David Day Master of Engineering Thesis

Assessing the Financial Implications of Selling Dairy Digester-Generated Electricity to the Electric Grid by David Day Ithaca, New York August 2007 Table of Contents Table of Contents .1 List of Tables .3 List of Figures Acknowledgements Background Purpose Literature Review Methodology 11 4.1 Biogas Rate Calculation Using Cow Manure .12 4.1.1 Biogas Production Rates with Dairy Cow Manure 13 4.2 Biogas Rate Calculation Using Food Waste Substrates 14 4.3 Engine-Generator Set Determination 17 4.3.1 Engine-Generator Feed Requirements 18 4.4 Single Engine vs Multiple Engine Configuration: .22 4.4.1 Example: 190eKW Engine vs x 100eKW Engines 23 4.5 Smaller or Larger Engine Size Comparison: 27 4.5.1 Example: 75kW vs 85kW Engine 27 4.6 Revenue Calculations: 31 4.7 AD System Expense Determination: 38 Results 42 5.1 Scenario 1: Annual Revenue with Respect to Biogas Production 42 5.2 Scenario 2: Maintaining a Consistent Methane Content 50 5.3 Scenario 3: Implementing an AD system with the Use of Food Wastes 52 5.3.1 Example 1: Mesophilic with Fats Substrate 53 5.3.2 Example 2: Mesophilic with Molasses Substrate 53 5.3.3 Example 3: Mesophilic with Chicken Manure Substrate 53 5.3.4 Example 4: Mesophilic with Beer Residue Substrate (570kW) 56 5.4 Scenario 4: Simulating Varying Annual Revenue Values .57 5.4.1 Trial 1: Example from Scenario with Fluctuating LMBP Prices .60 5.4.2 Trial 2: Example from Scenario with Fluctuating LMBP Prices .61 5.4.3 Trial 3: Example from Scenario with Fluctuating LMBP Prices .62 5.5 Scenario 5: Using a Single or Multiple Engine Configuration .63 5.5.1 Model 1: Multiple Engine Configuration with Fluctuating LMBP Prices 64 Discussion 65 Improvement Opportunities 70 Conclusion 71 Appendix 73 9.1 References .73 9.2 Consulting .73 9.3 Biogas Production Rates Using Food Substrates 74 9.3.1 Biogas Production Using Potato Sludge 74 9.3.2 Biogas Production Using Chicken Manure 75 9.3.3 Biogas Production Using Market Waste 77 9.3.4 Biogas Production Using Organic Waste .79 9.3.5 Biogas Production Using Beer Residue 80 9.3.6 Biogas Production Using Grass Material 82 9.3.7 Biogas Production Using Maize Silage 84 9.3.8 Biogas Production Using Fruit Residue 85 9.3.9 Biogas Production Using Molasses .87 9.3.10 Biogas Production Using Fats .89 9.3.11 Biogas Production Using Food Residues .90 9.4 List of Initial Capital Expenses from Previous Case Studies .92 9.4.1 AA Dairy Initial Capital Expenses 92 9.4.2 Noblehurst Initial Capital Expenses 93 9.4.3 Spring Valley Initial Capital Expenses 93 9.4.4 Patterson Initial Capital Expenses 93 9.5 List of Annual Expenses from Previous Case Studies 94 9.5.1 Noblehurst Annual Expenses 94 9.5.2 Spring Valley Annual Expenses .94 List of Tables Table 1: Biogas Production Rates with Dairy Cow Manure 14 Table 2: Coefficient Ranges for Food Substrates 16 Table 3: Engine-Generator Feed Requirements .19 Table 4: Comparison of Various Engine Configurations 24 Table 5: Comparison of Cumulative Energy Production for Two Engine Configurations 26 Table 6: Comparison of Energy Production between Two Different Generator Sizes 28 Table 7: Comparison of Cumulative Energy Production between Two Different Engine Sizes 30 Table 8: LMBP Sample Data Provided by NYISO 32 Table 9: Sample Data Analysis of LMBP Prices for April 2006 32 Table 10: Compiled Sample Data to Generate Random LMBP Values 38 Table 11: Sample List of Annual and Capital Expenses 39 Table 12: Engine-Generator Expenses .42 Table 13: Average Annual Revenue with Respect to Biogas Production Rate .44 Table 14: List of Capital and Annual Expenses with Respect to Engine Size 46 Table 15: Annual Income Changes with Respect to Methane Content 50 Table 16: Annual Net Gain/Loss with Increasing Methane Content .52 Table 17: Summary of Revenue and Simple Payback Period Extracted from Examples 54 Table 18: Summary of Revenue and Simple Payback Period Extracted from Example 56 Table 19: Compiled Data of Varying LMBP Prices from 2000 to 2006 58 Table 20: LMBP Percentage Change from Year 2000 .59 Table 21: Probability of LMBP Percentage Change 60 Table 22: Fluctuating LMBP Prices for Trial 61 Table 23: Fluctuating LMBP Prices for Trial .61 Table 24: Fluctuating LMBP Prices for Trial .62 Table 25: Sample Data for Utilizing a Multiple Engine Configuration with Fluctuating LMBP Prices 64 Table 26: Biogas Production Using Potato Sludge 75 Table 27: Biogas Production Using Chicken Manure .76 Table 28: Biogas Production Using Market Waste 78 Table 29: Biogas Production Using Organic Waste 80 Table 30: Biogas Production Using Beer Residue 81 Table 31: Biogas Production Rates Using Grass Material .83 Table 32: Biogas Production Rates Using Maize Silage 85 Table 33: Biogas Production Rates Using Fruit Residues .86 Table 34: Biogas Production Rates Using Molasses .88 Table 35: Biogas Production rates Using Fats 90 Table 36: Biogas Production Rates Using Food Residues .91 Table 37: List of Initial Capital Expenses for AA Dairy 92 Table 38: Capital Cost Per Cow for AA Dairy 93 Table 39: List of Capital Expenses for Noblehurst 93 Table 40: Capital Cost Per Cow for Noblehurst 93 Table 41: List of Capital Expenses for Spring Valley 93 Table 42: Capital Cost Per Cow for Spring Valley 93 Table 43: List of Capital Expenses for Patterson .94 Table 44: Capital Cost Per Cow for Patterson 94 Table 45: List of Annual Expenses for Noblehurst 94 Table 46: Annual Cost Per Cow For Noblehurst .94 Table 47: List of Annual Expenses for Spring Valley 94 Table 48: Annual Cost Per Cow For Spring Valley 94 List of Figures Figure 1: New York State LMBP Zones 10 Figure 2: Biogas Production Rates with Dairy Cow Manure 14 Figure 3: Potential Biogas Production Rates with Food Substrates 15 Figure 4: Engine-Generator Feed Requirements .20 Figure 5: Comparison of Energy Production between Two Engine Configurations .25 Figure 6: Comparison of Cumulative Energy Production for Two Engine Configurations 26 Figure 7: Comparison of Energy Production between Two Different Engine Sizes .29 Figure 8: Comparison of Cumulative Energy Production between Two Different Engine Sizes 30 Figure 9: Average LMBP Prices for Each Zone during April 2006 33 Figure 10: Standard Deviations of the Fifteen Zones within New York State 34 Figure 11: Standard Deviation of New York State Zones excluding New York City and Long Island 35 Figure 12: Standard Deviation of LMBP Prices from August 2005 to July 2006 36 Figure 13: Average LMBP Prices for August 2005 to July 2006 37 Figure 14: Averages for the Initial Capital Investments Per Cow 40 Figure 15: Averages for Annual Expense Per Cow 41 Figure 16: Average Annual Income with Respect to Biogas Production Rates 44 Figure 17: Initial Capital Investment with Respect to Biogas Production Rates 47 Figure 18: Annual Revenue and Expense with Respect to Biogas Production Rates .48 Figure 19: Simple Payback Period with Respect to Biogas Production Rate 49 Figure 20: Annual Income Changes with Respect to Methane Content 51 Figure 21: Compiled Data of Varying LMBP Prices from 2000 to 2006 58 Figure 22: Multiple Simulations Demonstrating Fluctuating LMBP Prices 63 Figure 23: Estimated Annual Revenue with Respect to Cow Population and Increasing LMBP Prices 67 Figure 24: Annual Revenue with Respect to Comparable Cow Population and Food Substrate 69 Figure 25: Biogas Production Using Potato Sludge 75 Figure 26: Biogas Production Using Chicken Manure 77 Figure 27: Biogas Production Using Market Waste 79 Figure 28: Biogas Production Using Organic Waste .80 Figure 29: Biogas Production Using Beer Residue 82 Figure 30: Biogas Production Rates Using Grass Material .83 Figure 31: Biogas Production Rates Using Maize Silage 85 Figure 32: Biogas Production Rates Using Fruit Residues .87 Figure 33: Biogas Production Rates Using Molasses 88 Figure 34: Biogas Production rates Using Fats .90 Figure 35: Biogas Production Rates Using Food Residues .92 Acknowledgements I would like to express my sincere gratitude for the guidance and support that Professor Scott has provided to me this past year Without his efforts, I not believe that this thesis would be as detailed as