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Anaerobic Digestion to Reduce Organic Waste at the University of Florida

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Anaerobic Digestion to Reduce Organic Waste at the University of Florida
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Colligan, Michael
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Anaerobic digestion ( jstor )
Biogas ( jstor )
Digestion ( jstor )
Dining ( jstor )
Electricity ( jstor )
Food wastes ( jstor )
Landfills ( jstor )
Municipal solid waste ( jstor )
Organic waste ( jstor )
Universities ( jstor )

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Abstract:
This report serves as a proposal for the implementation of an anaerobic digestion system on the University of Florida campus for the purpose of reducing food waste and generating renewable energy. Anaerobic digestion is a natural process in which organic matter is broken down by microorganisms in the absence of oxygen, with the two major end products being biogas and solid digestate. Biogas can be converted to electricity and digestate can be used as an organic fertilizer. Different anaerobic digestion system technologies are compared to determine a system with optimal efficiency and biogas yields. An analysis of the University of Florida waste stream reveals the average amount of food waste generated at the University of Florida annually. This amount is then used to determine the potential savings in landfill tipping fees as a result of the decrease in discarded food waste, savings in electricity, fertilizer sales, and other sustainablility-related benefits the proposed digester could provide the university. ( en )

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Copyright Michael Colligan. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.

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1 Using Anaerobic Digestion to Reduce Organic Waste at the University of Florida Michael Colligan Kathryn Frank, Mentor

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3 Introduction Currently in the Unit ed States, there are millions of tons of waste being discarded into landfills every year. About one fifth of all the discarded waste is food waste, which has the lowest rate of recovery out of all the major municipal solid waste categories, which also inc lude paper, wood, plastics, metals, and glass products (epa.gov). Food waste being discarded into landfills is an environmental concern because it causes high emissions of methane, a greenhouse gas associated with global warming, into the atmosphere. Th is report focuses on the anaerobic digestion of food waste from the University of Florida. Anaerobic digestion is a natural process during which microorganisms break down food waste in the absence of oxygen, resulting in the production of potential renewa ble energy sources. The process creates a source of renewable energy, and is has the potential reduce the dependence on fossil fuels such as oil and coal. The implementation of an anaerobic digestion system is proposed for the University of Florida at th e end of the report based on comparisons made between different anaerobic digester technologies. Based on an analysis of the University of Florida food waste stream, calculations are made to show the potential economic benefits the system can contribute t o the university, as well as potential environmental benefits that would help the University of Florida stand out as a leader in sustainability.

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4 Methodology The unsustainable practice of discarding food waste into landfills serves as inspiration for t his report. Anaerobic digestion was selected because the technology has been proven to be a sustainable method of waste management, and can provide renewable energy sources while cutting down on the amount of greenhouse gas emissions in the atmosphere. D igestion systems are used mainly in Europe and have not been implemented at a mainstream level yet in the United States. The technology is currently being considered as a waste management option by the WCA Waste Corporation, the official sustainability an d recycling partner of the University of Florida. The overall goal of the report is to propose a system to be used on the UF campus as a method of reducing the volume of food waste, providing electricity and fertilizer that can benefit the university fro m a monetary standpoint, and help further establish the university as a role model for sustainability. To determine the best system to use at UF, dig ester technology and their respective benefits as well as potential barriers for implementation were rese arched. Digestion systems at the University of California, Davis and Morrisville State College in New York were examined as case studies because they are examples of universities that chose to implement anaerobic digestion systems with the main goal of pr oviding their campuses with a renewable electricity source. An undergraduate thesis by UF graduate Ryan Graunke about the anaerobic digestion of food waste from Broward D ining Hall was also looked into, which concludes that the food waste from UF has high organic content and has the potential to be used very efficiently in an anaerobic digester. An analysis of the current food waste stream of the UF campus

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5 helped determine what kind of annual capacity would be the most appropriate for the proposed digeste r. Comparisons were made between different digester technologies with a focus on system efficiency and yields of biogas. Biogas was a primary focus because it has the potential for conversion into electricity. Other potential benefits that were research ed include reduction in landfill tipping fees, and biofertilizer sales. Based on cost analyses and economic feasibility studies, a potential capital investment and operations costs and final revenue were able to be determined.

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6 Food Waste Facts and Figu res The United States generates about 251 million tons of municipal solid waste or trash, annually (epa.gov). Organic waste, which consists of food waste, paper, and yard waste, is the largest component of the municipal solid waste stream. Food waste c omprises 14.5% of the total municipal solid waste stream, or about 36.7 million tons. Presently, about 87 million tons of waste are recovered through recycling or composting, meaning 164 million tons of waste are discarded into landfills every year. Only 2% of food waste is currently being recovered each year, therefore about 34.6 million tons of food waste are being discarded into landfills annually. Food waste has the lowest percentage out of all the municipal solid wastes for recovery; paper, yard tri mmings, metals, glass, plastics, and wood all have higher rates of recovery. Tables 1 and 2 below contain 2012 data from the Environmental Protection Agency. Category Percentage Paper and Paperboard 27.40% Food Waste 14.50% Yard Trimmings 13.50% Plas tics 12.70% Metals 8.90% Rubber, Leather, Textiles 8.70% Wood 6.30% Glass 4.60% Other 3.40% Table 1 Total MSW Generation (251 Million Tons) Table 2 Waste Recovered (87 Million Tons) Category Percentage Paper and Paperbond 51.20% Yard Trimmings 22.60% Metals 8.80% Other 5.70% Glass 3.70% Plastics 3.20% Wood 2.80% Food Waste 2.00%

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7 It is important to divert food waste from landfills for a variety of reasons, which will be discussed later in the report. The use of anaerobic diges tion is a sustainable option for advancing food waste management in the United States. Anaerobic Digestion Figure 1 .1 Anaerobic Digestion Process Source: americanbiogascouncil.org Biological Process During the process of anaerobic digestion, organic waste material is broken down and digested by microorganisms in the absence of oxygen. The process begins when organic material seen in Figure 1.1 between steps 1 and 2. Food waste manure and

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8 animal wastes, biosolids, fats, oils, and grease are organic materials that can be fed into a digester (epa.gov). The biological process of the decomposition of the waste inside the digestion tank consists of four main stages: hydrolysis, ac idogenisis, acetogenesis, and methanogenesis. During hydrolysis, bacteria transform the organic matter into p roteins, carbohydrates and fats, which are then transformed into to amino acids, monosaccharides and fatty acids respectively (wtert.eu). During acid ogenesis, bacteria transforms the end products of the hydrolysis stage into volatile fatty acids and alcohols. During the acetogenesis stage, the fatty acids and alcohols are converted by acetogenic bacteria into acetic acid, carbon dioxide, and hydr ogen. During the fourth and final stage, the methanogenesis stage, methanogenic bacteria convert the hydrogen and acetic acid from the previous stage into carbon dioxide and methane ( marmara.edu ). Refer to Figure 1.2 below for a simple visual representat ion of the biological process. End Products The two main final products of the anaerobic digestion process are biogas and digestate. Biogas typically consists of 40 75% methane (CH 4 ), 25 55% carbon dioxide (CO 2 ), 0 1% ammonia (NH 3 ), 0 1 0% water (H 2 O), 0 5% nitrogen (N 2 ), 0 Figure 1.2 Biological Process Diagram Source: appropedia.org

