food to help consumers realize the interconnection shared between ecological systems and food systems”. This is primarily accomplished through the use of two innovative growing systems developed by the company; the Rotating Living Wall and Living Furniture.
The goal of this master’s program through these sets of experiments was to understand not only the production potentials of these two systems, but the financial aspects as well to determine economic viability in specific case scenarios. The Rotating Living Wall was tested through the growing of 12 varieties of microgreens. Experiments were performed from June 2014 to June 2015 to understand differences in seasonal yields, differences in yields based on variety of microgreen, yield comparison to a traditionally grown microgreen control group; both on a yields per/trough method as well as a yields per/ft.² method, rotational timing, moving versus stationary growth, differences in growth based on media depth, and differences in production yields from supplemental lighting.
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Performance criteria were based on measuring fresh weight, dry weight, height, and SPAD-meter readings (soil plant analysis development). Differences in yields throughout seasons were significant as well as differences between the Rotating Living Wall systems compared to the control group. The use of LED supplemental lighting provided significant differences in yields throughout winter season growing. Rotational timing, media depth, as well as physical movement of plants showed minimal or no significant influence on yields. By establishing the potential revenues and various costs that are part of growing with the Rotating Living Wall system, financial viability was analyzed showing that these systems can be profitable when used in State College, PA, within certain operating parameters.
Living Furniture, which is a small scale aesthetic aquaponics system, was tested through the course of ten trials to understand not only the yield potentials for a variety of microgreens, but the operating costs as well. Number of fish and fish food mass did not result in significant differences in production yields with chelated iron supplementation, but did result in significant differences for water chemistry (specifically concentrations of ammonia, nitrite, and nitrate). Water chemistry overall did prove to be better in the Living Furniture systems compared to a control setup tank with a standard mechanical filter. Chelated iron supplementation resulted in significant improvement for overall production of the systems; even resulting in the aquaponic systems surpassing the production yields from control-grown microgreens produced in a commercial potting mix.
The research completed throughout these studies has not only provided a base line of operation for both these systems, but has also given insight into future studies and research that can be completed for further optimization and increased efficiency. Developed and improved growing systems may have the potential to provide solutions for fighting food deserts and ultimately the big picture of world hunger.
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Table of Contents Page
List of Figures vii List of Tables xi
Acknowledgements xii
Chapter 1 Literature Review 1
1.1 Current Global Food Statistics and Future Predictions 1 1.2 Vertical Farming 4 1.3 Controlled Environment Agriculture (CEA) 6 1.4 Innovative Growing Systems and Current Use of CEA 7 1.5 CEA through LED utilization 9 1.6 Realizations of CEA and Energy Consumption 11 1.7 Microgreen and Organic Food Trends 13 1.8 Urban Agriculture and Urban Farming 15 1.9 Urban Agriculture Implementation 16 1.10 Realizations of Urban Farming 17 1.11 Benefits of Urban Farming 19 1.12 CEA and Urban Farming 19 1.13 Review and Preface 20 1.14 GreenTowers 21 1.15 Aquaponics 22
Chapter 2 Rotating Living Wall 28
2.1 Introduction 28 2.2 Materials and Methods 28 2.2.1 System Design and Construction 28 2.2.2 Production Experiments Methods 33 2.2.3 Experimental Setup and Layout 37 2.2.4 Process 40 2.2.5 Performance Criteria 43 2.2.6 Light Analysis Methods 44 2.2.7 Financial Analysis Methods 46 2.3 Results and Discussion 49 2.3.1 Production Experiments Results 49 2.3.2 Light Analysis Results 59 2.3.3 Financial Analysis Results 62
Chapter 3 Living Furniture 68
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3.1 Introduction 68 3.2 Materials and Methods 68 3.3 Results and Discussion 80 3.4 Financial Analysis 81 3.5 Discussion 82
Chapter 4 Conclusions and Future Direction 83
4.1 Conclusions for Rotating Living Wall 83 4.2 Future Direction and Research 84 4.2.1 Passively Rotating Living Wall Integration 84 with Commercial Aquaponics Systems 4.2.2 Research for the Future 89 4.3 Conclusions for Living Furniture 90 4.4 Future Direction and Research for Living Furniture 90 4.5 Future Predictions 92
References 93
Appendix A Statistical Outputs Rotating Living Walls 98 Appendix B Statistical Outputs Living Furniture 104 Appendix C Light Analysis Data 109
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List of Figures Page
Figure 1.1-1. USDA Economic Research Service Food Access Research Atlas (US) 2
Figure 1.1-2. USDA Economic Research Service Food Access Research Atlas 2 (NY, PA, MD, DC)
Figure 1.1-3. USDA Economic Research Service Food Access Research Atlas 3 (NY-Philadelphia)
Figure 1.1-4. US Households By Food Security Status, 2013 3
Figure 1.7-1. USDA Economic Research Service U.S. Organic Food Sales (2012) 14
Figure 1.7-2. USDA Economic Research Service U.S. Certified Organic Cropland (2012) 14
Figure 2.2.1-1. Overall System Layout 28
Figure 2.2.1-2. Friction Drive 29
Figure 2.2.1-3. Gutter Trough J Bolt 29
Figure 2.2.1-4. Gutter Troughs 29
Figure 2.2.1-5. C.A.P. ART-DNE Digital Adjustable Recycling Timer 30
Figure 2.2.1-6. Framing 30
Figure 2.2.1-7. 3D SketchUp Model (Front View) 31
Figure 2.2.1-8. 3D SketchUp Model (Side View) 31
Figure 2.2.1-9. 3D SketchUp Model (Trough Detail) 32
Figure 2.2.1-10. 3D SketchUp Model (Alternative Frame) 32
Figure 2.2.2-1. 12 Varieties of Microgreens 34
Figure 2.2.2-2. Oscillating Linear Actuator Bench 36
Figure 2.2.3-1. Greenhouse Setup 37
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Figure 2.2.3-2. SketchUp Model of Experimental SetUp 37
Figure 2.2.3-3. General Experimental Layout 38
Figure 2.2.3-4. Experimental Setup in Greenhouse (Summer) 38
Figure 2.2.3-5. Experimental Setup in Greenhouse (Fall) 39
Figure 2.2.3-6. Experimental Setup in Greenhouse (Winter) 39
Figure 2.2.3-7. Experimental Setup in Greenhouse (Spring) 40
Figure 2.2.4-1. Vacuum Seeder Manifold 41
Figure 2.2.4-2. Shop Vacuum 41
Figure 2.2.4-3. Seeding Template 41
Figure 2.2.4-4. Jig and Hopper 42
Figure 2.2.4-5. Hedge Trimmer 42
Figure 2.2.4-6. Harvested Product 43
Figure 2.2.5-1. SPAD Meter 43
Figure 2.2.7-1. Two Fluorescent Light Fixtures 46
Figure 2.2.7-2. Metal Halide Light Fixture 47
Figure 2.2.7-3. LED Light Fixture 47
Figure 2.2.7-4. Light Meter 48
Figure 2.2.7-5. Energy Consumption Meter 48
Figure 2.3.1-1. Annual Production Overview of Harvestable Product (Walls vs. Flats) 49
Figure 2.3.1-2. Annual Production Overview Fresh Weight Ratios (Walls vs. Flats) 50
Figure 2.3.1-3. Annual Production Overview of Dry Weight (Walls vs. Flats) 50
Figure 2.3.1-4. Annual Production Overview Dry Weight Ratios (Walls vs. Flats) 51
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Figure 2.3.1-5. Annual Production Overview; Production/Ft.² Comparison 52 (Walls vs. Flats)
Figure 2.3.1-6. Annual Production Overview; Production/Ft.² Ratios 53
Figure 2.3.1-7. Annual Microgreen Variety Performance Overview (Trough Basis) 53
Figure 2.3.1-8. Annual Microgreen Variety Performance Overview (Ft.² Basis) 54
Figure 2.3.1-9. Comparison of Wall System Rotational Rates 55
Figure 2.3.1-10. Differences in Fresh Weight Based on Media Depth 56
Figure 2.3.1-11. Differences in Dry Weight Based on Media Depth 56
Figure 2.3.1-12. Differences in Fresh Weight Based on Lighting Type (Winter) 57
Figure 2.3.1-13. Differences in Dry Weight Based on Lighting Type (Winter) 57
Figure 2.3.1-14. Differences in Fresh Weight Based on Lighting Type (Spring) 58
Figure 2.3.1-15. Differences in Dry Weight Based on Lighting Type (Spring) 58
Figure 2.3.2-1. Flat Trough Seasonal Wall/Flat Ratio 60
Figure 2.3.3-1. Supplemental Lighting Production Differences 67
Figure 3.2-1. Experimental Setup Unit 69
Figure 3.2-2. Manifold Pipe 69
Figure 3.2-3. Manifold Pipe with Rockwool Cubes 70
Figure 3.2-4. GreenTowers Living Furniture 70
Figure 3.2-5. Experimental Setup (Beginning) 71
Figure 3.2-6. Control Unit with Standard Mechanical 72 Filter Positioned on Opposite Side
Figure 3.2-7. Plastic Plug Trays Provide Support for Foamboard Floor 72
Figure 3.2-8. False Floor Constructed of Foamboard with Drainage Holes 73
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Figure 3.2-9. Collection Bucket 73
Figure 3.2-10. Growing Eight Varieties of Microgreens 74
Figure 3.2-11. Growing Four Varieties of Microgreens 74
Figure 3.2-12. Chelated Iron (DTPA) 76
Figure 3.2-13. Re-filling with De-chlorinated Tap Water 76
Figure 3.2-14. Growing Trials with Chelated Iron and De-chlorinated Tap Water 77
Figure 3.2-15. Testing Water Chemistry 78
Figure 3.2-16. Seeding 78
Figure 3.2-17. Growing 79
Figure 3.2-18. Fresh Product (Chard) 79
Figure 4.2.1-1. Passively Rotating Hydroponic Living Wall within a 85 Vertical Greenhouse
Figure 4.2.1-2. Architect’s Rendition of Implementation in 86 Existing Infrastructure
Figure 4.2.1-3. Architect’s Rendition of a Stand-Alone 86 Unit within an Urban Area
Figure 4.2.1-4. Passively Rotating Living Wall with 87 Integrated Aquaponics System (Overview)
Figure 4.2.1-5. Passively Rotating Living Wall with 87 Integrated Aquaponics System (Aquaponics)
Figure 4.2.1-6. Passively Rotating Living Wall with 88 Integrated Aquaponics System (Growing)
Figure 4.4-1. Living Interiors Piece 91
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List of Tables Page
Table 2.3.2-1. Seasonal and Total Light Data 59
Table 2.3.3-1. Light Outputs and Energy Consumption 66
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Acknowledgements
I can honestly say that the completion of this thesis marks the end of an era. Six years ago was the beginning of my college career at Penn State at nineteen and it was the most challenging time of my life that I have gone through. I learned so much from that event, especially the importance of good people. With that incredible challenge also came six years of learning, adventure, and growth that I didn’t even know was possible. I’ve said this before, and I will say it again; “the right people make all the difference”. With that being said, these past six years have given me the privilege of meeting so many extraordinary people that I am happy to call mentors, friends, and even family.
I would first like to thank the members of my committee for their unending support and everything they have done.
Thank you Andy Lau for hosting “Ethics of Star Trek”. That is one class I will never forget. Thank you as well for connecting me with the right people to make the technical aspects of this project possible.
Thank you Mark Gagnon for all of your support from “The Ag Springboard Competition”, to personal mentorship, as well as all of the time and energy invested into the good of GreenTowers.
I would like to thank Rob Berghage for taking me on as a graduate student and turning all of the insanity associated with my program into something real and worthwhile. Thank you for your patience as well as all the good laughs in Hort 131 and 453.
Lastly, thank you Dan Stearns. There was a period of time throughout my freshman year that I was considering leaving Penn State. You honestly gave me a home in the Landscape Contracting program along with some really valuable life direction. Also, thank you for all the opportunities you’ve provided. It has been an honor working with you.
A special thanks to the founders of GreenTowers is also due. Dustin Betz, Mike Zaengle, and Jared Yarnall-Schane, thank you for all of your hard work and dedication to the good of GreenTowers and to the real world application of all the research. Your inspiration and enthusiasm to urban agriculture and entrepreneurship is truly indescribable.
Thank you as well to two people that I respect greatly; Jim Sellmer and Scott Diloreto. Jim you have shown me the satisfaction that comes from teaching and having an impact on students. You’ve also shown me the importance of understanding the big picture as well as the details that need to be present when doing anything in life. Scott, thank you for all of your help in the greenhouses and showing me how to be a competent horticulturist. Thanks just for all of the general life advice too.
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I would like to give a special thanks to Dr. Richard Mistrick and AJ Scanlon as well for completing the light analysis for this project and giving really valuable insight for future design of urban agricultural systems.
Thank you to Peter Vanco and Mike Basedow for all of your help with statistics; I owe both of you beyond words.
Thank you to the CoSpace and New Leaf Initiative for catalyzing GreenTowers and supporting everything it has done. The community that has been built from the two organizations has been incredibly supportive.
Lastly, thank you to all of the people that have supported me from outside my program as well. I have been very blessed.
Thank you to all of my students. It has truly been a joy being a teaching assistant and some of my best memories have come from time spent in Hort 466 and 408.
I’d like to say thanks to the Savage family; Jim, Lori, Jess, Jill, and Andy for being my second family that I have really needed throughout these past few years, along with everyone who has come to dinner on Sunday nights.
Also, thank you to Erin Ponsonby for all of the incredible times from Auburn to Lisbon. You truly remind me of what it means to live life as an adventure and the importance of being human.
Lastly, thank you to my parents, sisters, and brothers-in-law. I love all of you and these past six year would not have been possible without your help along the way.
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“Buy land, they’re not making it anymore” -Mark Twain
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Chapter 1 Literature Review
1.1 Current Global Food Statistics and Future Predictions
The United Nations states that the current world population of 7.2 billion people is expected to reach over 9.5 billion by the year 2050 (UN DESA, 2013). In the next 35 years, the entire world will have the task of supporting an additional two billion lives on a planet that is already struggling to provide an acceptable and stable food supply as well as an effective means of food distribution. The Food and Agriculture Organization of the United Nations (FAO) has indicated that world hunger is significant and wide spread, stating “805 million people are estimated to be chronically undernourished in 2012-2014” (FAO.org, 2014). This is equivalent to one in nine people and is most severe in developing regions such as sub-Saharan Africa and Southern and Western Asia (FAO IFAD and WFP, 2014). Fighting world hunger and developing stronger food security are complex challenges and can only be addressed through multiple innovative solutions.
Studies have shown that the majority of undernourished people reside within Sub- Saharan Africa, comprising “more than a quarter of the world’s undernourished people, owing to an increase of 38 million in the number of hungry people since 1990-92” (FAO IFAD and WFP, 2014). From these studies, as well as others concentrating on the severity of world hunger in developing regions, it becomes easy to focus solely on this particular aspect and lose sight of the other equally important aspects that need to be considered when approaching this global challenge as a whole. Availability is not the only aspect of food security; access, stability, and utilization need to be considered as well (FAO IFAD and WFP, 2014).
Moving away from Sub-Saharan Africa and looking at the United States, one may believe that the latter is minimally affected by the global issue of world hunger due to its abundant availability of crops and food products. However, considering access as a component of food security, it can easily be seen that the United States is food insecure as well due to the presence of “food deserts”. These are defined as “urban neighborhoods and rural towns without ready access to fresh, healthy, and affordable food” (USDA ERS, 2015). Figure 1.1-1 shows the areas in green within the Unites States that experience both low income and low access to food. The following figures; 1.1-2 and 1.1-3 show the northeast portion of the United States; specifically New York, Pennsylvania, Maryland, and Washington DC and further analyze these geographic areas for low income, (blue), low access, (pink), and low income and low access, (green) (USDA ERS, 2015).
In 2013, approximately 14.3% of US households were food-insecure, with 5.6% of households facing very low food security (Figure 1.1.4). This is defined as “normal eating patterns of one or more household members were disrupted and food intake was reduced at times during the year because they had insufficient money or other resources for food” (USDA ERS, 2013).
