More guidance and evaluation is needed to guide adopters, especially in light of the large capital investment needed for ADS (averaging $1-1.5 million for a 1000-cow dairy) and the increase in new adopters expected with new incentives from the White House’s June 2014 “Biogas Roadmap” to accelerate adoption of digesters to reduce U.S. dairy sector GHG emissions by 25% by 2020, and the MOU between the National Associate of Clean Water Agencies and the National Milk Producers Federation released September 2014 to improve water quality and environmental benefits on dairy farms, with anaerobic digesters listed as the first example of new partnership initiatives.
According to AgSTAR, there have been 200 new on-farm digesters built in the US since 2003, but many ADS lack any biogas scrubbing systems. Existing ADS operators and new adopters will benefit from our systematic analyses, documentation, and reporting on existing select systems and development of relevant educational outreach materials. This information will lead to farmers making better informed decisions about what biogas scrubbing technology is right for them and increase output of their EGSs with the least system cost.
Biogas scrubbing is perceived by 88% of ADS practitioners, extension specialists, and funding agencies as one of the most important barriers to wider-spread ADS adoption and success in the marketplace, and there is no doubt that the lack of implementation of H2S scrubbing equipment is holding back the biogas industry. 85% of farmers indicated they need a better understanding of scrubbing operational and maintenance conditions, quantifiable benefits of different types of scrubbing systems and the costs associated with operating biogas scrubbers. With the increasing use of ADS, more evaluation and guidance information is needed to guide adopters, especially in light of the large capital investment needed for ADS available in the current market. With greater adoption rates, ADS could result in large increases in on-farm energy production, increased opportunities for on-farm GHG reductions, and increased opportunities for nutrient reductions from manure, as digestion allows for post-treatment harvesting and transport off-farm of nutrients or more appropriate application of nutrients on-farm. Providing famers with unbiased information about the efficacy and economics of ADS through access to information and demonstration of viable H2S scrubbing for EGS, on-farm sulfur analyses, and detailed economic costs of ADS with H2S scrubbing systems could increase on-farm energy production on US farms and lead greater ADS profitability and adoption rates on US dairy farms.
Solution and benefits
To address the deficiency in available knowledge, the project will assess the efficiencies, cost, maintenance and consistency of two external biological H2S scrubbers, one in-vessel system with air injection, one physical-chemical system, and one combined bio-air injection system, and convey the findings to farmers, key advisors, industry professionals, government officials, lenders, and policy makers through our extension and education efforts. We will demonstrate the effectiveness, cost, and degree of usability for the three most promising types of H2S scrubbers available on the current marketplace with existing scrubbers systems, which will increase our likelihood of success.
At this point, one or two types of system have NOT emerged as preferable due to lack of unbiased data on initial and operation/maintenance costs, and reliability. The importance of proper biogas treatment in order to grow the ADS field cannot be over emphasized. Reliability of biogas end-use equipment is a major concern amongst farmers, both current ADS adopters due to EGS downtime/maintenance and future adopters due to these uncertainties.
The results will be normalized to a “per cow” or “per lactating cow equivalent” basis in order to translate results to medium and smaller-scale farmers. The online survey initiated for this work identified 5 farmers with ADS without a H2S scrubbing that want to install a scrubber, 3 farmers with underperforming H2S scrubbers that want to improve them, 4 farmers with well performing H2S scrubbers but want more information on further optimization, and 11 additional farmers that are very likely (4) or somewhat likely (7) to install a new ADS on their farm in the next 1-3 years. In addition, many farmers expressed their interested in investigating second-generation biogas technologies, such as biogas upgrading for vehicle fuel, pipeline injection, or solid oxide fuel cells with which H2S removal is imperative. Dairy producers, government agencies, NGOs, and entrepreneurs throughout the US will benefit from the project results and extension/outreach materials developed from this project. We will educate, demonstrate directly, and advise farmers on how to create an on-farm successful biogas system that can be used with both EGS and next-generation technologies.
Our online survey results showed that >85% of respondents felt it was “very important” to receive: 1) better understanding of scrubbing operation/maintenance conditions, 2) pros/cons of different types of scrubbers, and 3) costs associated with operating scrubbers, with 50% expecting to install or improve their scrubbing system in the next 1-3 years.
