The article presents analysis of the influence of selected methods alongside with devices applied to process oil waste from engine power room plants on the changes in oil waste morphology in order to improve burning conditions in auxiliary boilers. Study results facilitated the choice of the most favourable method, in view of environmental protection, of preparing oil waste to burn so that the waste is transformed into fuel for auxiliary boilers on the ship. Burning oil waste entails changes in its morphology, therefore, measurements of toxic emissions of CO and NOx have been conducted for each of the different processing methods.