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9 2% oxygen (O 2 ), and 0 1% hydrogen (H 2 ) ( renewable energy concepts.com ). Two different types of digestate are produced during anaerobic diges tion, one during the acidogenesis stage and another during the methanog enesis stage. Acidogenic digestate is solid organic material and consists of mostly cellulose and lignin ( Sengupta 37). Methanogenic digestate is a sludge or liquid material that contains high levels of nutrients such as phosphate and ammonium (Pullen 125). Temperature Ranges There are three different temperature ranges for anaerobic digestion. Psychrophilic digesters operate at about 68F. Mesophilic digesters operate at temperatures between 95 and 105F. Thermophilic digesters operate at temper atures between 125 and 135F ( ecy.wa.gov ). Alkalinity and pH Alkalinity refers to the buffering capacity of water to neutralize acids (wastewaterhandbook.com). The pH scale is a measure of how acidic or basic a substance is, and ranges from 0 to 14 with a pH of 7 being neutral, numbers higher than 7 more basic and numbers less than 7 are more acidic (epa.gov). During the process of anaerobic digestion, fluctuations in alkalinity and pH can affect the efficiency of the methane forming organisms. Hig her alkalinity allows for more resistance to changes in pH level during digestion (wastewaterhandbook.com). The optimal pH level for the

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10 anaerobic digestion process is between 6.8 and 7.2 ( biotechnologyforbiofuels.com ), since acidic conditions can hinder methane production ( seas.columbia.edu ). Benefits Anaerobic digestion provides a high amount of environmental and economic benefits. The process itself produces biogas and digestate which are offset non renewable energy sources such as the fossil fu els oil and coal Digestate contains nutrients including phosphorus, nitrogen, and potassium, and can be used as fertilizer. Biogas is a sustaina ble source of potential renewable energy that can be used in fue l cells or combined heat and power systems to create electricity. The anaerobic digestion of food waste diverts the waste from being discarded into landfills, where it decomposes and releases methane into the atmosphere. Methane is a greenhouse gas that has 21 times the global warming potential tha n carbon dioxide (epa.gov). Diverting food waste from landfills also helps businesses and institutions save money on disposal of their trash by decreasing the amount of landfill tipping fees they need to pay.

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11 Applications Figure 1.3 Biogas powere d bus in Sweden Source: http://dailyfusion.net/wp content/uploads/2013/10/6059640252_beabfa107 1_o 1100x500.jpg?be108a Biogas can be readily used in any application designed for natural gas (biogas.ifas.ufl.edu). These inc lude heating and water heating, and cooking. It can be used in fuel cells or internal combustion engines to produce electricity. It can also be converted into vehicular fuel. Many European countries use biogas as fuel for public transportation vehicles. Sweden even launched a biogas powered train in 2005 ( harvestpower.com ). Combined Heat and Power (CHP) systems are a type of gas turbine, or combustion turbine that can Figure 1.4 CHP System Diagram Sou rce: http://www.proenviro.com/UK/_images/services/CHP_diagram.jpg

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12 be powered by biogas. CHP systems have a heat exchanger that recovers heat from its gas turbine exhaust that converts it into thermal energy, as seen in Figure 1.4 (epa.gov). Fuel cells generate heat and electricity through a chemical reaction between oxygen and hydrogen, and can function with biogas from digesters (epa.gov). Go vernment Incentives Right now there is a federal tax credit under the American Recovery and Reinvestment Act of 2009. The act allows owners of anaerobic digestion systems to apply for a corporate investment tax credit equal to 30% of the cost of the facil ity, and eligibility lasts until December 31, 2016 (epa.gov). In Florida, there is government incentive for anaerobic digestion under the Florida Net Metering program, in which owners of the systems can receive credits for generating more power than they use ( cleanenergyauthority.com ). Current Status in the United States Anaerobic digestion is currently operational in the United States in the form of three different types of facilities: municipal solid waste, agricultural waste, and wastewater treatment ( 2g cenergy.com ). There are at least 192 operational digesters located on farms according to the Environmental Protection Agency. There are at least 1,500 wastewater treatment centers in the United States that have functioning digestion systems

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13 For municipal solid waste, there are a few digestion systems that operate only for food waste and some that combine food waste with wastewater. A case study on the food waste anaerobic digester at the University of California, Davis is discussed in d etail later in this report. Other food waste digesters are located at the University of Wisconsin and in California as part of the Gills Onions Project, Zero Waste Energy in San Jose, the Orange County Food Waste Pilot Plant in Orange County, the Montere y Zero Waste Pilot Plant in Monterey, and the Inland Empire Environ in Chino ( 2g cenergy.com ). The food waste systems have not reached the same level of popularity in the United States as the wastewater and agricultural waste systems, but anaerobic digest ion has been a proven success in being a sustainable waste management option. Figure 1.5 Digestion Facility in San Jose, California Source: http://zerowasteenergy.com/what we do/our projects/city of san jose/

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14 Types of Anaerobic Digesters While anaerobic digesters all have the same basic function of holding organic waste in the absence of oxygen in the proper conditions for producing biogas, there are a number of different designs for digestion systems that can be categorized as either passive, low rate, or high rate systems. A few of the most common examples of each category are below. Passive Systems In passive systems, a bio gas recovery component is added to an already existing treatment component (extension.org). Covered Lagoon A covered lagoon anaerobic digestion system uses an already existing lagoon to trap biogas underneath an impermeable cover. It contains two cells, as seen in F igure 2.1. The first cell is covered and the second cell is uncovered. The first cell is fed manure or other waste influent and the anaerobic digestion process then takes place. Biogas is stored and can be recovered from the first cel l. The second cell serves as an Figure 2 .1 Illustration of Covered Lagoon System Source: epa.gov

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15 odor control treatment center and an effluent storage center. Inflow of influent to the first cell remains constant to ensure the efficient breaking down of the manure (extension.org). Covered lagoons operate at the psych rophilic temperature range. They are not heated, so the digestion process may be affected by fluctuations in temperature. Biogas recovery rates from covered lagoons are seasonal and typically low. The solid sludge from the waste influent could remain st ored in the lagoon for a period of up to twenty years, while liquid waste retention time is typically 30 to 60 days. The main advantages associated with c overed lagoon system s are low cost and simple system operation ( climatetechwiki.org ). Low Rate Syst ems In low rate systems, animal waste flowing through the digester is the main source of the methane forming microorganisms (extension.org). Complete Mix Digester Figure 2.2 Illustration of Complete Mix System Source: climatetechwiki.org Figure 2.3 Complete Mix Digester So urce: extension.org