Project Objectives from Revised Proposal:
- Evaluate biogas scrubbers operating on five NE farms to document: a) efficacy of different H2S scrubbers b) effect of H2S on EGS operation, c) determine the extent of differences in on-farm sulfur concentration, d) economic cost/benefit of scrubber operation, and e) practical aspects of daily operation and maintenance of AD systems and biogas scrubbers;
- Create a Farmer’s Guide to Dairy-Derived Biogas: Production, Scrubbing and Utilization;
- Host five field days in the NE;
- Develop and deliver extension/outreach materials including at least 4 Fact Sheets, 5 Case Studies, 6 popular press article/newsletters, journal articles, and field day presentations to ≈ 150-200 dairy farmers, installers, government agents, and NGOs, with all materials available free on Cornell’s PRO-DAIRY Environmental Systems program website, extension and Livestock Learning Center.
Performance Targets from the Revised Proposal:
By project conclusion, biogas scrubbing performance and cost benefits will be determined on five dairy farms with digesters. By project conclusion, 10 dairy farmers with 5,000 total cows will install new biogas scrubbers and 10 additional farmers (with 2500 cows) will improve/update their existing scrubbers. As a result, these 20 farms will realize a total of 6 MW of additional generation capacity with a value of $4,500,000/year. The results and recommendations from the study will be written into the Biogas Guide, Fact Sheets, Case Studies, and popular press and journal articles. The results and recommendations will be used by at least 10 dairy farmers (>5,000 total cows) to guide new scrubber installation and/or improvements to existing units, resulting in enhanced engine-generator set output, i.e. higher capacity factors.
Challenges to Meeting Performance Targets:
The price of milk is currently at all-time lows, with many/mots dairy farmers in the NE losing money every year. The 30% federal tax break for renewable energy installations, which many digester operators use (including one of our collaborating farmers that submitted for upgrade his H2S scrubber and EGS), expires at the end of 2016 and is not expected to be renewed with the new political climate. The largest H2S scrubber installer and operator in New York went out of business last year, leaving many farmers with existing H2S scrubbing systems without any technical support or periodic calibration capabilities. These challenges are beyond the control of the grant PIs, but are very real challenges to the entire AD industry.
Based on the limited literature available, it is predicted that of the four H2S scrubber system types outlined for testing, the air injection system will be the least effective in terms of removing H2S in the biogas, but will have the lowest maintenance time and capital costs, while the physical scrubber will be the most effective H2S removal mechanism but have the highest time and cost commitment.
The treatments chosen represent a diversity of existing H2S scrubbing systems that will each be evaluated for 8 months over a 20-month period using our two previously purchased continuous monitoring system (see attached experimental design), with evaluation conducted during various times of the year (testing over 2-month periods during summer and winter) to determine efficacy.
- Kilby Farm has a covered lagoon digester with food waste co-digestion on 600-cow farm in Colora, MD with a biological-chemical H2S scrubber and 110 kW EGS.
- Sunny Side Dairy Farm in Venice Center, NY is a 3,300 milking cow and 1,400 heifer farm with a plug flow digestion system for a 1000 kW EGS and 1.5 mmBTU broilers, with a biological scrubber.
- Spruce Haven Farm in Auburn, NY processes manure from 2,000 cows with an innovative, low cost anaerobic digester that includes a 450 kW EGS and a biological scrubber.
- Reinford Farm in Mifflintown, PA has 550 cows and a RCM complete mixed digester co-digested with culled produce from supermarkets for a 140 kW EGS with air injection H2S scrubbing.
- Reinford-Frymoyer Farm-LLC in Mifflintown, PA has 430 cows, a 225 kW EGS and biological scrubber with air injection using biogas from a RCM mixed digester co-digesting dairy manure with culled produce from supermarkets.
