Economic assessment of biogas purification systems for removal of both H2S and siloxane from biogas

Biogas is a promising renewable biofuel, but hydrogen sulfide (H2S) and siloxanes are major obstacles in the conversion of bioenergy from biogas because they damage biogas-processing equipment. This study evaluated two biogas-purification systems for a simultaneous efficient removal of H2S and decamethylcyclopentasiloxane (D5), and compared their economic performance. An acidic biotrickling filter (BTF) was operated continuously for 90 days to investigate its performance under different H2S and D5 concentrations. Meanwhile, commercial iron-oxide-based adsorbents (IOBAs) and activated carbon (AC) were used in adsorption filters for H2S and D5, respectively. The results show that in terms of the ratio of D5 and H2S concentration (R-D5:H2S) and pH of the recycling liquid, which are crucial BTF operating parameters, high elimination for both H2S (1.86 kg/(m(3).d)) and D5 (0.282 kg/(m(3).d)) was achieved at R-D5:H2S of 3.7:16 and pH of 0.86. Economic analysis confirmed that BTF-AC was more profitable than IOBA-AC adsorption over a life span of 10 years because the pre-removal of D5 by a BTF significantly decreased the costs of IOBAs and AC, despite BTFs requiring a higher initial capital investment. In terms of the economic benefit of biogas production of 1200 Nm(3)/h, the competitive annual cost of 90.5 k$/year indicated that BTF was more profitable, yielding both cost saving and the benefit of providing heat. The advantage of BTF-AC adsorption was a more radical D5-abatament, enabling profit by selling the electricity produced from biogas to the grid. (c) 2020 Elsevier Ltd. All rights reserved.