ENGINE power limitations on ships would likely deliver minimal reductions in carbon emissions unless they are acute, according to new research by the International Council on Clean Transportation.

The new report unveiled by the US-based environmental non-governmental organisations on Tuesday comes just a couple of months before governments and organisations convene to discuss again the potential short-term measures to slash greenhouse gas emissions from ships, during two week-long environmental negotiations in London thart begin in late March.

Engine power limitation is an option that has featured in proposals on these short-term GHG measures that have been under discussion for almost a year. 

But the ICCT’s report suggests EPLs would have to be intense if they were to have a concrete impact in emissions reductions.

“We find that, due to the ongoing prevalence of slow steaming, EPL measures would need to be aggressive in order to contribute to IMO’s climate goals,” the ICCT said.

The means that a 30% engine power limit would yield “negligible cuts” in CO2 for the 2018 fleet, the report warned.

The ICCT said it found that intermediate EPLs of 40% 50% would reduce CO2 emissions between 1% and 4%, depending on ship type and size.

“The most aggressive EPL scenario modelled, 60%, would reduce CO2 fleetwide in 2030 by about 6% if applied only to ships already in service in 2018, and up to triple that amount if also applied to newer ships,” the ICCT said.

ICCT said it assessed the fuel and CO2 savings of 10% to 60% EPL strategies in 2018 and 2030 for container ships, bulk carriers, and oil tankers, which collectively accounted for more than half of the CO2 emissions from international shipping in 2015.

The results vary based on the ship type and size. For example, containerships above 14,500 teu showed a 15.3% reduction in CO2 emissions under a 60% EPL scenario, while those between 12,000 teu and 14,500 teu showed a 7.7% emissions cut. On the other hand, bulk carriers of 200,000 dwt and above with the same EPL rate recorded a 12.1% reduction.

While mandatory speed limits faced opposition at the IMO last year, EPLs have had important backers. BIMCO has previously proposed curbing power to reduce emissions, while EPLs are one of the options shipowners could use to meet a proposal by Japan that would impose energy efficiency requirements on the existing fleet, known as EEXI.

The ICCT believes EPLs are likely the easiest way for older ships to meet Japan's EEXI requirements “because it requires minimal changes to the ship and does not change the underlying performance of the engine”.

Engine power limitation, as well as other potential short-term measures, are primarily geared towards fulfilling the more immediate of the IMO targets; reducing the carbon intensity of the global fleet by at least 40% by 2030 compared with 2008.

The ICCT has previously calculated that when the IMO set that target in 2018, the global fleet had already achieved an estimated 30% reduction compared with 2008 due to “widespread slow steaming by ship operators”.

The IMO will revise its intitial GHG strategy, including the specific emissions targets, in 2023.