ADD A MICROTURBINE TO A FLUSHED DAIRY MANURE ANAEROBIC LAGOON SYSTEM AND MONITOR PERFORMANCE

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1 1 of 29 ADD A MICROTURBINE TO A FLUSHED DAIRY MANURE ANAEROBIC LAGOON SYSTEM AND MONITOR PERFORMANCE Prepared by Douglas W. Williams, Professor BioResource and Agricultural Engineering Department California Polytechnic State University San Luis Obispo, CA 93402, USA, Telephone: Partners California State University Research Initiative (CSU-ARI) Capstone Microturbines Dates of Contract Begin: July 1, 2001 End: December 31, 2002 Grant Number Submission Date: September 19, 2003 Funds for this Project were provided by the Western Regional Biomass Energy Program (WRBEP) and the US Department of Energy (DOE). Such support does not constitute an endorsement by the Department of Energy or the Western Regional Biomass Energy Program of the views expressed in this report. Abstract. A 14,000-cubic meter covered lagoon anaerobic digester, constructed under previous grants, was monitored for gas production, wastewater treatment efficiency and other parameters when treating approximately 350,000 liters of flushed dairy manure from 300 diary cows, calves and heifers. Based on an approximate 40-day HRT, the digester yielded 70 cubic meters of methane per day while reducing the COD by almost 60%. A 30-KW microturbine electric generating system was then installed and tested. When fueled with biogas containing 60% methane, the microtubine was successfully operated at from 15 to 25 KW at thermal efficiencies of 20 to 25%. Hours per day of operation ranged from 2 to 15 hours, due to gas blockages in the cover and piping system, and excess moisture in the biogas which created problems with the microturbine gas pressure booster. Assuming these problems can be overcome, it was estimated that the potential electrical and thermal energy benefits would total $10,000 annually while reducing methane emissions from the dairy lagoon amounting to 100 pounds per day or 18 tons per year, which is equivalent to over 380 tons of carbon dioxide per year. Table of Contents Page Table of Contents... 1 Executive Summary.2 Introduction...4 Objectives..4

2 Procedures.6 Conclusions and Recommendations.12 References..13 Appendices: Appendix A: Data and Discussion for Baseline Lagoon Operation Appendix B: Data from Microturbine Testing Period Appendix C: Biogas Analyses Appendix D: Influent and Effluent Nitrogen Analyses Appendix E: Raw Microturbine Emissions Data Appendix F: Raw Biogas and Microturbine Performance Data Executive Summary Work Description This report summarizes the results of data collection from the lagoon-type methane recovery system at the Cal Poly dairy, which has approximately 300 cows, calves and heifers. The project at present consists of a 14,000 cubic meter (4 million gallons) earthen lagoon, with pump and piping to transfer the dilute dairy manure wastewater from the solids separator to the new lagoon. Also included is a 45-mil thickness, reinforced polypropylene lagoon cover of approximately 4600 square meters including Styrofoam floats, weights, tie-down and gas manifold system. This covers approximately 90% of the total lagoon surface area. The existing biogas handing system includes piping to condensate trap, gas meter, gas blower and continuous-ignition flare. A 30 KW microturbine with associated compressor and heat exchanger has also been obtained for converting the biogas into electricity. The lagoon-microturbine system has been operating for 9 months in order to obtain the following operating parameters wastewater flows, biogas production, and estimated electrical production. The microturbine produces from 15 to 25 KW at an efficiency of 20 to 25 %, and with reduced NOX emissions of 3 ppm. This project will provide the following environmental and economic benefits: odor control by capturing the manure gases including ammonia; preventing methane, a significant greenhouse gas, from escaping into the atmosphere; and providing the economic benefit of electricity and process heat worth $10,000 annually. Objectives The first objective of this Work was to complete the installation of the 30 KW Microturbine Electric Generation system at the existing Covered Lagoon Anaerobic Digester. The second objective was to determine the operating characteristics of the 30 KW Microturbine Electric Generation System when fueled with biogas from the Covered Lagoon Digester System. The third objective was to estimate the energy and environmental benefits of the combined systems. Summary of Funded Activities Performed 1. The remainder of the project installation was completed including the second lagoon cover, the biogas handling system, and the microturbine electric generation system. Measurements of the performance of the covered lagoon in converting the dairy manure volatile solids into methane gas were carried out. 2. The microturbine system was operated and test results of its performance were measured and recorded. 3. Assessments were made of the applicability of this microturbine system in converting the methane generated from the covered lagoon into electricity for powering the dairy parlor activities. The microturbine exhaust emissions were measured, and the reductions in methane emissions from the lagoon were also determined. 2 of 29