There are 5 ADS and 4 types of H2S scrubbing installations in which the biogas scrubbing efficiency, and ADS costs/maintenance will be accessed. Biogas composition pre- and post-biogas cleanup will be measured for a total of 8 months to capture seasonally variations using two custom-made assemblies consisting of a portable continuous gas analyzer for CH4, CO2, O2, and H2S (Siemens Model # 7MB2337-3CR13-5DR1), a data acquisition system (Campbell Scientific), and a Sage gas meter (Model # SIG-05-15-SVA-05LP). The assembly allows for continuous measurement and logging of all parameters before and after H2S scrubbing. The Reinford Farm with in-vessel air injection-only will use the monitoring assembly as a standalone unit and only quantify the biogas composition (CH4, CO2, O2, and H2S) leaving the digester.
An economic analysis will be performed for each ADS by collecting and analyzing: 1) annual cost and cost savings for each scrubbing system, 2) biogas utilization and electricity sales, 3) maintenance and on-going ADS operational costs, and 4) valuation of time spent operating the ADS using an annualized cost-benefit analysis (AgSTAR Protocol, 2011).
- Data collection
The two equipment assemblies will be rotated among the five project-collaborating farms in order to reduce expensive equipment costs while still allowing for determination of the effect of scrubbing on biogas quality over time and carrying temperatures. Collected data include biogas production, composition and utilization, H2S reduction, temperature, total sulfur content for water, manure, forage, and co-substrates, and all economic cost items for owning, operating and maintaining the ADS system. All monitoring equipment will be calibrated, installed and used per the manufacturer’s recommendations. Meter data will be continuously logged. Information collected by the biogas system will be downloaded at regularly scheduled monthly visits or transmitted to Cornell daily if internet is accessible on-site. Data will be managed and analyzed in a custom developed MS Excel spreadsheet for this project. Collected data will be reviewed in accordance with QA/QC procedures, with ANOVA and Tukey-Kramer post-hoc statistical analyses of the reviewed data.
- Farmer input
The collaborating farms and PDs have worked together previously and are eager to gain information on improving their H2S scrubbing and biogas utilization efficiency. The farmers will operate and maintain their ADS and scrubbers and supply records of time and costs spent on their ADS system. Farms will receive at least two reports during the project, with graphs/charts on their system performance and optimization strategies. Each farmer will contribute 10-15 hours of labor over the 2-year project period, help organize and conduct the workshops on their farms, and provide feedback on the Fact Sheets, Biogas Guide, and workshop materials.
- Additional information: Other relevant features of the proposed research
The research will be the first encompassing quantification of ADS operating costs and scrubber efficiencies in the Northeast (and US). One advantage of our approach is that without construction or experimental manipulation the likelihood of project delays is greatly reduced. The AgSTAR “Safety Practices for On-Farm Anaerobic Digestion Systems” will be used as a guide for the producers and project team. In addition, the Advisory Board created for this project includes the AgSTAR Program Manager, the head of the Energy Innovation at Green Mountain Power and the Deputy Chair of the USEPA Farm, Ranch, and Rural Communities Federal Advisory Committee.
Through our survey, we have received contact information for > 40 interested participants in ADS workshops and/or scrubbing installation/upgrading. We will deliver workshop advertisements to > 2,000 dairy farmers in the Northeast through extension meetings, newsletters (i.e. Livestock and Poultry Learning Center), and e-mail networks (i.e. Dairy Farmers of America and Northeast Dairy Producers Association). Recruitment materials will include a link to an additional online survey about current ADS practices and ADS learning objectives to guide our extension programming. Our Advisory Board will assist in steering farmers interested in installing/upgrading scrubbers to us in order to meet our performance targets.
- Delivery methods
We will integrate performance and cost results into a Farmer’s Guide to Biogas Production, Scrubbing and Utilization, written in easy-to-understand language with detailed and practical information for anaerobic digestion processes, factors affection biogas composition, increasing biogas production, assessing biogas cleanup feasibility, and biogas effect on maintaining successful end-use equipment. Overall, such a comprehensive publication is not in existence today and will be a welcome resource by current and future ADS owner/operators.
We will develop and deliver educational materials through the Guide, at least four Fact Sheets, six popular press articles/newsletters, write/updated five case studies, two peer-reviewed journal publications, and five field days (one in Maryland, Pennsylvania and Vermont, and two in New York) to dairy farmers, policy makers, governmental agencies, extension educators, lenders, and NGOs to disseminate lessons learned. We will deliver oral presentations at dairy industry meetings, academic conferences, and other related events in the Northeast. All materials will be posted on Cornell’s PRO-DAIRY, eXtension, and dairy industry email list-serves in the NE region.