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Figure 1.1-1. USDA Economic Research Service Food Access Research Atlas (United States)
Figure 1.1-2. USDA Economic Research Service Food Access Research Atlas (NY, PA, MD, DC)
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Figure 1.1-3. USDA Economic Research Service Food Access Research Atlas (NY-Philadelphia)
Figure 1.1-4. US Households by food security status, 2013
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From these figures and statistics established by the USDA, it is evident that “food deserts” are prevalent throughout the United States and have had crippling effects for millions of individuals. Providing greater access to food throughout the United States has the potential to alleviate “food deserts” and raise awareness for access to fresh, healthy, and affordable food. However, questions still need to be answered in regards to how this can be done. One theoretical solution referred to as “vertical farming” provides some insight.
1.2 Vertical Farming
The concept of “vertical farming” was popularized initially by Dr. Dickson Despommier and his book, “The Vertical Farm” in 2010.
Dr. Despommier’s background in microbiology, ecology, and social science directly affected the perspective of the “The Vertical Farm”. The intention of what he wrote was not to produce the detailed blue-prints needed to physically implement a successful vertical farm, but instead analyze the broader perspective of agriculture and how humans have evolved with its process over the course of time. One of the more prominent insights involved the idea of the non-sustainable properties of cities. The basic premise was that through modern technology, humans have been able to live in very densely populated areas that consume more resources than can be produced. Waste products are also generated at a rate where processing is not possible, and essentially what have been created are non-sustainable environments that are continually expanding. The United Nations estimates that nearly 66% of the world’s population will reside in urban areas by the year 2050 (UN DESA, 2014). This being the case, 66% of the world population could potentially be living through non-sustainable means, resulting in conditions that will likely lead to disastrous consequences (Despommier, n.d.).
Dr. Despommier further developed his theories by relating the concept of a city to an ecosystem. In a natural ecosystem, the production or output of the system can be no greater than the energy that it receives; meaning an ecosystem is defined by the received energy; essentially sunlight. A rainforest receives a large amount of energy throughout the year and therefore produces much more in terms of vegetation, wildlife, and other natural resources. Comparatively, the production in an alpine forest is not nearly as great due to the lower levels of energy it receives throughout its existence. Dr. Despommier states that, “natural ecosystems cannot exceed biomass production which is regulated by the amount of incoming energy. Cities and urban centers by comparison do not follow this same regulation.” This is the main reason for their inherit lack of sustainable properties (Despommier, 2010).
Food production within the bounds of cities, with effective recycling and waste management would permit urban environments to become more sustainable over time. Despommier’s “vertical farming” is the proposed solution for making this a reality and much thought has been generated for this concept. A great number of concepts, ideas, and theories have been brought together to make this a working theoretical model. However, Despommier has not necessarily considered the logistics, financials, and practicalities that would make “The
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Vertical Farm” a functioning reality. His idea of “The Vertical Farm” would result in efficient agricultural production providing the following advantages:
-Year round crop production -Controlled environmental conditions (weather is controlled; no flood or drought) -Reduction of pesticides, fertilizers, and herbicides -Efficient use of water as well as recollection and treatment of water (gray and black) -Reduction in the use of fossil fuels (regarding transportation of food) -Elimination of agricultural runoff damage -Drastic reduction in production losses from shipping and storage -Strengthening in the national economy as well as local economies by providing employment ffor both the construction and operations of vertical farms -Security of natural resources -Potential return of farmland to natural forest land; restoring natural ecosystems -Addition of aesthetic value to urban properties -Increase in property values -Contribution to city “greenery” -Contribution to educational value for young people
(Despommier, 2010, p.145-175)
These advantages and positive changes in agriculture would be true for vertical farming, but “The Vertical Farm” envisioned by Dr. Despommier has multiple issues. Developing a new breed of skyscraper in a city with custom grow space, lighting, utilities, and other sophisticated features could potentially cost hundreds of millions of dollars just for construction alone. Significant barriers for entry for any company, organization, or group of investors would be prohibitive. The amount of energy required to power “The Vertical Farm” also remains as a significant issue. This is where heavy criticism lies along with Dr. Despommier’s lack of technical background. The design of the vertical farm is essentially floors of growth stacked in a “skyscraper-like” fashion, where a very large percentage of the growth floors are essentially shaded to the natural light. Supplemental lighting would be required for adequate production levels. This additional energy, combined with the energy required to maintain high grow temperatures; especially in temperate climates will demand significant amounts of energy from an urban area’s power grid; consuming additional forms of non-renewable energy. The advantages of a vertical farm may stay true if alternative energy such as solar, wind, geothermal, and digested methane is utilized. However, challenges still exist in “fueling” an entire vertical farm from these sources alone (Cox et al., 2010).
A counter-article, “’Vertical Farming’ Doesn’t Stack Up” written by Stan Cox and David Van Tassel discussed the potential pitfalls of Dr. Despommier’s theoretical model. Agreement was made that there is a pressing need for change in the world’s agricultural production methods. However, emphasis was made that increased fossil fuel energy consumption is the most significant issue. If the 53 million acres of wheat produced by the United States annually was grown indoors via vertical farming, eight times the amount of energy generated annually
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by the United States would be required just for lighting alone. In perspective, wheat production only comprises 15% of all agricultural land within the United States. 85% of the nation’s crops would still be left over for consideration. Corn production was noted as well, stating that this would require even greater amounts of energy; potentially 40 times the amount produced annually by the U.S. Cox and Van Tassel closed the discussion by stating that there are other general impracticalities with “The Vertical Farm” in terms of heating and cooling. Pesticides would still be required as well to combat insects and diseases such as powdery mildew, aphids, and mites (Cox et al., 2010).
From the perspective of Cox et al., “The Vertical Farm” fails to serve as a solution that could ever be implemented for practical food production in urban environments, especially in an effort to eliminate “food deserts”. However, inspiration is provided for innovation in growing systems, and traces of “vertical farming” can currently be observed in the form of controlled environment agriculture practices.
1.3 Controlled Environment Agriculture
According to Merle H. Jenson of the University of Arizona, controlled environment agriculture (CEA) can be defined as “the modification of the natural environment to achieve optimum plant growth” (Jensen, 2002). In “Controlled Environment Agriculture in Deserts, Tropics and Temperate Regions - A World Review” the aspects of CEA are outlined; including modification of both the aerial and root environments through control of air temperatures, root temperatures, light, water, humidity, carbon dioxide, and plant nutrition. These controls can be established primarily through the utilization of hydroponics, aquaponics, or aeroponics taking place within some form of greenhouse structure (Jensen, 2002).
One of the inherent and defining aspects of CEA is the high initial capital investment as well as the higher operational costs compared to traditional agriculture, or simply open field agriculture (OFA). Although this may be perceived initially as a negative, the benefit that comes with CEA is significantly higher productivity, potentially leading to year-round production in certain geographical regions. However, justification for the implementation of CEA can only come from high price demands for fruits and vegetables. Additional details and descriptions were given in the article concerning heating, cooling, and ventilation mechanics, computer control with the use of sensors, and variations of hydroponic growing such as deep water culture, nutrient film technique, and media or aggregate based systems. All of these factors can contribute to the efficiency as well as the profitability of CEA (Jensen, 2002).
Hydroponics can be defined as the science and cultivation of plants through the utilization of nutrient-rich solutions in place of soil. Cultivation also can take place with or without the mechanical support of media, such as sand, gravel, vermiculite, rockwool, perlite, peat moss, coir, or sawdust. The advantages of hydroponic growing coincide with the advantages associated with CEA, including maximum yield potential, conservation of resources, and generally more control of the growing environment. Disadvantages coincide as well, and include higher initial costs as well as more intensive management (Jones, 2005).
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Aeroponics is a form of hydroponics, but is specialized in the sense that plant roots are incased in a container and sprayed with a nutrient-solution mist. Advantages to this system are once again more precision and control, but specifically use of significantly less water; upwards of 95% and greater oxygen levels. Temperatures of the root zones can be maintained more efficiently as well due to the lower volume of water used in the process (Christie, and Nichols, 2004).
Aquaponics is essentially an additional form of hydroponics, but utilizes fish waste as an organic nutrient solution for the growth of plants. This process additionally differentiates itself in that plants filter the fish waste to provide clean water and improved water chemistry (Aquaponics Journal, n.d.). More information will be given later in the literature review regarding the specifics of this growing method.
1.4 Innovative Growing Systems and Current Use of Controlled Environment Agriculture
Specific examples of controlled environment agriculture (CEA) can be found in companies today, such as the following:
SkyGreens located in Singapore has developed a patented technology that utilizes a thirty foot aluminum structure that rotates troughs of soil along a vertical plane in a large industrial greenhouse. Rotation of the troughs provides even distribution of sunlight to the plants being grown, eliminating the need for supplemental lighting. The rotation of the system is accomplished by a waterwheel which is driven by collected rainwater stored at the top of the roof, requiring minimal energy input. The company claims that rotation of the entire system requires only the energy to power a single 40 watt light bulb. Through the utilization of this system, Skygreens states that it can produce ten times the yield per square foot compared to traditional farming. To continue with the milestones of their success, SkyGreens provides over seven percent of the produce for the city of Singapore with the use of only a single 3.2 acre site. “Skygreens” does have plans for further expansion (Technology, 2014).
This type of CEA is successful in terms of implementation and production; however two significant drawbacks to this concept prevail. The entire operation requires several acres for implementation, and the initial capital invested into SkyGreens was over $20 million dollars (Eaton, 2013).
Verticrop provides yet another example of CEA with specific focus on space- optimization. Verticrop has created a series of rotating trays, stacked and connected with a beam in a staggered orientation. The beam hangs from the top of a moving track, where it moves and receives even distribution of light by allowing for exposure to different angles of the sun or supplemental lighting. The Verticrop system functions within a controlled environment such as a greenhouse and can be established within a relatively small space with fairly high production yields. In terms of practicality, and affordability, it shows great promise for the future of growing and potentially “vertical farming” in the future (The Technology Alterrus, n.d.).
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BrightFarms is essentially a greenhouse design/build company and “finances, designs, builds and operates greenhouse farms at or near supermarkets, cutting time, distance, and cost from the produce supply chain”. BrightFarms formed out of the non-profit, New York Sun Works in 2006 and has grown to be multi-million dollar company specializing in the implementation of innovative and efficient crop production greenhouses located at or near supermarkets. The company currently has seven commercial-scale production greenhouses utilizing hydroponic growing practices, and has partnered with seven major supermarket chains such as Giant, Waldbaum’s, and Pathmark (BrightFarms, n.d.).
One particular trend that is apparent within CEA systems is modularity; meaning the system is independent of the surrounding environment and infrastructure, allowing for a “plug and play” type configuration.
One specific example of a modular system used within the realm of CEA is the ZipGrow Tower produced by BrightAgrotech located in Laramie Wyoming. The ZipGrow Tower is essentially a piece of gutter type material that is oriented vertically. Rockwool or a similar type of substrate slides within the gutter material and allows plants to grow out the sides. Nutrient rich solution is pumped into the top of the “tower” and flows through to the plants, eventually draining at the bottom to be recirculated. The nature of the system provides versatility; allowing plants to be grown hydroponically or aquaponically. Due to the simplicity of the system, expansion and addition of more “towers” into an existing hydroponic or aquaponic system can be completed relatively easily (ZipGrow towers, n.d.).
An even more complete and contained example of a modular CEA system is UFU, which stands for urban farm unit. This apparatus consists of a 20’ shipping container with a traditional greenhouse attached on top. The lower container portion houses an aquaponics system while the top contains space for hydronic grow beds. Damien Chivialle designed the unit and has constructed four separate UFUs located throughout Europe in Zurich, Berlin, Brussels, and Levuen. His design has piqued the interest of a number of individuals, but it seems as though Chivialle is more interested in demonstrating the units rather than mass producing them for consumer use. No company page or additional information could be found (Morgan, 2013).
Bioponica is yet another company based in Atlanta, Georgia, and offers a diverse means for growing through the means of CEA. The original system offered is the Biogarden, and essentially is composed of multiple components (tubs, tanks, tubes, and framing) that can be set up for either hydroponic or aquaponic growing. Various numbers and sizes of the components make for scale-able systems. For example, the Biogarden 20’ 2/2 4L has two large cylindrical tanks for supporting fish and eight grow beds stacked in four levels. This structure allows for aquaponic or hydronic growth through various growing techniques; deep water culture, flood and drain, or nutrient film. The Biogarden systems also come with estimated annual production yield figures for each specific model, including annual lettuce, microgreens, tilapia, and wheatgrass yields. The largest version available (20’ 2/2 4L) has the associated annual estimate yields of 210 lbs of tilapia and 1,968 lbs of lettuce, 1,104 lbs of microgreens, or
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3,744 lbs of wheatgrass. Although these figures are available, no assumptions on light level, temperature, or number of harvests could be found. The system occupies an area of 240 square feet, weighs 13,827 lbs, and retails for $8935 (Bioponica Systems, 2015).
In addition to just offering the systems for growing food, Bioponica also offers what they refer to as “the boxcar farm” which includes a kitchen and processing facility within a shipping container equipped with the Biogarden system. Also included is an on-site juice bar, café, and retail product store. Essentially what is being offered is a “plug and play” “farm to food” operation (Bioponica Systems, 2015).
The last system Bioponica offers is The Biopharmacy, a medical marijuana processing and extraction facility. “The Biofarmacy comes complete with kitchen, cannabis extraction equipment hookup, office, work rooms and retail, so the entire facility is built within one or more shipping containers.” (Bioponica Systems, n.d.). Bioponica is capitalizing on this concept by offering a “plug and play” solution that satisfies the multiple permits required for marijuana processing in a modular unit. Although this apparatus may not fall within the category of food production, relevancy can be attained through understanding side aspects of companies that have built their businesses around CEA (Bioponica Systems, 2015).
1.5 Controlled Environment Agriculture through LED Utilization
The previous examples of (CEA) share the common characteristic of incorporating the use of greenhouse coverings; utilizing primarily natural sunlight and sun energy. However, research and review showed a common trend emerging, which is exchanging the standard greenhouse environment for the use of LED (light emitting diode) technology in traditional buildings for greater control and potential energy efficiency. In terms of light used for photosynthesis, three parameters are taken into consideration; spectral quality, amount, and direction. The true advantage of LED technology is the adaptive capability of producing refined light conducive to photosynthesis based on these three categories. The spectrum of light utilized specifically for photosynthetic activity is 400-700 nm which resides in the blue and red regions of the visible light spectrum (Taiz & Zeiger, 2006). LEDs can be manufactured to produce only these spectrums of light with up to 50 percent energy conversion efficiency. Because of this development, the University of Florida has been able to research specific “prescriptions” for different crops. Kevin Folta, chairman of the university’s horticultural sciences department stated, “every single plant will have a set of rules for light that will allow you to maximize the presence of the compounds you want.” (Ideas Lab Staff, 2014). Additionally, LEDs have the ability to produce higher levels of light. Light in terms of photosynthesis is referred to as photosynthetically active radiation or (PAR) and can be expressed in terms of energy (W m⁻²) or quanta (μmol m⁻² s⁻¹). For reference of an established baseline, direct sunlight corresponds to an approximate 2000 μmol m⁻² s⁻¹ reading or 1000 W m⁻² (Taiz & Zeiger, 2006).
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Due to advancing LED technology, resulting in price reductions as well as increased energy efficiency, several companies have come into existence, taking use of this growing technique and related systems (Clancy, 2014).
Freight Farms, based in Boston, Massachusetts utilizes shipping containers as CEA units. Insulated walls as well as hydroponic grow beds are utilized within the container to allow for vegetable production through the use of high intensity LED lights. What they have essentially created are mobile urban farms. Descriptions are made regarding the units and how high quality produce can be grown. “The vertical towers create a high density growing environment with four rows providing space for over 4,500 plants. Drip irrigation, nutrient delivery system and spectrum focused lighting supports climate conditions to maximize plant development.” (LGM 2015, n.d.). Although the apparatus is described, no information is given regarding operation costs as well as production rates for the entirety of the system (LGM 2015, n.d.).