3 3 of 29 Methodology 1. The covered lagoon digester performance parameters were obtained both by direct measurement and by sending samples to commercial laboratories for analysis. These actual results were then compared with the theoretical performance of the digestion system using an empirical kinetic equation designed specifically for dairy manure digestion. 2. The microturbine performance parameters were recorded from the instrumentation included in the microturbine control panel and system. 3. The air emissions factors were measured with a portable, hand-held emissions probe. Important Findings 1. The actual biogas production was less than half the predicted biogas production, due mainly to leaks in the cover and less-than-complete collection of the manure solids from the cows. Treatment of the flushed manure was almost 70 % reduction in COD in the unheated covered lagoon at temperatures less than 20 C. 2. The microturbine produced from 15 to 25 KW of electricity at efficiencies of 20 to 25 % of the energy contained in the biogas. 3. The exhaust emissions from the microturbine were less than 3 ppm of NO x and the estimated economic return in electricity was over $6000 per year. Capturing the waste heat from the microturbine exhaust would add almost $4000 to this annual return. Introduction The total manure produced by dairy cows in the state of California is 33,000,000 tons/year. As presently handled, dairy manure produces undesirable odors, biogas, and nutrient overloads resulting in air and water pollution. California Polytechnic State University (Cal Poly) has devised a system at its dairy to capture methane, a naturally emitted manure biogas, and convert it into a usable energy source to create electric power. By incorporating a Covered Lagoon Digester System with a Microturbine Electric Generation System, manure s undesirable byproducts can be transformed into valuable assets for a dairy farmer. If the total manure produced by dairy cows in the state of California could be converted to methane, the theoretical energy production would be 20 trillion BTU which would be enough to power a 200-megawatt power plant. At the Cal Poly dairy, about 90 percent of the manure is deposited on concrete, flushed through a solids separator, and pumped into a 14,400 cubic meter covered lagoon. As the manure is anaerobically digested by bacteria located at the bottom of the lagoon, methane is produced and is trapped underneath a floating cover, collected, and piped over to be used to fuel a 30 kw microturbine electric generator. Figure 1 shows the system that is installed at the Cal Poly dairy, and the specific information on the design and construction of the covered lagoon digester and methane collection system was discussed in detail by Williams and Gould-Wells (2003), Williams and Frederick (2001) and Williams and Hunn (2002). Objectives 1. The first objective of this project was to report on the baseline operating parameters of the Covered Lagoon Digester System in treating flushed dairy manure. 2. The second objective was to determine the operating characteristics of the 30 KW Microturbine Electric Generation System when fueled with biogas from the Covered Lagoon Digester System. 3. The third objective was to estimate the energy and environmental benefits of the combined systems.

4 4 of 29 Figure 1. Microturbine Electric Generator System and Covered Lagoon Digester System Procedures Baseline Operating Parameters of the Covered Lagoon Digester Crucial baseline parameters established for the Cal Poly digester are as follows: Lagoon Digester Volume Based on the length, width, and depth of the lagoon as measured in meters. Influent Flow Rate Rate of the flushed manure entering the lagoon as measured in liters. Hydraulic Retention Time Volume of the lagoon divided by the daily influent flow as measured in days. Average Biogas Production Average production of biogas as measured in cubic meters per day. Methane Concentration in Biogas Biogas concentration as measured in percent by volume. Carbon Dioxide Concentration in Biogas CO 2 concentration as measured in percent by volume. Air Concentration in Biogas Air concentration as measured in percent by volume. Hydrogen Sulfide in Biogas H 2 S concentration as measured in percent by volume.\ Lagoon Digester Temperature Average temperature of the lagoon contents as measured in degrees C. Influent COD Concentration Chemical Oxygen Demand as measured in milligrams per liter. Effluent COD Concentration Chemical Oxygen Demand as measured in milligrams per liter.

5 5 of 29 COD Reduction Reduction in COD from influent to effluent as measured in percent. Total and Volatile Solids Percentage Percent of dry solids in the influent and percent of organic solids in the dry solids. Influent and Effluent Lagoon ph Effluent Total Nitrogen These baseline parameters were continuously measured during a period of time from January 1, 2002 through May 31, The detailed data and related discussion from this period are in Appendix A. The average daily values for these parameters are listed in Table 1 below. Table 1. Covered Lagoon Digester Baseline Operating Parameters Parameter Average Value Units Lagoon Volume m 3 Influent Flow Rate 365,000 l./day Hydraulic Retention Time 40 days Average Biogas Production 127 m 3 /day Methane Concentration 55 % Carbon Dioxide Concentration 10 % Air Concentration 35 % Hydrogen Sulfide Concentration - ppm Methane Production 70 m 3 /day Lagoon Temperature 15 o C Influent COD Concentration 4300 mg/l Effluent COD Concentration 1800 mg/l COD Reduction 59 % Influent Total Solids 0.5 % Influent Volatile Solids 0.4 % Influent ph 7.64 Effluent ph 7.04 Effluent Total Nitrogen 330 mg/l Comparison with Theoretical Biogas Production Volumetric Methane Production Rate. The following is a mathematical relationship (Gunnerson, G.C., Stuckey, 1992) that allows one to predict volumetric methane production: V s = (B o S o /HRT) x [1 (K / ((HRT x u m ) 1 + K))] Where: V s = B o = S o = specific yield (volumetric methane production rate in cubic meters per day per cubic meter of digester); ultimate methane yield in cubic meters of methane per kilogram of volatile solids added; influent volatile solids concentration in kilograms per cubic meters of liquid;