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16 The complete mix digester is a heated, enclosed tank that has either a mechan ical, hydraulic, or gas mixing system as seen in Figure 2.2 (epa.gov). Most complete mix digesters operate at the mesophilic temperature range The system operates as a typical continuous flow system; the incoming waste influent displaces the volume ins ide the tank, and an equal amount of effluent flows out the other side. The waste remains in the tank for a period of about twenty to thirty days to ensure proper biogas production. Mixing can either be done continuously or intermittently meaning occasi onally. Complete mix digesters work best when the influent contains 3 to 6% solid material ( okstate.edu ). The main advantage of a complete mix digester is the high conversion rate of solids to gas. The main disadvantage is th e cost of installation and c osts and energy required for the mechanical mixing ( climatetechwiki.org ). Plug Flow Digester A plug flow digester is a long, narrow tank made of concrete with either a flexible or rigid cover (epa.gov). The plug flow digester system is s imilar to the complete mix digester system in that the influent displaces the volume of waste in the storage tank and an equal amount of effluent flows out the other side. The difference betw een the two 2.4 Illustration of a Plug Flow Digester Source: epa.gov

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17 systems is that the waste influent is not mechanical ly mixed, so particles are prevented from settling at the bottom (extension.org). The solid content of the manure influent should be between 10 and 20%. The retention time for plug flow digesters is typically between fifteen and twenty days. High R ate Systems In high rate anaerobic digestion systems, ethane forming mi croorganisms are trapped to increase digester efficiency (extension.org). Fixed Film Digester Fixed film digesters are also known as anaerobic filters or attached growt h digesters. They contain woodchips or plastic rings upon which methane forming microorganisms grow. The manure influent is fed into the column and passes by the microorganisms. Fixed film digesters typically handle influent with 1 to 5% solid Figure 2.5 Illustration of a Fixed Film D igester Source: extension.org Figure 2.6 Fixed Film Digester at the University of Florida Source: extension.org

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18 content, so solid separators are needed to pre treat the manure in fluent and remove particles. There is a fixed film digester at the University of Florida as seen in figure 2.6, located on the University of Florida Dairy Research Farm. The digester is able to pr oduce 6,000 cubic feet of biogas per day (epa.gov). Suspended Media Digester Figure 2.7 Diagram of an Upflow Anaerobic Sludge Blanket (UASB) Source: http://web.deu.edu.tr/atiksu/ana58/vege05.g if Suspended media digesters suspend microbes in a constant upward flow of liquid, with the flow designed to let smaller microbes out but keep larger microbes trapped inside. Microorganisms are able to form around the large r particles. There are two common types of suspended media digesters, the Upflow Anaerobic Sludge Blanket (Figure 2.7) and the Induced Blanket Reactor (Figure 2.8). The main difference between the two is the Upflow Anaerobic Sludge Blanket treats waste influent that is less than 3% total solids while the Induced Blanket Reactor treats waste i nfluent that is 6 to 12% solids (extension.org). Figure 2.8 Diagram of an Induced Blanket Reactor Source: http://www.extension.org/sites/default/files/w/3/36/Sch ematic_drawing_of_induced_bed_reactor_(IBR)_dige ster_courtesy_conly _hansen_utah_state_400px.jpg

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19 Sequencing Batch Digester The sequencing batch digester operates in a series of four stages, as seen in Figure 2.9. In the first stage, the waste influent is f ed into the system. The second stage is known as the react stage during which the waste influent and microbes are mixed together During the third stage, the solids settle, and in the last stage the effluent is removed. T he cycle can be repeated up to four times per day to ensure constant generation of biogas. Sequencing batch digestion systems are most efficient when treating waste influent with less than 1% solid content (extension.org). Figure 2.9 Sequencing Batch Digester Diagram Source: extension.org

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20 Anaerobic Digesters for Municipal Solid Waste Technology for municipal solid waste specific anaerobic digesters can be categorized into single or multi stage, continuous stream or batch, high solids or low solids. Batch vs. Continuous Batch digesters are simpler than contin uous flow digesters. Batch digestion systems consist of loading waste influent into the digester tank and waiting while the natural anaerobic digestion process takes place. After it does, the waste effluent is manually removed and the process is repeated Retention time differs due to external factors such as outdoor temperat ure or season. In a continuous flow digester, influent is regularly fed into the digester, and he waste moves through the system either by the force of newly fed influent or a by a mechanical mixer. Continuous flow digesters produce biogas continuously, without interruption during the processes of loading new influent or unloading effluent (epa.gov). Wet vs. Dry Wet digestion processes are typically mesophilic and contain in fluent that is mostly water and less than 15% solid material. Dry digestion processes are typically thermophilic and contain 20 to 45% solid incoming organic material (epa.gov).

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21 Digester Types Single Stage Wet Systems Figure 4.1 Waasa Process Source: calrecycle.ca.gov The Waasa system and the BIMA system are examples of single stage wet digesters for municipal solid organic waste. Figure 4.1 shows a basic diagram of the Waasa process. First, a pulper pre tre ats the municipal solid waste influent and removes debris. The waste is then pumped into a pre chamber that helps stabilize and manage the overall system flow, and eventually pumped into the main digestion tank that contains a mechanical mixer ( calrecycle .ca.gov ). The BIMA process is a similar self mixing system that uses the biomass it generates to create different pressure differentials within the digester which has the potential to reduce its costs in annual operation and maintenance ( entec biogas.com ). Advantages of single stage wet systems include simple operation and low operation costs. A main disadvantage is that they consume a high amount of water and heat (calrecycle.ca.gov).

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22 Single Stage Dry Systems Organic Waste Systems, Waste Recover y Systems, Inc., and Kompogas AG are companies that utilize single stage dry digester systems with the Dranco process, SteinmŸller Valorga process, and Kompogas process, respectively. Figure 4.2 shows illustrations of simple diagrams for each of these pro cesses, all of which take place in modified plug flow digesters. These dry, or high solid, processes handle influent that consists of 20 to 40% total solids ( calrecycle.ca.gov ). The Dranco process was developed in the 1980s and operates at the thermophi lic temperature range. Influent is entered at the top of the digester and works its way down to the bottom where digestate is removed. It has a separate mixing pump outside of the digester tank that handles the digestate ( calrecycle.ca.gov ). The SteinmŸ ller Valorga process treats pre sorted organic solid waste that consist of 25 to 30% total solids and uses pressurized biogas for mixing ( calrecycle.ca.gov ). The system can operate at either mesophilic or thermophilic temperature ranges depending on influ ent composition type. Generated biogas is injected in the bottom of the digester to help with mixing and maintaining an efficient flow of solids. The Kompogas system has internal rotors that help homogenize the influent ( calrecycle.ca.gov ), making it di fferent than the other two systems. The system operates at thermophilic temperatures. Advantages of single stage dry systems are that they have relatively inexpensive capital costs and use a small amount of water. The main disadvantage is that they requ ire special waste handling equipment that can be expensive (calrecycle.ca.gov).

