An apparatus comprises parallel first and second exhaust gas passageways, a urea injection system, a hydrolysis catalyst, and an SCR catalyst. The urea injection system is configured to inject urea into the first exhaust gas passageway. The hydrolysis catalyst is positioned in the first exhaust gas passageway to generate ammonia at least partially from urea injected into the first exhaust gas passageway by the urea injection system. The SCR catalyst is positioned downstream to reduce NOx with the generated ammonia. An associated method is disclosed.