6 6 of 29 HRT = hydraulic retention time in days; K = a dimensionless kinetic coefficient = e (0.06 x So) ; and u m = maximum specific growth rate of the microorganism in day -1 equal to 0.013(Temp) The equation states that for a given influent volatile solids concentration and a fixed hydraulic retention time, the volume of methane produced per cubic meter per day varies with the ultimate methane yield of feedstock, the maximum growth rate of the microorganisms and the kinetic coefficient. The ultimate methane yield, B o, which is given as 0.20 for dairy cattle manure, is a value that varies with both animal type and diet. The influent volatile solids concentration, S o, is the previously calculated volatile solids value of 3.92 kg V.S. per cubic meter of digester per day. The hydraulic retention time, HRT, was previously found to be about 40 days. The kinetic coefficient, K, was calculated to be Finally, the maximum specific growth rate, u m, at a temperature of about 15 C is equal to The following table shows these values as well as the calculated value of the predicted volumetric methane production rate, V s. Table 2. Volumetric Methane Production Rate Bo = 0.2 So = 3.92 kg V.S./ cu.m. digester per day HRT = 39.5 days K = um = day-1 Vs = cu.m. CH4/cu.m. Digester-Day Knowing the predicted specific yield in cubic meters of methane per cubic meters of digester per day, one can calculate the theoretical daily production of methane in cubic meters per day. The predicted daily methane production is equal to the volumetric methane production rate multiplied by the digester lagoon volume. (Daily Methane Production (Predicted) = V s x Digester Volume). Using this equation and the previously calculated specific yield and digester volume values, the predicted methane production is equal to about 190 cubic meters per day. The actual methane production was only 70 cubic meters per day, or less than 40 % of the theoretically predicted production. Operating Characteristics of the Microturbine When Fueled with Biogas The following section describes the microturbine performance from July 1, 2002 through March Table 2 summarizes the results of this testing, showing biogas utilized, microturbine kilowatt setting, and kilowatt-hours generated. The data can be divided into roughly 1-month periods, during which times the microturbine power setting was maintained at specific KW levels. A complete listing of these data is included in Appendix B. During the first part of July 2002, when the power was set at 15 KW, the average daily running time was 3.6 hours, the biogas consumption was 44 cubic meters per day, and the net electrical output was just over 28 kwhrs. When the power setting was increased to 20 KW later in July, the daily running time dropped slightly to 3.4 hours, the biogas consumption increased to almost 54 cubic meters per day, and the net kwhrs increased dramatically to 47 kwhrs per day. When the setting was raised to 25 KW, the average daily running time dropped dramatically to 2.4 hours, accompanied by a drop in biogas consumption to 38 cubic meters per day and a net electrical production of only 31 kwhrs per day. The microturbine was then reset to 15 KW, and the resulting daily hours, biogas, and net electricity were only 1.6 hours, 22 cubic feet and 14 kwhrs respectively. In comparison with the baseline parameters in Table 1, where over 100 cubic meters per day were reported, the biogas production after July 2002 was markedly lower. Reasons for this change are addressed later in this section of the paper.

7 7 of 29 Table 3. Microturbine Performance Summary Time Period Hours/Day of Operation Ave. KW Microturbine setting m 3 /day Biogas Kwhrs/day Net Energy July 1-9, July 25-Aug 8, Aug 9-18, Aug19-Sept 19, October November December January February March During the initial 2-1/2 month testing phase, the microturbine was set to run as many hours per day as there was biogas available. In almost all instances, the reason for the microturbine shutting down was a fuel fault reading shown on the control panel. The situation that would trigger this readout was a drop in the Btu value of the biogas, due to possible air intrusion as the biogas was depleted from under the lagoon cover. This air intrusion would occur when the microturbine compressor was pulling biogas from under the cover at a slight negative pressure. It was also suspected that biogas was being lost from the same leak points that air intrusion occurred. Biogas leaking would occur when the microturbine was off, and a slight positive pressure under the cover would be forcing some of biogas out through the leak points. One of the suspected leak points was the soil under the area where the cover was attached to the lagoon bank. In order to correct this situation, a second plastic sheet was placed on the ground under the lagoon cover at the attachment area on the bank of the lagoon. Low microturbine production was experienced during the months of September and October 2002 because the covered lagoon liquid level was lowered by two feet during those months in anticipation of heavy rainfall in November and December that could exceed the runoff capacity of the overflow lagoon. When the level of the covered lagoon was lowered to this extent, it resulted in the outlet pipe s being above the level of the lagoon. Therefore, since the lagoon level was below the outlet to the overflow lagoon, the only way to remove liquid from the covered lagoon was via the recycle pump which had its inlet in the exit area of the covered lagoon. Later in November, when the lagoon level was restored to its full capacity, the biogas production, and thus microturbine performance, increased, as shown in Table 2. Yet, even this increase was not as high as the production achieved during the initial testing in the summer months, and this was due in part to the lower lagoon temperatures in November and December (~15 o C) compared with July and August (~21 o C). One very interesting result of the microturbine testing was observed in December On December 17 biogas utilization peaked at 100 cubic meters, as did net electrical output at almost 100 kwhrs. Because a very heavy rainfall occurred on the 17 th, and this resulted in significant water accumulation on the lagoon cover, it is speculated that this water pushed the lagoon cover down onto the water surface such that the