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23 Figure 4.2 Dranco, Kompogas, and Valorga Processes Source: calrecycle.ca.gov Multi Stage Systems Figure 4.3 Typical Multi Stag e Digestion Process Source: calrecycle.ca.gov Typical mutli stage anaerobic digesters have two separate stages, as seen in figure 4.3. The first stage contains a high solid influent and hydrolysis occurs. The second

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24 stage contains a low solid influent and methanogenesis occurs in this stage (calrecycle.ca.gov). The German digestion system Biotechnische Abfallverwertung GmbH & Co. KG (BTA) is an example of a multi stage process. The BTA process uses a pulper similar to the Waasa system t hat helps process the municipal solid organic waste influent. The Super Blue Box Recycling (SUBBOR) system is another example of a multi stage anaerobic digestion process. This system operates at the thermophilic temperature range and treats influent of high solid municipal solid waste as well as inorganic material ( deepdyve.com ). Figure 4.4 below provides a simple illustration of the SUBBOR process. Some advantages to the multi stage systems are that they can handle higher loading rates than single sta ge systems, have more flexibility and can tolerate fluctuations in loading rate, and a smaller footprint. The disadvantages are that they are more complex and expensive than single stage systems (calrecycle.ca.gov). Figure 4.4 SUBBOR Process Source: calrecycle.ca.gov

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25 Batch Systems There are several examples of batch digestion systems for municipal solid organic waste. The BIOCEL process operates at the mesophilic temperature range and treats influent of organic solid wastes ( n cbi.nlm.nih.gov ). The Sequential Batch Anaerobic Composting (SEBAC) system was developed at the University of Florida in the early 1990s. An illustration of the process can be seen in Figure 4.5 below. The goals for the SEBAC system design were to eliminate the need for mixing and minimize handling. As of 2008 no full scale SEBAC systems have been built (calrecycle.ca.gov). Advantages of batch systems are low cost and simple operation. The main disadvantage is that they have less efficient degradation of organic material than they other types of systems (calrecycle.ca.gov). Figure 4.5 SEBAC System Source: calrecycle.ca.gov

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26 Case Stud ies Morrisville State College In 2006, construction of the anaerobic digester at Morrisville State College in Morrisville, New York was comple ted. The justification for installing the digester on the Morrisville State College campus was to treat dairy manure and organic waste produced on campus, and to use the biogas to run a combined heat and power generation system (people.morrisville.edu). The main goals of the project were electricity savings, heating savings, nutrient control, odor reduction, pathogen reduction, and reduction of methane emission. This anaerobic digestion system was researched because it was designed with the intention of treating organic waste from the Morrisville State College campus, as well as saving money on electricity with converted biogas, which are similar goals of the University of Florida digester proposal of this capstone. Source: http://documents.morrisville.edu/public /academics/programs/bigphotos/MethaneDigester.jpg

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27 The type of digester system used is a h ard top plug flow system. It is a rectangular, in ground concrete tank that consists of two sides separated by a concrete wall. Each side has an additional wall that separates the digester from two grit chambers where the primary heat exchanges occur. T he heat exchangers in the digester maintain the optimum level of 98¡F. The inside of the digester is coated with a layer of coal tar epoxy, a layer of polyurethane, and poly urea in order to create a biogas tight tank. The combined heat and power generat ion system officially began operation on February 28, 2007. Biogas is collected from the two sides of the chamber and fed into an internal combustion engine (ICE). The ICE is attached to a 50 kW generator, which utilizes biogas at an average rate of 23,2 87 cubic feet per day. The average generator electrical output is 40.3 kW, which is equivalent to annual electricity production of 341,885 kilowatt hours (kWh) per year. Funding for the project was provided by the New York State Energy Research and Develo pment Authority the New York State Department of Agriculture and Markets, and the United States Department of Energy (people.morrisville.edu). The total cost for the digester project was $935, 987. The digester and construction process cost was $779,99 2 (people.morissville.edu). Additional costs included the consultant fee, testing of the concrete, and tank sealing. The use of energy from the biogas created by the ICE can generate $1,985 worth of electricity each month, or about $24,000 worth of annua l savings.

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28 University of California, Davis The University of California Renewable Energy Anaerobic Digester Project (READ) was launched on April 22, 2014. The digester system influent contains food waste from UC Davis campus dormitories, dining halls, local restaurants and agricultural waste (epa.gov). The READ project can serve as a model for the proposed University of Florida digester system It treats food waste from a University campus of about 35,415 students ( budget.ucdavis.e du ) with the intention of using the biogas to generate electricity. The UC Davis campus also has similar goals as the University of Florida regarding waste management; they have a sustainability initiative with the goal of being a zero waste campus by the year 2020. The READ project was a combined effort between UC Davis, the United States Department of Energy, the California Energy Commission, and CleanWorld. CleanWorld is a company that develops anaerobic digestion technology and digesters. They specialize in hel ping companies reach their "zero organic waste" initiatives (cleanworld.com) Their digester is a multi stage high rate, high solid thermophilic system that is designed for handling organic food waste This type of system allows for a short retention tim e, high biogas output, and enhanced destruction of pathogens in the waste. The digester handles 50 tons of waste per day, with about 20 tons coming from Source: http://www.theaggie.org/wp content/uploads/2013/11/biodigestercorrect.jpg

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29 the UC Davis campus. Total biogas production totals 211,000 standard cubic feet per day ( americanbiog ascouncil.org ). The digestion system is a very sustainable addition to the UC Davis campus and surrounding area. The digester is able to convert biogas into 5.6 million kWh of clean electricity annually, which is equivalent to savings of about $840,000 in energy costs. The energy is fed directly to the campus energy grid using patented technology invented by UC Davis professor Ruihong Zhang The solid effluent is used as sustainable fertilizer. The digester can produce four million gallons of fertiliz er and soil amendments per year, which can be used on about 145 farms in California. The system can also reduce annual greenhouse gas emissions by 13,500 tons (news.ucdavis.edu). Broward Dining Hall Thesis by Ryan Graunke In 2008, an undergraduate rese arch thesis project by UF graduate Ryan Graunke and UF professor Ann C. Wilkie was published, entitled Converting Food Waste to Biogas: Sustainable Gator Dining ." The project focuses on the use of a small scale anaerobic digester with the intention of bi ogas production and potential impleme ntation for Broward Dining Hall, which is one of the major sources of food waste on the University of Florida Campus. The study specifically studies the use of anaerobic digesters for breaking down organic waste from t he dining hall and using the biogas as supplemental energy. Ryan Graunke won the Advancement of Sustainability in Higher Education (AASHE) Award for Student Research on Campus Sustainability for this research project.