Podponics, based in Atlanta, Georgia offers a CEA unit very similar to Freight Farms in that the system is constructed from a used shipping container and utilizes LED grow lights in conjunction with hydropnic systems to essentially create “mobile urban farms”. The cost of a unit could not be found, along with any figures regarding production yields or operating costs. The company does review the advantages of using a shipping container as an urban farming unit, but no additional information is available (PodPonics, n.d.).
AeroFarms is a comparable company to BrightFarms in that the business focuses on the design, construction, and implementation of high efficiency greenhouse structures in close proximity to supermarkets and other food outlets. However, Aerofarms differentiates itself through the use of highly sophisticated aeroponics growing systems. The use of patented cloth medium, high efficiency misters, and LEDs are incorporated for maximum efficiency growing. Aerofarms is currently planning to construct their new corporate headquarters in Newark, NJ, which will also serve as the world’s largest indoor vertical farm. This operation will encompass 69,000 square feet from the former Grammer, Dempsey, and Hudson steel plant in the Ironbound section of Newark and has received an initial investment of $39 million from Goldman Sachs (Aerofarms, n.d.).
In regards to CEA growing through the use of LED technology, there are currently two “indoor commercial farms” that reflect the growing nature and potential for “vertical farming” to become a reality. These two examples are the partnerships of Royal Philips with Green Sense Farms located outside Chicago (Philips City Farming, 2014), and General Electric with Mirai, an indoor farming company in Japan (LED Lighting GE, 2014).
Royal Philips and Green Sense Farms formed a partnership to develop a solution for ever-increasing urbanization and population growth throughout the world. The solution they have developed involves the construction of multiple story industrial shelving units equipped with high-tech and high-efficiency LED lighting. Plants are essentially grown hydroponically in layers within a warehouse where all aspects of the growing process can be precisely monitored
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and controlled. This includes the placement of plants, water and nutrient levels, and the specific wavelength of light received by the plants. Royal Philips and Green Sense Farms have essentially been able to mechanize the entire “growing process”. The operation claims that 20- 25 harvests can be completed per year while using 85% less energy; providing consumers with fresh local produce (Philips City Farming, 2014).
General Electric and Mirai have also come together to form the world’s largest “indoor commercial farm” within a former Sony factory located in Miyagi Prefecture in eastern Japan. Occupying a 25,000 square foot area, the operation is able to produce 10,000 heads of lettuce every day. Japanese plant biologist, Shigeharu Shimamura, who has lead the major developments of the operation stated, “the system allows him to grow lettuce full of vitamins and minerals two-and-a-half times faster than an outdoor farm. He is also able to cut discarded produce from 50 percent to just 10 percent of the harvest, compared to a conventional farm. As a result, the farm’s productivity per square foot is up 100-fold”. Additional farms are planned to be implemented within the future in Hong Kong and the Far East of Russia. Shimamura stated as well, “Finally we are about to start the real agricultural industrialization” (LED Lighting GE, 2014).
From these examples, it is evident that food can be grown year round through the utilization of CEA due to the refined control of all growing aspects. Simply stated, growing healthy food is absolutely possible when all resources are openly available. However, production itself from both a monetary and a carbon-footprint perspective do need to be considered, especially in regards to large-scale implementation.
1.6 Realizations of Controlled Environment Agriculture and Energy Consumption
Louis Albright, director of Controlled Environment Agriculture Program at Cornell University, wrote an article in Greenhouse Management, “Are ‘plant factories’ viable greenhouse alternatives?” and addressed the high energy demands and potential carbon production of these “plant factories” or “indoor farms”. (Albright, 2014) In the article, he discussed three topics; practical crops for “plant factories”, the carbon footprint of a “plant factory”, and the potential for renewable energy utilization through photovoltaic panels to provide artificial light for “plant factories” (Albright, 2014).
He began with wheat production, and established a case study where 1.6 pounds of wheat can be harvested per year in a square foot with traditional open field agriculture, and the value of said 1.6 pounds of wheat would sell for $0.24 in a reasonable market. In this scenario, a daily light integral of 55 mol/m² would be expected. Producing that same energy through artificial lighting would require 466 kWh ft.⁻² yr⁻¹ and at $0.10/kWh would result in an electricity cost of $46.60 ft.⁻² yr⁻¹ for that same 1.6 pounds of wheat. This would be the equivalence of paying over $17 just to cover the energy costs alone for a loaf of bread. From this case study, it is clear that the concept of growing wheat solely from artificial light is not practical or economically viable (Albright, 2014).
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Albright makes another case study regarding lettuce production, specifically addressing the numbers and figures involved with the carbon footprint of shipping food vs. the carbon footprint that would result from the same food being produced in a plant factory. Using a similar process as in the wheat case study, it can be calculated that transporting lettuce from California to New York would result in a 0.7 lbs of CO₂/lb of lettuce carbon footprint. Although this may seem high, a plant factory would require 577 mol ft. ⁻²/year⁻¹ which is equivalent to 144 kWh ft.⁻² yr⁻¹ to produce 26 lb ft.⁻²/year⁻¹. This corresponds to 5.55kWh/lb of lettuce and with a power station producing 1 lb CO₂/kWh, 5.55 lbs of CO₂/lb of lettuce would be produced, ultimately showing that a “plant factory” would create 7.9 times the carbon footprint of traditionally grown lettuce. Once again, Albright makes his case in justifying the impracticalities of “plant factories” (Albright, 2014).
Albright does take into consideration that the carbon footprint issue could be mitigated through the utilization of renewable energy sources such as solar, harnessed through photovoltaic cells. He once more extrapolates from established figures and data to conclude that one acre of lighted growing area would require seven acres of photovoltaic panels to generate sufficient light needed for photosynthesis. Although this form of implementation is possible, logistics issues, general impracticalities, and significant initial capital investment once again make “plant factories” unfeasible. Albright ends the article by stating, “Simply put, sunlight by itself, has no carbon footprint. The same is not true of fossil-fuel power plants. This remains the Achilles heel of plant factories and skyscraper farms.” (Albright, 2014).
From Albright’s article, it can be deduced that growing with solely artificial light does not have the merit to be a practical and environmentally-sound solution for feeding the additional population growth expected within the next 35 years even when considering renewable solar energy. However, an article within Produce Grower, “Getting Cozy with ‘Zero Emissions’” gives valuable insight regarding innovative growing that can be environmentally sound as well as cost-effective (Mosby C., 2014).
The article described a greenhouse operation in Maine, called Cozy Acres Greenhouses run by owners Jeff and Marianne Marstaller. The original greenhouses within the property were heated by Propane throughout winter months and burned approximately 10,000 gallons per year. Due to the Maine Department of Agriculture program, “Farms for the Future” and the USDA’s Rural Energy for America Program (REAP) the Marstallers received two grants, allowing for the installation of a ten-ton geothermal heating system, as well as 30 kilowatt photovoltaic system. With these two systems operational, Jeff Marstaller stated, “We believe we have the only fully heated greenhouse with zero emissions in the northern states”. The original investment for these two systems was estimated at $200,000, but was made possible through the original grants and paid for itself through yearly cost savings and tax credits. An additional aspect to consider is the competitive marketing advantage Cozy Acres Greenhouses has gained through their use of renewable energy, “Electricity from the Sun. Heat from the Earth. Emissions at Zero…Mother Nature approved.” This marketing effort in union with becoming organically certified has attracted the interest of local restaurants, cafes, bakeries, and even
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WholeFoods to buy from Cozy Acres Greenhouses contributing to the economic viability of innovation invested greenhouses (Mosby, 2014).
In Mosby’s article, the realization is evident that economic viability in food production is derived not only from innovative technology and investment in sustainable energy sources, but also high demand for currently trending niche items such as organic food, microgreens, etc. In the broader and plainer perspective, it can essentially be stated that growing food is only profitable if consumers are willing to pay a price that justifies the costs and inputs of production. Advertising and promoting to the correct market segments as well as producing high-demand crops are crucial for economic viability, especially if growing is to be considered in urban areas.
1.7 Microgreen and Organic Food Production Trends
Microgreens are a popular trending and high-value food item which has considerable viability for successful urban agriculture implementation, according to a University of Kentucky extension article, “Microgreens” by Tim Coolong, 2012. The article defined microgreens as “young, tender, edible crops that are harvested as seedlings”. The growing time frame for microgreens is only 7-14 days and can be grown in soil or hydroponically. Regardless of the growing methodology, short harvest cycles can result in high potential for profitability, especially if demand from high-end restaurants, health-conscious consumers, or health food stores is present. Microgreens can have a potential market price of $25-$50 per pound in particular niche markets (Coolong, 2012). Specific examples of microgreens include Daikon Radish, Purple Kohlrabi, Mizuna, Red Giant Mustard, and many more. Johnny’s Selected Seeds supplies over 100 different varieties (MicroGreens, 2015).
Additional justification for this market price of $25-$50 per pound could be found within an article written by Joe Lamp’l in The Seattle Times. Lamp’l stated that the high price can be justified through the incorporation of microgreens in gourmet and upscale meals served at upscale restaurants. The primary selling points of microgreens are the “freshness, nutrition, color, texture, and flavor” (Lamp’l, 2010).
Demand for organic food production, especially within the United States has grown considerably as well and also contributes merit to the potential success of growing within urban areas. The USDA estimated that U.S. organic food sales were $28 billion in 2012; where fruits and vegetables comprised 43% (Growth Patterns in the U.S. Organic Industry, 2013).
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Figure 1.7-1. USDA Economic Research Service U.S. organic food sales (2012)
This trend has also resulted in an increase of organic certification in cropland as well as pasture and rangeland, and can be seen by the graph below (Growth Patterns in the U.S. Organic Industry, 2013).
Figure 1.7-2. USDA Economic Research Service U.S. Certified Organic Cropland (2012)
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1.8 Urban Agriculture and Urban Farming
Throughout the previous sections, the subject of controlled environment agriculture (CEA) has been discussed in terms of methods, implementations, and companies that practice its utilization. The definition is essentially a method of growing crops; usually without soil where all aspects of growth are controlled and managed either under a greenhouse environment to take use of natural light or within a traditional building where LEDs serve as the light source in lieu of natural light (Jensen, 2002). There is currently no aspect of the definition that dictates where CEA is implemented spatially or geographically.
In contrast, urban farming or urban agriculture can be defined by the UN FAO as, “an industry that produces, processes and markets food and fuel, largely in response to the daily demand of consumers within a town, city, or metropolis, on land and water dispersed throughout the urban and peri-urban area, applying intensive production methods, using and reusing natural resources and urban wastes to yield a diversity of crops and livestock.” (FAO.org, n.d.). Although the UN FAO’s definition is descriptive, the simpler definition of urban agriculture is producing food within or around a city environment or urban area. Expanding growth and interest in urban agriculture is evident and can mainly be attributed to 50% of the world’s population living within urban environments, where land or space suitable for growing food is significantly limited (FAO.org, n.d.).
Urban agriculture serves as a fairly broad topic and the majority of information regarding the subject falls within the non-scholarly realm, focusing primarily on publicity for specific urban farms, events, or organizations. Urbanfarming.org serves as an example and has created the "Urban Farming 100 Million Families and Friends Global Campaign™" This campaign encourages 100 million people to grow their own gardens in an effort to aid in world hunger, empower individuals, and build community relations. Tutorial videos, contacts, program guidelines, and educational forums are provided for those interested in urban farming (Urban Farming, n.d.).
An additional organization that has made significant contributions to urban agriculture is the RUAF foundation, which is “an international network of seven regional resource centers and one global resource center on Urban Agriculture and Food Security.” RUAF offers numerous services including technical support, policy advice, and training to local and national governments to promote urban agriculture (The RUAF Foundation | RUAF - Resource Centres on Urban Agriculture and Food Security, n.d.). Also involved in the development of urban agriculture is the USDA and the American Planning Association (Urban Agriculture, n.d.).
The Technology Education and Design (TED) foundation has contributed multiple presentations regarding the importance of urban agriculture and the success that can be accompanied with progressive implementation as well. One of the most notable articles, “Stephen Ritz: A teacher growing green in the South Bronx” shares the success of a school teacher who inspired his students to pursue careers in urban agriculture implementation.
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(Stephen Ritz, n.d.) Urban Farm is a magazine that promotes the topic through stories, products, and advice (UrbanFarmOnline.com, 2015). Also supporting urban agriculture is The Huffington Post, which has published nearly 100 stories and articles written mostly in favor and support for the subject (Urban Agriculture, 2015).
In terms of historical background, the practice of urban agriculture can be traced to the ancient Egyptians; incorporating extensive gardens into cities and landscapes. The Hanging Gardens of Babylon have received significant attention for the legend of their beauty and impressive scale, but even more notable is that these gardens are thought to have incorporated aquaponics. There is no direct evidence to support this, but it is plausible and interesting to consider that the science of aquaponics can have such a rich history throughout the entire world (Sace, 2013). Throughout history as cities have developed, agriculture has been incorporated into their development through various methods. However, the most significant recorded surge of urban agriculture came with World War II. In support of the war effort, Americans were urged by the government to plant “Victory Gardens” to supplement the nation’s food supply. “By 1943 more than 20 million of these gardens came into existence and produced an estimated 10 million tons of fruit and vegetables which accounted for 41 percent of that year’s production.” (Hodgson et al., 2011). However, after the war ended and development accelerated at unprecedented rates throughout the country, these gardens slowly disappeared. It wasn’t until the USDA started an urban garden program that specialized in extension which brought these gardens back to life within the United States. The arrival of the “Green Movement” has contributed to an increase in urban agriculture as well (Hodgson et al., 2011).
1.9 Urban Agriculture Implementation
Urban agriculture implementation can be accomplished through multiple means and often is the manifestation of creativity and the desire to grow food with readily available space and materials. One example includes growing plants via the use of containers and soil. A wide variety of edible vegetation can be grown through use of this traditional method, with the advantage of being able to utilize standard store-bought or custom made containers made from readily available materials. “Urban Agriculture-Ideas and Designs for the New Food Revolution” written by David Tracey serves as a reference for small scale urban agriculture implementing. Hanging baskets, window boxes, living walls, and raised beds are included within this book (Tracey, 2011).
A distinct area that can be utilized for urban agriculture is roof space. Roofs can often be overlooked as usable growing area, but if utilized correctly, can be very productive and affective means of urban agriculture implementation. Roofs can be utilized as either rooftop gardens or converted to green roofs, and are distinctly different. Rooftop gardens involve the addition of grow space on the top of a roof to create a garden-like atmosphere. In the majority of cases, no major modifications are involved with the roof or supporting structure (Whittinghill & Rowe, 2012).
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The structure of a green roof is significantly different compared to a standard roof, and is engineered for specific purposes. A typical green roof has several functions, but the most imperative is storm water management. The structural makeup consists of an impermeable membrane, and lightweight media that will support the growth of specific plants, along with other necessary layers and components. The depth of the media ranges depending on the type of roof and load bearing capacity of the building. Extensive green roofs have shallow media and support mostly sedum and other types of low maintenance plants primarily for storm water management. The roof essentially captures the water from the initial rainfall and then slowly releases it over time through evaporation and evapotranspiration. Intensive roofs can have a media layer up to a foot deep or greater. Through intensive green roofs, edible produce can be grown and be an integral part of urban agriculture. However, this is not a widely utilized practice at this point in time. “The role of green roof technology in urban agriculture” written by Leigh J. Whittinghill and D. Bradley Rowe confirms that this is the case. The majority of green roofs are constructed primarily for storm water management practices and are designed with a certain plant selection. By growing edible vegetation instead of cover crops, the intended functionality of a green roof could be significantly altered. However, additional research and development in green roof technology could allow this implementation to be possible in the future (Whittinghill & Rowe, 2012).