8 8 of 29 biogas was forced to migrate to the Styrofoam cells and thus to the gas manifold at the lagoon bank. From the maximum observed in mid-december, biogas utilization and resulting electrical production began to fall, and in January 2003 the average hourly use was 4.0 hours per day, at a setting of15kw. This resulted in an average biogas production of 32 cubic meters per day, with a net energy production of 36 kwhr/day. In February 2003, hourly usage averaged 3.7 hours at a setting of 20 kw. The resultant biogas production averaged 34 cubic meters, and produced a net energy production of 47.0 kwhr/day. The change from 15 kw to 20 kw between January and February 2003, and the resultant increase in net kwhr/day, shows a more efficient utilization of the biogas. During the first week of March 2003, it was discovered that the biogas pipeline was partially blocked by a dirty flame check. This blockage was subsequently removed, and as a result, the hourly usage, the biogas consumption, and kwhrs production increased dramatically to over 15 hours/day, over 127 cubic meters/day, and 143 kwhrs/day, respectively. These performance figures compare favorably with the baseline gas production reported in Table 1. To measure exhaust emissions from the microturbine, tests were run on August 16, 2002 when the microturbine was set at 25 kw power output. Table 4 summarizes these test results along with performance data at 15 kw and 20 kw power settings. Table 5 summarizes the average gas analyses from two different samplings, with the complete results included in Appendix C. To determine the concentrations of the various biogas constituents, samples of the gas were collected in a Tedlar bags and sent to a commercial laboratory for analysis with the use of a gas chromatograph. Table 4. Microturbine Performance at 3 Different Power Settings and Emissions at 25 KW Microturbine Power 15 kw 20 kw 25 kw Setting Hours of Operation 4.15 hrs Biogas 59 m 3 73 m 3 82 m 3 Microturbine Efficiency 20% 23% 25% Exhaust Emissions NOx 3 ppm CO 200 ppm Table 5. Biogas Constituent Analysis Parameter Average Value Units Methane Concentration 73.1 % Carbon Dioxide Concentration 15.3 % Air Concentration 11.6 % Hydrogen Sulfide Concentration 405 ppm Energy and Environmental Benefits The overall goal of this project is to recover as much energy as possible from the waste of the dairy cows and re-incorporate that energy back into the Cal Poly electrical grid for the benefit of the dairy. Cal Poly s dairy produces a monthly electric bill of almost $3,000, which results in a yearly expenditure of nearly $35,000. When the Microturbine Electric Generation System is operating at its optimal performance rate, the predicted energy production of the microturbine system is just over 52,000 kwh per year. This energy, at a rate of $0.12 per kwh, is worth about $6,240 which is about 18% of the dairy s yearly energy costs. In addition to the above electrical output, when operating at the optimal run time of 15 hours per day, the

9 9 of 29 exhaust heat energy produced by the microturbine can be recovered at a rate of 100,000 Btu/hr and is worth about $3,300 annually when compared to the average $6 per 1 million Btu cost of natural gas. The total economic benefits of the Microturbine Electric Generation System, including electricity and process heat, can then be estimated to be worth ~$10,000, or about 28% of the Cal Poly dairy s $35,000 annual electrical usage. The actual energy production of the Microturbine Electric Generation System, as explained above, falls well below the anticipated production which was expected to be between 40% to 50% of the energy needed for the Cal Poly dairy. Primarily because of design flaws in the lagoon cover, less methane was able to be collected than originally calculated, and a properly designed operations system should be able to maximize the energy and heat production of the microturbine system. The environmental benefits of a Covered Lagoon Digester System, although not quantified in a measurable economic value, are considerable. By virtue of the cover capturing the gas emissions from the dairy manure, both odor and the release of greenhouse gases are considerably reduced. Methane is a very potent greenhouse gas and is twenty-one times stronger than carbon dioxide. The methane emissions from the dairy at Cal Poly can be calculated as being almost 100 pounds per day or 18 tons per year and is therefore equivalent to over 380 tons of carbon dioxide per year. It is anticipated that in the future greenhouse gas credits will be available to the dairy farmer, and the farmer will be paid for capturing methane from a dairy lagoon. Conclusions and Recommendations The conclusions and recommendations that can be reached from the results of this study are the following: The greatest restriction on energy production of the microturbine system is the amount of methane available as fuel. In order to maximize methane production, a consistent flow of influent liquid entering the digester lagoon is necessary. Inconsistencies in the influent flow rate can potentially cause large fluctuations in the digester lagoon level, and therefore affect the hydraulic retention time of the liquid. Consistent influent flow will increase the hydraulic retention time and allow for increased production of methane. Increasing the amount of livestock in the dairy would also increase the amount of animal waste. This, in turn, would increase the volatile solids concentrations since the amount of flush water would not increase. An increase in volatile solids would increase methane production considerably. Increased conversion rates of the volatile solids into methane would improve overall methane production rates. Improved conversion rates can be accomplished by introducing heat into the liquid or by mixing the liquid in the lagoon. While mixing would be nearly impossible in a lagoon of this size, heating the lagoon contents would not be as difficult. In fact, the exhaust heat produced by the microturbine would be the perfect heating source, and it could be sent directly back into the digester lagoon via the heat exchanger installed next to the microturbine. The next phase of this project will be to set up the system to test this heating concept. Several methods might be used to minimize air intrusion into the lagoon digester system, thus improving the quality of the biogas. An anticipated improvement for this project will be to incorporate a bank-to-bank cover on the lagoon digester. In the current configuration, about 90% of the lagoon is covered, leaving small areas where the valuable methane can escape. Acknowledgements The authors gratefully acknowledge the California State University Research Initiative (CSU-ARI) and the Western Regional Biomass Energy Program (WRBEP) for providing funding for purchase, installation and initial operation of the equipment utilized at the Cal Poly Covered Lagoon Digester.