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30 The type of digester used in this s tudy was a 30 gallon daily fed system made of reused polyethylene drums. The digester was placed in an open field to allow for maximum sunlight in order to maintain an average digester temperature of 30¡C. The pH was monitored to ensure approximate neutr ality (pH 7.0), whi ch is ideal for methanogenesis (biogas.ifas.ufl.edu). Each day for a period of twelve days, homogenized plate scraps were poured into the digester and mixed, and biogas production was measured by water displacement. The main concept of the experiment was to create a closed loop system between Broward Dining Hall and the digester. Food waste would go from the dining hall to the digester, and the energy from the biogas would be fed back to the dining hall. The main goals were to reduce solid waste and also create ca rbon neutral, renewable energy. The results showed that based on the experiment, the total amount of biogas generated per day was 1,413 cubic feet (biogas.ifas.ufl.edu). The waste from Broward Dining Hall consisted of al l biodegradable products, and the average organic content of the waste was 95%. Broward Dining Hall was a n appropriate place to do this study because the dining hall employees were already sorting out the non digestible waste and separating it from the or ganic waste to begin with. This research provides support for the larger scale anaerobic digestion system for the whole University of Florida campus proposed in this capstone, because it provides measurable results of biogas production and shows that the food waste from a UF dining hall has great biogas yielding potential due to its high organic content.

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31 Analysis of University of Florida Waste Stream Data for the University of Florida waste stream comes from the Audit of Solid Waste Management Practi ces and Generation at the University of Florida The waste audit was prepared for the UF Office of Sustainability and published in October 2009 by the UF Department of Environmental Engineering Sciences. Total annual waste generation at UF is about 18,00 0 tons, or about 50 tons per day. The av erage recycling rate is about 36.5 %, which accounts for about 6,600 tons annually. This is similar to the average recycling rate in the United States, which according to the 2012 data from the Environmental Prot ect ion Agency is about 34.5% (epa.gov). The amount of waste discarded into landfills every year is about 11,000 tons. The landfill where the waste from Alachua County goes is the New River Regional Landfill, located forty miles north of Gainesville in Raifo rd, F lorida. Categories The University of Florida divides its waste into five categories: municipal solid waste, construction and demolition debris, recyclable material, medical waste, and hazardous waste Municipal solid waste is defined as Waste produ ced in dormitories, academic buildings, dining halls, recreational facilities and other campus buildings that is primarily composed of paper, organics, and plastic and disposed of by students, faculty and staff during standard activities ( purchasing.ufl.e du ). This capstone will focus on the municipal solid waste portion of the waste stream because it contains the orga nic waste from campus that is discarded to landfills.

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32 Municipal solid waste accounts for nearly half of the total UF waste stream, with ab out 48% or 8,6 40 tons per year. Recyclable material accounts for about 36.5%. The largest components of the recycled material on campus are paper and yard waste, which is waste composed of soil, branches and leaves and is produced during campus landscapi ng maintenance. Construction and demolition debris account for 13%, medical waste for 2%, and hazardous waste at 0.5%. Construction and demolition debris is the waste generated during the construction, demolition or renovation of campus structures such as buildings or roads ( purchasing.ufl.edu ). The UF Physical Plant Division, which is responsible for solid waste management at the University of Florida, has a recycling yard where some construction and demolition debris can be deposited into ( ppd.ufl.edu ). Medical waste is potentially hazardous pharmaceutical waste that comes from Shands Hospital and the Veterinary Hospital on campus. Hazardous waste is chemicals or solvents that come from laboratories ( purchasing.ufl.edu ). The UF Physical Plant Divisi on requires that all chemical waste and biomedical waste has to be speicially handled and discarded by the UF Environmental Health and Safety Department ( ppd.ufl.edu ). Table 4 shows a summary of the main waste categories on campus and their respective per centages and tonnages

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33 Table 4 Summary of major waste category tonnage and percentages Municipal Solid Waste Stream Data Figure 3.1 Breakdown of the Municipal Solid Waste portion of the University of Florida Waste Stream Figure 3.1 above shows the major components of the municipal solid waste stream on campus an d their percentages of the total. Organic waste is the largest portion ""#! $%#! &%#! %#! '#! $#! $#! $#! G$-6E&%R"4%H4,'")()B6/4O%/)&4567#-4O#$-6A4 ()*+,-./! 0+12)! 34,562.7.8+982/! 08+/:-.! 0)4;<.:/! =8+//! >2:+8! (:?2)! Category Annual Tonnage Percentage of Waste Stream Municipal Solid Waste 8,640 48% Recyclable Material 6,570 36.50% C & D Debris 2,340 13% Medical Waste 360 2% H azardous Waste 90 0.50%

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34 of the municipal solid waste stream at UF, accounting for one third, or about 2,851 tons annually. This amount represents about 16% of the total UF waste stream. Paper is the next la rgest portion, at 29%. Non recyclable material account s for 19% of the waste stream. Non recyclable material is defined as, material for which there is either no method or no currently feasible method of recovery (purchasing.ufl.edu). Plastics account for 9%. Products that have the potential to be reused or donated such as old binders, electronics, or apparel account for 4%. Glass accounts for 2%, metal for 2%, and all other waste that does not fit a category the remaining 2%. Organic Waste Stream Analysis Figure 3.2 Analysis of the Organic Waste Portion of the Municipal Solid Waste Stream @A#! %#! B#! C#! G$-6E&%R"4%H4S$06")(4567#-4>%$#)%"4%H4#.-4 ,O54O#$-6A4 D44;!E+/:2! F+);!E+/:2! G,-H+8!I71)4;<.:/! 08+,:!J+9!E+/:2!

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35 This capstone focuses on the anaerobic digestion of food waste since it is the major component of organic waste on campus Figure 3.2 provides an analysi s of the organic waste portion of the UF municipal solid waste stream. Food waste accounts for 80%, which is about 2,281 tons annually, or 6.25 tons daily. Additional components of the organics portion include yard waste (9%), animal byproducts (6%), and plant lab waste (5%). The three largest contributors of food waste are Greek housing, dormitories, and dining areas. The Reitz Union, Gator Corner Dining, and Broward Dining Hall are t he major dining areas on campus. It should be noted that the waste a udit specifically mentions that anaerobic digestion on a few occasions. An example from executive summary of the audit: The relatively high percentage of organics (food waste, food contaminated paper, and paper products such as paper towels) suggests tha t implementation of an organics treatment system such as anaerobic digestion or composting is logical next for further investigation. Such technologies are currently employed to a limited extent on parts of campus and to a very large level at other univers ities ( purchasing.ufl.edu ). The audit says that diverting organic waste would be the next step for achieving a more sustainable waste management system on campus.

