A method for reducing the amount of CO 2 discharged into the atmosphere with the exhaust gas stream emitted by a hydrocarbon-fueled internal combustion engine used to power a vehicle, the method comprising: a. passing the hot exhaust gas stream from the ICE to a first waste heat recovery zone on board the vehicle and contacting the high temperature exhaust gas stream with at least one heat exchanger having an inlet for receiving the hot exhaust gas stream from the ICE for passage in heat exchange relation and a discharge outlet for discharging a cooled exhaust stream at a lower temperature, the waste heat recovery zone further including at least one heat recovery device for converting the waste heat in the exhaust gas stream to electrical and/or mechanical energy; b. passing the cooled exhaust gas stream to a membrane separation zone that is in fluid communication with the exhaust gas stream discharge outlet of the waste heat recovery zone and in contact with at least one membrane module having a membrane with a permeate side to which CO 2 permeates, the permeate side having a CO 2 discharge outlet, and a retentate side that is in contact with the cooled exhaust gas stream, the retentate side including a treated exhaust gas stream outlet, wherein a portion of the electrical and/or mechanical energy converted by the heat recovery device in step a) is used to create a pressure differential across the CO2 separation membrane; c. passing the CO 2 from the permeate side of the membrane module to a densification zone and using a portion of the electrical and/or mechanical energy converted by the heat recovery device in step a) to reduce the temperature and volume of the CO 2; d. transferring the densified CO 2 to a storage zone for temporary storage on board the vehicle; and e. passing the treated exhaust gas stream having a reduced CO 2 content to an exhaust gas conduit that is in fluid communication with the treated exhaust gas stream outlet of the membrane module and discharging the treated stream into the atmosphere. a. passing the hot exhaust gas stream from the ICE to a first waste heat recovery zone on board the vehicle and contacting the high temperature exhaust gas stream with at least one heat exchanger having an inlet for receiving the hot exhaust gas stream from the ICE for passage in heat exchange relation and a discharge outlet for discharging a cooled exhaust stream at a lower temperature, the waste heat recovery zone further including at least one heat recovery device for converting the waste heat in the exhaust gas stream to electrical and/or mechanical energy; b. passing the cooled exhaust gas stream to a membrane separation zone that is in fluid communication with the exhaust gas stream discharge outlet of the waste heat recovery zone and in contact with at least one membrane module having a membrane with a permeate side to which CO 2 permeates, the permeate side having a CO 2 discharge outlet, and a retentate side that is in contact with the cooled exhaust gas stream, the retentate side including a treated exhaust gas stream outlet, wherein a portion of the electrical and/or mechanical energy converted by the heat recovery device in step a) is used to create a pressure differential across the CO2 separation membrane; c. passing the CO 2 from the permeate side of the membrane module to a densification zone and using a portion of the electrical and/or mechanical energy converted by the heat recovery device in step a) to reduce the temperature and volume of the CO 2; d. transferring the densified CO 2 to a storage zone for temporary storage on board the vehicle; and e. passing the treated exhaust gas stream having a reduced CO 2 content to an exhaust gas conduit that is in fluid communication with the treated exhaust gas stream outlet of the membrane module and discharging the treated stream into the atmosphere.