**Kazimierz Witkowski**

Mechanical Faculty, Faculty of Marine Engineering, Gdynia Maritime University, Morska Street 83, 81-225 Gdynia, Poland; k.witkowski@wm.umg.edu.pl

Received: 19 May 2020; Accepted: 17 June 2020; Published: 20 June 2020

**Abstract:** The article's applications are very important, as it is only a dozen or so years since the current issues of protection of the atmosphere against emissions of toxic compounds from ships. The issue was discussed against the background of binding legal norms, including rules introduced by the IMO (International Maritime Organization) in the context of the MARPOL Convention (International Convention for the Prevention of Pollution from Ships), Annex VI, with the main goal to significantly strengthen the emission limits in light of technological improvements. Taking these standards into account, effective methods should be implemented to reduce toxic compounds' emissions to the atmosphere, including nitrogen oxides NOx and carbon dioxide CO2. The purpose of the article was, based on the results of our own research, to indicate the impact of the effectiveness of selected methods on reducing the level of nitrogen oxides and carbon dioxide emitted by the marine engine. The laboratory tests were carried out with the use of the one-cylinder two stroke, crosshead supercharged diesel engine. Methods of reducing their emissions in the study were adopted, including supplying the engine with fuel mixtures of marine diesel oil (MDO) and rapeseed oil ester (RME)-(MDO/RME mixtures) and changing the fuel injection parameters and the advance angles of fuel injection. The supply of the engine during the tests and the mixtures of marine diesel oil (MDO) and rape oil esters (RMEs) caused a clear drop in emissions of nitrogen oxides and carbon dioxide, particularly for a higher engine load, as has been shown. The decrease of the injection advance angle unambiguously makes the NOx content in exhaust gas lower.

**Keywords:** ships diesel engines; exhaust gas emission; fuel mixtures; rapeseed oil methyl ester; marine diesel oil; fuel injection parameters