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36 Proposed Digester for the University of Florida Comparisons Comparisons wer e made between different types of anaerobic digestion systems for organic solid waste to determine the best type of system to use for the University of Florida waste stream. To determine the best the best type of anaerobic digester for food waste, tempera ture, flow type, stage amount, and solid content are taken into consideration. Based on the waste audit data, total food waste generated is equal to 2,280.96 tons annually. It should be noted that currently the at the University of Florida, f ood waste ge nerated at the Reitz Union, Gator Corner Dining, and Fresh Food Company are composted ( ppd.ufl.edu ). For the sake of this capstone, it is assumed that all the food generated would be used as influe nt for the anaerobic digester, so this tonnage figure that includes all food waste will be used to determine the optimal digester for the campus. Temperature Multiple studies have shown that anaerobic digesters that operate in thermophilic temperature ranges yield more biogas than systems operating in mesoph ilic ranges. One study produced by researchers the Technical University of Denmark found that biogas yields from thermophilic digesters could potentially yield double the amount of biogas than mesophilic digesters ( iwaponline.com ). A report by the Eštvš s Lor‡nd University outlined advantages of thermophilic systems compared to mesophilic systems, that included larger biogas output, more methane in the biogas, and shorter retention times for the thermophilic systems (aloki.hu). A study published by resea rchers from the Beijing

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37 University of Chemical Technology concluded, The performance of AD however increases with an incre asing temperature, stressing the advantages of the thermophilic operation with its higher metabolic rates, higher specific growth rat es, and higher rates of the destruction of pathogens along with higher biogas production ( sciencedirect.com ). Some disadvantages of the thermophilic system are that they have a higher energy demand for heating, have higher initial costs, and are more sen sitive to sudden temperature changes (aloki.hu). The advantages of thermophilic systems outweigh the disadvantages with regards to system efficiency and biogas yields. Single Stage vs. Multi Stage Multi stage digesters have been shown to be better f or organic solid waste than single stage systems for system efficiency and biogas yields. One study published by the American Chemical Society stated Two stage anaerobic digestion (AD) for integrated biohydrogen and biomethane production from organic ma terials has been reported to promise higher process efficiency and energy recoveries as compa red to traditional one stage AD" (pubs.acs.org). Another study from Columbia University stated that multi stage digesters are more efficient, because they consist of different vessels for the hydrolysis and acidogenesis processes of digestion, and each vessel maintains optimum conditions for these processes to happen, rather than a single stage digester where the whole processes happens in one place ( seas.columbia. edu ). A document published by the environmental consulting service CH2M Hill determined that multi stage systems have potentially higher gas yields, but have higher costs and more potential technical issues ( ewmce.com ). The advantages outweigh the disadv antages for multi stage systems for a

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38 digester to be used on the UF campus that would use less than 2,500 tons of waste per year. Flow As stated before, continuous digesters produce biogas continuously, without any interruption during the processes of loading in new influent or unloading effluent after it makes its way through the system (epa.gov). Batch reactors are filled with influent and after the natural processes of digestion have occurred the effluent can be emptied ( seas.columbia.edu ). A stud y published in Agricultural Engineering International compared batch and continuous digesters specifically for biogas yields from municipal solid waste Their research concluded that amount of methane produced by the batch digester was four times less tha n the continuous digester ( cigrjournal.org ). It would be better to use a continuous digester rather than a batch digester for the University of Florida system for the reasons of higher biogas yield and shorter retention time. Influent Solid Content Wet, or low solid anaerobic digestion processes are more typically associated with agricultural waste from farms or wastewater sludge treatment, while dry, high solid systems are typically used for treating municipal solid waste ( iswa.org ). The use of a dry, high solid system would be more appropriate to use on the University of Florida campus because the proposed digester would be treating an organic food waste influent and not wastewater or animal wastes. Research shows that the treatment of municipal solid waste with wet, low solid systems have been tried in the past and were largely unsuccessful due

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39 to influent impurities ( aikantechnology.com ). Compared to wet systems, dry systems have a higher tolerance for influent impurities. These impurities co uld be items such as stones or glass that make their way into the influent by accident Dry digestion systems have also been shown to have higher biogas yields ( waste management world.com ) and require less energy during operation for the heating process. For these reasons, and the reason of dry systems typically treating organic portions of municipal solid waste, the use of a dry high solid system would be the better choice for the digester on campus. Proposal After comparing the different tech nologies and types of digestion systems, it is determined that the most ideal type of digester to use on the University of Florida campus is a two stage, continuous flow system that operates at the thermophilic temperature range and treats dry, high solid organic waste influent. As stated before, this decision for the type of digester is based on how well the system fits with the organic waste stream content and size from UF, as well as biogas yield and system efficiency. Two stage, thermophilic systems a re shown to have higher biogas yields and are more stable and efficient. Continuous flow systems have a stable and constant biogas production rate compared to batch systems. The digester is to be used for the organic waste portion of the UF municipal sol id waste stream, and dry, high solid systems are more typically used for this type of waste stream rather than wet, low solid systems, which are used mainly for agricultural waste and wastewater sludge.

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40 Costs The digestion system cost figures used for t he first set of cost data come from a 2006 publication by the Democritus University of Thrace in Greece entitled Approximate cost functions for solid waste treatment facilities." The report is a comprehensive study of the initial and operating costs of d ifferent anaerobic digestion systems in Europe. The study makes note that data for predicting the cost of an aerobic digestion system is scarce and that each facility is different with regards to factors such as facility size, influent composition, and wa ste management policies ( sagepub.com ). The study has data for an anaerobic digestion in Germany that has an annual capacity of 2,500 tons, which is similar to the University of Florida food waste stream of 2,280.96 annual tons, so data for this system i s used to estimate the cost of the proposed UF digester. Converted from Euros to dollars, and adjusted for inflation, the initial capital inv estment for the system is $736,497.52 and annual cost is $73.96 per inputted ton, for a total of $168,699.80 per y ear based on the UF food waste tonnage ( sagepub.com ). Data from another study published in 2010 by the Business Economics group at Wageningen University, Hollandseweg determined that the operating cost of an anaerobic digester for food waste was equal t o $45.58 per ton of waste based on a digester with an annual capacity of 3,375 tons of food waste ( sciencedirect.com ), which is equal to an annual cost of $103,996.16 based on the UF waste food waste stream. The annual influent amount is relatively simila r to the digester proposed for the UF campus, so this data for operation cost is averaged with the Democritus University is equal to an annual operation cost of $136,332.98.