10 10 of 29 References Gunnerson, C.G., Stuckey Integrated Resource Recovery Anaerobic Digestion. The International Bank for Reconstruction and Development, Washington, D.C. Pp Hunn, David Operations Design and Evaluation of Cal Poly Dairy methane collection system. Unpublished Senior Project, Bio Resource and Agricultural Engineering Dept., Cal Poly, San Luis Obispo, CA. Johnson, E Personal communication about Cal Poly Dairy annual electrical usage. Cal Poly Energy & Utilities Manager, San Luis Obispo, CA. February 12, Williams, D.W., Frederick, J. J Microturbine Operation with Biogas from a Covered Dairy Manure Lagoon. Presented at the 2001 ASAE Annual International Meeting, held in Sacramento, California on July 30-August 1. Pp Williams, D. W. and Hunn, D Biogas Production from a Covered Dairy Lagoon Digester and Utilization in a Microturbine. Presented at Bioenergy 2002, Boise, Idaho, September, Williams, D.W. and Gould-Wells, D Biogas Production from a Covered Dairy Lagoon Digester and Utilization in a Microturbine. ASAE Paper No, , Presented at the ASAE Annual Meeting, Las Vegas, NV, July, Appendix A: Data and Discussion for Baseline Lagoon Operation Lagoon Dimensions and Volume. The lagoon volume was calculated to be about 14,400 cubic meters at a liquid depth of 3.7 meters. Knowing the dimensions of the lagoon s upper perimeter and the slope of the banks, average length and width dimensions were obtained. The volume of the lagoon was calculated by multiplying the average width, W avg, by the average length, L avg, by the measured depth, D, of the liquid in the lagoon (Lagoon volume = W avg x L avg x D). Liquid Flow Rate Entering Lagoon. The daily volume of liquid being fed into the digester lagoon was determined by multiplying the daily pump operation time, in minutes, by an average flow rate of 1.58 cubic meters per minute (cu.m./min) that was measured using the Beckman Flowmeter. Because of losses that occur over the solids separator and overflow of the concrete block tank for the sump pump, it was determined that approximately 70% of the initial pump flow reached the lagoon. Figure A-1 shows the variations in the average daily flow into the lagoon over a period of about three months. The overall daily flow, averaged over the three-month period, was 365 cubic meters per day. Figure A-1. Daily influent flow rate over a 70-day period. Hydraulic Retention Time. Hydraulic retention time, HRT, is the average time that a liquid stays in a reactor before it is discharged. In this case, it is the amount of days that the influent liquid remains in the digester lagoon before it is pumped into the secondary, or effluent, lagoon. It is equal to the active volume of the

11 11 of 29 lagoon digester divided by the flow rate of the entering liquid (HRT = Lagoon Volume / Liquid Flow Rate Entering Lagoon). A hydraulic retention time of about 40 days was calculated since the lagoon volume is 14,400 cubic meters and the liquid flow rate entering the lagoon is 365 cubic meters per day. Digester Lagoon Temperature. An average digester lagoon temperature of 15 C was determined based on the data collected using a thermocouples at various locations and depths. These data showed a temperature range of 11 C to 19 C with the temperature rising over time. Methane concentration in biogas. In a typical anaerobic digestion process, the biogas that is produced is comprised of about 60% methane and 40% carbon dioxide. Using a Fyrite Meter, an average carbon dioxide concentration for Cal Poly s lagoon was measured. Table A-2 shows an average carbon dioxide percentage of 9.8 %. Table A-1. Temperature and Carbon Dioxide Measurements Date Temp, C CO2% 4/17/ /18/ /19/ /20/ /21/ /15/ Average To determine the methane concentrations in the biogas, a sample of the gas was hand-pumped into a Tedlar bag and analyzed with the use of a gas chromatograph, and this analysis resulted in a methane concentration of about 55%. Since the carbon dioxide concentration is about 10%, the remaining 35% was assumed to be air. Therefore, if the air intrusion is ignored, the theoretical anaerobic biogas is composed of 85% methane and 15% carbon dioxide. Biogas Production. The biogas, which is pulled off of the lagoon with the use of a centrifugal gas blower, is ideally comprised of just methane and carbon dioxide. But, due to some air intrusion, the biogas also contains a certain percentage of nitrogen and oxygen. Figure A-2 shows the daily biogas production from mid January through mid March. The data, when averaged, was approximately 4430 cubic feet per day, or 126 cubic meters per day. At a methane concentration of 55%, the actual volumetric methane production rate can be calculated to be almost 70 cubic meters per day. As shown, there were large variations over the period of time the data was collected, from a minimum of 50 cu.m/day to over 600 cu.m/day. Figure A-2. Daily biogas production from January to March 2002 Chemical Oxygen Demand. Table A-2 shows the chemical oxygen demand (COD) for the influent and effluent liquid of the digester lagoon over a three-month period. An important aspect of this methane collection system is the reduction in COD from the influent liquid to the effluent liquid, which can be seen above. The 59% reduction in COD is a direct relation to the reduction in volatile solids and total solids of the digested liquid as well.

12 12 of 29 Table A-2. Chemical Oxygen Demand (COD) of Lagoon Influent & Effluent. Date Tested Time Run # Influent (mg/l) Effluent (mg/l) Diff (mg/l) % Reduction 3/1/02 3:30 PM % 4/3/02 1:30 PM % 4/3/02 1:30 PM % 4/3/02 2:15 PM % 4/3/02 2:15 PM % 5/2/02 2:45 PM % Avg % Volatile Solids and Total Solids. The influent chemical oxygen demand of 4317 mg/l in Table A-2 is equivalent to 0.43% COD. This percentage is converted to a volatile solids (V.S.) percentage by multiplying it by a volatile solids/cod ratio equal to This ratio is obtained from a manure production and characteristics table in the 1997 ASAE Standards handbook. This calculated volatile solids percentage of 0.39% is equivalent to kg V.S. per kg of influent liquid. By converting kilograms of influent into cubic meters of influent per day, a volatile solids value of 3.92 kg V.S. per cubic meter of influent per day can be obtained. In relation to the volatile solids are the total solids (T.S.) from which the volatile solids are extracted. An empirically determined volatile solids to total solids ratio of 0.81 produces a total solids value of kg T.S. per kg of influent liquid. Digester Lagoon ph. Digester ph readings were taken to ensure the fact that the lagoon acidity levels were within allowable limits. An average influent ph of 7.64 and an average effluent ph of 7.04 were measured, both of which are very close to the desired neutral ph of Effluent Total Nitrogen: Samples were drawn weekly from the lagoon effluent and a composite sample was sent to a commercial laboratory for nitrogen analysis. Appendix B. Data from Microturbine Testing Period Table B-1. Microturbine Performance, July1 to December 30, Cum. Date Hours KW Cu ft/day 100 cu ft/day Kwhrs/day 1-Jul Jul Jul Jul Jul Jul Jul Jul Jul Cum. Date Hours KW Cu ft/day 100 cu ft/day Kwhrs/day

