Techno-economic assessment of biogas plant upgrading by adsorption of hydrogen sulfide on treated sewage–sludge

Highlights: • Three processes were considered: desulfurization by adsorption, in-situ sorbent regeneration and its production. • The steam for regeneration was studied considering it as a bought external utility and as an in-situ produced utility. • From the cash flow analysis, the cost of the overall desulfurization process was between 2.5 and 4.0 c€/Nm³. • A sensitivity analysis was carried out to consider the uncertainty of the methodology. • The competitiveness of the technology seems to be promising versus other biogas H₂S removal technologies. - Abstract: Biogas plant upgrading by adsorption of hydrogen sulfide on treated sewage–sludge was techno-economically assessed. Three different processes were included in the study: the desulfurization of biogas by adsorption, the in-situ regeneration of the adsorbent and its production from sewage-sludge. Biogas plant upgrading was performed for a flow rate of 1000 Nm³/h of biogas with a H₂S concentration of 2000 ppmv and a breakthrough concentration of 200 ppmv, which is the technical limit value for internal combustion engines. The cost due to the steam required for the in-situ regeneration was evaluated in two different scenarios: as a bought external utility and as an in-situ produced utility, installing an electric or a biogas steam boiler. According to the cash flow analysis carried out, all the options require a similar minimum selling price for the upgraded biogas (about 0.27–0.29 €/Nm³), with a cost of the overall desulfurization process between 2.5 and 4.0 c€/Nm³.