NOx-reduction technique that recirculates a portion of exhaust gas back into the engine intake, lowering combustion peak temperature.
Regulatory detail & full definition
Alternative to SCR for IMO Tier III compliance. Works by displacing oxygen and adding inert (already-burned) gas to the cylinder, lowering peak combustion temperature and thus thermal-NOx formation. Typical recirculation rate 30-40% on slow-speed two-strokes. Uses scrubber + cooler in the EGR line because exhaust is wet/sooty.