Monitoring on-farm Dairy Anaerobic Digestion Biogas H2S Scrubber Performance and Economics

Abstract. Anaerobic digestion (AD) produces renewable energy in the form of methane (CH4)-enriched biogas. Hydrogen sulfide (H2S) is formed in the produced biogas in trace quantities (up to 8,000 ppm). H2S can cause corrosion damage to biogas-fueled engine-generator sets (EGS), resulting in high maintenance costs and/or lost revenues for farmers. There is a need for thorough understanding of optimal H2S scrubbing operational and maintenance parameters, quantifiable advantages and disadvantages of different types of scrubbing systems, and the capital and operational costs associated with H2S scrubbers, and for this information to be conveyed to farmers using or interested in using AD systems. To address these knowledge deficiencies, the efficacy of H2S scrubbing systems on two dairy farms in NY was being evaluated, with financial analyses conducted on each AD scrubber operation.

Biogas production (cfm) and H2S, CO2 and CH4 concentrations in the biogas were quantified on existing biological H2S scrubbing systems for 7 months. Two continuous biogas monitoring systems (Siemens Ultramat 23) were used to analyze the biogas streams, with data collected and transmitted with Campbell Scientific (CR1000) dataloggers. Data on scrubber and engine-generator maintenance costs (parts and labor) was collected, and indicate that the annual economic savings of reduced oil-change frequencies was not more than the annual cost of owning and operating the biological treatment systems.