Biogas Utilization Technologies Evaluation Section 1

FINAL TECHNICAL MEMORANDUM Las Gallinas Valley Sanitation District - Biogas Utilization Technologies Evaluation PREPARED FOR: Las Gallinas Valley Sanitation District REVIEWED BY: Jim Sandoval/ CH2M HILL Dru Whitlock/ CH2M HILL PREPARED BY: Dan Robillard / CH2M HILL DATE: April 19, 2014 PROJECT NUMBER: 479699 Section 1 - Introduction Project Vision The Las Gallinas Valley Sanitary District (LGVSD or District) wastewater treatment plant (WWTP) needs to upgrade its aged cogeneration system by 2016 to meet new air quality standards. Accordingly, the LGVSD wants to evaluate biogas utilization alternatives to understand the long range option that best addresses economic, environmental, technical and social drivers. Project Description In 2012 LGVSD contracted CH2M HILL to visit the WWTP, identify the air emissions regulations and permitting issues that impact LGVSD’s equipment, and recommend a path forward for further analyses, including an evaluation of whether LGVSD should replace or upgrade its internal combustion engine and a recommended approach to track air quality and climate change regulatory and permitting issues that may impact the WWTP. The findings, recommendations and proposed second tier follow-on work items are summarized in a September 21, 2012 Technical Memorandum by CH2M HILL. After considering the recommendations of the Technical Memorandum, LGVSD requested that CH2M HILL implement an updated version of the proposed second tier scope of services, including 1) evaluation of biogas utilization alternatives, 2) assessment of the digester heating and biogas handling systems, 3) development and operations options for a new cogeneration system, and 4) an annual update that summarizes air quality and climate change regulations that may impact LGVSD operations and developments. This technical memorandum will present the results of Tasks 1 – 3. Task 4 was delivered to LGVSD staff on January 30, 2014, as a separate technical memorandum. Executive Summary Four alternatives for biogas utilization were analyzed for both economic and non-cost factors: microtrubines, compressed natural gas (CNG) vehicle fill station, pipeline injection, and just removing the existing engine. The economic evaluation estimated the construction costs, the annual operations and maintenance costs, and calculated a present worth assuming a 20 year lifespan. A present worth analysis is an estimate of the value that an investment of money has over a fixed lifespan. The analysis uses a discount rate for the devaluation of equipment and an interest rate of the investment. If a present worth has a positive value, the annual operations and maintenance cost are less than the expenditures. If it is negative, the annual operations and maintenance cost are more than the expenditures. A non-cost decision analysis methodology was also used to make subjective comparisons among the alternatives, rating them among several factors that are generally not directly affected by costs. The non-cost factors are the result of 1) the issues comparison chart that staff from LGVSD and its board filled out to determine a ranking and LGVSD BIOGAS UTILIZATION ANALYSIS.DOCX/[INSERT DOCUMENT LOCATOR] 1 COPYRIGHT [INSERT DATE SET BY SYSTEM] BY [CH2M HILL ENTITY] • COMPANY CONFIDENTIAL LAS GALLINAS VALLEY SANITATION DISTRICT - BIOGAS UTILIZATION TECHNOLOGIES EVALUATION weighted score for each criteria, and 2) an engineering evaluation of each alternative to rate how well each technology meets those criteria. Multiplying the criteria weight by the engineer’s rating for each criterion and adding them all up results in the total non-cost factor score. The analysis shows that the lowest cost alternative is removing the existing engine, followed by a microturbine system. For non-cost factors, the microturbine alternative scored highest overall and somewhat higher than removing the existing engine, but the difference is small. As demonstrated by the annual operations and maintenance (O&M) present worth values, the microturbines alternative produces savings from energy generation that are higher than the costs to operate. Two values are listed under the CNG vehicle fill station for O&M present worth in Table 1-1 below. The first value of $400,000 assumes that all the biogas available is actually used in a vehicle. Since this scenario is not realistically possible, an assumption using the equivalent of 20 gallons of gasoline per day was evaluated. The result of this calculation is the second value listed—($1,020,000). A summary of the cost and non-cost factor results is shown in Table 1-1. An estimate of the O&M staff time per year for each alternative is also listed in the table. The cost for this time is factored into the O&M present worth estimate. Table 1-1 Summary of Alternatives Analysis Remove Existing Microturbines CNG Vehicle Fill Pipeline Injection IC Engine (Add Station Boiler/Flare) Construction Cost ($1,170,000) ($2,200,000) ($2,900,000) ($8,400,000) Estimated Staff O&M 144 260 250 250 (hours/yr) Annual O&M Present ($380,000) $100,000 $400,000 / ($500,000) Worth ($1,020,000) Total Present Worth ($1,550,000) ($2,100,000) ($2,500,000) / ($8,900,000) ($3,920,000) Non-Cost Factor 678 706 584 650 Score If the non-cost factor score is then divided by total present worth (in millions of dollars) for each alternative, the result is a benefit to cost ratio, which is shown in Figure 1-1 below. 