Method for reducing emissions from a hydrogen combustion engine

A method for reducing emissions from a hydrogen combustion engine includes: a first step in which a controller obtains an HO concentration at a front end of an SCR catalyst, an SCR temperature, and a NO/NOx ratio derived from a DOC; a second step in which the controller calculates a predicted NOx purification rate based on the HO concentration, the SCR temperature, and the NO/NOx ratio; and a third step in which the controller calculates a urea dosing amount that aligns with the predicted NOx purification rate and performs control to dose the calculated dosing amount of urea.