A biogas upgradation system with reduced methane slippage comprising: a pre-treatment unit, a drying unit, a methane enrichment unit, and a methane recovery unit; said pre-treatment unit includes a blower, a biogas inlet for feeding a raw biogas stream into the blower, the blower configured to suck and pressurize the raw biogas stream up to 0.7 bar g from said biogas inlet, an Activated Carbon Filter, ACF, configured to receive the raw biogas stream through the blower for removing hydrogen sulphide, a pre-cooler configured to reduce the temperature of the pretreated hydrogen sulphide free biogas coming from said ACF; said drying unit includes an Moisture Separator, MS to remove water vapor from said cooled biogas obtained from said pre-cooler, a pair of drying towers (22, 23) configured to remove residual water vapor from the cooled biogas obtained from said MS; said methane enrichment unit includes a first pair of MPSA, Medium Pressure Swing Adsorption, towers (31, 32) up to 0.7 bar g (1.7 bar absolute) configured to extract methane from the dried biogas coming out from said drying tower (22, 23), a biogas surge tank configured to collect product gas, which is rich in methane obtained from said first pair of MPSA towers (31, 32); characterized in that said methane recovery unit includes a Vacuum Suction Port, VSP configured to convey the exhaust stream coming out from said drying tower (22, 23) and said MPSA towers (31, 32) to a Vacuum Discharge Port, VDP through a vacuum pump, a biogas buffer balloon to store the exhaust stream coming out from said VDP through vacuum pump, a blower configured to suck and pressurize the stored exhaust biogas stream from the biogas buffer balloon, a pre-cooler configured to reduce the temperature of stored biogas coming out from the biogas buffer balloon, a Moisture Separator MS configured to remove water vapor from said cooled gas obtained from said pre-cooler, a second pair of MPSA towers (49, 50) configured to extract remaining amount of methane obtained from the dried biogas stream of the MS, a biogas surge tank configured to collect persisting amount of methane. a pre-treatment unit, a drying unit, a methane enrichment unit, and a methane recovery unit; said pre-treatment unit includes a blower, a biogas inlet for feeding a raw biogas stream into the blower, the blower configured to suck and pressurize the raw biogas stream up to 0.7 bar g from said biogas inlet, an Activated Carbon Filter, ACF, configured to receive the raw biogas stream through the blower for removing hydrogen sulphide, a pre-cooler configured to reduce the temperature of the pretreated hydrogen sulphide free biogas coming from said ACF; said drying unit includes an Moisture Separator, MS to remove water vapor from said cooled biogas obtained from said pre-cooler, a pair of drying towers (22, 23) configured to remove residual water vapor from the cooled biogas obtained from said MS; said methane enrichment unit includes a first pair of MPSA, Medium Pressure Swing Adsorption, towers (31, 32) up to 0.7 bar g (1.7 bar absolute) configured to extract methane from the dried biogas coming out from said drying tower (22, 23), a biogas surge tank configured to collect product gas, which is rich in methane obtained from said first pair of MPSA towers (31, 32); characterized in that said methane recovery unit includes a Vacuum Suction Port, VSP configured to convey the exhaust stream coming out from said drying tower (22, 23) and said MPSA towers (31, 32) to a Vacuum Discharge Port, VDP through a vacuum pump, a biogas buffer balloon to store the exhaust stream coming out from said VDP through vacuum pump, a blower configured to suck and pressurize the stored exhaust biogas stream from the biogas buffer balloon, a pre-cooler configured to reduce the temperature of stored biogas coming out from the biogas buffer balloon, a Moisture Separator MS configured to remove water vapor from said cooled gas obtained from said pre-cooler, a second pair of MPSA towers (49, 50) configured to extract remaining amount of methane obtained from the dried biogas stream of the MS, a biogas surge tank configured to collect persisting amount of methane.