13 13 of Jul Jul Jul Jul Jul Jul Aug Aug Aug Aug Aug Aug Aug Aug Cum. Date Hours KW Cu ft/day 100 cu ft/day Kwhrs/day 9-Aug Aug Aug Aug Aug Aug Cum. Date Hours KW Cu ft/day 100 cu ft/day Kwhrs/day 19-Aug Aug Aug Aug Aug Aug Sep Sep Sep Sep Sep Sep Sep

14 14 of 29 Cum. Date Hours Cu ft/day 100 cu ft/day Kwhrs/day 2-Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Cum. Date Hours KW Cu ft/day 100 cu ft/day Kwhrs/day 4-Nov Nov Nov Nov Nov Nov Nov Nov Nov Nov Nov Nov Nov Nov Nov Nov Nov Nov Cum.

15 15 of 29 Date Hours KW Cu ft/day 100 cu ft/day Kwhrs/day 2-Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Appendix C. Biogas Analyses Table C-1: ANALYTICAL REPORT: Environmental Analytical Service, Inc., San Luis Obispo, CA BTU By ASTM 3588 SDG: Source Test Fuel Analysis Laboratory ID: 03 Client: Williams Engineering Associates Date Sampled: 08/19/03 Sample ID: #3 Date Received: 08/20/03 Sam_Type: SA Date Analyzed: 08/20/03 QC_Batch: GC5 Wt.% Adjusted Compound Mole Weight Specific Specific Calorific Net Cal Calorific Net Cal % % Gravity Gravity BTU/ft3 BTU/ft3 Fraction Fraction Hydrogen Oxygen Nitrogen Methane Carbon Dioxide Carbon Monoxide Hydrogen Sulfide Ethane E Ethylene Acetylene Propane E Propene i-butane n-butane

16 16 of 29 i-pentane n-pentane 2.8E E E ,2-Dimethylbutane Cyclopentane 8.93E E E ,3-Dimethylbutane Methylpentane Methylpentane 5.52E E E n-hexane 3.69E E Cyclohexane 1.51E E E E E-05 Hexane E % Total 100 CHONS Wt % % C Table C-1: ANALYTICAL REPORT: Environmental Analytical Service, Inc., San Luis Obispo, CA (continued) CARBON SPECIFIC GRAVITY FRACTION (%) HYDROGEN GROSS CALORIFIC VALUE, BTU/ft dry OXYGEN GROSS CALORIFIC VALUE, BTU/ft wet NITROGEN NET CALORIFIC VALUE, BTU/ft dry SULFUR NET CALORIFIC VALUE, BTU/ft wet SDCF EXHAUST PER SCF FUEL Total 100 COMPRESSIBILITY FACTOR (Z) (60F,1 ATM) EPA 'F' Factor (60F,1 Atm) SDCF/MMBTU ASTM 3588 H2S By EPA 15 GC/FPD SDG: Source Test Fuel Analysis Laboratory ID: 03 Client: Williams Engineering Associates Date Sampled: 08/19/03 Description: #1 Date Received: 08/20/03 Sam_Type: SA Date Analyzed: 08/20/03 QC_Batch: GC4 Spike MDL H2S % % Flag QC Sample Lab No. ppmv ppmv ppmv Recovery RPD Method Blank BO8213A U LCS QC08213A LCD QC08213B RL MDL H2S MDL H2S Sample ID Description ppmv ppmv ppmv Mg/m3 Mg/m3 Flag #

17 17 of 29 Table C-2. AtmAA,Inc, Calabasas, CA Report Date: March 4, 2003 Client: California Polytechnic State University Project Location: San Luis Obispo, CA Client Project No.: Date Received: February 24, 2003 Date Analyzed: February 24, 2003 Methane and carbon dioxide were measured by thermal conductivity detection/gas chromatography CD/GC). Hydrogen sulfide was analyzed by gas chromatography with a Hall electrolytic conductivity detector operated in the oxidative sulfur mode. Table C-2. AtmAA,Inc, Calabasas, CA (cont) AtmAA Lab No.: Sample I.D.: Bio Gas Bio Gas Lagoon #1 Lagoon #2 Components (Concentration in %, v) Methane Carbon dioxide (Concentration in ppmv) Hydrogen sulfide Michael L. Porter Appendix D. Influent and Effluent Nitrogen Analyses Doug Williams Log Number: 02-C3056 Williams Engineering Associates Order: J Buckskin Drive Received: 03/20/02 Los Osos, CA REPORT OF ANALYTICAL RESULTS SAMPLED SAMPLE DESCRIPTION SAMPLED BY TIME MATRIX ================================ ======================== ============== ================== Lagoon Effluent D. Williams 03/20/02@ Aqueous ================================ ======================== ============== ================== ANALYTE RESULT * R.L. UNITS METHOD ANALYZED Total Nitrogen Value mg/l Calculated Nitrate as N Not Detected 1 mg/l EPA /21/02 Nitrite as N Not Detected 1 mg/l EPA /21/02 Total Kjeldahl Nitrogen mg/l EPA /29/ * R.L. - Reporting Limit. 'RESULTS' reported as "Not Detected" means not detected above R.L. CREEK ENVIRONMENTAL LABORATORIES Lab Director, Orval Osborne Page 2 Doug Williams Log Number: 02-C3057 Williams Engineering Associates Order: J Buckskin Drive Received: 03/20/02 Los Osos, CA REPORT OF ANALYTICAL RESULTS SAMPLED SAMPLE DESCRIPTION SAMPLED BY TIME MATRIX ================================ ======================== ============== ================== Lagoon Influent D. Williams 03/20/02@ Aqueous