1.10 Realizations of Urban Farming
Nathanael Johnson wrote in an article, “Urban farms won’t feed us, but they just might teach us” about the various aspects which make urban farms unviable for substantial food production. He initially repeated the historical statistics stated by Hodgson et al.; that during World War II, Americans were able to produce 40 percent of the nation’s fruit and vegetables through “Victory Gardens” and asked if this concept of independent food-production could ever be implemented in today’s times with the same level of success. After interviewing urban farmers, he deduced that the possibility of such success did not seem likely due to three constraints commonly predominating in urban areas; space, time, and money (Johnson N., 2014).
In urban areas, space or land is highly valued and the utilization must be justified through profitability and effectiveness. Johnson quoted Eli Zigas, food systems and urban agriculture program manager of the urban planning nonprofit SPUR, in regards to growing through the use of a one to two acre urban farm. He stated, “It can be a substantial amount of food, but for a dense area, compared to the number of people who live nearby, it’s a small dent”. Traditional agriculture would simply not be viable within a city. However, Johnson did state that the problem could be solved with vertical farms due to the nature of the systems and the ability to grow up rather than out. However, he also stated that “truly heroic amounts of food” would need to be produced to justify the construction of such a structure (Johnson N., 2014).
The value of time within a city is also to be considered just as high as the land due to the fast-paced nature of urban environments. For example many of the individuals that could
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benefit from their own urban agriculture implementation also work two to three part-time jobs, not allowing them to fully partake and attain the given benefits. Affluent city residents may have greater potential to partake in self-urban agriculture implementation, but to achieve a majority participation would require significant incentive that would convince individuals such as young professional to choose gardening over other activities such as “drinking, Tinder, and electronic music” (Johnson N., 2014).
The last constraint to consider within cities regarding urban farming is simply money. Johnson reiterated that there is space within cities such as vacant lots for farming to occur, but in very few circumstances does farming this limited land result in profitability due to the higher cost of living. Johnson refered to another source, David Lepeska who investigated urban farms; finding that success could only be found in nonprofits supported by outside funding, and high- end producers able to sell to fine restaurants and a wealthier client base willing to pay a premium. Johnson reiterated that an urban farm can only function and be financially viable when all three aspects; space, time, and money are present (Johnson N., 2014).
Additional constraints were addressed in the literature not only in the United States, but throughout the entire world as well. Several constraining factors in the growth of urban agricultural listed by Deelstra & Girardet included restrictive policies, lack of supportive services, unfeasible implementation of environmental technologies, and lack of organization and representation from urban farmers. However, one of the largest constraints was simply available funding (Deelstra & Girardet, 2000).
Yves Cabannes wrote an article, “Financing Urban Agriculture” describing the result of sending research teams out to 17 different cities throughout the world to study how urban agriculture was financed by urban farmers. The researchers analyzed many aspects including shortcomings of institutions both public and private that allow for viable vertical farms and discovered the following information: Credit and loans were available for urban farming, but credit was scarce, and many institutions were reluctant to give loans for the purpose. Government also played a significant role in urban agriculture and was largely responsible for success or failure. In addition, a large percentage of urban farmers were poor and unable to attain funds. In order for success, a majority of urban farmers needed the following: additional infrastructure, urban agricultural inputs, and technical support. The final conclusion was that insufficient funding for urban agriculture resulted in insufficient food supplies for cities throughout the world (Cabannes, 2012). Godfrey Hampwaye came to the same conclusions in an article, “Benefits of Urban Agriculture: Reality or Illusion?” Hampwaye analyzed four Zambian cities, and concluded that urban farming was only a successful means in regards to food supply and poverty alleviation if implemented properly (Hampwaye, 2013).
Proper urban agriculture implementation often corresponds to addressing the regulations, laws, ordinances, codes, and procedures of the city or urban area where implementation is taking place. Cities or other forms of geographically defined regions have their own distinct policies with associated nuances, and one extension publication from the University of Missouri titled “Urban Agriculture-Best Practices and Possibilities” by Mary K.
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Hendrickson and Mark Porth provided an overview. Details involved with establishing land devoted to urban agriculture are provided with a large portion concentrated on proper zoning as well as city ordinances. The authors also noted the importance of water access, electricity, non-contaminated soil, involvement with food policy councils, and establishment of local food system infrastructure. The message this article conveyed was that for successful urban agriculture implementation to occur, proper procedures needed to be established with the specific governing body of the urban area. An established relationship with the governing body provided a sense of order and regulation that could better involve the people and government to succeed with developing the surrounding urban space in a positive way for the local community (Hendrickson & Porth, 2012).
1.11 Benefits of Urban Farming
Great challenges are associated with urban farms in regards to attaining financial viability along with the inherent disadvantage of non-significant food production. However, multiple benefits are inherently present through the implementation of urban farming such as education, the “growing of good citizens”, improvement of communities, city-greening, culture- building, and increased biodiversity (Johnson N., 2014).
An article written by Tjeerd Deelstra and Herbert Girardet contributed to Johnson’s statement by listing their observed benefits of urban agriculture such as “microclimate improvement, conservation of urban soils, waste and nutrient recycling, water management, increases in biodiversity, decreases in global warming and atmospheric pollution, and increases in environmental awareness” (Deelstra & Girardet, 2000). Gil Doron provided his own list of benefits in “Urban Agriculture: Small, Medium, and Large”) which included many of the same listed by Deelstra & Girardet. However, Doron also recognized numerous social benefits that can be attained through urban agriculture implementation, including stress relief, community building, and most importantly “the breakdown of barriers between people with regard to differences in age, ethnicity, class, and gender” (Doron, 2005). Urban agriculture not only brought people together, but also provided community members with a sense of pride and ownership for their surroundings (Doron, 2005).
1.12 Controlled Environment Agriculture and Urban Farming
The realization to be made in examining the definitions of controlled environment agriculture and urban agriculture is that the two remain distinctly different and do not overlap strictly by definition. For example, growing tomatoes hydroponically in a greenhouse constructed in a forest would constitute as CEA, but would not constitute as urban agriculture. Growing cucumbers in a raised bed on an apartment patio located in Philadelphia would constitute as urban agriculture, but would not be considered CEA. However, overlap of the definitions is present and evident in many of the previous examples such as FreightFarms and Skygreens. With this realization in mind, it becomes crucial to understand that growing within urban environments, especially with the intention of larger scale profitable production, is usually only attainable with CEA integration (Johnson N., 2014).
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1.13 Review and Preface
Several deductions can be made regarding the concept of increasing food access to aid in the elimination of “food deserts” through innovative agricultural practices.
“Vertical Farming” today is unfeasible due to significant initial capital investment as well as energy-intensive processes and attached high-carbon footprints, but does provide inspiration for the future of farming.
Through controlled-environment agriculture, crop production at high volumes can be implemented anywhere in any place with or without natural sunlight; but still include the potential disadvantages associated with the “Vertical Farming” concept; significant initial capital investment as well as energy-intensive processes and high-carbon footprints. Some forms of renewable energy as well as utilization of natural light can help to alleviate these drawbacks.
Urban agriculture does have multiple benefits for urban communities such as city- beautification, community development, and education, but when practiced within traditional means, does not have the capability to provide a significant percentage of food required to supplement food requirements of an urban area’s population.
Based on the information provided, one could assume that effective and practical growing implementation for improving food access may possibly reside in the integration of controlled environment agriculture and urban agriculture with the utilization of natural sunlight. Effectiveness of this particular growing implementation would also have a higher probability of success if initial capital investment remains relatively low, can be utilized in small or “unusable” spaces, and can produce trending niche food or crop items such as microgreens or organic produce with reatively low maintenance.
Although the literature provides insight into the profitability of certain agricultural production implementations, many unknowns still reside with the systems that are currently in operation today in regards to operating costs, volume and revenue required for profitability, as well as carbon footprint of production and distribution.
No scholarly works could be found that investigate the entirety of financial and production aspects of a given agricultural production implementation system in a specific area to understand the various aspects and nuances that are part of the practical and economic viability. Therefore, this scenario has provided the opportunity to research such a system for potential effectiveness in agricultural production based on the previously outlined criteria. One system that has this potential is referred to as the “Rotating Living Wall” produced by Green Towers LLC, “An Urban Agricultural Design Company”.
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1.14 Green Towers
GreenTowers began originally as a pitch team comprised of five individuals that competed in the 2012 Ag Springboard competition. Success followed with additional competitions and seed funding. The original concept proposed by GreenTowers was the implementation of micro-urban farming in cities to aid in the elimination of food deserts by means of recycled shipping containers converted into aquaponic greenhouses positioned vertically. This would allow for organic food production to take place within a minimal footprint and crops could be grown up instead of out. Due to impracticalities involved with converting a shipping container into a greenhouse, GreenTowers pivoted away from this concept and built a business around the concept of incorporating nature into working and living environments as well as developing agricultural production systems that can be built into urban areas affectively, practically, and aesthetically. GreenTowers transitioned from a student team to a full time business and LLC in November of 2013. The current founders and owners of GreenTowers are:
Dustin Betz President and Biological Systems Designer
Bachelor of Science in Biology with minors and interdisciplinary honors studies in Horticulture and Engineering Entrepreneurship, Pennsylvania State University.
Jared Yarnall-Schane Vice President of Sales and Operations
Bachelor of Science in Mechanical Engineering with minors in Leadership Development and Engineering Entrepreneurship, Pennsylvania State University.
Mike Zaengle Vice President of Design
Bachelor of Architecture, Pennsylvania State University
Jonathan Gumble Vice President of Research and Development
Bachelor of Science in Landscape Contracting, Pennsylvania State University.
Company information can be found at http://www.greentowersusa.com/.
GreenTowers LLC currently comprises three divisions;
Living Interiors and Furniture BeeCoSystem Urban Agricultural Production “Rotating Living Wall”
The research for this thesis analyzes the Rotating Living Wall which is essentially a moving conveyor system, enabling plants to be grown on a vertical plane with minimal
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maintenance. This prototype was tested for one year (June 2014-May 2015) of microgreen production to understand the potentials and weaknesses of this system.
The research for this thesis also analyzes “Living Furniture” which is essentially a small scale (10 gallon) aquaponics system using common goldfish as the nutrient source for growing microgreens under fluorescent light. This prototype was tested for a year of microgreen production as well to understand the potentials and weaknesses of this system.
Aquaponics serves as the basis for “Living Furniture”, and therefore a literature review regarding this subject was completed as well.
1.15 Aquaponics
The basic premise of aquaponics is that aquaculture or fish farming is combined with hydroponics. Fish are raised in tanks, producing soluble wastes rich in plant nutrients, especially ammoniacal nitrogen. The water is recirculated through a biological filter where microbes converts the ammonia to nitrite, and then to nitrate. The nitrate and other nutrients in the waste serve as essential nutrients for plant growth, which are then recirculated to hydroponic grow apparatuses where plants are able to utilize these nutrients for growth. After the plants absorb the nutrients, the remaining water is circulated back to the original fish tank. The major advantage of this system is the symbiotic relationship that occurs between the fish and plants. In a traditional fish farming or aquaculture environment, a portion of the water is frequently changed due to the buildup of waste produced by the fish, and in a traditional hydroponic environment, artificially derived nutrients are utilized. With aquaponics systems, minimal addition of supplemental nutrients is required and minimal removal of waste given that the volume of fish and plants are grown at proportional rates. Therefore, fish feed remains as the only substantial input required for an aquaponics system (Sace, 2013).
The roots of aquaponics can be traced back to the Aztec peoples who resided around the marshes of Lake Tenochtitln where suitable farmland was scarce. These people developed a solution for farming by making floating rafts fashioned from reeds called “chinampas”. These rafts were mounded with nutrient rich soil collected from the bottom of the lake. Seeds were planted on these soil-covered rafts and as plant growth occurred, the roots developed through the rafts, enabling the absorption of water and nutrients provided by the fish in the lake. Essentially, the Aztec peoples utilized the same core processes that are in modern day aquaponic systems over 1000 years ago (Sace, 2013).
The Chinese used the same process thousands of years ago in a similar manner. Floating cages were built for ducks, which allowed their waste to be deposited in a pond of finfish. The finfish received nutrients from this waste which was then diverted to a lower pond of catfish. The catfish lived from the waste of the finfish, then producing waste as well. This nutrient-rich water was utilized for irrigation in rice and vegetable fields (Jones, 2002).
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The Incas utilized a similar process by digging ponds within the mountains and leaving a small “island” in the center. Rainwater would fill these ponds, and would then be stocked with fish. Geese would fly from nearby land to roost on these islands and catch fish, leaving behind their own waste. This waste fertilized the land making it ideal for farming. The entire concept resulted in a harvest which provided three sources of food; geese, fish, and vegetative crops (Jones, 2002).
Some of the earliest studies of modern-day aquaponics can be found in publications from an organization referred to as The New Alchemy Institute. This institution formed by John Todd, Bill McLarney, and Nancy Jack Todd existed from 1969 to 1991 and was founded with the intention to step away from modern large-scale agricultural practices, and focus instead on more efficient integrated agricultural solutions that have less dependence on the consumption of fossil fuels. The studies are archived at Green Center Incorporated - Falmouth, MA (New Alchemy Institute and Green Center Archives - Falmouth, MA., n.d.). The majority of studies focused on the concept of building natural ecosystems within enclosed greenhouse-like structures. Temperature control was primarily regulated by the sun and large volumes of contained water which served essentially as a climate buffer enabling growing to take place during winter. Tilapia and lettuce were used primarily for the studies and they described a basic form of the aquaponics technology. The Institute was able to produce a large number of fish in these solar tanks, while growing plants hydroponically at the surface level of the water. A layer of plastic mesh was used to prevent the fish from eating the plants’ roots (Todd, 1977).
Further developments in aquaponics research were spearheaded by Mark McMurtry and Doug Sanders of North Carolina State University. They effectively created the first closed loop aquaponics system utilizing sand-filtration grow beds. The nutrient-rich water from the fish culture unit dripped through sand that served both as the biological filter and the growing substrate material. After the water passed through the sand, it was re-circulated back to the fish tank (Diver, 2000).
Through their research, McMurtry and Sanders discovered some of the key concepts and background information for modern-day aquaponics systems such as conservation of water and resources, intensive production of fish, and lastly reduced operating costs for aquaponics compared to using aquaculture and hydroponics independently of one another. The reciprocating biofilter for flood and drain systems was developed as part of their research program as well. Additional principles of modern aquaponics systems established included consumption of less than 1% of water used in traditional aquaculture practices, efficient utilization in arid or semi-arid climates for crop production, organic production, advantages of reciprocating biofilters, importance of the waste removal in aquaculture system components, and the ratio of biofilter volume to fish tank volume (Diver, 2000).
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Tom and Paula Speraneo utilized the same system developed by North Carolina State University, but made an enhancement by using gravel grow beds in an ebb and flow system. The Speraneos were successful in the utilization of this system, producing 45-70 pounds of produce per pound of tilapia. One of the major factors contributing to the success of their system was utilizing tilapia hybrids which are more tolerant to cool water temperatures (Diver, 2000).
Dr. James Rakocy became the next notable authority of aquaponics with studies completed as the director of the aquaponics research team at the University of the Virgin Islands. He and his team have done extensive research regarding large-scale use of deep water culture grow systems. He is a strong proponent of using this type of system in both developing countries and arid climates. Dr. Rakocy has published many extensive research reports for the science of aquaponics and is considered to be the most notable expert in the aquaponics field (Diver, 2000).
His article, Recirculating Aquaculture Tank Production Systems: Aquaponics-Integrating Fish and Plant Culture, was a comprehensive overview of both aquaponics and the specific system that he studied throughout his career with the University of the Virgin Islands. In terms of design and operation it can be considered one of the most trusted and noted resources in aquaponics and provides insight into the calculations that are necessary to construct a functioning aquaponics system. Rakocy began with the aquaculture component of the system and defined several key terms. The first was the critical standing crop which he stated was the maximum biomass of fish a system can support without restricting fish growth. This is the key for maximum efficiency in terms of nutrient production which directly correlates to maximum crop production. In order to obtain this conditional status, three stocking methods can be utilized: sequential rearing, stock splitting, and multiple rearing units. All methods have their advantages and disadvantages, but all three should ultimately result in establishing the critical standing crop which Rakocy states in general for aquaponics systems does not exceed 0.5 pound/gallon (Rakocy et al., 2006).
