A power source is provided for use with selective catalytic reduction systems for exhaust-gas purification. The power source has a first cylinder group fluidly connected to a first air-intake passage and a first exhaust passage, wherein the first air-intake passage is configured to provide air at a first set of characteristics. The power source also has a second cylinder group fluidly connected to a second air-intake passage and a second exhaust passage, wherein the second air-intake passage is configured to provide air at a second set of characteristics different from the first set of characteristics. An ammonia-producing catalyst may be disposed within the first exhaust passage and configured to convert at least a portion of a fluid in the first exhaust passage into ammonia. Further, a merged exhaust passage may be configured to connect the first exhaust passage and the second exhaust passage downstream of the ammonia-producing catalyst to facilitate a reaction between ammonia and NOx to at least partially remove NOx from the merged exhaust passage.
U.S. GOVERNMENT RIGHTS
 This invention was made with government support under the terms of Contract No. DE-FC05-00OR22806 awarded by the Department of Energy. The government may have certain rights in this invention.