TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The methane oxidation catalyst comprises palladium.The palladium is impregnated in a wash coat comprising alumina. The wash coat is deposited on a ceramic support comprising silicon carbide or magnesium aluminum silicate.The wash coat is deposited on a metallic support.The methane oxidation catalyst includes rhodium, cerium oxide, oxygen storage component, e.g. cerium oxide and combination of cerium and zirconium, and a scavenger for hydrogen sulfide.The methane oxidation catalyst is a three-way catalyst.The methane oxidation catalyst comprises noble metal(s), i.e. palladium, platinum, and rhodium.    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Components: The second set of points on the engine map is associated with when the engine is operating within a predetermined high engine speed range and within a low engine load range.The low engine load range is defined when the engine is operating at less than 20% of maximum engine load.The high engine speed range is defined when the engine is operating with a speed that is greater than or equal to 80% of maximum engine speed.The second set of points on the engine map is associated with when the engine is operating within an engine speed range and within an engine load range.The methane oxidation catalyst promotes the oxidation of methane when the engine is fuelled with a lean fuel mixture and promotes the reduction of nitrogen oxides to nitrogen when the engine is fuelled with a rich fuel mixture.The controller is programmed to recognize predefined conditions when the vehicle or machine is stationary and to command the engine to operate at a point that is one of second set of points on the engine map for the lesser of a time or until the vehicle is no longer stationary.The sensor(s) is a lambda sensor with a sensing probe disposed in the exhaust manifold or the exhaust pipe upstream from the methane oxidation catalyst.The lambda sensor is operable to send signals representative of the measured lambda value to the electronic controller.The sensor(s) comprises a first mass flow sensor associated with the intake air manifold and a second mass flow sensor associated with the fuel supply pipe.The two mass flow sensors are operable to send signals representative of the respective air and fuel mass flow rates to the electronic controller.The electronic controller is programmable to calculate lambda of a charge formed in the combustion chamber.The sensor(s) comprises a first temperature sensor associated with the intake air manifold; a first pressure sensor associated with the intake air manifold; a second temperature sensor associated with the fuel supply pipe; and a second pressure sensor associated with the fuel supply pipe.The electronic controller is programmable to process data collected from the two temperature sensors and two pressure sensors to calculate lambda of a charge formed in the combustion chamber.Preferred Parameters: The engine speed range is 2500-2800 rpm.The engine load range corresponds to when inlet manifold pressure is less than 85 kPa absolute and temperature of exhaust gas exiting the combustion chamber is greater than or equal to 600, preferably 650-800degreesC.Preferred Methods: The rich fuel mixture is produced by reducing air mass flow rate to the engine.The air mass flow rate is reduced by throttling air flow through an intake air passage; by opening a waste gate valve when the methane-fuelled engine is equipped with a turbocharger; by controlling the geometry of a variable geometry turbocharger; or by controlling the nozzle of a variable nozzle turbocharger.The method includes fuelling the methane-fueled engine with a fuel mixture comprising methane and hydrogen, activating a spark plug to promote ignition of the lean and rich fuel mixtures, advancing timing for activating the spark plug to an earlier time when fuelling the engine with the lean fuel mixture, fuelling the engine with natural gas, oxidizing methane in exhaust gas in the presence of palladium provided by the methane oxidation catalyst, controlling the engine to deliver the exhaust gas to the methane oxidation catalyst at greater than 600, preferably 650 to less than 800degreesC when operating the engine with the rich fuel mixture, controlling the lean fuel mixture to have an average lambda of 1.3-2.0, impregnating the palladium into a wash coat comprising alumina, depositing the wash coat on a ceramic support comprising silicon carbide or magnesium aluminum silicate, commanding the engine to operate at a point that is one of second set of points on engine map for time as a step in the start up sequence for the engine, and depositing the wash coat on a metallic support.Preferred Properties: The lean fuel mixture has an average lambda of greater than or equal to 1.3, preferably 1.3-1.7.The rich fuel mixture has an average lambda less than or equal to 1.0, preferably 0.90-1.0.