The solids removal component was then reviewed in the article. The majority of the solid waste should be removed before it enters into the hydroponic grow beds; however some solids should be introduced for the process of mineralization to occur. Mineralization allows for the release of several nutrients that would have to be introduced into the system otherwise, resulting in additional inputs and costs. The article described several methods for removing solids from a system and states that sand filters will require additional maintenance opposed to gravel filters or even swirl filters. He described the solids removal component utilized at the University of the Virgin Islands and describes a three part system consisting of a clarifier, filter tank, and a degassing tank (Rakocy et al., 2006).
The next process involved in aquaponics is the biofiltration step. Once the solids are removed, ammonia (NH4) is present in potentially toxic concentrations. The process of nitrification converts the ammoniacal nitrogen to nitrite and then to nitrate which is relatively non-toxic to fish and serves as the primary nitrogen source for the plants growing in the
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hydroponics component. Nitrification is made possible through two types of bacteria; Nitrosomonas and Nitrobacter living within various types of media such as sand or gravel. The nitrification process does result in acidification, so the addition of a base solution is often necessary throughout the operation of the system. Rakocy stated that the pH for the entire aquaponics system should be maintained near 7.0 to allow for both nutrient availability and nitrification. The subject of hydroponic systems was then discussed with a focus on the various apparatuses which are often utilized. They included the flooding and draining of various forms of media, nutrient film technique (NFT), and deep water culture (DWC) sometimes referred to as floating raft systems. There are associated advantages and disadvantages with each particular system (Rakocy et al., 2006).
After the nutrient rich water flows through the hydroponic portion of the system, purified water is recirculated; first to a sump, and then to the fish tank. The sump is the lowest point in the aquaponics system and will usually have two pumps. One will serve as the circulating pump for the aquaculture tank, while the other will serve as a pump for the hydroponic subsystems. The sump also serves as the area where additional non-chlorinated water can be introduced (Rakocy et al., 2006).
Additional figures and guidelines were stated in the article with the majority applying to commercial size aquaponics systems utilizing Tilapia and floating raft hydroponics. However, principles that apply to aquaponics systems in general regardless of size include, optimum water temperature remaining at 75°F, maintaining high dissolved oxygen levels, (DO), nitrogen toxicity occurs at levels over 2,000 parts per million, low nitrogen levels promote fruiting, high levels of nitrogen promote vegetative growth, and the addition of iron chelate supplement (Rakocy et al., 2006).
The article also discussed plant selection for aquaponics systems. Rakocy states that culinary herbs result in the highest level of income and will result in the most profitability. Fruits will not produce the same result due to longer cultivation time. Lettuce can be very profitable due to its short growth period. As with fish harvesting, there are several methods for crop harvesting; staggered cropping, batch cropping, and inter cropping. Each has its own advantages and disadvantages depending on the particular crop species being grown (Rakocy et al., 2006).
The remainder of the article provided calculations necessary for designing a functioning aquaponics system. The end harvest quantities were assumed, and based on these assumptions, the calculations were worked backwards. These amounts were figured for the square footage of grow space required, which translates to the amount of fish feed required. This determined the number of fish, which could be used to determine the amount of water needed to sustain that stocking density. The system could then be designed from these calculations (Rakocy et al., 2006).
Rakocy ended the article by discussing the economics that are involved with aquaponics and indicated that it could be a profitable enterprise if certain conditions were met. He agrees
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with the general notion that aquaponics in general cannot be considered profitable or unprofitable. The profitability of a particular aquaponics system is dependent upon where the system is located and the particular markets within the area of operation (Rakocy et al., 2006).
Within the literature review, one paper was found that thoroughly analyzes the financial viability of a specific aquaponics operation. “Aquaponics: Community and Economic Development” is a thesis written by Elisha R Goodman in her fulfillment of attaining a Master Degree in City Planning at the Massachusetts Institute of Technology. Her entire thesis was based on a case study conducted with Growing Power which is an aquaponics production facility located in Milwaukee Wisconsin. She studied the cash flow analysis of the facility to determine if aquaponics could serve independently as a viable business venture in a temperate climate. The value of this paper was that it took a specific aquaponics production scenario and analyzed the details of the operation. Throughout her case study she collected data from Growing Powers’ production methods including all development and operating costs. The development costs included items such as the building and materials to construct the facility. The operating costs included items such as water, fish feed, fish, seed, electricity, heat, labor, and overhead. Analysis was completed for the yearly income based on the value of the fish and crops produced throughout the year to determine cash flow and potential profitability.
After completing the analysis, Goodman determined that Growing Powers’ production units were not profitable at current size or means of operation. However, at the end of her thesis she did apply economies of scale, showing mathematically that if the systems utilized yellow perch and lettuce at a larger scale, it would be profitable (Goodman, 2011).
The value in Goodman’s work is showing that aquaponics can be a potentially profitable business based on production alone, and also showing that analyzing aquaponics systems for profitability must be completed on a specific case basis. Throughout her literature review, she shows multiple articles and a wealth of information regarding the design, implementation, and biological processes involved with aquaponics, but very few conclusive financial analyses were conducted. Nine different articles were reviewed in an effort to financially analyze various aquaponics systems, but none showed promise of being either conclusive or definitive. One master’s thesis, “An Economic Analysis of Integrating Hydroponic Tomato Production into an Indoor Recirculating Aquacultural Production System” from Auburn University stated that stand alone aquaculture production of either catfish or Tilapia would lose money annually, but adding hydroponic tomato production, would result in an annual profit. Although this appears to be promising, the entire case study was theoretical and the numbers were derived from a wide array of sources throughout the literature review. Once again, issues remain in that a specific system in a specific location, with a specific market is not being analyzed. The remaining articles provide glimpses of financial data and mostly confirm the established principle that both aquaculture and hydroponics are more profitable when functioning together in the same process than functioning separately (Goodman, 2011).
There are numerous articles relevant to aquaponics. However, the vast majority of these articles discuss optimizing the specific mechanical, biological, and chemical processes that are
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involved with a particular system; usually of commercial size and capacity. No scholarly literature could be found for aquaponics systems of significantly smaller scale such as one comprised of a ten gallon aquarium for microgreen production.
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Chapter 2 Rotating Living Wall
2.1 Introduction
The experiments completed for this thesis were done to analyze the production and financial potentials of GreenTowers’ products, one specifically being the Rotating Living Wall.
2.2 Materials and Methods
2.2.1 System Design and Construction
The Rotating Living Wall is essentially a custom-built vertical conveyor system comprised of readily-available parts and components. The structural frame of the conveyor was constructed of pressure-treated 2x4s, (Figure 2.2.1-6.) and 4 wheelbarrow wheels served as the conveyor rollers. The track or belt was a combination of electrical metal tubing connected through threaded rod and chain. An electric motor rotated a bicycle wheel through the use of a friction drive, which was directly connected to a shaft; also connected to the wheelbarrow wheels. (Figure 2.2.1-2.) Consequently, the electric motor rotated the conveyor system and was controlled by a C.A.P ART-DNE digital adjustable recycling timer (manufactured by Custom Automated Products; 420 Harley Knox. Blvd. Perris, CA 92571). This specific timer allowed for precision movement intervals of the system. (Figure 2.2.1-5.) On each rung of the conveyor, hung an individual grow trough that could easily be taken on and off the rungs. This grow trough was constructed of a 30.5” long section of 5.5” aluminum gutter closed at each end with caps. Two holes were drilled on the back side of the gutter to attach bent J-bolts (Figure 2.2.1- 3.); allowing the trough to be pitched slightly for better exposure of sunlight. The conveyor system’s track comprised twelve rungs which could hold the equivalent twelve grow troughs.
Figure 2.2.1-1. Overall System Layout
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Figure 2.2.1-2. Friction Drive Figure 2.2.1-3. Gutter Trough J Bolt
Figure 2.2.1-4. Gutter Troughs
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Figure 2.2.1-5. C.A.P ART-DNE Digital Adjustable Recycling Timer
http://www.qcsupply.com/10025-art-dne-adjustable-cycle-timer.html
Figure 2.2.1-6. Framing
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Figure 2.2.1-7. 3D SketchUp Model (Front View)
Figure 2.2.1-8. 3D SketchUp Model (Side View)
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Figure 2.2.1-9. 3D SketchUp Model (Trough Detail)
*Note:
The implementation of the Rotating Living Wall system was comprised of twelve troughs and occupied a footprint of approximately eight square feet. However, an alternative frame could be implemented where two pieces of structural steel support both sides of the conveyor and attach to the floor and roof of the greenhouse structure. (Figure 2.2.1-10.) A frame such as this would essentially have a footprint of only the conveyor itself, equivalent to approximately 4.66 square feet.
Figure 2.2.1-10. 3D SketchUp Model (Alternative Frame)
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2.2.2 Production Experiment Methods
The intention of the experiments performed for the Rotating Living Wall prototypes was to understand the various factors that affect the performance and ultimately the production yields of a “vertical conveyor plant system” that utilizes primarily natural sunlight, while also understanding performance in a specific location throughout the duration of one year or four seasons. The factors tested included the following:
Seasonal Yields Growth in Vertical System Vs. Growth on a Horizontal Plane (Light Penetration) Variety of Crops Rotational Timing Movement Vs. Stationary Full Media Depth Vs. Half Depth Artificial Lighting
Variety of Crops
Due to the limited space within the Rotating Living Wall prototype, as well as the desire for financial viability, microgreens were chosen to be grown within the system. As stated in the literature review, microgreens can be sold for $25-$50 per pound and can be harvested at only several inches tall; making them the ideal selection. A variety of microgreens were chosen for these experiments, specifically:
Basil (Dark Opal) Chinese Cabbage (Kogane) Choi Pac Choi (Red) Collard (Champion) Hon Tsai Tai Kale (Toscano) Kohlrabi (Purple) Mizuna Mustard (Red Rain) Radish (Daikon) Red Cabbage Tatsoi
By growing twelve types of microgreens, each variety could be grown in a single wall system trough within each growing trial, while also understanding which varieties were best suited based on production of highest plant mass. The varieties can be shown below. (Figure 2.2.2-1. 12 Varieties of Microgreens)
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Figure 2.2.2-1. 12 Varieties of Microgreens
Images from “Johnny’s Selected Seeds”
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Seasonal Yields
The Rotating Living Wall was designed to function within a greenhouse enclosure to primarily utilize natural sunlight for growing. Due to its inherent design concept, the production yields of the system will fluctuate with the changing of seasons due to differences in temperature and light levels. Sixteen trials were completed; four in summer, four in fall, four in winter, and four in spring; essentially encapsulating an annual production “snapshot” of the system and the differences in production throughout the seasons.
Growth in Vertical System Vs. Growth on a Horizontal Plane (Light Penetration)
The design of the Rotating Living Wall does produce shadowing within the system, limiting the amount of light available to the grow troughs, especially with certain trough positions located near the bottom or back sections. Of the sixteen trials testing the walls, twelve trials incorporated growing the equivalent number of grow troughs on a traditional flat surface for comparison (trials in summer, fall, and spring).
Rotational Timing
The Rotating Living Wall was capable of turning at various intervals throughout the day to achieve even distribution of sunlight for the grow troughs within the system. To understand the effects of different rotational rates, each wall was attached to a separate timer. Wall 1 rotated the slowest; one trough position per seven hours. Wall 2 rotated the second slowest at one trough position every 5 hours. Wall 3 rotated one trough position every 3 hours, and Wall 4 rotated one trough position each hour. This procedure was done for the summer and fall for a total of eight trials.
Movement Vs. Stationary
In addition to the presence of shading, the Rotating Living Wall also “moved” the plants growing within the system. To understand potential effects of the movement itself, a bench was constructed to oscillate a portion of the flat growing plants in the four summer trials. (Figure 2.2.2-2.)
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Figure 2.2.2-2. Oscillating Linear Actuator Bench
Full Media Depth Vs. Half Depth
The cost of growing media is one of the highest and most significant costs in microgreen production. Therefore the amount of media required to support adequate growth, but no more should be used. In the fall and spring trials, half of the flat troughs utilized for comparison of wall production had foam-board inserts to simulate the effects of half-filled media troughs.
Artificial Lighting
By the end of fall trials, it was evident that substantial yields could no longer be achieved through the limited sunlight available. Therefore, just the walls were tested in the winter season with different types of artificial lighting. Specifically:
No lighting Fluorescent Metal Halide LED (Light Emitting Diode)
In spring trials, LED and Metal Halide lighting were still being tested. However, fluorescent lighting was replaced by white colored grow troughs to understand if the reflective properties of the surface could enhance light penetration and ultimately potential yields of the system.
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2.2.3 Experimental Setup and Layout
To test all of these factors within a year’s time frame, the following experimental setup (Figure 2.2.3-1. and Figure 2.2.3-2.) was constructed within the Tyson greenhouses at the Pennsylvania State University in University Park, PA.
Figure 2.2.3-1. Greenhouse Section
Figure 2.2.3-2. SketchUp Model of Experimental Setup
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Figure 2.2.3-3. General Experimental Layout
By using this experimental layout with 96 troughs, (Figure 2.2.3-3.) enough data was collected throughout 16 trials to not only understand the big picture of growing throughout the year in both the vertical and control groups but also test the other factors as well.
Figure 2.2.3-4. Experimental Setup in Greenhouse (Summer)
96 Troughs Total; 48 Troughs in Wall Systems and 48 Flat Troughs; 4 Walls of 12 Rotating at Different Rates; 2 Groups of 24 Flat Troughs; One Group Stationary; One Group Oscillating
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This configuration (Figure 2.2.3-4.) allowed for comparison between the wall and flat control groups while also testing the factors of physical movement and rotational timing.
Figure 2.2.3-5. Experimental Setup in Greenhouse (Fall)
96 Troughs Total; 48 Troughs in Wall Systems and 48 Flat Troughs; 4 Walls of 12 Rotating at Different Rates; 2 Groups of 24 Flat Troughs; One Group Filled Completely with Media; One Group Half-Filled with Media
This configuration (Figure 2.2.3-5.) allowed for comparison between the wall and flat control groups while also testing the factor of media depth as well as continuing to test rotational timing.
Figure 2.2.3-6. Experimental Setup in Greenhouse (Winter)
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48 Troughs Total; 4 Walls of 12; one with no lighting, one with fluorescent lighting, one with metal halide lighting, one with LED lighting
This configuration (Figure 2.2.3-6.) was used to test different forms of artificial lighting.
Figure 2.2.3-7. Experimental Setup in Greenhouse (Spring)
96 Troughs Total; 48 Troughs in Wall Systems and 48 Flat Troughs; 4 Walls of 12; one with no lighting, one with white colored troughs, one with metal halide lighting, one with LED lighting; 2 Groups of 24 Flat Troughs; One Group Filled Completely with Media; One Group Half-Filled with Media
This configuration (Figure 2.2.3-7.) allowed for comparison between the wall and flat control groups while continuing to test the factor of media depth during a warmer season as well as continuing to test artificial lighting and a more reflective trough.
2.2.4 Process
Seeding
Accurate seeding was required throughout the trials to maintain consistency, and the standard recommended seeding rate for microgreens according to Johnny’s Seeds is approximately ½” spacing or less. (Microgreens, 2015) Each grow trough had a footprint of approximately 1.165 square feet, and at ½” spacing, 336 seeds were required per trough.
In order to maintain this consistency and accuracy, a vacuum seeder (Figure 2.2.4-1.) was constructed that consisted of a twelve gallon shop vacuum cleaner (Figure 2.2.4-2.), nylon tubing, and PVC pipe with 28 plastic pipette tubes. Twelve “passes” would essentially seed a single trough (Figure 2.2.4-3. ) and could be completed within three minutes.
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Figure 2.2.4-1. Vacuum Seeder Manifold Figure 2.2.4-2. Shop Vacuum
Figure 2.2.4-3. Seeding Template
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Growing
The variety of microgreens chosen were categorized as fast growing from Johnny’s Seeds and had a recommended growing period of 10-15 days. The full 15 days were chosen as the growing period and kept consistent throughout the trials; allowing comparisons to take place. (Microgreens, 2015) SunGro Sunshine Mix 4 Aggregate Plus was utilized as the growing media for these experiments.