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41 The Democritus University of Thrace study explicitly states that their reported costs do not include the same items, which could consist of design, land excavation, tax, transportation costs or revenue from the end products. The cost data covers a wide range of different composting, landfilling, and digestion facilities, and all cos t components are not available for every unique system in the study ( sagepub.com ). The Wageningen University study states that the operation and maintenance costs are based on digester maintenance and the operation of a built in combined heat and power sy stem (sciencedirect.com). The digester at Morrisville State College had an initial capital cost of $779,992, which is similar to the dollar amount used to represent the cost of the proposed UF digester. This cost is broken down into components that inclu de site excavation, concrete, metal, wood, and plastic work, thermal and moisture protection, and mechanical and electrical work (people.morrisville.edu). To summarize, the final costs determined by analyzing the available data are a n initial capi tal cost of $736,497.52 and an annual operation cost of $136,332.98. Economic Benefits Landfill Tipping Fees Waste from Alachua County is hauled from the Levada Brown Environmental Park, which houses the transfer station and hazardous waste collectio n center for the county, to the New River Regional Landfill in Raiford Florida. The current tipping fee for hauling is $48.08 per ton of waste ( alachuacounty.us ). The amount of food waste generated annually from the University of Florida campus is equal to 2,280.96 tons based

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42 on the data from this report. The proposed anaerobic digestion system on the UF campus would theoretically divert all of the food waste generated on campus from the landfill, so the total amount of money saved from the reduction of tipping fees would potent ially be equal to $109,668.56 per year. Tipping Fee X UF Food Waste $48.08 2,280.96 tons = $109,668.56 Electricity Generation Biogas can be converted to electricity, as previously mentioned, through technologies such as fuel cells, combined heat and power (CHP) systems, or internal combustion engines. Biogas yields vary for different digesters, and the proposed digester in this capstone has been chosen largely based on its potential for highest biogas yields for the pur pose of generating electricity. A number of studies on biogas yields from organic municipal solid waste streams have come up with different, but similar, biogas yields for various digesters. These numbers are: 333 m 3 /ton from a study by the Environmental Protection Agency ( academia.edu ), 91 136 m 3 /ton from the California Integrated Waste Management Board ( globalmethane.org ), 91 181 m 3 /ton from the Regional Information Service Centre for Southeast Asia on Appropriate Technology ( globalmethane.org ), an average of 101 m 3 /ton by the Global Methane Initiative ( globalmethane.org ). The average of these numbers is about 171 m 3 /ton. Based on the tonnage from the UF waste stream (2,280.96), the total annual biogas generation annually would be about 390,044 cub ic meters.

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43 Data for electricity potential from biogas is varied but similar. One source says one cubic meter of biogas can generate 1.5 kWh of electricity (collections.infocollections.org), while source another says about 2 kWh ( biogas info.co.uk ). The average amount that will be used for the calculation for the digester in this report is 1.75 kWh per cubic meter of biogas. This means the total kWh of electricity that could be potentially generated by the biogas would be 682,557 kWh annually. The aver age price of one kWh in Gainesville is 12.37 cents ( electricitylocal.com ) so the total amount of electricity potentially generated could be equivalent to $84,432.30 The ratio between this kWh and dollar amount is equal to 8.08407446. Another couple st udies determined that the average kWh per ton of digested waste is equal to 272.2 kWh/ton ( biogas info.co.uk ) and 222.3 kWh/ton (ac.els cdn.com), for an average of 247.25 kWh/ton. That kWh figure multiplied by the 2,280.96 tons of annual UF food waste is 563,967.36 kWh generated per year. This equates to an annual electricity savings of $69,762.76. The ratio between these kWh and dollar values is 8.08407466, which is nearly identical to the other ratio above. Since the ratios of these two outcomes are s o similar, the average is used for this report. The total average of the dollar amounts, which will be the final concluded amount of e lectricity money saved is equal to $77,097.53 per year. Method 1: M 3 of Biogas per Ton of Waste X UF Food Waste 17 1 m 3 /ton X 2,280.96 tons = 390,044 m 3 Total Biogas X kWh per m 3 390,044 m 3 X 1.5 kWh = 682,557 kWh Total kWh X Price per kWh 682,557 kWh X 12.37 cents = $84,432.30 kWh/$ Ratio: 8.08407446

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44 Method 2: kWh pe r Ton of Waste X UF Food Waste 247.25 kWh/ton 2,280.96 tons = 563,967.36 kWh Total kWh X Price per kWh 563,967.36 kWh 12.37 cents = $69,762.76 kWh/$ Ratio: 8.08407466 Average of two dollar amounts: $77,097.53 Biofertilizer Biogas is not the only end product of anaerobic digestion that can have monetary benefits. The other end product, digestate, has the poten tial to be used as fertilizer due to its high amount of nutrients. It could potentially cut down university costs for synthetic fertilizers, or sold by the university to farms. For example, the UC Davis digeste r generates enough digestate to produce of 4 million gallons of fertilizer, and the fertilizer is used at farms in California. Since digesta te is created during the natural process of anaerobic digestion, it is a sustainable alternative to using artificial fertilizer. An economic feasibility study of anaerobic digestion from the University of Wisconsin determined that about 70% of inputted d igester waste influent could become digestate that can be sold as fertilizer (krex.k state.edu). The study sets a price per ton of fertilizer at $29.85/ton (adjusted for inflation), based on rising demands in organic fertilizer. Based on the UF waste str eam data, this is equal to 1,596.67 annual tons of biofertilizer generated, for a potential revenue of $47,660.60 per year. UF Food Waste X 70% 2,280.96 tons = 1,596.67 tons Tons X Sale Price 1,596.67 tons X $29.85/ton = $47,660.60

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45 Reve nue Capital and annual operation costs for the proposed digester for the UF campus were determined to be $736,497.52 for capital investment and an annual operation cost of $136,332.98. Potential saving in tipping fees is $109,668.56 per year. Savings o n electricity costs is $77,097.53. The sale of organic biofertilizer has a potential revenue of $ 47,660.60 per year. These three figures equal an annual total of $234,426.69. Subtracting the annual operation costs equals a total annual revenue of $98,09 3.71. Based on this annual revenue, the initial capital investment of $736,497.52 could be completely payed off in 7.5 years. This payback period length makes sense based on published feasibility studies, one of which determined the average payback perio d for an anaerobic digester ranges from 5 to 16 years ( researchgate.net ), and another said 5 to 10 years ( netregs.org.uk ). Annual Operation Cost Monetary Gains: Tipping Fee + Electricty + Fertilizer $136,332.98 $109,668.56 $77,097.53 $47,66 0.60 = $234,426.69 $234,426.69 $136,332.98 = $98,093.71 Other Benefits The economic and environmental benefits of anaerobic digestion and the proposed anaerobic digester for the University of Florida have been detailed in this report. There are ways the implementation of an anaerobic digestion system on the UF campus could benefit the university in ways related to sustainability as well. As previously mentioned, the current status of anaerobic digestion of food waste is scarce

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46 right now in the United States, and one of the main barriers of implementation is a lack of public awareness of its potential benefits. The University of Florida is one of the top rated universities in the nation, and implementing a digestion syste m could be a substantial way for attracting more attention to the technology and its benefits. Many universities across the country have recycling and composting programs in place, but having a anaerobic digestion technology incorporated into the campus w aste management system could set the UF sustainability program apart from the other schools. The digester could be used to help raise awareness at the university about the importance of not wasting food, and UF could potentially serve as inspiration for m any more schools across the country to consider investing in anaerobic digestion technology on their own campuses.

