Vehicles running on compressed natural gas (CNG) are a promising option to significantly decrease automotive CO2 emissions. However, considerable amounts of methane are emitted by the exhaust of CNG powered engines which are difficult to convert by standard catalytic converters. Yet, by combining the catalyst with an efficient heat exchanger, the temperature level of the catalyst can be raised for enhanced conversion performance. Experimental results of stationary tests performed with a heat-integrated laboratory-scale system are shown. A special cold start strategy required for fast system heating is presented based on a detailed transient simulation study and a new system layout is described.