## 5 Discussion  
For further studies related to fuel consumption and emissions, it is important to study the power of the ship's main engine when the ship moves at a constant speed, depending on the ratio of the ship's draft to the depth of the channel, which is typical for ships sailing  
Figure 12: The fuel consumption of a standard LNG tanker sailing at a speed of 7–8 knots at sea and when entering the port of Klaipeda, obtained by calculation and experiments (sailing distance 5 n. miles). \begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \hline
**T/H** & **0** & **0.1** & **0.2** & **0.3** & **0.4** & **0.5** & **0.6** & **0.7** & **0.8** & **0.9** \\ \hline N, kW & 2220 & 2253 & 2287 & 2375 & 2486 & 2731 & 3108 & 3619 & 4040 & 5106 \\ CO\({}_{2}\) (LNG), kg & 675 & 691 & 716 & 725 & 788 & 872 & 1000 & 1175 & 1399 & 1688 \\ CO\({}_{2}\) (diesel), kg & 922 & 945 & 976 & 1011 & 1075 & 1197 & 1360 & 1600 & 1907 & 2298 \\ SO\({}_{3}\) (diesel), kg & 0.28 & 0.29 & 0.31 & 0.32 & 0.34 & 0.37 & 0.43 & 0.50 & 0.60 & 0.72 \\ CO (LNG), kg & 3.80 & 3.85 & 3.92 & 4.00 & 4.21 & 4.62 & 5.31 & 6.14 & 6.91 & 8.7 \\ CO (diesel), kg & 6.40 & 6.50 & 6.62 & 6.90 & 7.22 & 7.93 & 9.01 & 10.5 & 11.7 & 14.8 \\ NO\({}_{x}\) (LNG), kg & 5.1 & 5.2 & 5.3 & 5.5 & 5.7 & 6.3 & 7.2 & 8.3 & 9.3 & 11.7 \\ NO\({}_{x}\) (diesel), kg & 12.9 & 13.1 & 13.3 & 13.8 & 14.2 & 15.8 & 18.0 & 21.0 & 23.4 & 29.6 \\ PM (diesel), kg & 0.69 & 0.70 & 0.71 & 0.72 & 0.74 & 0.82 & 0.93 & 1.10 & 1.21 & 1.53 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Standard-LNG-tanker-generated emissions during entrance to Klaipeda port, as shown in Figures 9 and 10.  
in ports. Research on the variation of the power of the ship's main engine at shallow depths in the evaluation of the fullness factor of the ship's hull should cover a wider range of ship types and designs. In addition, additional aspects of further research such as ships turning in turning basins and ship towing to and from quays, including the performance of tugs at low clearances, are important for finding methods to reduce environmental impact. These could be further directions of research. The research results presented in the paper are critical because they clearly showed the importance of finding optimal methods for ships to enter and leave ports safely, primarily to ensure the safety of shipping (safety first) and at the same time reduce energy (fuel) demand and emissions. In this way, further complex studies are very important for the safety of shipping in the approaches to ports while constituting as low a possible impact on the environment. The results of the scientific literature review showed that a specific methodology for assessing the trajectory of a ship's movement in shallow depths is important for pre-determining the ship's maneuverability and safe navigation in port entrances and internal port navigation channels. At the same time, in order to reduce non-standard situations as much as possible, especially when ships pass near port infrastructure and ships moored at the quays, further studies of the controllability of ships in difficult conditions, especially regarding the effect of tides on the trajectories of ships, are important. The change in the power of the ship's engines at shallow depths is important; therefore, the developed methodology for estimating the power of a ship's engines when the ship is sailing at a shallow depth is extremely important in ensuring the safety of shipping in ports. At the same time, for ships with relatively low-power engines, such as some bulkers, a preliminary assessment of the capabilities of such ships and further research is very important. Vessels with relatively weak main engines often have to use maximum or near-maximum main engine power when navigating port navigation channels in bad weather conditions where there is very little clearance, which requires high fuel consumption and generates high emissions. Therefore, according to the authors, similar studies are very important and may be another direction for future research.