it currently stands I would also like to express my sincere thanks to my colleagues here at Cornel University: Crystal Powers, Stefan Minott, Rodrigo Labatut, and Cheryl Hou Their knowledge and experiences have helped to shape and fine tune every detail of my findings Lastly, I would like to thank my family for their continued loving support on all my endeavors Background Anaerobic digestion (AD) has shown to be a promising technology for farm sites with a high manure production rate It has the potential to aid in the management of biomass waste, the generation of green energy (electricity and heat), and the reduction in environmental pollution such as odor and animal wastes AD allows for the biochemical degradation of various organic wastes (i.e food processing waste, animal waste, etc.) that are then converted to a resourceful by-product, biogas After digestion, the digested materials in some cases are fed into separator equipment to separate the digested materials into separated roughage or fiber (solids) and separated liquid The separated fiber can be transferred to a compost area, and the recovered solids can be sold as compost As for the liquid effluent, this can be pumped to a plastic-lined liquid storage lagoon for storage, and then spread onto the land It is important to note that the primary product of interest for this study is the generated biogas and consequently energy production, and thus the separator equipment and separation process were not investigated into further detail Instead, the primary focus remains around the digestion process and biogas production for conversion of electricity Biogas can act as a fuel source to produce electricity and heat It consists primarily of methane (~50-60%), carbon dioxide (~40-50%), and small traces of other gases such as hydrogen sulfide The biogas can be fed directly into a modified enginegenerator set that normally runs on fossil fuels such as natural gas and diesel fuel Biogas combustion results in production of heat from the engine, which can then be used to maintain the specific temperature range (mesophilic or thermophilic) of the anaerobic digester Additionally, biogas combustion allows for the generation of electricity which can be used to either provide electricity directly on-site or sold to the local energy grid as a source of revenue.1 Though AD does have a number of benefits and has the potential to serve as an additional source of revenue, there are multiple risks and key factors that continue to discourage individuals from implementing the system onto their farms One risk of implementing an anaerobic digester is the high initial capital costs that can cause a financial burden for the operator Another risk is the complication of operating and New York State and Energy Corporation (www.nyseg.com) maintaining the process on the farm This can prove to be both financially and labor intensive, which can cause additional strain on farming operations One cannot deny the numerous risks and financial burdens that can come from implementing an anaerobic digester, but it is important to consider the positive and negative impacts that are associated with an AD system With the continuous increase in environmental regulation and standards and the continued search for a renewable fuel source, the implementation of anaerobic digesters may prove to be a favorable option that can outweigh the associated negative impacts Purpose The objective of this project is to study the financial implications of selling anaerobic digester generated electricity to New York State grid with respect to the associated initial capital and annual costs of producing the electricity to be sold Though in some cases the electricity produced by an anaerobic digester is primarily used on-site, it would be interesting to see the potential annual revenue that could be generated through the selling of electricity to the grid By pre-determining the potential annual revenue and the respective costs associated for producing the electricity, it maybe possible to show financially that an anaerobic