18 18 of 29 ================================ ======================== ============== ================== ANALYTE RESULT * R.L. UNITS METHOD ANALYZED Total Nitrogen Value mg/l Calculated Nitrate as N Not Detected 1 mg/l EPA /21/02 Nitrite as N Not Detected 1 mg/l EPA /21/02 Total Kjeldahl Nitrogen mg/l EPA /29/ * R.L. - Reporting Limit. 'RESULTS' reported as "Not Detected" means not detected above R.L. CREEK ENVIRONMENTAL LABORATORIES Lab Director, Orval Osborne Doug Williams Log Number: 02-C7315 Williams Engineering Associates Order: J Buckskin Drive Received: 06/21/02 Los Osos, CA REPORT OF ANALYTICAL RESULTS SAMPLED SAMPLE DESCRIPTION SAMPLED BY TIME MATRIX ================================ ======================== ============== ================== Dairy Wastewater Influent Doug Williams 05/22/02@ Aqueous ================================ ======================== ============== ================== ANALYTE RESULT * R.L. UNITS METHOD ANALYZED Total Nitrogen Value mg/l Calculated Nitrate as N Not Detected 1 mg/l EPA /21/02 Nitrite as N Not Detected 1 mg/l EPA /21/02 Total Kjeldahl Nitrogen mg/l EPA /01/ * R.L. - Reporting Limit. 'RESULTS' reported as "Not Detected" means not detected above R.L. CREEK ENVIRONMENTAL LABORATORIES Lab Director, Orval Osborne Page 2 Doug Williams Log Number: 02-C7316 Williams Engineering Associates Order: J Buckskin Drive Received: 06/21/02 Los Osos, CA REPORT OF ANALYTICAL RESULTS SAMPLED SAMPLE DESCRIPTION SAMPLED BY TIME MATRIX ================================ ======================== ============== ================== Dairy Wastewater Effluent Doug Williams 05/22/02@ Aqueous ================================ ======================== ============== ================== ANALYTE RESULT * R.L. UNITS METHOD ANALYZED Total Nitrogen Value mg/l Calculated Nitrate as N Not Detected 1 mg/l EPA /21/02 Nitrite as N Not Detected 1 mg/l EPA /21/02 Total Kjeldahl Nitrogen mg/l EPA /01/ * R.L. - Reporting Limit. 'RESULTS' reported as "Not Detected" means not detected above R.L. CREEK ENVIRONMENTAL LABORATORIES Lab Director, Orval Osborne Appendix E: Raw Microturbine Emissions Data Microturbine Exhaust Emissions: August 9, 2002 Dairy Waste Lagoon Parameter Units #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 Time 10:54:00 11:02 11:09 11:13 11:17 11:21 11:27 11:31 11:36 11:46

19 19 of 29 Temperature (exit exhaust) F % Oxygen % % CO 2 % CO ppm NO ppm NO 2 ppm NOx ppm % Efficiency % Excess Air % Pump l/m Battery Volts % O 2 Reference % cco ppm cno ppm cnox ppm Microturbine Performance Output 26.4 kw 25.4 kw 25 95,000 rpm Temp (TET) 1100 F Note: The values in bold have been corrected for an oxygen reference of 15%, which is considered to be standard. Appendix F: Raw Biogas and Microturbine Performance Data Date Start Time Stop Time Biogas, ft3 % CO2 KW set KWhrs Pump Hrs Microturbine Hrs Comments 24-Apr 2:07 438,892 off 3:30 438,944 on 29-Apr 11:31 448,869 turned on blower, 510 cubic feet/ hour 5:00 455,872 off 30-Apr 3:00 455, cubic feet per minute, on- burning 5:30 459,543 off 1-May 1:57 2:05 459, cubic feet per hour, burns 2-May 3:51 465,541 7-May 2:25 482, May 11:47 512,755 off 15-May 2:47 522,562 off 16-May 1:01 527,344 off

20 20 of May 11:22 541,501 off 21-May 1:00 546,171 off 22-May 3:53 580,591 running, 30 cubic feet per minute 30-May 1:05 588,840 burning 8-Jun 5:30 613,000 no burn, noisy meter 10-Jun 6:00 609,880 gas hooked up wrong- ran backward 11-Jun 3:00 605,646 off 17-Jun 5:23 627,956 gas on, not burning, walked cover 5:38 628,444 burning 18-Jun 5:12 631,210 burning 19-Jun 10:35 633,819 burns 10:45 633,981 not burning 19-Jun 5:36 638,316 burns after walking on cover 20-Jun 5:21 638,524 Intermittant burn 21-Jun 5:00 641,534 walked on cover, full burning 22-Jun 5:18 645,531 Shut off blower- let gas collect till Thurs. 24-Jun 5:13 645,780 Started- burn 8:22 648,171 Stopped 27-Jun 5:30 653,620 Running 28-Jun 3:22 655,636 Shut valve to flare 1-Jul 11:55 655,638 Off, shut blower off & spark off 655, KW 6 cubic feet per minute 655, KW 8 cubic feet per minute 655, KW 11 cubic feet per minute 655, KW 14 cubic feet per minute 656, KW turned on blower, 510 cubic feet/hour 656, KW no blower, 9 cubic feet/minute, 540 cfh 2-Jul 10:20 656, KW 16 KWhr 2:01 658,454 Stopped, fuel fault, 3-Jul 10:54 658,454 19% checked flame- ok- and CO2 10:58 658,476 one failed start-up 11:05 658, KW 53 KWhr start-up ok, 8 1/2 cubic feet per minute 12:17 658, KWhr 4:01 659, KWhr fuel fault, shut down 4-Jul 2:20 659, :57:51 2 false starts 2:26 659, KW 83 KWhr re-start, start ok, 7 cubic feet/minute 7:13 661, KWhr 5-Jul 4:27 661, KW 99 KWhr :58:00 first start ok, 8 1/2 cubic feet per min 6:22 662, KWhr electric meter sticks, 7 cubic feet/ min 6:55 662,261 first start- shut down 662,263 second start- shut down 7:06 662,275 third start- shut down 7:20 6,622, :00:00 fourth start- ok, 7 cubic feet per minute