Harvesting
After the 15 day growing period was complete, each trough of microgreens was harvested. A jig and hopper (Figure 2.2.4-4.) allowed the microgreens to be collected into a bag quick and efficiently by means of a battery operated hedge trimmer (Figure 2.2.4-5.). The end result of the harvest can be seen in Figure 2.2.4-6.
Figure 2.2.4-4. Jig and Hopper Figure 2.2.4-5. Hedge Trimmer
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Figure 2.2.4-6. Harvested Product
2.2.5 Performance Criteria
To understand the performance of the microgreens grown within the trials and analyze the various treatments, four criteria were utilized:
Fresh Weight (Harvested Product) Dry Weight Height SPAD (Soil Plant Analysis Development) (a measure of chlorophyll and nitrogen status)
Figure 2.2.5-1. SPAD Meter
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Fresh weight was measured as soon as harvesting was completed by weighing each sample.
Dry weight was measured approximately one week after harvest. Samples were dried in a forced air circulation drying oven at 60ºC.
5 sub-sample measurements were taken from each trough to estimate height. A tape ruler with cm markings was used to measure each microgreen sub-sample from the surface of the media to the highest point of the plant. (480 readings for 96 troughs or one trial)
5 sub-sample measurements were taken from each trough for SPAD. (480 readings for 96 troughs or one trial)
A SPAD meter (Figure 2.2.5-1.) essentially serves as a chromometer and gives an estimate of chlorophyll content to understand the health and vigor of plants. (Chlorophyll Meter SPAD- 502Plus, n.d.)
ANOVA or Analysis of Variance was used to evaluate the treatment effects from utilizing the fresh weight, dry weight, length, and SPAD data. Minitab 17 Statistical Software was used to run the analysis as well as create the statistical figures found in the appendices.
2.2.6 Lighting Analysis Methods
When optimizing growth within a greenhouse CEA environment, the limiting factor for plant growth needs to be considered. In open field agriculture, deficiencies of nutrients within the soil, drought and limited water uptake, or limiting light levels due to shade prevent plants from growing to optimum potential. Within an environment such as a “factory farm”, these limiting factors are managed to optimize the relationship between plant production and inputs. Temperature can be set to an ideal consistent setting, the ideal light spectrum and intensity can be produced through LEDs, and the optimum nutrient levels can be provided through aquaponic or hydroponic solutions.
With the Rotating Living Wall, growing can take place within a managed or modified environment given that the system is placed within a greenhouse structure. Although soilless media was utilized for the duration of the experiments performed, a hydroponic or aquaponic nutrient system could be integrated with further research and development. Temperature can be managed within reason as well due to the relative lower cubic volume of air occupied by a vertically integrated system. Therefore, the only factor that is least precisely controlled and manipulated is light. As stated previously, the advantages of growing with natural light are lower upfront costs from additional hardware and systems, as well as removing the costs associated with consumption of fossil fuels, or any form of indirect supplied energy. However, the associated disadvantages are minimal control of natural light levels as well as just simply lacking substantial light for growing in certain geographical areas at certain times of the year. For example, a high tech hydroponic greenhouse operation located in New York City may be
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able to supply fresh produce in the summer season, but throughout the winter months it will not be able to produce anywhere near the same volume due to the lower levels of sunlight associated with the winter season.
The experiments for the Rotating Living Wall were performed to gain insight on what that change in production would be as the seasons progressed throughout the year. The key factor to be understood was that potential production was solely dependent on the light levels associated with a specific geographical area and these can vary significantly year to year; especially if changes are made to the immediate location of operation. Therefore potential production of a system utilizing natural sunlight can only be estimated from repeated consistent growing trials over a course of several years in a given location.
However, another potential method for estimating potential production yields could be derived from weather data recorded for a specific geographical area and used in conjunction with a light simulating program. This type of program often utilized within architectural engineering practices, is capable of taking 3D generated models of buildings and rooms, and placing them in projected environments. The program then takes the weather data and runs a simulated light model throughout given time frames. Dr. Richard Mistrick; Associate Professor of Architectural Engineering at Penn State University with his student AJ Scanlon used the program DAYSIM in conjunction with RADIANCE to essentially produce a lighting simulation for the Rotating Living Walls and plain flat troughs located in the specific greenhouse section where the experiments took place for the year, encompassing all 16 trials. A SketchUp model was provided, imported into the program, and then oriented. Once the model was positioned, the simulation was run, using the “average weather data program” for State College, Pennsylvania. Five points were selected from each trough and a reading of foot candles was recorded for each point (480 in total) every hour for the year of production, amounting to over 4 million readings. These readings were then organized for understanding the change in light levels throughout the year for both the wall systems as well as the flat troughs, and also understanding the difference in light levels between the two setups.
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2.2.7 Financial Analysis Methods
From Coolong’s extension article, (Coolong, 2012) as well as The Seattle Times (Lamp’l, 2010), $25-$50/pound can be justified as a realistic price for microgreens. However, this is only in particular niche markets. In many areas, the demand at this price point would not exist and in a more rural area, a market price of $15/pound or less could be considered more reasonable. When understanding the profitability of microgreen production, one of the key factors is simply the market price that can be attained, which ultimately determines profitability. For the following case studies based on the data collected throughout the Rotating Living Wall experiments, $15/pound, $25/pound, and $50/pound were considered.
The other aspects that were evaluated were the costs associated with production. These costs included materials (media and seeds), utilities (electricity for motors, lighting, and heating), and the cost of labor required for operations. For the case study performed, one Rotating Living Wall unit operating for one year within State College, Pennsylvania was considered, and the data collected for all twelve microgreen varieties was used for the financial analysis.
Lighting was also analyzed in terms of the costs of operation. In terms of choosing supplemental lighting for crop production, it may seem intuitive to utilize LED technology strictly from the standpoint of greater production yields and the increasing popularity. However, analyzing the energy consumption with the light output for all forms of supplemental lighting used throughout the experiments was completed as well. This included the testing of:
two fluorescent fixtures (Figure 2.2.7-1.) one metal halide light fixture (Figure 2.2.7-2.) one LED light fixture (Figure 2.2.7-3. )
Figure 2.2.7-1. Two Fluorescent Light Fixtures
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Figure 2.2.7-2. Metal Halide Light Fixture
Figure 2.2.7-3. LED Light Fixture
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Light testing was completed through the use of a light meter (Apogee Instruments' Model QMSW-SS) as shown below. (Figure 2.2.7-4.)
Figure 2.2.7-4. Light Meter
Energy consumption testing was completed through the use of an energy consumption meter (P3 International, Kill A Watt EZ, Model P4460) as shown below. (Figure 2.2.7-5.)
Figure 2.2.7-5. Energy Consumption Meter
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2.3 Results and Discussion
2.3.1 Production Experiments Results
Growth in Vertical System Vs. Growth on a Horizontal Plane (Light Penetration)
Fresh Weight
The amount of harvestable product or fresh weight was significantly different (higher) for the microgreens grown in the flat troughs throughout the growing trials. This was likely due to the lower light levels or lesser light penetration that is conditional of the wall systems. Throughout 12 trials of growing, it was calculated that the wall system on a per trough basis produced approximately 79% of fresh weight compared to the flat troughs. (Figure 2.3.1-1.)
Figure 2.3.1-1. Annual Production Overview of Harvestable Product (Walls Vs. Flats)
The ratios of fresh weight produced by the wall systems to flat troughs can be seen for each individual trial below. (Figure 2.3.1-2.)
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Figure 2.3.1-2. Annual Production Overview Fresh Weight Ratios (Walls Vs. Flats)
Dry Weight
Dry weight was significantly different (higher) for the microgreens grown in the flat troughs throughout the growing trials as well. This was likely again due to the lower light levels or lesser light penetration that is conditional of the wall systems. Throughout 12 trials of growing, it was calculated that the wall system on a per trough basis produced approximately 74% of dry weight compared to the flat troughs. This can be shown below. (Figure 2.3.1-3)
Figure 2.3.1-3. Annual Production Overview of Dry Weight (Walls Vs. Flats)
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The ratios of dry weight produced by the wall systems to flat troughs can be seen for each individual trial below. (Figure 2.3.1-4.)
Figure 2.3.1-4. Annual Production Overview Dry Weight Ratios (Walls Vs. Flats)
Length
The average length of microgreens grown in the flat troughs compared to the wall systems was significantly different; specifically that microgreens grown in the flat troughs were taller. Due to the higher light levels found in the flat troughs, these microgreens grew larger.
SPAD
The average SPAD readings taken from the microgreens grown in the flat troughs were significantly different (higher) compared to those obtained from the microgreens grown in the wall systems. This can be explained through higher chlorophyll contents of the microgreens resulting from greater amounts of light received in the flat troughs.
Production per Trough Vs. Production per Square Foot
Although growing with the traditional flat environment (control) produced more microgreens per trough unit, another measurement that needs to be considered is the production of microgreens per square foot of greenhouse area. With the Rotating Living Wall system, more troughs can fit within a given square footage, therefore making the production
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per square foot significantly greater than traditional flat growing. Understanding a more general principle, a taller Rotating Living Wall system could produce even significantly greater production rates per square foot. The figure below shows the ratio of pounds of fresh microgreens grown per square foot by the wall systems to the pounds of fresh microgreens grown per square foot by the flat trough control group for each trial. On average, the wall systems produced 2.25 times the fresh weight of microgreens per square foot compared to the control troughs. (Figure 2.3.1-5.)
Figure 2.3.1-5. Annual Production Overview; Production/Ft.² Comparison (Walls Vs. Flats)
The individual ratios are shown for each trial below. (Figure 2.3.1-6.)
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Figure 2.3.1-6. Annual Production Overview; Production/Ft.² Ratios
Crop Performance Based on Variety of Microgreen
Differences in growth characteristics were significant when comparing the varieties of microgreens in regards to fresh weight, dry weight, length, and SPAD. Therefore, different varieties of microgreens will affect yields and ultimately the performance of the Rotating Living Wall. These differences in fresh weight can be seen below both in the wall systems as well as the (control) flat troughs. (Figure 2.3.1-7.)
Figure 2.3.1-7. Annual Microgreen Variety Performance Overview (Trough Basis)
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From calculating the square footages of the wall systems as well as the flat (troughs), average annual production per square foot could be determined for each variety of microgreen. Radish performed the best, followed by Chinese Cabbage, Mizuna, Tatsoi, Mustard, Kohlrabi, Red Cabbage, Choi Pac Choi, Collard, Kale, Hon Tsai Tai, and lastly Basil. (Figure 2.3.1-8.)
Figure 2.3.1-8. Annual Microgreen Variety Performance Overview (Ft.² Basis)
Rotational Timing
There was no significant effect of rotational timing on any of the evaluated factors. Throughout the eight trials evaluated, no significant differences were evident in regards to fresh weight, dry weight, length or SPAD. When observing entire production of the wall systems for eight trials, each system produced approximately 11 pounds of microgreens; varying only by approximately half of a pound. There were minimal differences in dry weight as well. (Figure 2.3.1-9.)
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Figure 2.3.1-9. Comparison of Wall System Rotational Rates
Movement Vs. Stationary
No significant differences were evident in fresh weight, dry weight, length, or SPAD when comparing moving and stationary flat treatments.
Full Media Depth Vs. Half Depth
Significant difference was found in terms of fresh weight with the deeper troughs producing the higher fresh weight yields. (Figure 2.3.1-10.) However, when considering that the average difference in production between the two treatments was only 10 grams from using only half the media, it would be logical from a financial standpoint to utilize half-filled media troughs to reduce costs. One bale of Sungro Sunshine #4 Mix Aggregate Plus (3.8 cu.ft.) costs $33.60 and will fill 24 troughs completely. This is equivalent to $1.40 per trough. By only using half the volume of media for each trough, the cost is reduced to $.70 per trough. Even at $25/pound, a reduction in 10 grams or .02 pounds would result in only a loss in revenue equivalent to $0.50. Significant difference was found in length comparison as well and can mostly be attributed to the microgreens having a larger reservoir of water within the deeper media. Differences in dry weight as well as SPAD readings were not significant. (Figure 2.3.1-11.)
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Figure 2.3.1-10. Differences in Fresh Weight Based on Media Depth
Figure 2.3.1-11. Differences in Dry Weight Based on Media Depth
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Artificial Lighting
Significant differences in fresh weight were found with LED lighting producing the greatest yields, followed by metal halide, then fluorescent, and lastly no lighting at all. (Figure 2.3.1-12.) Significant differences in dry weight were found as well following the same progression. (Figure 2.3.1-13.) Differences in length as well as SPAD readings were not significant.
Figure 2.3.1-12. Differences in Fresh Weight Based on Lighting Type
Figure 2.3.1-13. Differences in Dry Weight Based on Lighting Type
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In the spring trials, the wall systems were tested once more for differences in production yields based on the use of LED lighting, metal halide lighting, no lighting, and in place of fluorescent lighting, gloss white gutter grow troughs.
Significant differences in fresh weight were found with LED lighting producing the greatest yields, followed by metal halide, the white grow troughs, and lastly no lighting at all. (Figure 2.3.1-14.) Significant differences in dry weight were found as well following the same progression. (Figure 2.3.1-15.) Differences in length as well as SPAD readings were not significant.
Figure 2.3.1-14. Differences in Fresh Weight Based on Lighting Treatment (Spring Trials)
Figure 2.3.1-15. Differences in Dry Weight Based on Lighting Treatment (Spring Trials)
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2.3.2 Light Analysis Results
Results of Light Levels throughout Seasons
From the data collected, it can be shown that the light energy levels of state college vary greatly throughout the year. A single point within a flat trough was estimated to receive just over 6.1 million foot-candles of light during a two week growing trial within the month of July. However, in trial 9 which spanned over the Winter Solstice, that same point only receives approximately 1.2 million foot candles over the same two week period. Therefore, only 20% of the light energy is available at this time of the year in State College, PA. This approximate 20% remained true for the wall systems as well. (Table 2.3.2-1.)
Table 2.3.2-1. Seasonal and Total Light Data
Results of Light Levels between Wall Systems and Flats
When comparing the average light levels of the wall systems over the course of the year to the average light levels of the flat troughs, the ratio of foot-candles was calculated at 0.62. This ratio was calculated based on the ratios associated with each individual trial, which do fluctuate. The lowest ratios were found in summer as well as late spring with a value of 0.57. The highest ratios were found in trials 6, 8, and 10 (fall and winter) with values of 0.72. From principle it can be stated that the vertical growing plane utilized by the “Rotating Living Wall”
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system does take advantage of the lower angle of the sun. Although this may be true, only approximately 20% of the maximum light levels are present in the time frame when this is relevant. (Figure 2.3.2-1.)
Figure 2.3.2-1. Flat Trough Seasonal Wall/Flat Ratio
Correlation between Light Levels and Production Yields
Although the lighting simulator modeling program is capable of producing very exact data for this specific growing operation, additional real-world factors did exist while the experiment took place for determining the actual physical measured yields. Although a significant correlation was not found between the light data and the microgreen yields, the lighting simulator still provides value.
The value of the simulator comes from having the ability to calculate the relative difference in light levels between growing systems and displaying the change in light levels throughout the course of the year. When comparing the quantities of microgreens produced by the wall systems, the greatest quantity; 2.19 pounds produced in the first trial compared to 0.54 pounds produced in trial 9 provides a figure of 24%. As stated previously, the lowest light level produced by the simulator in winter was only approximately 20% of the highest light level found within summer. Although rather crude, this does show a moderate relation between the light levels and microgreen production. In terms of the .62 average annual foot candle ratio, the annual microgreen production ratio when relating the wall systems to the flats corresponds to .79. Although this is not a direct correlation either, the lighting simulator program was able to show that a significant difference in light levels was present and therefore a significant difference in fresh weight microgreen production would result.
