Abstract: An integrated NOx after-treatment system for an internal combustion engine includes (a) a fuel supply subsystem for supplying an inlet fuel stream to the engine fuel intake, (b) an air supply subsystem for supplying an inlet oxygen-containing air stream to the engine air intake, (c) a fuel processor to which a fuel stream having substantially the same composition of the engine inlet fuel stream is directed, the fuel processor converting the fuel stream directed to the fuel processor to an outlet stream comprising H2 and CO, (d) an adsorbent bed subsystem that cycles between an adsorbent state in which constituents from the engine exhaust stream are adsorbed and a desorption state in which the constituents are desorbed and converted to at least one of SO2 and an environmentally-benign component selected from the group consisting of N2, H2O and CO2, and (e) a recirculation stream for directing at least some of the fuel processor output stream to the engine air intake.