The interested participants in upgrading or installing new H2S scrubbing system will participate with PDs in individual consultations and creation of a new farmer-to-farmer listserv for participants interested in learning from others’ experiences.
- Curriculum topics
The Farmer’s Guide to Biogas Production, Scrubbing and Utilization will provide the necessary information to: (1) factors affecting biogas composition, (2) determine biogas production potentials under a range of scenarios, including with co-digestion, (3) determine biogas scrubbing needs and capabilities with various scrubbing systems, (4) provide predictive capabilities for biogas production and scrubbing throughout the year, and (5) document operating costs for a range of sophistication in biogas scrubbing systems to better understand capital and labor needed for on-going operation.
The field days will cover a range of topics with lessons learned from collaborating farmers, including general anaerobic digestion ABCs, methods for increasing biogas production (co-digestion), H2S scrubbing, and operating more efficient EGS for electricity production.
- Beneficiary support
In addition to regular updates to collaborating farmers, additional farmers interested in upgrading or installing new H2S scrubbing systems will be provided with one-on-one support by the PDs and part-time extension agent by phone, e-mail, or in-person. A listserv will be created to link farmers in the Northeast with ADS to help facilitate farmer-to-farmer communication. The information from the collaborating farms will be consolidated into Fact Sheets and Case Studies, which will be published online and widely distributed. In addition, sections of the Field Day presentations will be recorded and posted online for widespread access to the presented information.
Milestone 1: Initial meetings with Advisory Board and farmers within four months of contract execution to: 1) receive feedback on project commencement and the developed logbook to record generator performance, maintenance efforts and costs, and 2) determine project baseline for capital costs, maintenance time and maintenance expenses.
Part 1 of this Milestone has been completed. A meeting was held with each farmer at the start of the project to explain the project, objectives and milestone. Additional informal meetings have been held with the farmers as we collect data to update them on our progress and gather information on their system operations and expenses. One New York dairy farm with a H2S scrubber on the project was replaced with a different farm with an H2S scrubbing system from the same manufacturer, due to AD system shutdown at the original farm. Ten months of biogas data was collected from the new farm.
An Advisory Board was held in April 2016, with all Advisory Board members participating (in person or by phone). During the meeting, we received feedback on the project commencement and possible improvements and discussed current scenarios of anaerobic digestion in Northeast US. In addition, Advisory Board members discussed different dairy groups they are associated with in their area (VT, NY and PA) that could be targeted for extension events. In addition, new information on permitting for air emissions implemented in various states that have implications for digester operators was discussed and subsequently, and as a result, in addition to the series of four (4) H2S scrubbing Fact Sheets, a series of four (4) Fact Sheets were written on EGS emission. All eight (8) Fact Sheets have been posted on the Cornell PRO-DAIRY Dairy Environmental Systems web site (see: http://www.manuremanagement.cornell.edu/Pages/Popular_Pages/Fact_Sheets.html) and the information will be incorporated into future extension efforts.
Future Work on Milestone 1: We will continue to collect information on the baselines for capital costs of the scrubbers, as well as the maintenance time and maintenance expenses. We have developed expense form for the farmers to use to assist in continual collection of this data.
Milestone 2: Provide quantified information to five diary farmers on their biogas- scrubbing performance and cost-benefit, specifically for two farms with external biological scrubbers, one with an in-vessel system using air injection, one physical-chemical scrubber, and one combined bio-air injection system. The five farmers will receive information on their H2S scrubbing evaluation, their economics, and improved scrubber and ADS maintenance/optimization within 24 months of contract execution. Dozens of farmers will also receive this information during field days hosted on their farms in order to impart this knowledge to fellow farmers by April 2017.
Overall: Data was collected over 10 months at four out of the five farms involved in the project. The farmers were updated on how to improve scrubber performance and how their practices affected the composition of the biogas. In addition, the presence of the project biogas monitoring systems demonstrated the importance of properly maintaining and calibrating the equipment used to measure gas quality; particularly H2S. Often, farm owned monitoring equipment was either not working at all, or generally under reporting values of H2S when compared to project measured calibrated values.
