Regulating the speed of ships will result in an immediate reduction of ships’ emissions by 4%, with further reductions of 20-30% possible over time.
This is according to CE Delft’s most recent study released yesterday, Regulating speed: a short-term measure to reduce maritime GHG emissions.
The report indicates that by regulating the speed of ships, shipping emissions would be put on a declining pathway and therefore contribute to reaching the goals of the Paris Agreement. 
CE Delft looked at three different ship types, a container fleet, a dry bulk fleet, and a crude & product tanker fleet. They estimate that with 10%, 20%, and 30% speed reductions introduced to ships over a period of 2018-2030, the CO2 savings would vary. Figure 1 shows these savings and figure 2 shows the total savings of CO2 estimated between 2018 and 2030 with different speed reductions in place.
The container fleet has the highest reduction potential, with 34mt (10% speed reduction enforced) of CO2 and 85mt (30% speed reduction enforced) of CO2 estimated to be saved per annum.
Figure 1. Relative CO2 emission reduction potential for alternative speed regimes.
Figure 2. Annual absolute CO2 emission reduction potential for the three ship types under three alternative speed regimes.
For the entire period between 2018-2030, a 10% speed reduction would enable 990 Mt savings of CO2 to be achieved, while a 20% speed reduction would result in savings of 1,830Mt of CO2 and a 30% speed reduction would lead to 2,510Mt in savings of CO2 emissions, including all three ship types.
There is some thought that slow steaming could affect longer trade routes as this will take longer at lower speeds.
A bulk carrier transporting oilcake from Buenos Aires to Rotterdam, usually taking 21.8 days on an average speed of 12.2 knots, will increase its time of voyage to 24.2 days with a 10% decrease in speed. A 20% reduction in speed would increase the voyage time further to 27.3 days, and a 30% decrease would raise it to 31.2 days.
Voluntary speed reduction schemes have been used previously to cut emissions. This includes the virtual arrival scheme, which enables a ship to sail at a lower speed and arrive just in time, reducing fuel consumed throughout the voyage. However, according to CE Delft, voluntary schemes only work well when there is a mutual benefit to both, but when it is more profitable for one party not to comply, the voluntary scheme will often not work.
Therefore, in order to effectively reduce emissions, speed regulations have to be mandatory. An enforcement system to deter ships from not complying, according to CE Delft, is what will need to occur.
Figures 1 and 2 taken from CE Delft study, 2017.
Fathom-News
editor@fathom-mi.com
