Abstract: Systems and methods are provided for performing selective catalytic reduction on engine exhaust using ethanol from the engine fuel as the reducing agent. Fuel from a fuel tank or other fuel source can be passed through a separation module to produce a fuel stream with a reduced ethanol content and an ethanol-enriched fraction. After combustion of fuel under lean conditions, the combustion exhaust can be exposed to a catalyst system in the presence of the ethanol-enriched fraction.