The results from the study to date showed that the average methane (CH4) concentration was found 56.2 ± 0.1%, with a high of 61% and low of 49% CH4 (Figure 1, top). During the same time, the average hydrogen sulfide concentration (H2S) was found to be 1938 ± 23 ppm (Figure 1, bottom). The range of hydrogen sulfide concentrations varied from a high of 3300 ppm to below 100 ppm H2S due to inconsistent treatment with the air injection system, possibly due to clogging, insufficient air injection, or variability in the feedstock sulfur concentrations. The highest concentration of oxygen (0.5%) in the biogas corresponded to the lowest hydrogen sulfide concentration, indicating excess air was used to achieve maximum biogas desulfurization, as there was additional O2 in the air that was not utilized. Lower air injection rates could remove hydrogen sulfide until the oxygen is completely depleted, as observed during the remainder of the study period, where the oxygen concentration in the biogas output was nearly 0%. A slight increase the air injection rate could have a positive effect on reducing the hydrogen sulfide coming out of the digester, but as the air injection rate goes up, the amount of CH4 dilution will also increase, due to O2 and N2 in the air. Furthermore, it was observed that liquid food waste addition, instead of solid food waste, led to a positive effect of higher biogas production with a higher methane percentage due to the higher ease of degradability of the liquid feedstock. However, this also contributed to a higher concentration of hydrogen sulfide in the biogas.
One of the PA farms had issues with clogging of their air injection pump for scrubbing out the H2S (which they were unaware of before project commencement), and we explained how they could observe the data gathered by the biogas monitoring unit to predict if and when they might have further clogging issues. The farmer noticed that after fixing the pump, they were able to change the oil in the EGS less frequently due to higher quality biogas. We had discussions with the farmers, approximately monthly, while the monitoring units were on their farms, to discuss the collected data and its implications in order to help them gauge the performance of their scrubbing systems and the effects of a cleaner biogas stream on their EGS units.
At the end of December 2016, the gas analyzer system started malfunctioning and the system had to be uninstalled for repairs. The on-farm biogas was tested using the Landtec handheld gas meter during farm visits. On February 4th, the test results showed that the CH4 concentration was 49.9% with a 50.1 % CO2 concentration. The H2S concentration was observed to be 1800 ppm, with 0% O2 and N2 concentration. This indicated that the airflow pump was not injecting air into the digester due to possible clogging of the inlet gas tubing, and this resulted in a higher H2S concentration in the biogas. The farmer was advised to unclog the gas line in order to reduce H2S concentrations in the biogas coming out of the digester.
The biogas was tested again on June 9th, and the CH4 concentration was observed to be 63.6%, with 35.8% CO2 concentration. The H2S concentrations (3233 ppm) and the percent CH4 were higher, on average, than the observed values during the study period in 2016. The farmers had informed us that the feedstock was changed from solid food waste to liquid food waste recently, and this is likely the reason behind the increased CH4 and H2S concentrations.
It should be noted that solid food waste may have a higher biogas and methane potential (but this is highly dependent on the type of feedstock), but it requires more time for complete breakdown. Liquid food waste generally has more soluble organics, which may result in higher utilization. However, if the liquid feedstock has a high sulfur content, then it may also lead to higher H2S concentrations in the biogas. The residence time inside the digester was kept constant, so an apparent increase in the biogas output was observed when the feedstock was changed from a solid waste stream to a liquid waste stream. A liquid food waste stream could be a better resource because it can lead to a higher output with a short residence time, and it allows the farmer to accept more waste, which may lead to higher tipping fees. The increased CH4 production can also lead to increased electricity generation.
In addition to the high CH4 concentrations, the biogas had a higher concentration of H2S, as mentioned previously. A sample test using a handheld biogas analyzer showed a 0% concentration of O2 with a 0.7% balance (N2). This indicated that even though the air injection system was functioning and adding air into the digester, the oxygen was being used up completely. It is possible that due to the higher biogas production and increased concentrations of H2S, the air injection rate was inadequate to desulfurize the biogas sufficiently.
