Quantifying and demonstrating scrubbing H2S from farm-based anaerobic digestion systems

View the project final report

• 2016 annual report

Commodities

Practices

• Energy: anaerobic digestion

Problem and justification  A main operational challenge to on-farm anaerobic digestion systems (ADS) has been operational interruption of biogas-fueled engine-generator sets (EGS) due to damage from hydrogen sulfide (H2S) in biogas, resulting in high maintenance costs and/or lost revenues. The uncertainties associated with EGS operation and biogas scrubber ability to reduce H2S affects profitability, EGS effective lifetime, electricity production, and overall interest by farms in ADS. A survey administrated to prepare this proposal showed 87% of farmers and extension agents surveyed in the NE (48 respondents) indicated a greater understanding of H2S scrubbing systems and costs associated with owning and operating ADS was “very important.” With the increasing use of ADS and the large capital investment required for ADS, more guidance and evaluation information is needed for adopters. To address these knowledge deficiencies, the efficacy of H2S scrubbing systems on five existing farms will be evaluated, with financial analyses of each ADS operation.   Beneficiary audience, approach and solution  ADS are a promising renewable energy technology that reduces greenhouse gas (GHG) and odor emissions and improves water quality. Providing famers, farm advisors, policy makers, and lenders with un-biased information is critical for growth of this technology. Demonstration of H2S scrubbing options, with detailed economic costs of ADS operation could increase US on-farm energy production and lead to greater ADS profitability and adoption rates. Currently, there are 90 ADS in the Northeast. AgSTAR has identified > 250 additional NE dairy farms candidates for installation with existing ADS technology. Medium-scale farm inclusion would add 350 additional candidate farms in NY alone. This project will: 1) evaluate multiple strategically-selected biogas scrubbers operating on five NE farms to document: a) effect of H2S on EGS operation, b) determine the extent of differences in on-farm sulfur concentration, c) economic cost/benefit of scrubber operation, and d) practical aspects of daily operation and maintenance of ADS and biogas scrubbers; 2) create a Farmer’s Guide to Dairy-Derived Biogas: Production, Scrubbing and Utilization; 3) host five field days in the NE; 4) 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.

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 MWh 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.

 
Milestones for beneficiary learning

Each milestone will be evaluated and verified throughout the project to ensure timeliness of project products and knowledge transfer.

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.

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.

Milestone 3: Provide > 700 people, including famers, 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.

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.

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.