On-farm trials of practical options for hydrogen sulphide removal from piggery biogas

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Manure-derived biogas is increasingly used at Australian piggeries to produce heat and generate electricity. However, high concentrations of hydrogen sulphide (H2S) in piggery biogas is discouraging further use, because of a lack of practical, cost-effective H2S removal options. To address this issue, on-farm trials were conducted at two piggeries. One trial tested H2S oxidation; adding small amounts of air to biogas, upstream of a low-cost enhanced surface treatment vessel which was fabricated on-farm with intrinsic safety measures. Covered anaerobic pond (CAP) effluent provided a convenient, low-cost nutrient source for the biofilm of naturally-occurring microorganisms in the packed column. This treatment was effective, removing over 90% of the H2S in a single pass and reducing H2S concentrations from 4000 ppm to <400 ppm. Another trial tested chemisorption performance of natural, iron-rich red soil, mixed with a ground sugar cane mulch bulking agent, in comparison with cg5 commercial media (iron-oxide pellets). The red soil removed H2S, but had a substantially lower capacity (similar to 2 g Sikg red soil) than the cg5 (similar to 200 g Sikg media). Accordingly, red soil is unlikely to be feasible as a primary treatment medium, but may be useful for final polishing after an oxidation step has removed most of the H2S. Crown Copyright (C) 2018 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers. All rights reserved.