# Economic Feasibility of Retrofitting an Ageing Ship to Improve the Environmental Footprint
## 3 Gas Emissions  
### Voyage Description  
The Black Sea region is an important economic area with significant potential for using LNG as an alternative fossil fuel for shipping, reducing exhaust gas emissions and complying with the requirements of the IMO and EU regulations for reducing the carbon footprint from transportation. Around 35% of natural gas and oils imported to the EU are produced in onshore or offshore facilities in the Black Sea region. The development of LNG facilities in this region will soon have a significant environmental and economic impact. Short sea shipping routes are ideal candidates for Dual fuel technology since LNG supply is frequently available and there is no need for colossal LNG storage on board. The route selection is based on the cycle's length and selected ports between EU and non-EU countries. The length of the cycle of Varna-Poti-Varna is 1234 nautical miles. The parameters of the route are shown in Table 7.  
For stopping and sailing from the ports of Varna and Poti, 30 min is provided separately, which will always be conducted on diesel or heavy fuel and will not affect the analysis. If it is assumed that the average loading and unloading in the port of Poti and Varna takes 20 h, it is assumed that the ship will have the following cycle of operation: \begin{table}
\begin{tabular}{c c c} \hline
**Load, \%** & **Gas (t/h)** & **Gas (m\({}^{3}\)/h)** \\ \hline
100 & 0.807 & 1.80 \\
85 & 0.700 & 1.55 \\
75 & 0.610 & 1.35 \\
50 & 0.335 & 0.78 \\ \hline \end{tabular}
\end{table} 
Table 6: LNG consumption at different loads. \begin{table}
\begin{tabular}{c c c c} \hline
**Parameter** & **Varna Quay-Pilot Station** & **Sea Passage** & **Pilot Station-Poti Quay** \\ \hline Distance, nm & 10.0 & 600.0 & 7.0 \\ Engine load, \% & 50\% & 75\% & 50\% \\ Speed, kn & 10.0 & 14.3 & 10.0 \\ Time, h & 1.0 & 42.0 & 42 min \\ \hline \end{tabular}
\end{table} 
Table 7: Voyage parameters. \begin{table}
\begin{tabular}{c c c c} \hline
**Load, \%** & **Power, kW** & \multicolumn{2}{c}{**Specific Consumption**} \\  & & **Diesel, g/kWh** & **Gas + Pilot, kJ/kWh** \\ \hline
100 & 5400 & 186 & 7400 \\
85 & 4590 & 185 & 7524 \\
75 & 4050 & 187 & 7457 \\
70 & 3780 & 188 & 7551 \\
65 & 3510 & 189 & 7646 \\
60 & 3240 & 190 & 7740 \\
50 & 2700 & 192 & 7929 \\
25 & 1350 & 213 & 9379 \\
10 & 540 & 265 & \\ \hline \end{tabular}
\end{table} 
Table 5: Performance of the ship. * 21 h (loading, unloading/manoeuvring in Varna--30 min for mooring and unmooring from the port),
* 1.00 h passage in manoeuvring mode--Varna Canal--at 50% load;
* 42 h passage Varna pilot station--Poti pilot station--a speed of 14.3 kn;
* 0.75 h passage in manoeuvring mode--50% load--Poti pilot station--Poti port;
* 21 h (loading, unloading/manoeuvring in Poti port);
* 0.75 h passage in manoeuvring mode--Poti port--Poti pilot station--a speed of 10 kn;
* 42 h passage Poti pilot station--Varna pilot station--a speed of 14.3 kn;
* 1.00 h passage in manoeuvring mode--Varna Canal--at 50% load--a speed of 10 kn;  
In this context, the complete cycle is about 129.5 h and there will be a passage of 85.5 h at sea using LNG as fuel. For one month of 30 days, 5.55 complete cycles will be performed between Varna-Poti-Varna and each cycle is 87.5-84 h at a 75% load and 3.5 h at a 50% LNG load. Therefore, it leads to 485.6 h on LNG or Diesel per month, 466.2 h at a 75% load and 19.42 h at a 50% load. Within one month, the ship will consume 353 tonnes/month of diesel at 75% and 10.1 tonnes/month of diesel at a 50% load. Natural gas consumption is estimated at 284.3 tonnes/month at a 75% load and 8.4 tonnes/month of gas at 50%. If the vessel uses only natural gas, it will consume 292.7 tonnes per month and 3512.4 tonnes per year. For a complete cycle of Varna-Poti-Varna, the ship will need 51.2 tonnes/cycle gas at a 75% load leading to 113.78 m\({}^{3}\) and 1.16 tonne/cycle gas at a 50% load of about 2.6 m\({}^{3}\)  
The required amount of gas per cycle will be 52.36 tonnes or 116.38 m\({}^{3}\) of gas, respectively.