The International Maritime Organisation (IMO) is seriously considering placing speed limits on cargo ships in the name of reducing emissions and cost saving.
A study commissioned by maritime environment non-profit Seas At Risk is being presented by the United Nations in London this week which says the shipping industry could use 27% less engine power by slowing just 10%, reducing a voyage’s energy consumption by 19%.
The world’s shipping giants are under rising pressure to slash emissions by adopting ultra low-sulphur fuels, and the SAR study suggests further cost savings can be made not only in bunker-fuel (the low-quality remnants of convention fuel refinery products), but also baseline emissions could be slashed by some 24% simply by slowing down by 20%.
The report says as a rule of thumb, there is a “cubic relationship” between ship speed and main engine fuel consumption, meaning for every measured unit of speed increase there is a proportional consumption of fuel and increased voyage time.
Black carbon emissions are also a focus of the report, which in arctic regions such as the poles, means a reduction in absorbed sunlight (which is typically reflected by snow) and slower rate of polar melting.
There are also the inherent reductions in harmful NOx emissions, hydrofluorocarbons, nitrous oxide, methane, sulphur oxide (SOx) and carbon dioxide, which will benefit human health, plus a slower nautical seed will reduce underwater noise which is well reported to affect sea life.
The IMO 2020 rules for the shipping industry come into affect from January 1, 2020, whereby the limit for sulphur in fuel oil used on board ships operating outside designated emission control areas will be reduced to 0.50% m/m (mass by mass). In designated emission control areas (ECAs) the limit will remain at 0.10%.
The current limit is 3.50% meaning the change will be significant and means most ships will switch to new type of compliant fuel oil, called “very low sulphur fuel oil” (VLSFO), or marine gas/diesel oil.
Typical container ships can consume around 300 tonnes of fuel per day and emit 1000 tonnes of carbon dioxide in that time, more than some of the lowest-emitting countries.
In 2018, Danish shipping conglomerate Maersk reported it was looking at another US$2 billion added to its already enormous US$3.37 billion annual fuel bill from 2020 as a result of the new fuel rules.
Currently, the shipping industry is working toward a 50% greenhouse gas emissions reduction target compared with 2008 by 2050 under the MARPOL amendments of 2016 which also require ships of gross 5000-tonnes or more to collect and submit fuel oil consumption data, including proxies for “transport work”, to their flag State from 1 January 2019 for aggregation and submission to IMO.
However, Maersk says it isn’t in favour of reducing voyage times.
“Maersk remains opposed to speed limits,” regulatory affairs director Simon Christopher Bergulf says.
“We rather support the principle of applying power limitation measures. Focusing on power instead of speed limits will help deliver on the CO2 reduction targets set by the IMO, whilst rewarding the most efficient ships,” he explains.
Cargo ships trialled speed limits during the Global Financial Crisis of 2008, which saw a 12% rate of knots reduction saving daily fuel consumption by 27%.
The the time Maersk spokesperson Bo Cerup-Simonsen told The Guardian “Slow steaming is here to stay – its introduction has been the most important factor in reducing our CO2 emissions in recent years, and we have not yet realised the full potential”.