digestion system can be a profitable and low-risk investment Literature Review Anaerobic digestion depends upon a number of factors and parameters that can affect the amount of biogas generated, its methane content, the amount of electricity produced, and finally the revenue that can be generated The following components were used to help develop the data and results of this project: Volatile solids content of biomass Potential methane and biogas production values from biomass Required engine-generator set and its respective biogas feed requirement Pre-determined market value of electricity Costs for implementing AD system The details and calculations for each of the above factors will be described within the methodology section of this document Research shows that methane production is not only dependent upon the amount of biomass present, but also the amount of volatile solids (VS) contained within the biomass The VS can vary from various organic wastes, but in this project it was assumed to be relatively constant for dairy cows (8.5% of cow manure) This assumption can be made based on the conclusion that dairy cows are fed a relatively consistent diet at a consistent rate, which causes the biosolids production rate and volatile solids content to be relatively constant It is important to note that the use of food wastes can increase the biogas production rates, which can consequently help to increase the revenue generated from both selling of electricity and tipping fees which are generated from the acceptance of food wastes from various groups In this project however, the tipping fees are not factored into the cost benefit analysis because it important to focus on the financial implications of selling AD generated electricity to the New York State electric grid Another factor that must be considered is that engine-generator sets, normally run on natural gas (or diesel), can be modified slightly to utilize a biogas feed The difference, however, between the two gases is the methane content percentage, and thus the amount of energy that can be obtained from the feed As a general rule of thumb, it is commonly accepted that natural gas can achieve ~1000 Btu/ft and generally has the methane content of 95% or greater Biogas, on the other hand, is generally accepted to have the methane content in the range of 50-60% This reduced methane content causes the reduced energy content to be 500-600 Btu/ft3, and thus a reduction in the amount of power that can be produced from the engine-generator sets The calculations and details will be discussed within the methodologies section The next parameter that must be discussed in detail is the selling of electricity to the New York State electric grid The amount of payment is dependent upon the amount of electricity sold to the grid and the “Hourly Locational Based Marginal Price” (LMBP h) which is dependent upon market demand The LMBP value is determined by the New York Independent System Operator (NYISO) hourly Day ahead LMBP value Fifteen NYISO Market Data Website (www.nyiso.com/public/market_data/pricing_data.jsp) 9.3.6 Biogas Production Using Grass Material Comparable Biogas Production Range (m^3/hr) Cow Population 50 25.234 26.917 55 27.758 29.608 60 30.281 32.300 65 32.805 34.992 70 35.328 37.683 75 37.852 40.375 80 40.375 43.067 85 42.898 45.758 90 45.422 48.450 95 47.945 51.142 100 50.469 53.833 105 52.992 56.525 110 55.516 59.217 115 58.039 61.908 120 60.563 64.600 125 63.086 67.292 130 65.609 69.983 135 68.133 72.675 140 70.656 75.367 145 73.180 78.058 150 75.703 80.750 155 78.227 83.442 160 80.750 86.133 165 83.273 88.825 170 85.797 91.517 175 88.320 94.208 180 90.844 96.900 185 93.367 99.592 190 95.891 102.283 195 98.414 104.975 200 100.938 107.667 205 103.461 110.358 210 105.984 113.050 215 108.508 115.742 220 111.031 118.433 225 113.555 121.125 230 116.078 123.817 235 118.602 126.508 240 121.125 129.200 245 123.648 131.892 250 126.172 134.583 Table 31: Biogas Production Rates Using Grass Material The above table displays the values for the upper and lower boundary range at