Performance and Economic Results for Two Full-scale Biotrickling Filters to Remove H2S from Dairy Manure-derived Biogas

Abstract

Abstract. Anaerobic digestion (AD) of dairy manure produces renewable energy in the form of biogas. Hydrogen sulfide (H2S) is formed in the produced biogas in variable quantities (up to 8,000 ppmv). H2S can cause corrosion damage to biogas-fueled engine-generator sets (EGSs), resulting in high operating temperatures, high maintenance costs, and/or lost revenues for farmers. Biotrickling filters are a common technology for H2S removal, however, there is a need for information about the performance, capital, and operational costs associated with biotrickling filters to better inform producers using or considering such systems. Keywords: Click here to enter keywords and key phrases, separated by commas, with a period at the end

Evaluation of Hydrogen Sulfide Scrubbing Systems for Anaerobic Digesters on Two U.S. Dairy Farms

“…Zicari (2003) tabulated data for different proprietary iron-oxide based adsorbents, where the capital costs ranged from $8000 to $43,600 and the operating costs ranged from $8290 to $23,840 for a biogas stream with 4000 ppm of H 2 S and a gas flow rate of 1350 m 3 /d, which is comparable to the average daily biogas flow rates for both farms in this study [2]. These cited costs were much lower than the costs associated with owning and operating the BTF units in the study conducted by Shelford et al (2019) [4]. The operational, maintenance, and utilities costs for BTF systems in their study ranged from $17,050 for farm 2 to $32,563 for Farm 1, which are comparable to the operational costs of iron oxide scrubbers, but the capital costs were at least four times higher.…”

“…The operational, maintenance, and utilities costs for BTF systems in their study ranged from $17,050 for farm 2 to $32,563 for Farm 1, which are comparable to the operational costs of iron oxide scrubbers, but the capital costs were at least four times higher. The proprietary iron-oxide scrubbers examined by Zicari (2003) had high H 2 S removal efficiencies and low H 2 S output concentrations (up to 100% and less than 1 ppm) compared to the lower efficiencies (80.1% and 94.5%) and higher H 2 S output concentrations (450 and 150 ppm) seen in the study by Shelford et al (2019) [4,12]. However, on larger farms, the operating costs associated with iron oxide scrubbers may be much higher due to the larger volume of biogas to be treated and the higher handling and disposal costs of the spent media [12].…”

“…A previous study investigated the performance and economic benefits of two BTF systems on NY farms and found that the total annual cost to own and operate the scrubbers may not justify the capital and maintenance costs of the scrubber systems compared to increasing the frequency of oil changes [4]. It was suggested that longer monitoring periods may be necessary to understand the benefits of H 2 S scrubbing on major generator overhauls.…”

“…The scrubber system capital costs were confirmed, and the scrubber maintenance costs were collected for at least one year from each farm. Untreated and treated biogas were analyzed to detect daily and seasonal differences using two portable continuous biogas testing and monitoring systems (Siemens Model #7MB2337-3CR13-5DR1, Siemens AG, Munich, Germany) for CH 4 (0% to 100%), CO 2 (0% to 100%), O 2 (0% to 100%), and H 2 S (0-5000 ppm), with a Campbell Scientific CR1000 data logger and acquisition system, and gas meters (Model #9500, Thermal Instrument Co, Trevose, PA, USA; Model #FT2, Fox Thermal, Marina, CA, USA) and assembled as described in Shelford et al 2019 [4]. The monitoring system were moved and installed at each farm for the study period (73 and 179 days).…”

“…They suggested the use of an external biological scrubber to achieve outlet H 2 S concentrations of <100 ppm and increase the life of combined heat and power (CHP) units and decrease the frequency of oil changes. In practice, digester manufacturing companies in the US have recommended limits of 500 ppm H 2 S in the biogas [4]. The variable H 2 S concentrations during the study period indicated variable treatment efficiency.…”