Slower ship speeds make massive difference to emissions

More evidence about the significant contribution slower speeds can make to reducing emissions from shipping has come from a new American study. The study reinforces the thinking behind speed limits for ships proposed by the California Air Resources Board, and confirms findings in a T&E study published earlier this year.

Like with most mechanised means of transport, the faster a ship travels, the more fuel it consumes and the more emissions it produces. Slow steaming is already common practice in the shipping industry. It was widely used by ship operators as a way to cope with overcapacity resulting from the economic downturn and the subsequent drop in international trade over the past five years. Recent data indicate a drop in shipping emissions since 2007, the result – to large extent – of slow steaming.

Since 2009, the California Air Resources Board (CARB) has proposed a series of speed reduction policies as a way of reducing shipping emissions to air. These have been evaluated in a study funded by CARB and the US Environmental Protection Agency, which looks at the impact of limiting cruising speeds to 15 knots or below, compared with current cruise speeds. The study found that reducing ships’ speed to 12 knots would reduce soot emissions by 70%, carbon dioxide by 60% and nitrogen oxides by 55%.

In February, T&E and Seas at Risk published a study commissioned from the Dutch consultancy CE Delft to explore the legal, technical and environmental aspects of regulated slow steaming as a way to tackle the climate impact of shipping. It showed that reducing average speeds by 10% would cut carbon emissions by 19% across the world fleet.

T&E shipping officer Antoine Kedzierski said: ‘This study confirms what we are currently seeing: slower speeds contribute to significant emissions reductions. The international shipping community must build on this experience and make sure ship speeds don’t go up again once the global economy starts to recover. Slow steaming is a no-brainer – it has already been tried and found to succeed, it delivers important emissions reductions and fuel savings for the industry. We hope it will now be considered by regulators as a serious option to improve the efficiency of the shipping industry.’