Abstract Biogas upgrading to biomethane is a necessary process for biohydrogen production from renewable source. In this work, absorption processes using water and diethanolamine (DEA) as absorbent were modeled in Aspen Plus software. The purpose was to find the optimal operating condition for sustainable production of biomethane using multi-criteria perspective considering technical, environmental and economic aspects. The absorption system was modified by including one additional absorber unit for improving biogas upgrading efficiency. The performance of the biogas upgrading system was evaluated and compared in terms of methane recovery, methane content in biomethane, and energy consumption. Effects of operating conditions such as operating pressure in absorber, concentration, and total flow rate of absorbents were investigated. The results revealed that the performance of the modified absorption system was superior to the conventional system. The methane content in biomethane, methane recovery, and energy consumption increased with the increase of operating pressure in the absorbers. Increasing concentration and total flow rate of absorbents increased the methane content in biomethane and the energy consumption but decreased the methane recovery. The optimal operating condition could achieve 96%v/v of methane content in biomethane with methane recovery of higher than 95%v/v in the modified water absorption system. The optimum operating pressures of absorber Units 1 and 2, and total absorbent flow rates were at 13 and 5 bar and 16,000 kmol/h, respectively.