Based on previous on-site visits and interactions with the farmer, it was noticed that prior to the feedstock change, the flow rates were, on average, 50 – 55 scfm (or 3000 scf/hr – 3300 scf/hr). However, after the feedstock change, the flow rate increased to ~ 4000 scf/hr, out of which the unused biogas was being flared off. However, during early September, the generator efficiency dipped and the biogas used for energy generation was reduced substantially, as seen in Figure 2. The generator was shut down mid-September for a week, and after maintenance and repairs, the generator was fully functional again, with the average flow rates of ~ 4000 scf/hr, similar to August flow rates. The data shown here is a fair representation of the biogas production rate on the farm, and the digester usually maintains a steady flow of biogas throughout the year since it is kept at a constant temperature. The farmer informed us that they produced a total of 689,656 kWh of electricity from June ’16 to April ’17, out of which 285,906 kWh was in excess and not used on the farm.
The results from the study showed that in the first three months of the study period, no major differences were seen between the hydrogen sulfide (H2S) concentrations in the pre-scrubbed (715 ± 58 ppm) and post-scrubbed biogas (695 ± 58 ppm) (Figure 3). The average methane (CH4) concentration was 65.1 ± 0.3 % in the pre-scrubbed biogas and 66.2 ± 0.2 % in the post-scrubbed biogas. The farm in MD has an iron oxide scrubber that the farmer filled with rusted scrap iron and steel scrapings. Due to the low surface area of the scrap metal and the high volume of biogas passing through the scrubber, the media was saturated within a short period of time. The scrubbing media was changed twice in the following three months to induce a treatment effect. It was noticed that a change in the media led to a cleaner product after scrubbing (41 ± 9 ppm H2S compared to 66 ± 13 ppm H2S before scrubbing) (Figure 4). The biogas had a low concentration of H2S during this time, probably due to lower temperatures, as the digester was never heated. The methane concentration during this period was consistent in the pre (62.7% ± 0.2) and post scrubbed (62.8% ± 0.3) biogas. The average daily biogas flow rates varied from a high of 42,450 scf/day from June to October 2016 to a minimum of 1,788 scf/day during January – February 2017. The farm produced 47,158 kWh from August to December 2016 (Figure 5) at an average rate of 360 kWh/day. Overall, the biogas was of high quality due to the high methane content and low concentrations of H2S. The methane concentrations remained largely unchanged during the entire study period, while the biogas quantity fluctuated with tempreature. It is optimal for the H2S concentration in the biogas to be less than 500 ppm (most optimal < 250 ppm) to prevent damage to the engine generator, as higher H2S concentrations can lead to more engine down time due to H2S corrosion of the system.
During periods of generator activity from June 2016 to December 2016, the biogas flow rate was continuous and consistent (Figure 6). The gas flow was intermittent during the logging period of May 2017 (Figure 7) because biogas was not being pumped to the generator continuously. The biogas flowed through the flowmeter only when the gas pressure inside the digester was higher than the atmospheric pressure. It was also noted that singular spikes in the gas flow rate was caused when strong winds forced the gas to flow out of the digester. It is probable that similar intermittent flow was observed after the generator stopped functioning in December, due to the pump not extracting biogas from the digester continuously to run the generator. It should also be noted that the MD farm did not run the generator continuously during its operation, and hence did not produce the optimal amount of energy from the biogas produced.
New York Systems
An example financial table with the characteristics, performances and costs of the two NY farm systems over the course of the data collection period are shown in Table 1. The two biogas scrubber systems in NY are both biological scrubbers, the system at Farm 1 performs better. On Farm 1 there is an advantage in that the digester supplies two EGS, and so biogas flow through is maintained during routine EGS maintenance as one EGS would still be working during this time. In addition, Farm 1 has a solid cover over their digester, while Farm 2 has a flexible cover that posed problems during the winter months when snow and rain would build up on top and restrict the collection and flow of biogas, resulting in system slowdowns or shutdowns. This difference in system performance can be verified by examining the Capacity factor (how much power was actually produced divided by how much power could have been produced over the same period) of the two farms shown in Table 1. The capacity factor is less than one due to system shutdowns for maintenance or outages, and also due to operating the systems at below design capacity due to inadequate biogas flow or other maintenance problems (overheating of engine heads, etc.)
