## 3 Results
### Testing the Composition of the Exhaust Gas
The additives of effective microorganisms in liquid form and ceramic tubes had the best effect of reducing \(\mathrm{NO_{x}}\) concentrations, with a decrease of approximately 6% after application. Figure 9 shows the dependence of \(\mathrm{NO_{x}}\) in the flue gas on the concentration of silver additives and effective microorganisms for a 30 kW load. For pure fuel, the \(\mathrm{NO_{x}}\) content was 1222 ppm. With a 2% additive concentration there was also a decrease in \(\mathrm{NO_{x}}\) for all additives. For the silver solution, a \(\mathrm{NO_{x}}\) concentration of 1174 ppm was obtained, for the colloidal nanosilver this was 1200 ppm and for the liquid microorganisms this was 1220 ppm, while for the effective microorganisms in ceramic form a \(\mathrm{NO_{x}}\) amount of 1190 ppm was observed. As with the 20 kW load, the largest decrease was observed for the 4% silver solution. Figure 8: \(\mathrm{NO_{x}}\) content in exhaust gases for three different additive concentrations at a load of 20 kW. Again, the greatest impact on the decrease in NO\({}_{\rm x}\) concentration in the flue gas came from the effective microorganisms in both forms at a 5% concentration. For the effective microorganisms in both forms, the NO\({}_{\rm x}\) content was similar at around 1100 ppm. Thus, the decrease was approximately 11%. The silver solution and colloidal nanosilver showed no positive effect on the NO\({}_{\rm x}\) concentration in the flue gas for this loading, as the NO\({}_{\rm x}\) content was 1189 ppm and 1240 ppm, respectively. In order to explain why there was a reduction in the exhaust gas content of nitrogen oxides, it is necessary to refer to the studies conducted on the subject. On the basis of data from the literature [57, 58, 59], it was indicated that emissions of NO\({}_{\rm x}\) (a mixture of NO, NO\({}_{2}\), N\({}_{2}\)O, N\({}_{2}\)O\({}_{3}\) and N\({}_{2}\)O\({}_{4}\)) increase with increasing combustion temperatures reaching up to 2400\({}^{\circ}\)C in marine engines. Oxides are formed in the combustion chamber due to the oxidation of atmospheric nitrogen. Primarily, nitrogen oxide is formed, and nitrogen dioxide is formed secondarily from the formed oxide. The contribution of fuel-derived nitrogen is negligible. The results of [PERSON]'s [60] study of the increase in NO\({}_{\rm x}\) content in the exhaust gas at temperatures above 1500 K increases tenfold for every 100 K increase in temperature. Taking the above into account, a number of methods have been proposed and implemented to reduce NOx emissions, which results in lower combustion temperatures (e.g., feeding engines with fuel-water emulsion, exhaust gas recirculation, delaying fuel injection). On this basis, it can be argued that the tested additives could have influenced the reduction in the combustion temperature and, as a consequence, the reduction in nitrogen oxides. However, the test stand equipment did not allow the measurement of the combustion temperature. We are also not aware of a direct cause-and-effect relationship between the effect of the additive used and the combustion temperature in the cylinder, nor are there known publications in which this problem was described. Another toxic compound found in exhaust gases is carbon monoxide, which is a product of incomplete combustion or combustion with insufficient air. Figure 10 shows the dependence of CO in the exhaust gas on the concentration of silver additives and effective microorganisms for idling. For pure fuel, the CO content was 434 ppm. With a 2% addition of silver solution, there was a significant decrease in CO to 364 ppm compared to other additives, a reduction of 16%. The addition in ceramic form of effective microorganisms resulted in a decrease in carbon monoxide to 389 ppm. For liquid effective microorganisms and colloidal nanosilver, the CO content was similar at 397 and 398 ppm, respectively.