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Future Potential
The experiments performed in the real-world environment of the greenhouse have inherent conditions that have the potential to affect the yields of the microgreens throughout the year; other than just light levels. Some of these conditions include fluctuations in temperatures, seed viability, inconsistencies in the growing media, and potential lack of water. In future growing operations with hydroponic techniques, computer control of temperature and moisture, and multiple data collectors, it is perceivable that microgreen production yields from a specific system could be predicted throughout the seasons with relative accuracy. Again, data would most likely have to be collected over several years with very precise control of the growing environment. However, if higher level mathematics were utilized for this type of application to better understand the correlations between all of these factors and crop yields, informed decisions could be made regarding the various design and installation phases of large scale implementations of the “Rotating Living Walls” or similar growing systems.
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2.3.3 Financial Analysis Results
Revenue
The total amount of microgreens produced within a year from one system in State College, PA totaled 19.06 pounds. Keeping with 19.06 pounds as the expected average annual production for a wall system operating within 4.66 ft.², the following potential revenues are calculated:
$15/pound: $285.90/year $61.35 revenue/ ft.² /year $25/pound: $476.5/year $102.25 revenue / ft.² /year $50/pound: $953/year $204.51 revenue /ft.² /year
Costs
When calculating costs, several assumptions need to be made regarding operations.
SunGro Sunshine Mix 4 Aggregate Plus was used as the growing media and can be purchased at $33.60/3.8 cu. ft. bale if purchased in bulk; quoted from Griffin Greenhouse Supplies. One bale is able to fill 24 troughs completely.
Seed costs were based on the purchased costs for the twelve types of microgreen seeds used throughout the experimental trials (supplied by Johnny’s Seeds). Approximately 336 seeds were utilized for each growing trough.
Electricity costs for the rotational motion provided by the 20 watt motor were based on 8 cents/kWh and 2 hour rotation intervals at 10 seconds of movement for each movement (12 rotations). Therefore,
(20 W or .02 Kw) * (120 seconds or .03 hours) * (8 cents/kWh or $.08/kWh) =
$.000048/day or approximately $.02/year
Heating costs were calculated from the greenhouse energy cost estimator by Greenhouse Engineering NRAES – 33 Robert Aldrich and John Bartok.
The Rotating Living Wall can fit within an enclosure approximately 1.2’x4’x8’. The advantage to this configuration is that the whole growing apparatus can be positioned so the back side can be directly against the south wall of a building or similar type structure. This significantly reduces heat loss and still allows for good light exposure.
The labor involved with the operations of one “Rotating Living Wall” consisted of media prep work, seeding, watering, and harvesting. Therefore, the estimated time for each of these labor components would be the following:
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media prep: 30 minutes seeding: 15 minutes watering: 15 minutes harvesting: 30 minutes
The cost of this labor time ultimately depends on the hourly rate of the worker being paid. Due to the relative simplicity of the labor; $8/hour could be justified.
Based on these assumptions, the following costs are associated with the operation of a single Rotating Living Wall:
Materials
Media $1.40/trough 192 troughs/year $268.80 Seeds $0.12/trough 192 troughs/year $23.04
Utilities
Electricity for motor $.00005/trough 192 troughs/year $0.02 Heating $0.40/trough 192 troughs/year $76.80
Labor
1.5 hours at $8/hour for one grow period 16 grow periods/year $256
Total Costs 192 troughs/year $624.66
Profit Potential of Current Model
With these associated costs, economic viability of one Rotating Living Wall operating for a year within State College, Pa or area of similar climate and light levels can only be profitable if the microgreen demand is $50/pound or greater. At this price point, there is a $328.34 annual profit for one wall system; ($70.46 profit/ft.²/year).
Profit Potential of Alternate Model
One of the costs can be adjusted to increase the economic viability of the Rotating Living Wall. As noted previously, using only half-filled media troughs have very little effect on the yields of the systems. It can be estimated that the reduction in fresh weight of microgreens would only equal approximately half of a pound. By reducing the amount of media by half, the following costs are associated.
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Materials
Media $0.70/trough 192 troughs/year $134.40 Seeds $0.12/trough 192 troughs/year $23.04
Utilities
Electricity for motor $.00005/trough 192 troughs/year $0.02 Heating $0.40/trough 192 troughs/year $76.80
Labor
1.5 hours at $8/hour for one grow period 16 grow periods/year $256
Total Costs 192 troughs/year $490.26
When considering $15/pound, $25/pound, and $50/pound for profitability, again, only $50/pound would be profitable. However, prices such as $30/pounds and $35/pound would show merit, compared to the costs associated with using fully filled media troughs.
Profit Potential of “Hobby” Model
One other factor to take into consideration is that a single Rotating Living Wall could be maintained solely by the owner and labor would not be an associated cost. Instead of being paid directly for the work, one could consider this type of operation simply as a “hobby”. In this scenario, the owner would simply receive the profits or cost-savings as essentially “payment” for the work put into the system. The following costs would be predicted based on this type of operation:
Materials
Media $.70/trough 192 troughs/year $134.40 Seeds $0.12/trough 192 troughs/year $23.04
Utilities
Electricity for motor $.0001/trough 192 troughs/year $0.02 Heating $0.40/trough 192 troughs/year $76.80
Labor
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Total Costs 192 troughs/year $234.26
Potential Revenues
$15/pound: $285.90 $61.35 revenue/ ft.² $25/pound: $476.5 $102.25 revenue / ft.² $50/pound: $953 $204.51 revenue /ft.²
Even at $15/pound, and the use of one unit, marginal profitability would be achieved. At microgreen prices of $25/pound and higher, profitability has the potential to be substantial to the individual owner, especially if multiple units are implemented.
Business Potential
From this example of cost adjustment, it can be seen that operating a business solely from producing microgreens with these systems could not be viable due to the high operating costs especially in regards to labor and media. However, producing microgreens as a hobby by an individual with a single system does have potential for profitability even with relatively low price points for microgreens. Lastly, in order to make a microgreen production business viable through the use of the “Rotating Living Wall” systems, the use of growing media would have to most likely be replaced with a hydroponic or other form of nutrient system for lower operating costs and maintenance, and/or labor would have to be significantly reduced and replaced through automated systems; vacuum seeders, automatic harvesting machines etc. Although requiring significant upfront capital investment, this would allow for lower operating costs over time for potentially a much larger operation where profitability would have greater potential to be achievable.
Costs of Infrastructure
A fully functioning and enclosed Rotating Living Wall produced by GreenTowers retails for approximately $1500, and occupies 8 ft.²; equivalent to $188/ft.². According to Tim Coolong’s extension article, “Microgreens”, from the University of Kentucky, greenhouse space can be constructed at a range of $8-$30/ft.² and high tunnels even lower at $1.50/ft.². With this being evident, it can be assumed that the Rotating Living Wall System can only be financially justified within areas where space is limited such as urban environments or cities. In undeveloped areas, it would be logical to grow over a larger area and simply utilize a high tunnel covering. (Coolong, 2012)
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Financial Analysis of Artificial Lighting
The light output and energy consumption of fluorescent, metal halide, and LED lighting at varying distances can be shown below. (Table 2.3.3-1.)
Table 2.3.3-1. Light Outputs and Energy Consumption
From the table, it can be shown that when comparing light output, to energy consumption, LED outperforms metal halide by a factor of 1.86, and fluorescent by a factor of 6.09. Although LED fixtures may require initial significant investment, the greater light output and increased efficiency make LED lighting the best choice for crop production.
This ratio can be stated from two different perspectives. If both the metal halide and LED fixture consume the same amount of energy, the LED light produces approximately two times the amount of light. If the fixtures produce approximately the same amount of light, the LED fixture will only consume about half the energy.
From the chart, (Figure 2.3.3-1.) it can be shown that there is a significant increase in fresh weight production from the utilization of supplemental lighting, especially LED.
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Figure 2.3.3-1. Supplemental Lighting
The average difference in production of fresh weight between the wall system with LED lighting and the wall system without any supplemental lighting was approximately .57 pounds per growing trial. The 250 Watt LED lighting throughout the growing trials was on for 16 hours a day. The cost for this light usage can be calculated:
(250 W or .25 Kw) * (16 hours) * (8 cents/kWh or $.08/kWh) = $.032/day
Therefore, the cost of lighting one system for the duration of 15 days costs a total of $4.80. An increase in .57 pounds of microgreens can result in the following increase in revenue:
$15/pound: $9.00 $25/pound: $15.00 $50/pound: $30.00
From this information, it is evident that even at $15/pound, the operational costs of LED lighting pays for itself and is financially feasible, if the significant upfront costs of the lighting fixtures can be incurred.
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Chapter 3 Living Furniture
3.1 Introduction
The Living Furniture experimental design consisted of individual small-scale aquaponic units comprised of a 10 gallon aquarium, a submersible pump, and a media-based hydroponic grow bed. The intention of these experiments was to understand the factors that affect the production and functionality of a small-scale aquaponics system; specifically the number of goldfish and chelated iron supplementation. Fresh weight, dry weight and water chemistry were utilized as performance criteria.
3.2 Materials and Methods
Design and Construction
Living Furniture is essentially an aquaponics system made up of a 10 gallon aquarium and a media based hydroponic grow bed. For the units used in these experiments (Figure 3.2-1.), the grow bed was a plastic window box (6-in H x 23.75-in W x 7.875-in D) filled with GrowStones® which consist of recycled expanded glass. The pump (Hydrofarm AAPW160 160-GPH Active Aqua Submersible Pump) circulated the fish water into the hydroponic grow bed positioned above the aquarium. The water was distributed throughout the grow bed through the use of a custom-made manifold made of ½” “Genova” pipe with 14 holes (5/32”) spaced 2.5” apart (Figure 3.2-2.). A standpipe was installed at the bottom of the grow bed and allowed for a 1” water reserve at the bottom. As the water circulated, it poured through the standpipe and then flowed back into the tank. The trickling water provided aeration or dissolved oxygen for the aquarium. Within the grow bed, Grodan A-OK 1.5 Starter Plugs (Figure 3.2-3. ) were positioned next to the manifold holes where the microgreen seeds were planted. This allowed for consistent moisture throughout growing. For the experimental trials, standard fluorescent fixtures were hung above the grow beds to provide sufficient light levels.
Living Furniture produced by GreenTowers “contains” the components utilized in the experimental setup (aquarium, growbed, and plumbing) in a piece of custom-built furniture which can be seen in Figure 3.2-4.
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Figure 3.2-1. Experimental Setup Unit
Figure 3.2-2. Manifold Pipe
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Figure 3.2-3. Manifold Pipe with Rockwool Cubes
Figure 3.2-4. GreenTowers Living Furniture
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Figure 3.2-5. Experimental Setup (Beginning)
Six of these units were utilized and contained increasing numbers of common goldfish (Carassius, auratus). (Figure 3.2-5.)
The units were labeled by the following:
T5 Tank 5 with 5 goldfish T6 Tank 6 with 6 goldfish T7 Tank 7 with 7 goldfish T8 Tank 8 with 8 goldfish T9 Tank 9 with 9 goldfish T10 Tank 10 with 10 goldfish
A single unit was constructed to serve as a control where a standard mechanical filter was utilized for filtration and a separate plastic planter box filled with 1.5” of SunGro Sunshine Mix 4 Aggregate Plus was utilized for growing. (Figure 3.2-6.) Therefore, these two components functioned independently of one another. This unit was labeled as:
TR Reserve Tank with 7 goldfish
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This particular unit incorporated the use of an “elevated false floor”. The concept behind this was to allow a reservoir at the bottom of the grow bed. The elevated piece of foam board supported the grow media and water was allowed to percolate to the bottom of the planter box. (Figure 3.2-7. and Figure 3.2-8.) If excess water was present, it would rise near the bottom of the planter and then eventually exit through the bulkhead fitting shown below. The water would then drain into a bucket on the floor. (Figure 3.2-9.) This whole unit essentially allowed for traditional growing of microgreens on top of the fish tank while still providing proper drainage without having media enter into the fish tank.
Figure 3.2-6. Control Unit with Standard Mechanical Filter on Opposite Side
Figure 3.2-7. Plastic Plug Trays Providing Support for Foamboard Floor
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Figure 3.2-8. False Floor Constructed of Foamboard with Drainage Holes
Figure 3.2-9. Collection Bucket
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Process
All units were functioning and operational by mid-July 2014, allowing for the first trial to begin on July 22. For the first two trials, eight varieties of microgreens were tested for viability of use of a small scale aquaponics system. The following varieties of slow-growing microgreens were tested; Komatsuna, Sorrel, Scallions, Mustard, Cilantro, Beets, Arugula, and Chard. (Figure 3.2-10.)
Figure 3.2-10. Growing Eight Varieties of Microgreens
Komatsuna, Red Giant Mustard, Bulls Blood Beets, and Ruby Red Chard performed best, producing the highest fresh weight comparatively. Therefore these four microgreens were selected for the remaining eight trials. (Figure 3.2-11.)
Figure 3.2-11. Growing Four Varieties of Microgreens
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Of these remaining eight trials, four were completed with fixed fish feeding rates of the following:
T5 .20 grams of fish food per day T6 .24 grams of fish food per day T7 .28 grams of fish food per day T8 .32 grams of fish food per day T9 .36 grams of fish food per day T10 .40 grams of fish food per day
TR .28 grams of fish food per day
Through progression of the trials, de-ionized water was used to re-fill the tanks for the purpose of not having to de-chlorinate the water. No additives were introduced for the aquaponic or control units as well.
After observations of what appeared as potential toxicities and deficiencies especially within the komatsuna and mustard, feeding rates were adjusted based on the fish mass for trials 7 and 8. It was found that although the tanks had increasing numbers of fish, this did not necessarily correspond to proportionately increasing fish mass. The fish feeding rates were adjusted to the following:
T5 .20 grams of fish food per day T6 .20 grams of fish food per day T7 .21 grams of fish food per day T8 .28 grams of fish food per day T9 .37 grams of fish food per day T10 .32 grams of fish food per day
TR .22 grams of fish food per day
With no significant differences apparent after changing the feeding rate, chelated iron was added at a rate of 50 milligrams/1 gallon of water to each tank in the form of DPTA (Figure 3.2- 12.); for a total of 500 milligrams for each individual unit added every two weeks. De- chlorinated tap water was also used for replenishing the tanks with the purpose of introducing micronutrients and greater mineral content. (Figure 3.2-13.)
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Figure 3.2-12. Chelated Iron (DTPA)
Figure 3.2-13. Re-filling with De-chlorinated Tap Water
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The last two trials utilizing chelated iron and de-chlorinated tap water (Figure 3.2-14.) remained at the same feeding rate:
T5 .20 grams of fish food per day T6 .20 grams of fish food per day T7 .21 grams of fish food per day T8 .28 grams of fish food per day T9 .37 grams of fish food per day T10 .32 grams of fish food per day
TR .22 grams of fish food per day
Figure 3.2-14. Growing Trials with Chelated Iron and De-chlorinated Tap Water
Throughout the total duration of the trials, temperature, Ph, and water chemistry were monitored and tested (Figure 3.2-15.); specifically ammonia, nitrite, and nitrate. (API Freshwater Master Test Kit, Item #347 Bottle Kit)
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Figure 3.2-15. Testing Water Chemistry
Seeding
Seeding was done by hand and 8 seeds were placed in each Rockwool cube. The same seeding pattern was applied in the media bed unit. (Figure 3.2-16.)
Figure 3.2-16. Seeding
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Growing
Since slow growing microgreens were selected for these trials, the growing duration was kept at twenty days. The only actions required within the growing periods were fish feeding at the respective feeding rates and watering the single media bed. The tanks were replenished with water at an approximate rate of 1” per week. (Figure 3.2-17.)
Figure 3.2-17. Growing
Harvesting
Harvesting was done by hand with scissors; cutting took place at the surface of the rockwool cubes. The contents were weighed for fresh weight measurements (Figure 3.2-18.) and then dried at 60ºC for one week in a forced air circulation drying oven to attain dry weight measurements.
Figure 3.2-18. Fresh Product (Chard)
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3.3 Results and Discussion
Number of Goldfish
Without the addition of chelated iron, significant differences in total production weight were observed among the various tank units. The reserve or control tank produced the greatest microgreen mass, followed by tank unit 5 or the unit with the least goldfish, then followed by tank unit 8, tank unit 6, tank unit 9, tank unit 10, and lastly tank unit 7. The average difference between tank unit 5 and tank unit 7 was about 48 grams or approximately 1.7 ounces and was significant.
