Cost estimation of the above designs are given in Table 6. As can be seen, extra amortized capital cost is zero for both OSMAHRD and TSMAHRD in scenario one, as no additional membrane unit or parallel compressor is required. On the other hand, in scenario two, extra amortized capital cost of 61,870 $/yr and 722,424 $/yr is required for OSMAHRD and TSMAHRD, respectively. Comparing the results for the three cares of CO2concentration, SCPUF of OSMAHRD is always less than that of TSMAHRD, suggesting that the former is a better solution for the investigated feed conditions. Note that SCPUF of TSMAHRD rises (to 0.482 $/kmol, 0.515 $/kmol and 0.630$/kmol) following the increase of CO2mole fraction (to 0.15, 0.2and 0.35) in the feed. On the other hand, SCPUF of OSMAHRD for scenario two (0.422 $/kmol) is almost same as that of the reference case (0.421 $/kmol); this is because methane loss in the permeate stream is offset by the reduction in the utility cost, due to lower amount of inlet flow to the amine absorber.