## 3 Results
### Testing the Composition of the Exhaust Gas
An addition of 5% in each case resulted in an increase in nitrogen oxides compared to the 2% addition, although this increase still did not reach the carbon oxides value that occurred for pure diesel. The  
Figure 9: NO\({}_{\rm x}\) content in exhaust gases for three different additive concentrations at a load of 30 kW. highest value was found with the silver solution, which was 425 ppm. Slightly lower values were obtained for effective microorganisms in ceramic form (420 ppm) and colloidal silver (415 ppm). The lowest value was obtained for the liquid effective microorganisms, which was 398 ppm and is very similar to that of the 2% concentration. Analysing the results obtained, it can be concluded that the best result was with the additive at a concentration of 2%. For all samples, the values were lowest in comparison to MDO combustion, and especially for the silver solution. Further increases in concentration appear to be pointless, as this brings the carbon monoxide content closer to the values as without any additives. Figure 11 shows the CO content in the flue gas as a function of the concentration of silver additives and effective microorganisms for a 20 kW load. For pure MDO, the CO content was 935 ppm. Apart from this, the course of the characteristics was similar to that found for idling. With the 2% addition of silver solution, there was also a significant decrease in CO compared to other additives, to 667 ppm, which is almost a 29% reduction. The addition of colloidal nanosilver resulted in a decrease in carbon monoxide to 844 ppm. For liquid and ceramic effective microorganisms, the CO content was higher at 876 and 905 ppm, respectively. An addition of 5% also resulted in an increase in CO in each case compared to the 2% addition. The use of silver at this concentration resulted in higher levels of carbon oxides compared to MDO. After using the silver solution, the amount of CO in the exhaust gases was 957 ppm, and for colloidal nanosilver this was 971 ppm. For effective microorganisms, lower values were obtained than for silver and their content was at the level of 910 ppm for liquid effective microorganisms and 926 ppm for microorganisms in ceramic form. They are high enough that both the addition of silver and effective microorganisms are not worth using at this higher concentration. At a load of 20 kW, the best results were also obtained at a concentration of 2% for all samples. Therefore, increasing the additive concentration further is also not justified. Figure 12 shows the dependence of CO in the flue gas on the concentration of silver additives and effective microorganisms for a 30 kW load. For pure MDO, the CO content here was 1615 ppm. Apart from this, the course of the characteristics was very similar to that found with lower loads. In this case, with the addition of 2% silver solution, there was also a significant decrease in CO compared to other additives, to a value of 1206 ppm, i.e., decreasing by over 25%. Figure 10: CO content in exhaust gases for three different additive concentrations at a load of 0 kW. The addition of colloidal nanosilver resulted in a decrease in carbon monoxide to a level of 1518 ppm. For the effective microorganisms in liquid form and ceramic tubes, the CO content was higher at 1616 and 1658 ppm, respectively. With a concentration of 5% of each additive, the CO values approached those obtained for MDO and were approximately 1600 ppm. It also follows from the above that even at higher loadings further increases in additive concentration are not effective. Carbon monoxide is formed as a result of the incomplete combustion of hydrocarbons contained in the fuel. Its formation is also influenced by the combustion temperature and the heterogeneity of the fuel-air mixture in the engine combustion chamber. The likely reason for the decrease in CO in the exhaust gas is the improvement of the combustion process, as indirectly evidenced by the demonstrated reduction in fuel consumption.