a mesophilic temperature range with the use of grass material Please note that grass material is assumed to be grass clippings from lawns 80 Figure 30: Biogas Production Rates Using Grass Material The above figure displays the linear relationship between the comparable cow population and the biogas rate with the use of grass material Notice that there is a lower and upper boundary value in which the biogas rate can vary 9.3.7 Biogas Production Using Maize Silage Comparable Cow Population 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 Biogas Production Range (m^3/hr) 26.917 29.608 32.300 34.992 37.683 40.375 43.067 45.758 48.450 51.142 53.833 56.525 59.217 61.908 64.600 67.292 69.983 72.675 75.367 78.058 80.750 29.440 32.384 35.328 38.272 41.216 44.160 47.104 50.048 52.992 55.936 58.880 61.824 64.768 67.712 70.656 73.600 76.544 79.488 82.432 85.376 88.320 81 155 83.442 91.264 160 86.133 94.208 165 88.825 97.152 170 91.517 100.096 175 94.208 103.040 180 96.900 105.984 185 99.592 108.928 190 102.283 111.872 195 104.975 114.816 200 107.667 117.760 205 110.358 120.704 210 113.050 123.648 215 115.742 126.592 220 118.433 129.536 225 121.125 132.480 230 123.817 135.424 235 126.508 138.368 240 129.200 141.313 245 131.892 144.257 250 134.583 147.201 Table 32: Biogas Production Rates Using Maize Silage The above table displays the values for the upper and lower boundary range at mesophilic temperature range with the use of maize silage Figure 31: Biogas Production Rates Using Maize Silage The above figure displays the linear relationship between the comparable cow population and the biogas rate with the use of maize silage Notice that there is a lower and upper boundary value in which the biogas rate can vary 82 9.3.8 Biogas Production Using Fruit Residue Comparable Biogas Production Range (m^3/hr) Cow Population 50 39.029 42.057 55 42.932 46.263 60 46.835 50.469 65 50.738 54.674 70 54.641 58.880 75 58.544 63.086 80 62.447 67.292 85 66.350 71.497 90 70.253 75.703 95 74.155 79.909 100 78.058 84.115 105 81.961 88.320 110 85.864 92.526 115 89.767 96.732 120 93.670 100.938 125 97.573 105.143 130 101.476 109.349 135 105.379 113.555 140 109.282 117.760 145 113.185 121.966 150 117.088 126.172 155 120.990 130.378 160 124.893 134.583 165 128.796 138.789 170 132.699 142.995 175 136.602 147.201 180 140.505 151.406 185 144.408 155.612 190 148.311 159.818 195 152.214 164.023 200 156.117 168.229 205 160.020 172.435 210 163.923 176.641 215 167.825 180.846 220 171.728 185.052 225 175.631 189.258 230 179.534 193.464 235 183.437 197.669 240 187.340 201.875 245 191.243 206.081 250 195.146 210.286 Table 33: Biogas Production Rates Using Fruit Residues The above table displays the values for the upper and lower boundary range at a mesophilic temperature range with the use of fruit residue 83 Figure 32: Biogas Production Rates Using Fruit Residues The above figure displays the linear relationship between the comparable cow population and the biogas rate using fruit residue With the use of fruit residue, the upper and lower boundary gap is minimal, and thus represents a relatively constant biogas production rate 9.3.9 Biogas Production Using Molasses Comparable Cow Population 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 Biogas Production Range (m^3/hr) 45.758 50.334 54.910 59.486 64.062 68.638 73.213 77.789 82.365 86.941 91.517 96.093 100.668 105.244 109.820 114.396 118.972 123.548 128.123 132.699 48.786 53.665 58.544 63.422 68.301 73.180 78.058 82.937 87.816 92.694 97.573 102.452 107.330 112.209 117.088 121.966 126.845 131.723 136.602 141.481 84 150 137.275 146.359 155 141.851 151.238 160 146.427 156.117 165 151.003 160.995 170 155.578 165.874 175 160.154 170.753 180 164.730 175.631 185 169.306 180.510 190 173.882 185.389 195 178.458 190.267 200 183.033 195.146 205 187.609 200.024 210 192.185 204.903 215 196.761 209.782 220 201.337 214.660 225 205.913 219.539 230 210.488 224.418 235 215.064 229.296 240 219.640 234.175 245 224.216 239.054 250 228.792 243.932 Table 34: Biogas Production Rates Using Molasses The above table displays the