Table 2: Financial and Operational Summary for MD and PA systems
|System||MD Farm||PA farm 1|
|Size||Average number of milking cows||450||650|
|Engine Generator Capacity (kW)||110||140|
based on the
for each farm
|Average untreated H2S concentration (Avg ± Std. Err)||66 ± 13||N/A|
|Average treated H2S concentration (Avg ± Std. Err)||41 ± 9||1938 ± 23|
|Overall Removal Efficiency (%)||38||N/A|
|Avg Mass of H2S removed (lbs/hr)||0.001||N/A|
(based on one year of data, if available)
|H2S Scrubber system capital cost ($)||500||450|
|H2S Scrubber yearly maintenance ($/yr)||0||2,000|
|H2S scrubber cleanout labor ($/yr)||0||0|
|H2S Scrubber media replacement cost ($/yr)||650||0|
|Generator yearly maintenance and repair cost ($/yr)||2,500||29,000|
Future Work: Data will be gathered from the fifth farm, a second PA dairy farm that has both air injection as well as a separate biological scrubbing system starting in 2018. Labor, maintenance and utility (heat and electricity demand) costs for all systems will continue through the duration of the project to provide the best possible measure of the costs associated with operating these systems.
Changes or Issues in Work plan: There was a one to two-month delay in getting money dispersed to University of Maryland and Cornell University (subcontract), which resulted in initial delays in project commencement, but the project has commenced and is working within a new timeline that incorporates those initial delays. There were additional delays due to issues with the H2S sensors in the Siemens Biogas analyzers. Due to the high levels of H2S in the biogas, we have had to replace the sensors multiple times, which resulted in breaks in biogas collection periods. We will continue to monitor the H2S sensors and replace them, as necessary, and as the budget permits. Siemens is aware of the issue and has been working with us in troubleshooting the units.
We have been unable to get data on H2S levels on the second PA farm due to issues with the Siemens Biogas analyzer but are working to find a way to gather this data in 2018.
Milestone 3: Provide > 700 people, including farmers, essential information on scrubbing and biogas performance through the publication of a Biogas Guide, four Fact Sheets, five Case Studies, 6 popular press article/newsletters, and two journal articles by August 2018. The farmers will be able to use the Guide to determine: (1) factors affecting biogas composition, (2) biogas scrubbing materials and capabilities for different types of scrubbing systems, (3) operating costs for five ADS, and (4) managing and operating guidelines for EGS with different scrubbing system types. This comprehensive farmer-friendly guide currently does not exist, nor are publically developed data available on H2S scrubbing efficiencies and operating costs for maintaining ADS. This will be a welcome resource by current and future digester owner/operators. A preliminary outline of the Biogas Guide will be circulated to ten NE farmers for review and input.
We are in the final editing stage for the Biogas Guide, “Microaeration for Hydrogen Sulfide Removal in Biogas” Fact Sheet, and the Case Studies for each farm. The following Fact Sheets have been posted to the Cornell PRO-DAIRY website; “Hydrogen Sulfide and Biogas: Basics”, “Measuring Hydrogen Sulfide”, “Partial Budget Analysis”, “Iron Sponge Basics”, “Iron Sponge Design Considerations: Vessel Sizing”. Additionally, “Available technologies for hydrogen sulfide removal from biogas”, “Microbial underpinnings of H2S biological filtration” “Biotrickling filters for H2S – Overview of configuration and design” “Biotrickling filters for H2S – Improvement opportunities” Fact Sheets written as a part of a different collaboration but pertaining to this study are apart of the “Hydrogen Sulfide Removal From Biogas” Fact Sheet Series posted to the Cornell PRO-DAIRY website. The contents of the fact sheets have been presented at the University of Maryland Dairy Field day with 59 attendees and the Cornell AD Short Course with 66 attendees.