With the addition of chelated iron, these differences were no longer present. In fact production only varied among tank units by several grams with increased production volume as well. With chelated iron, it was evident that the number of fish (or fish mass) had minimal effects on the production level of the microgreens.
Chelated Iron
With chelated iron supplementation introduced for the last two trials in an effort to increase yields as well as aid in noticeably visible iron deficiencies, significant improvement in yields was made. Comparing tank units with chelated iron supplementation to those without, an increase in approximately 60 grams of microgreen fresh weight or just over two ounces could be observed. This increase came primarily from the komatsuna.
Water Chemistry
Without the addition of chelated iron and re-filling the tanks primarily with de-ionized water, significant differences in Ph, ammonia, and nitrate were observed. Ph was significantly lower in the reserve tank utilizing a traditional mechanical filter (about 6) in comparison to the aquaponic unit tanks (about 7.5). The reserve tank also experienced much higher ammonia levels; approximately .25 compared to 3. In terms of nitrate levels, tank units 5 and 6 experienced lower levels. Tank unit 5 specifically averaged nitrate levels of approximately 20, while the other tanks experienced nitrate levels of 100 and above. No significant differences could be observed in regards to temperature or nitrite. Once chelated iron was added to the aquaponic tank units, as well as de-chlorinated tap water, no significant differences could be observed in ammonia levels, nitrite levels, or temperature. Ph still remained lower in the reserve tank, and nitrate levels remained lowest in tank units 5 and 6; these levels being considered significantly different.
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3.4 Financial Analysis
Although Living Furniture is not meant to be used as a production system on a large scale, it is relevant to know the potential yields attainable with a 10 gallon aquaponic system as well as the associated costs.
Production, Costs, and Potential Savings
From the collected data it can be shown that the largest production of fresh microgreens observed was 170 grams or .375 pounds in three weeks. However, a more reasonable average would more likely be 120 grams or .25 pounds in three weeks. This would amount to the following potential value to the owner based on various microgreen market prices.
$15/pound: $3.75 $25/pound: $6.25 $50/pound: $12.50
When calculating costs, several assumptions need to be made concerning operations. The cost of the seeds were based on the cost of komatsuna, mustard, chard, and beet seeds as well as the use of 112 seeds/trial from Johnny’s Seeds. Lighting costs are based on 8 cents/kWh, and the use of fluorescent lighting 18 hours a day. Pump energy is based on 8 cents/kWh, and the use of a 5 watt pump, 24 hours per day. The cost of rockwool is based on the use of 14 cubes per trial at $13.50/98 (1.5”) plugs; extrapolated from use of a single Grodan sheet. The cost of fish food is based on feeding .25 grams of fish food per day and paying $9.50 for 200 grams of TetraFin flakes.
The costs associated with operating Living Furniture were based on the previous assumptions and are allotted for the 20 days of the growing trial:
Pump (electricity) $0.20 Lighting $1.00 Seeds $0.12 Rockwool $2.00 Fishfood $0.25
With these costs established, the break-even point can be calculated at $3.57. Cost- savings would be quite marginal at $15/pound ($0.18), but reasonable at much higher rates such as $50/pound ($8.93).
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3.5 Discussion
Although production density is fairly low with Living Furniture, additional tangible benefits are to be considered.
A small scale aquaponic unit not only provides better water quality and oxygen levels for fish compared to a standard aquarium utilizing a mechanical filter, but also provides personal food production with the only added costs being seed and rockwool cubes. The rockwool cubes may not even be a necessity for growing, potentially lowering the additional operating costs compared to a standard aquarium to just the cost of seeds. Also depending on the variety purchased, organic microgreens could be grown within the comfort of an individual consumer’s home with minimal energy inputs; reducing transportation costs and food miles attached to many food products offered today.
However, the true benefit that comes from Living Furniture is the experience of fresh picking microgreens and other vegetables from the comfort of one’s home. Additional benefits also include the sound of running water and the relaxation aspect of bringing nature within working and living environments.
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Chapter 4 Conclusions and Future Direction
4.1 Conclusions for the Rotating Living Wall Systems
The results from the specific prototype developed for testing as well as the general product concept support the following conclusions in regards to operating the Rotating Living Wall systems.
The specific variety of microgreen directly affected the performance of the Rotating Living Wall. In terms of production on a per/trough basis, radish will produce on average approximately four times more than basil. Within the wall system it can produce approximately eight times more. Therefore, the choice of microgreen makes a significant difference not only with production of fresh weight, but the economic viability of the system as well. Although having a variety of microgreens is important from a selling aspect, creating microgreen mixes from high-yielding types will play a significant role in profitability.
The season will also directly affect the production yields due to the varying levels of sunlight both observed throughout the trials and recorded through the lighting simulator. Fresh weight data from these trials shows that five times lower light levels found within the winter months correlated to approximately five times lower production yields. Depending on the specific confines of where the Rotating Living Wall functions, lower yields combined with higher utility costs, (heat and electricity for supplemental lighting) may make growing within this time frame prohibitively expensive.
The wall systems produce less microgreen weight per trough compared to the control flat troughs, due to the shaded areas found within the system; approximately 79% for fresh weight and 74% for dry weight. Recorded lengths and SPAD readings were lower as well. This ratio does fluctuate throughout the various seasons of the year, due to the changing angle of the sun. However, in terms of production/ft.², the walls outperform, producing on average 2.25 times the microgreens per square foot compared to the control flat troughs.
Rotational rate has no effect on production yields based on data collected for fresh weight, dry weight, length, and SPAD. This is due to the “averaging” effect the wall has by periodically rotating the positions of the growing plants. This is a valuable principle learned due to the fact that lower rotational rates require less energy for operation and will not affect plant growth.
The physical movement of plants which occurs in the Rotating Living Wall has no effect on production yields based on data collected for fresh weight, dry weight, length, and SPAD. This information is pertinent if continuous movement is desired from an “aesthetics” principle.
When growing microgreens with soilless media, 1.5” can be utilized for plant growth to sustain sufficient rooting structure and nutritional content. Although fresh weight may have a minimal increase with additional media, the cost drastically increases, reducing profitability.
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Artificial lighting usage in microgreen production with LED lighting not only can increase yields substantially (by up to two times as exemplified in these past specific trials), but high efficiency allows for relatively low utility costs, improving potential profit. Other types of lighting such as fluorescent and metal halide do have the potential to increase yields, but neither produce nearly the same yields as LED lighting. From the experiments performed throughout the winter season, it became evident that for profitability to be attained when growing with supplemental lighting, the upfront investment of LED lights should be made.
Financial viability of the Rotating Living Wall is possible in State College, PA. However, it must operate within the correct parameters and conditions to be profitable, especially in winter months where significantly lower light levels are present with increased utility costs. Potential revenue derived from the market potential of microgreens ultimately serves as the driving factor for profitability.
4.2 Future Concepts and Research for the Rotating Living Wall Systems
4.2.1 Passively Rotating Living Wall Integration with Commercial Aquaponics Systems
The Rotating Living Wall is an adaptive form of technology that can be utilized for hydroponic and aquaponic growing. The current version, (Figure 4.2.1-1.) incorporates a pump that not only circulates hydroponic solution through the grow beds, but also drives the rotational movement.
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Figure 4.2.1-1. Passively Rotating Hydroponic Living Wall within a Vertical Greenhouse
Designs are being completed by GreenTowers to scale this unit for substantial crop production. (Figure 4.2.1-2. and Figure 4.2.1-3.)
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Figure 4.2.1-2. Architect’s Rendition of Implementation in Existing Infrastructure
Figure 4.2.1-3. Architect’s Rendition of a Stand-Alone Unit within an Urban Area
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As stated in the Living Furniture chapter, the concept of utilizing a system already in use; consuming energy and resources for a specific purpose while pairing another system to produce crops may have the potential to be applicable for larger scale operations. An example of this could be the construction of a passively rotating living wall system; hydroponic or aquaponic, on the side of an existing building as depicted below. (Figure 4.2.1-4.)
Figure 4.2.1-4. Passively Rotating Living Wall with Integrated Aquaponics System (Overview)
Figure 4.2.1-5. Passively Rotating Living Wall with Integrated Aquaponics System (Aquaponics)
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Figure 4.2.1-6. Passively Rotating Living Wall with Integrated Aquaponics System (Growing)
In this specific example, an 800 gallon aquaponics system would be installed in the basement of a city building or other area that is not in use. (Figure 4.2.1-5.) The advantage of holding an aquaponics system in an environment such as this is increased temperature control as well as minimal light levels which will prevent algae growth. The water from the system could be pumped through the various floors of the building through PVC pipes to eventually reach the top of the hydroponic system conveyor enclosed within the greenhouse covering mounted on the outside of the building. (Figure 4.2.1-6.) The water of the system would build up on one side of the conveyor and drive the rotation. This principle would be similar to that of a waterwheel. This water would eventually drain at the bottom, be collected, and re-channeled back to the main aquaponics system.
By having the hydroponic conveyor mounted on the side of the building, natural sunlight could be utilized for growing, especially if mounted on a south facing wall. Heating costs would be minimized due to the insulated building wall and the low cubic volume of air within the greenhouse enclosure. Due to the aquaponics system being within an insulated area, additional heat loss strictly from the aquaponics tanks would be prevented as well.
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Although complex installation processes would be required, this form of implementation would provide multiple benefits. Large scale implementation of crop production could take place within an urban environment. The conveyor system could be designed to be very aesthetic, therefore potentially increasing property value and contribute to “city greening”. This concept in its entirety could greatly enhance urban properties, especially vertical surfaces by not only increasing the aesthetic aspects, but also by converting these surfaces into viable growing space.
4.2.2 Research for the Future
From the findings of the research conducted, a base line of operation has been established for the Rotating Living Wall. Additional research that can be conducted for further optimization and improvements of the system include the following:
Research could be completed to test additional varieties of microgreens. This research would mostly test shade-tolerant varieties with larger seeds that could potentially perform better in a shaded growing environment which is inherent of the Rotating Living Wall.
Research could be conducted to test spacing between troughs in the wall system. Increased space between grow troughs may increase light penetration, thereby increasing the potential yields. The Rotating Living Wall could essentially be constructed taller to allow for greater space between troughs but still have the same number of troughs. This testing could be done first by building virtual models of the Rotating Living Wall with different spacing and importing them into the lighting simulator program used for the previous studies. Along with trough spacing, the trough pitch angle could be tested as well. This would essentially minimize the time, money, and energy that would be required to build multiple physical models and complete growing trials throughout various seasons.
Research could be conducted on the use of reflective materials, light tubes, and fiber optics to increase light penetration and light levels without adding additional energy inputs. Pitching the conveyor at various angles to reduce shading could have similar effects. Testing the production rates of systems positioned in the front and back of one another is also a study that could be completed.
Research could be completed as well for different procedures used in the actual growing process. Fertigation could potentially be tested for increasing yields while also figuring the “cost to increase in fresh weight” ratio. Testing the financial aspects of reducing trial numbers but extending duration throughout the winter season for potential cost savings could be completed as well. Seeding density testing could also be done.
Lastly, research for the Rotating Living Wall has been completed with a motor driven, media based version. Testing a hydroponic or aquaponic reiteration of the Rotating Living Wall could also be completed.
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4.3 Conclusions for Living Furniture
From the experiments performed with the small-scale aquaponic units, representing GreenTowers’ Living Furniture, not only has proof of concept been created, but optimization has been achieved as well to show true viability of product. From these experiments, it has been shown that as few as five common goldfish can support the nutrient load required to grow several types of microgreens under supplemental fluorescent lighting with iron chelate supplementation.
Not only is this system functional, but it also provides additional benefits that are improvements upon a traditional ten gallon aquarium utilizing a standard mechanical filter. These benefits include improved water chemistry; specifically lower levels of ammonia and nitrate. Increased aeration or dissolved oxygen levels are present from water pouring into the aquarium from the grow bed (also eliminating the need for an air-stone that requires additional electricity). Lastly, the system is capable of growing crops, specifically microgreens with the only additional costs being seed and potentially rockwool.
*Note Although the production of microgreens does entail the use of some form of supplemental lighting, in many scenarios a traditional aquarium incorporates a light as well for aesthetic purposes. Living Furniture would essentially use the same amount of light but for growing microgreens rather than just solely aesthetic purposes.
In terms of operating parameters, the experiments performed show that chelated iron additives will significantly increase microgreen yields especially for “leafier” varieties. Under these growing conditions, it can also be shown that the number of fish/fish mass does not affect the fresh weight yields, but does have an effect on water chemistry, specifically being that less fish correlates to lower levels of nitrate.
Although substantial crop yields are not capable of being produced by Living Furniture, a broader innovation needs to be considered. The system essentially improves upon an existing aquarium by taking a system that already uses resources; essentially water and electricity, and improves upon it by using these same “spent resources” to give individuals the additional ability to grow their own fresh microgreens. Not only are the inputs for growing these microgreens low to begin with, there is also no additional energy spent to deliver these microgreens. The general concept of utilizing a system already in use; consuming energy and resources for a specific purpose while pairing another system to incorporate nature or produce crops may have the potential to be applicable in larger scale operations.
4.4 Future Direction and Research for Living Furniture
From the findings of the research conducted, a base line of operation has been established for Living Furniture. Additional research that can be conducted for further optimization and improvements of the system include the following:
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The experiments completed for Living Furniture were done solely with common goldfish. Research could be conducted on the use of other freshwater fish or aquatic life such as crayfish to understand if potential differences in yields would occur. Research could also be conducted on the effects of partial harvests as well as a greater number of plants on water chemistry. Testing additional varieties of microgreens as well as utilization of various forms of LED lights could also be done to test yield potential.
Lastly, Living Furniture can be scaled, as shown by the figure below. (Figure 4.4-1.) This is referred to as custom designed Living Interiors by GreenTowers, LLC, utilizing the same principles as Living Furniture. Research could be completed to optimize yields in larger systems by testing various fish/plant ratios. In this system, houseplants are being grown for aesthetic design rather than edible plants for food production.
Figure 4.4-1. Living Interiors Piece
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4.5 Future Predictions
As stated previously, by the year 2050 the population of planet Earth is expected to reach over nine billion people. Solutions need to be implemented now to face this global challenge. There shows great promise in the form of controlled environment agriculture, urban agriculture, and advances in traditional agriculture. GreenTowers as well as other companies provide not only the tools and innovation for growing in today’s urban environments, but also share the message that food security is a challenge that can and needs to be addressed by everyone. Although these solutions and innovations do exist, our global society needs to be pro-active and engaged to implement these solutions. Increasing global food security, fighting world hunger, and ultimately feeding the growing global population cannot be solved through innovative solutions alone. These global challenges must be understood and implemented by our global society to make for a better future.
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Appendix A
Statistical Outputs Rotating Living Walls
Rotational Rate Comparisons for Fresh Weight Production (NOT significant)
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Supplemental Lighting Comparisons for Fresh Weight Production (Significant)
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Stationary Vs. Moving Comparisons for Fresh Weight Production (NOT significant)
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Media Depth Comparisons for Fresh Weight Production (Significant)
*Note-Although statistically significantly different; means only differ by ten grams of fresh weight (.02 pounds)
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Media Depth Comparisons for Dry Weight Production (NOT significant)
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Wall Systems and Control Comparison for Fresh Weight Production (Significant)
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Appendix B
Statistical Outputs Living Furniture
No Chelated Iron; Number of Goldfish to Fresh Weight Production (Significant)
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Chelated Iron; Number of Goldfish to Fresh Weight Production (NOT significant)
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Chelated Iron Vs. Non-Chelated Iron Comparison (Significant)
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Water Chemistry; ammonia levels (Significant)
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Water Chemistry; nitrate levels (Significant)
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Appendix C Light Analysis Data
“Rotating Living Wall” Seasonal and Total Light Data
Flat Trough Seasonal and Total Light Data
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Light Simulation Data Sample
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