A internal combustion engine system (400, 500), comprising: a spark-ignited internal combustion engine (410, 510) powered by a gaseous fuel; an air intake (432, 532) in air providing communication with the internal combustion engine (410, 510); an exhaust system (420, 520) in exhaust gas receiving communication with the internal combustion engine (410, 510), the exhaust system (420, 520) comprising: a methane oxidation catalyst (470, 570) through which at least a portion of the exhaust gas flows, a first exhaust gas recirculation line (424, 524) in exhaust gas providing communication with the air intake (432, 532), a second exhaust gas recirculation line (426, 526) in exhaust gas providing communication with the first exhaust gas recirculation line (424, 524), and a nitrogen oxide reduction catalyst (464, 564) positioned within the first exhaust gas recirculation line (424, 524) downstream of the second exhaust gas recirculation line (426, 526); and a turbocharger having a turbine (460, 560) co-rotatably coupled with a compressor (440, 540), the turbine (460, 560) being in exhaust gas receiving communication with the internal combustion engine (410, 510) and exhaust gas providing communication with the methane oxidation catalyst (470, 570), and the compressor being in air receiving communication with the air intake (432, 532) and charge air providing communication with the engine (410, 510), wherein the second exhaust gas recirculation line (426, 526) is positioned upstream of the turbine (460,560). a spark-ignited internal combustion engine (410, 510) powered by a gaseous fuel; an air intake (432, 532) in air providing communication with the internal combustion engine (410, 510); an exhaust system (420, 520) in exhaust gas receiving communication with the internal combustion engine (410, 510), the exhaust system (420, 520) comprising: a methane oxidation catalyst (470, 570) through which at least a portion of the exhaust gas flows, a first exhaust gas recirculation line (424, 524) in exhaust gas providing communication with the air intake (432, 532), a second exhaust gas recirculation line (426, 526) in exhaust gas providing communication with the first exhaust gas recirculation line (424, 524), and a nitrogen oxide reduction catalyst (464, 564) positioned within the first exhaust gas recirculation line (424, 524) downstream of the second exhaust gas recirculation line (426, 526); and a turbocharger having a turbine (460, 560) co-rotatably coupled with a compressor (440, 540), the turbine (460, 560) being in exhaust gas receiving communication with the internal combustion engine (410, 510) and exhaust gas providing communication with the methane oxidation catalyst (470, 570), and the compressor being in air receiving communication with the air intake (432, 532) and charge air providing communication with the engine (410, 510), wherein the second exhaust gas recirculation line (426, 526) is positioned upstream of the turbine (460,560). a methane oxidation catalyst (470, 570) through which at least a portion of the exhaust gas flows, a first exhaust gas recirculation line (424, 524) in exhaust gas providing communication with the air intake (432, 532), a second exhaust gas recirculation line (426, 526) in exhaust gas providing communication with the first exhaust gas recirculation line (424, 524), and a nitrogen oxide reduction catalyst (464, 564) positioned within the first exhaust gas recirculation line (424, 524) downstream of the second exhaust gas recirculation line (426, 526); and a turbocharger having a turbine (460, 560) co-rotatably coupled with a compressor (440, 540), the turbine (460, 560) being in exhaust gas receiving communication with the internal combustion engine (410, 510) and exhaust gas providing communication with the methane oxidation catalyst (470, 570), and the compressor being in air receiving communication with the air intake (432, 532) and charge air providing communication with the engine (410, 510), wherein the second exhaust gas recirculation line (426, 526) is positioned upstream of the turbine (460,560).