Future Work: We will continue writing the Biogas Guide, which will be circulated to the Advisory Group and our farmer stakeholders for review prior to publication. We will continue working on the third Fact Sheet and the Case Studies. We will start writing the last Fact Sheet, 6 popular press article/newsletters, and two journal articles to be completed by August 2018.
Milestone 4: Host five field days to allow producers to see biogas scrubbing technologies and learn general information on ADS operation, biogas production, and H2S scrubbing options, and specific information on H2S scrubbing performance and economic viability for >100 farmers and their advisors for five the field days combined by August 2017.
We have contributed to or hosted two workshops, one in New York and one in Vermont. The VT Digester Operator’s Group was at Rosie’s Farm in Middlebury, VT on December 8th, 2016 with 60 participants. At this workshop, controlling H2S was a presented topic, and our work on H2S scrubbers was highlighted (see attachment that was distributed widely at the meeting). The other workshop was held at Sunny Side Farm in Venice, NY on January 7, 2016. This workshop was a hosted industry group meeting with 12 participants to discuss the implications of the closing of the largest H2S scrubber operator (ABC Scrubbers). Following the workshop, site visits were held at the operators affected by the ABC Scrubbers closure from January 19th – January 21st, 2016. In 2017 we participated in a field day at the University of Maryland Dairy in Clarksville and Cornell hosted an AD Short Course. The Maryland Dairy Field Day was held on October 18th, 2017 with a total of 59 participants. The effects of H2S and potential ways to control it was presented. The fact sheets produced were provided at the event and available digitally on the event page. The Cornell AD Short Course was held December 12th – December 14th with 66 participants. The information from the fact sheets was presented and shared in the proceedings.
Future Work: An additional Field day will be hosted in 2018 to provide the gathered information to the farmers. Opportunities to collaborate in our extension programming to expand the number of participants are continually being explored, and the future field day is currently being planned.
Milestone 5: PDs will consult and assist > 25 farmers on implementing H2S scrubbers on dairy farms or improving their existing scrubbing systems, work with collaborating farms to optimize their systems, and continue to implement advisory board suggestions, as appropriate, by project conclusion.
Through our assistance, the farmers at one PA farm were able to solve their clogging problems and were able to save $20,000 by not having to install a new air injection pump for their digester. Now, they are continuously maintaining their pump in order to prevent further clogging. The MD farmer has purchased a new scrubber to be installed in Spring 2017.
The written Fact Sheets will help convey the initial information from this project to the public.
Accurately measuring the concentrations of H2S over sustained periods on farm has proven to be challenging, even with industry leading equipment from Siemens. Frequent calibrations and diligent maintenance of the measuring equipment is essential to ensuring confidence in measured values. Siemens requires monthly calibrations and yearly replacement of the H2S sensor. Both of the NY farms use Inca gas analyzers (Union Instruments GmbH), and their manufacturer requires annual replacement of the H2S sensor, but does not specify a calibration schedule.
Only the two NY farm systems have their own gas analyzing equipment installed, primarily to take advantage of an incentive program by the New York State Energy Research and Development Authority (NYSERDA), which rewards farms for maintaining an H2S concentration below 300 ppm in order to receive the performance-based payments from NYSERDA. It was clear from comparing the measurements of the two systems (Project and existing on farm) that in one case (Farm 2) the Inca analyzer was rarely working at all. Farm 1 better maintained and monitored their equipment (replacing sensors etc.), however, it appeared that values measured by the farm owned equipment were lower than those measured by the project equipment. This is likely due to the with our calibrations. It seems clear that NYSERDA should require a validation/calibration check to ensure that their goal of incentivizing reduced H2S concentrations is actually met.
Future Work: We look forward to connecting with more farmers through our extension events and helping them with future H2S scrubbing needs. Two of our collaborating farmers have already purchased a new scrubbing systems due to our collaboration (MD system) or improved their existing system (PA farm).
Milestone Activities and Participation Summary
Performance Target Outcomes
By project conclusion, 10 dairy farmers with 5,000 total cows will install new biogas scrubbers and 10 additional farmers (with 2500 cows) will improve/update their existing scrubbers.
These 20 farms will realize a total of 6 MW of additional generation capacity.
The 6 MW of additional generation capacity will result in a $4,500,000/year value