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47 Barriers and Opportunities The University of Florida Office of Technology Licensing currently has a patent for its own anaerobic digestion system, with the intention of being used to divert a range of various types of wastes from landfills ( techn ologylicensing.research.ufl.edu). One of the types of waste influent is food waste. The patent description says the university is lookin g for a company to commercialize their digester, but this has not happened as of Spring 2015 when this report was written. There are a few common major barriers to implementing an anaerobic digestion system. One main barrier in the United States is the lack of technical and applied research and development, particularly a lack of performance data for anaerobic digestion system outcomes such as electricity yields and reduction of greenhouse gas emissions (epa.gov). As previously mentioned earlier in the report, the current amount of active the anaerobic digestion systems for food waste is scarce in the United States, with University campus food waste specific systems only currently operating at UC Davis and the University of Wisconsin. Another main barr ier in the United States is a general lack of the potential benefits of biogas, one of the main end products of anaerobic digestion. A higher amount of public awareness through campaigns promoting the anaerobic digestion process and technology by the gove rnment and private companies could help improve its popularity. The unawareness and lack of available performance data lead to another main barrier in the United States, which is biogas market uncertainty, which deters investors and policymakers from cons idering anaerobic digestion as a viable option for managing food waste (epa.gov).

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48 There are also financial and operational barriers that could hinder the implementation of anaerobic digestion systems on a large scale in the United States. Initial capit al costs are high for anaerobic digestion systems, and this can be a major financial barrier for implementation. The proposed system in this report has a payback period of 7.5 years, which could be unattractive from a business standpoint. Similarly, ther e is a lack of certainty of financial incentives for biogas systems ( nnfcc.co.uk ). The implementation of anaerobic di gestion systems also requires a high level of expertise regarding the process and operating and maintaining the system, which is limited ( eac quality.net ). The systems themselves require experts and knowledgeable service people available 24 hours a day in case of any technical problems ( biogas info.co.uk ). There is opportunity for the University to receive immense help with funding for a n anaerobic digester project from the Government or other institutions. Sections 9006 and 9007 of the U.S. Department of Agriculture's Rural Energy for America Program outline federal aid in the initial costs of anaerobic digestion systems. The program h as given over $40 million in funding to digester projects since 2003 (epa.gov). The case studies presented in this report for the digesters at Morrisville State College and University of California, Davis are examples of outside sources of funding aiding in the digestion systems. As previously mentioned, the funding for the Morrisville State College project was provided by the New York State Energy Research and Development Authority the New York State Department of Agriculture and Markets, and the United States Department of Energy. Some of the technology for the digester came from other outside sources. For example, the boiler that is used for heating the digester was donated for research purposes by the Performance Engineering Research Group in L ivoni a

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49 Michigan (people.morrisville.edu) The University of California, Davis project received public funding in the amount of $2 million from the U.S. Department of Energy and the California Energy Commission (news.ucdavis.edu). Due to the limited amount of data for successful anaerobic digestion of food waste in America, Florida state and federal government would make significant contributions to the University of Florida to aid in their implementation of a digester project.

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50 Conclusion The implementation of an anaerobic digestion system on the University of Florida campus has the potential to be of great benefit to the university and its surrounding environment. Based on the available digestion technology, the proposed system is a continuo us flow, two stage system that operates at the thermophilic temperature range and treats waste influent that fits into the dry, high solid content category. This type of system allows for an efficient, steady production of a high amount of biogas, meaning more potential for electricity generation. Anaerobic digestion has been shown to decrease greenhouse gas emissions, while also serving as a source of renewable energy product ion in the form of electricity as well as organic biof e rtilizer from solid diges tate. It is important for the University of Florida to consider incorporating anaerobic digestion technology into their waste management system, because doing so will help spread awareness of the anaerobic digestion process and its benefits to other colle ges and institutions around the United States, where the use of digestion is currently not considered a conventional method of diverting food waste fr om landfills. Having a renewable energy generator on campus will help establish UF as a leader in the tra nsition away from the dependence of fossil fuels in the United States.

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51 Works Cited Abhisheksingh, A. "Anaerobic Digestion." Web. . "Anaerobic Biological Treatment (Anaerobic Digestion)." ClimateTech Wiki Web. . "Anaerobic Digestion." International Conference on Solid Waste 1 Jan. 2011. Web. . "Anaerobic Digestion Process." WtERT 25 Nov. 2009. Web. . Arati, James. "Evaluating The Economic Feasibility of Anaerobic Digestion of Kawangware Market Waste." 1 Jan. 2006. Web. . Arsova, Ljupka. "Anaerobic Digestion of Food Waste: Current Status, Problems and an Alternative Product." Columbia University 1 May 2010. Web. . "Barriers and Constraints to Implementation of Anaerobic Digestion Systems in Swine Farms in the Philippines." Global Methane 1 Nov. 2010. Web. . "Biodigester Turns Campus Waste into Campus Energy." UC Davis 22 Apr. 2014. Web. . "Biogas Composition." Renewable Energy Concepts Web. . "Biogas Opportunities Roadmap." US Environmental Protection Agency 1 Aug. 2014. Web. . "Biochemistry of Anaerobic Dig estion." Marmara University Web. . "Biowaste: Dry Advice." Waste Management World Web. . Brummel er. "Full Scale Experience with the BIOCEL Process." 1 Jan. 2000. Web. .

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52 "Business Analysis of Anaerobic Digestion in the USA." Renewable Waste Intelligence 1 Mar. 2013. Web. . "Business Energy Investment Tax Credit." US Environmental Protection Agency 26 Sept. 2012. Web. . Cioabla Adrian, Ioana Ionel, Gabriela Alina Dumitrel, and Francisc Popescu. "Comparative Study on Factors Affecting Anaerobic Digestion of Agricultural Vegetal Residues." Biotechnology for Biofuels 6 June 2012. Web. . "Cleanworld Breaks Ground on Innovative Anaerobic Digestion Facility at UC Davis." UC Davis Web. . "Conserving & Renewing: E nvironmental Sustainability." WCA Waste Web. . "CPI Inflation Calculator." Web. . "Current Anaerobic Digest ion Technologies Used for Treatment of Municipal Organic Solid Waste." California Integrated Waste Management Board California Environmental Protection Agency, 1 Mar. 2008. Web. . "Dig ester Terminology, Abbreviations, and Units." Department of Ecology State of Washington. Web. . "Economic Feasibility of Anaerobic Digesters." Agri Facts, 1 June 2008. Web. "FAQ." The Official Inf ormation Portal on Anaerobic Digestion Web. . "Florida Net Metering." Clean Energy Authority 9 Sept. 2014. Web. . "Fu nding Programs for Developing Anaerobic Digestion Systems." U.S. Department of Agriculture 1 June 2012. Web. .

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