One embodiment is a method including providing an aftertreatment catalyst disposed in an exhaust stream of an internal combustion engine and a reductant that reacts with an amount Of NOx in the exhaust stream in the presence of the aftertreatment catalyst. The method includes interpreting a catalyst degradation value corresponding to the aftertreatment catalyst, and interpreting a nominal reductant value. The method further includes determining an adjusted reductant value in response to the catalyst degradation value and the nominal reductant value, and injecting the reductant into the exhaust stream at a rate based on the adjusted reductant value.