values for the upper and lower boundary range at a mesophilic temperature range with the use of molasses Figure 33: Biogas Production Rates Using Molasses The above figure displays the linear relationship between the comparable cow population and the biogas rate with the use of molasses Notice that there is a lower and upper boundary value in which the biogas rate can vary 85 9.3.10 Biogas Production Using Fats Comparable Biogas Production Range (m^3/hr) Cow Population 50 0.841 60.563 55 0.925 66.619 60 1.009 72.675 65 1.093 78.731 70 1.178 84.788 75 1.262 90.844 80 1.346 96.900 85 1.430 102.956 90 1.514 109.013 95 1.598 115.069 100 1.682 121.125 105 1.766 127.181 110 1.851 133.238 115 1.935 139.294 120 2.019 145.350 125 2.103 151.406 130 2.187 157.463 135 2.271 163.519 140 2.355 169.575 145 2.439 175.631 150 2.523 181.688 155 2.608 187.744 160 2.692 193.800 165 2.776 199.856 170 2.860 205.913 175 2.944 211.969 180 3.028 218.025 185 3.112 224.081 190 3.196 230.138 195 3.280 236.194 200 3.365 242.250 205 3.449 248.306 210 3.533 254.363 215 3.617 260.419 220 3.701 266.475 225 3.785 272.531 230 3.869 278.588 235 3.953 284.644 240 4.038 290.700 245 4.122 296.756 250 4.206 302.813 Table 35: Biogas Production rates Using Fats The above table displays the values for the upper and lower boundary range at a mesophilic temperature range with the use of fats 86 Figure 34: Biogas Production rates Using Fats The above figure displays the linear relationship between the comparable cow population and the biogas rate with the use of fats In this case, the use of fats causes a significantly large gap between the upper and lower boundary For example, at a 250 comparable cow population, the biogas production rates can range between 4.206m 3/hr and 302.813m3/hr Additionally, it was assumed that a production rate of any value within this range can occur 9.3.11 Biogas Production Using Food Residues Comparable Cow Population 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 Biogas Production Range (m^3/hr) 8.411 9.253 10.094 10.935 11.776 12.617 13.458 14.299 15.141 15.982 16.823 17.664 18.505 19.346 20.188 21.029 21.870 22.711 23.552 65.946 72.540 79.135 85.730 92.324 98.919 105.513 112.108 118.703 125.297 131.892 138.486 145.081 151.675 158.270 164.865 171.459 178.054 184.648 87 145 24.393 191.243 150 25.234 197.838 155 26.076 204.432 160 26.917 211.027 165 27.758 217.621 170 28.599 224.216 175 29.440 230.810 180 30.281 237.405 185 31.122 244.000 190 31.964 250.594 195 32.805 257.189 200 33.646 263.783 205 34.487 270.378 210 35.328 276.973 215 36.169 283.567 220 37.010 290.162 225 37.852 296.756 230 38.693 303.351 235 39.534 309.945 240 40.375 316.540 245 41.216 323.135 250 42.057 329.729 Table 36: Biogas Production Rates Using Food Residues The above table displays the values for the upper and lower boundary range at a mesophilic temperature range with the use of food residues Please note that food residues is considered to be a mixture of commercial and industrial organic wastes consisting of a wide range of wastes such as beer, sugar, wine, milk, alcohol, juice, meat products, and vegetable processing Figure 35: Biogas Production Rates Using Food Residues 88 The above figure displays the linear relationship between the comparable cow population and the biogas rate with the use of food residues The biogas production rate can vary a great deal as shown by the significantly large gap between the upper and lower boundary For example, at a 250 comparable cow population, the biogas production rate can vary between 42.057m 3/hr and 329.729m3/hr Additionally, it was assumed that a production rate of any value within this range can occur 9.4 List of Initial Capital Expenses from Previous Case Studies 9.4.1 AA Dairy Initial Capital Expenses Initial Capital Expenses Cost [$] Manure Pump $9,000 Engineering Design $20,000 Concrete Digester $160,000 Rebuild the Engine $2,000 Rebuild the Generator $9,000 Plumbing and Mechanical Sys $9,000 Cable to Utility Hook-Up $8,000 Electrical Engineer Consultant $18,000 Effluent Pump $3,000 Plastic Liner $42,000 Table 37: List of Initial Capital Expenses for AA Dairy The table above lists the initial capital expenses considered from the AA Dairy case study Notice that there are a number of various costs required to produce the anaerobic digester generated electricity Total Capital Required $280,000 Cost Per Cow $560 Table 38: Capital Cost Per Cow for AA Dairy The table above lists the total capital expense and cost per cow 9.4.2 Noblehurst Initial Capital Expenses Initial Capital Expense Cost [$] Digester Construction & $250,000 Materials Cover for Digester $60,000 Switching Equipment $18,000 Engine Building $43,500 Manure Storage $60,000 Others (Flares, Pumps) $14,200 Table 39: List of Capital Expenses for Noblehurst The table above lists the initial capital expenses considered from the Noblehurst case study Total Capital Required $445,700 Cost Per Cow $405.18 Table 40: Capital Cost Per Cow for Noblehurst The table above lists the total capital expense and cost per cow Notice in this case the total capital required is larger than AA Dairy’s capital requirement This is most likely due to the higher cow population of 1100 cows in comparison to 500 cows at AA Dairy 89 9.4.3 Spring Valley Initial Capital Expenses Initial Capital Expense Cost [$] Digester Construction & Materials $38,000 Pumps $2,300 Switching Equipment $5,000 Engine Building $2,000 Manure Storage $35,000 Cover for Manure Storage Pit $18,000 Others $15,350 Table 41: List of Capital Expenses for Spring Valley The table above lists the initial capital expenses considered from the Spring Valley case study Total Capital Required $115,650 Cost Per Cow $490.04 Table 42: Capital Cost Per Cow for Spring Valley The table above lists the total capital expense and cost per cow Notice in this case the total capital required is less than that of Noblehurst and AA Dairy This is most likely due to the lower cow population of 150 cows, and the total animal population of 236 9.4.4 Patterson Initial Capital Expenses Initial Capital Expense Cost [$] Digester Site Work $62,723 Digester Engineering Design $99,532 Digester Construction (i.e Cover, $495,930 Concrete) Digester misc $31,893 Electrical Wiring and Control Systems $317,476 Biogas Utilization Building $51,601 Table 43: List of Capital Expenses for Patterson The table above lists the initial capital expenses considered from the Patterson case study Total Capital Required $1,059,155 Cost Per Cow $641.91 Table 44: Capital Cost Per Cow for Patterson The table above lists the total capital expense and cost per cow Notice in this case the cost per cow is higher than the other three case studies 9.5 List of Annual Expenses from Previous Case Studies 9.5.1 Noblehurst Annual Expenses Annual Expenses Cost [$/yr] Maintenance, Repairs & Labor $37,675 Manure Spreading Cost $51,000 Table 45: List of Annual Expenses for Noblehurst The table above lists the annual expenses considered from the Noblehurst case study 90 Total Annual Expenses $88,675 Cost Per Cow $80.61 Table 46: Annual Cost Per Cow For Noblehurst The table above lists the total annual expenses and cost per cow considered from the Noblehurst case study 9.5.2 Spring Valley Annual Expenses Annual Expenses Cost [$/yr] Maintenance, Repairs & Labor $8,022 Table 47: List of Annual Expenses for Spring Valley The table above lists the annual expenses considered from the Spring Valley case study Total Annual Expenses $8,022 Cost Per Cow $33.99 Table 48: Annual Cost Per Cow For Spring Valley The table above lists the total annual expenses and cost per cow considered from the Spring Valley case study 91 ... specifications of each of the engine-generator sets offered Once the engine generator size has been determined, the amount of electricity generated and consequently the amount of revenue generated...Table of Contents Table of Contents .1 List of Tables .3 List of Figures Acknowledgements ... the Appendix section of this document for each respective table and graph of biogas production rates with the use of a specific food substrate Each table shows the range of biogas production