2 LGVSD BIOGAS UTILIZATION ANALYSIS.DOCX/[INSERT DOCUMENT LOCATOR] COPYRIGHT [INSERT DATE SET BY SYSTEM] BY [CH2M HILL ENTITY] • COMPANY CONFIDENTIAL LAS GALLINAS VALLEY SANITATION DISTRICT - BIOGAS UTILIZATION TECHNOLOGIES EVALUATION Benefit to Cost Ratio 500 450 400 350 300 250 200 150 100 50 0 Microturbines CNG Vehicle Fill CNG Vehicle Fill Pipeline Injection Remove IC Engine Station (low) Station (high) Figure 1-1 Benefit to Cost Ratio of Biogas Utilization Alternatives With the lowest cost and relatively high non-cost factor score, the remove IC engine and flaring the excess biogas has the highest benefit to cost ratio. Operational Parameters Table 1-2 below summarizes the biogas parameters that were used in the evaluation. Copies of biogas testing reports that formed the basis of these parameters are included in Appendix A. It should be noted that a new biogas flow meter was recently installed so there is no long term trending data on flow rates. The value used in this evaluation should be confirmed or adjusted before proceeding with any further development of biogas utilization options. TABLE 1-2 Biogas Parameters Summary of Biogas measurements and testing results Parameter Value Information Source Biogas Production Rate 50,000 standard cubic feet Plant staff estimate; trending data not available per day (scfd) Methane Content 63% From waste gas burner compliance report, Dec 16, 2013. Energy Value 638 British Thermal Units From waste gas burner compliance report, Dec 16, 2013. per cubic foot (Btu/cf) Siloxanes Content 1,500 parts per million Estimated from typical values at other WWTP facilities (ppm) Hydrogen Sulfide (H2S) Content 197 ppm From waste gas burner compliance report, Dec 16, 2013. Section 2 - Biogas Utilization Alternatives LGVSD’s existing internal combustion (IC) engine must meet the emission standards of Bay Area Air Quality Management District (BAAQMD) Rule 9-8-302 by January 1, 2016, and include the best available control technology applicable at the time the new unit is permitted. Assuming the rich-burn, internal combustion engine 3 COPYRIGHT 2014 BY CH2M HILL, INC. • COMPANY CONFIDENTIAL LAS GALLINAS VALLEY SANITATION DISTRICT - BIOGAS UTILIZATION TECHNOLOGIES EVALUATION continues to operate solely on digester gas, the pertinent emission standards are as follows: 70 ppm nitrogen oxides (NOx) at 15 percent oxygen, dry basis, and 2,000 ppm carbon monoxide (CO) at 15 percent oxygen, dry basis. An evaluation to determine if the engine can be brought into compliance with air emission standards and, if so, what equipment would be required to do so has been performed. The existing digester operation utilizes biogas as a fuel for a hot water boiler. The boiler supplies hot water to maintain proper temperature within the anaerobic digesters via a sludge heat exchanger. Detailed calculations for the amount of heat required are included in Appendix A. Since the existing digested sludge heat exchanger is nearing the end of its expected life, all alternatives assumed that the sludge heat exchanger, sludge recirculation pump, and hot water recirculation pump would be replaced. Existing IC Engine Retrofit Waukesha, the existing engine manufacturer, was contacted and was unwilling to guarantee they could provide equipment allowing the engine to meet the 70 ppm NOx requirement in the permit. Because the existing engine is a rich burn design, it is unlikely that exhaust cleaning through a catalytic converter would be sufficient enough to meet the permit. Additionally, if a catalytic converter was installed, the catalytic material would be spent quickly and need frequent replacement (several times per year). Furthermore, reinvesting in the engine would place the system at risk since replacement parts will become difficult and expensive to replace. Because this conversion would entail a high chance of failure from either the exhaust gas cleaning system or the engine itself, retrofitting the existing engine is not considered a viable option. Additional Biogas Utilization Alternatives The following additional biogas utilization alternatives were considered for suitability at the LGVSD WWTP. 1. New IC engine 2. Microturbines 3. Fuel Cells 4. Gas scrubbing and compression for natural gas fueling station for District fleet vehicles 5. Gas scrubbing for pipeline injection into a local natural gas pipeline Each alternative was initially screened to determine if they were unsuitable or unfeasible for further evaluation. A brief technology overview and subsequent initial screening of the above five alternatives is provided in Section 3. An economic analysis was conducted on the remaining viable alternatives with the results described in the Section 4 and Section 5 is a non-cost factor evaluation.

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