21 21 of 29 6-Jul 6:20 663, KWhr 18:07:58 first start- shut down 6:30 663, KW 18:11:00 third start- ok 7-Jul 6:10 665, :53:34 first start- shut down 6:12 665, KWhr 21:55:00 second start- ok, 8 cubic feet/ minute 6:37 665, KWhr Gas flow = 6.5 cubic feet per minute 8:16 666, KWhr Gas flow = 7.6 cubic feet per minute 8-Jul 7:29 666, KWhr :22:29 5 starts- shut down 7:42 666,950 sixth start- ok, 6 cubic feet per minute 9-Jul 226 KWhr 28:23:02 not running 10-Jul 2:58 668,226 20% 226 KWhr 28:25:02 Flared check CO2 3:14 668,240 First start, no compression 3:24 668,265 2 KW Third start, ok, 2 cubic feet per minute 3:43 668,300 Shut down and restart 3:50 668,316 Shut down, restart 3:54 668,321 Shut down, cool down 6:00 668, KWhr Did not auto-start 11-Jul 10:17 668, KWhr :50:30 Did not start, reset blower and flare, on 23-Jul 3:53 713, KW 68 KWhr No flare, 8 cubic feet per minute 24-Jul 3:55 715,336 19% 15 KW 73 KWhr :50:32 First start unsuccessful, 6.5 cfm 5:20 716, KW 87 KWhr Third start successful, 7.5 cfm 25-Jul 9:50 717, KWhr :59:33 off 4:22 717, KW 116 KWhr 39:10:00 8 cubic feet per minute 26-Jul 8:15 718, KWhr :02:00 First start unsuccessful 8:19 718, KW 160 KWhr Second start successful 8:47 719, KW 167 KWhr 28-Jul 1:47 720, KWhr :25:27 First start unsuccessful 1:52 Second start successful 2:12 720, KWhr 2:13 720,882 8 cubic feet per minute 29-Jul 5:00 722, :41:26 5:03 722, KW 258 KWhr First start unsuccessful 5:25 722,629 Second start successful 5:26 722, KW 264 KWhr 8 cubic feet per minute 30-Jul 9:30 724, KW 303 KWhr :44:28 First start unsuccessful 9:33 724,064 Second start successful 9:53 724, KW 308 KWhr 9:54 724,218 9:55 724, /2 cubic feet per minute 3:01 725, KWhr 55:20:43 Off 8:05 725,843 First start unsuccessful 8:08 725, KW 357 KWhr Second start successful 31-Jul 7:22 726, KWhr First start unsuccessful 7:26 726, KW 367 KWhr 56:16:18 Second start, ok

22 22 of 29 1-Aug 9:43 727, KW 383 KWhr :30:00 First start successful 9:53 727, KW 8 cubic feet per minute 1:08 729, KW 18 cubic feet per minute 1:13 729,180 7% Shut down 1:14 729, KW 436 KWhr Restart and Shut down 2-Aug 11:34 729,262 61:01:38 Restart, cool down 11:40 729, KW 436 KWhr :01:39 First start unsuccessful 11:44 729, KW 436 KWhr Second start, ok 12:02 729, KW 12:03 729, KW 440 KWhr 7 1/2 cubic feet per minute 3-Aug 1:30 730, KW 485 KWhr :25:31 First start unsuccessful 1:34 730, KW Second start, ok 1:49 731, KW 1:50 731, KW 490 KWhr 7 1/2 cubic feet per minute 4-Aug 10:05 732, KWhr :33:00 First start unsuccessful 10:08 732, KW 532 KWhr Second start, ok 10:11 732,724 10:12 732,733 10:13 732, /2 cubic feet per minute 5-Aug 3:37 734, KWhr First start unsuccessful 3:40 734,803 71:43:22 Second start, ok 6-Aug 10:46 735, KWhr First start unsuccessful 10:50 735, KW 612 KWhr 73:07:08 Second start successful, 9 cu. feet/min 10:57 735,685 10:58 735, KWhr 7 1/2 cubic feet per minute 7-Aug 10:31 737, KWhr :41:30 First start 10:36 737, KW 662 KWhr Second start, ok 10:38 737,775 10:39 737, /2 cubic feet per minute 3:01 740, KWhr 81:11:10 Shut down 8-Aug 10:38 740, KW First start unsuccessful 10:43 740,340 Second start ok 10:45 Start emission testing 10:46 740, cubic feet per minute 10:47 740,399 10:56 740,464 11:23 10 cubic feet per minute 11:30 740,809 11:31 740,819 11:35 740, cubic feet per minute 11:45 740, KW 741 KWhr 16 cubic feet per minute 11:45 740, KWhr 82:24:00 Manual shut down 9-Aug 10:31 740, KWhr :38:36 Gas to flare