IMO 4th GHG study: shipping’s emissions are still climbing

The International Maritime Organization’s (IMO) much-anticipated Fourth Greenhouse Gas Study, made public today, shows shipping’s emissions grew between the base year of 2008 and 2018 – with a sharp and notable 150% rise in methane emissions over the period under review.

The new Study, which was coordinated by CE Delft and authored by a wide range of industry and academic experts, builds on the findings on of the Third GHG study which was published in 2014.

Using a new voyage-based allocation of international shipping, the Study shows that CO2 emissions have increased from 701 million tonnes in 2012 to 740 million tonnes in 2018 – a 5.6% increase – but at a lower growth rate than total shipping emissions.

Using the vessel-based allocation of international shipping taken from the Third IMO GHG Study, CO2 emissions increased over the period from 848 million tonnes in 2012 to 919 million tonnes in 2018.

Due to ‘developments in data and inventory methods’, this Study is the first IMO GHG Study able to produce greenhouse gas inventories that can distinguish domestic shipping from international emissions on a voyage basis. Applying this method to 2008 emissions, the Study estimates that 2008 international shipping GHG emissions (in CO2e) were 794 million tonnes (using the method used in the Third IMO GHG Study, the emissions were 940 million tonnes CO2e).

Access to more accurate data in looking at the split between domestic and international emissions also shows that the estimated share of shipping emissions that can be attributed to domestic, national inventories has increased from 15% to 30%.

The 150% increase in methane emissions over the period is significantly greater than the uptake of LNG as a bunker fuel, which rose by only 28%. This could be explained by the optimisation of LNG engines for lower NOx emissions which may translate into higher methane emissions.

At present, the IMO does not regulate methane emissions, but a number of industry organisations have already made submissions to include methane in subsequent Energy Efficiency Design Index (EEDI) revisions.

The new Study found that carbon intensity has improved between 2012 and 2018 for international shipping as a whole, and for most ship types. The overall carbon intensity, as an average across international shipping, was 21 and 29% better than in 2008, measured in AER and EEOI, respectively, in the voyage-based allocation. In the vessel-based allocation, it was 22 and 32% better.

However, the pace of carbon intensity reduction has slowed since 2015, with average annual percentage changes ranging from 1% to 2%.

The study notes that ship emissions are projected to increase from about 90% of 2008 emissions in 2018 to 90-130% of 2008 emissions by 2050 ‘for a range of plausible long-term economic and energy scenarios’. The COVID-19 pandemic is also expected to result in a small but demonstrable reduction in emissions over the next few years.

During the period under the review, the Study has also charted a significant change in the bunker fuel mix. The proportion of heavy fuel oil consumption reduced by approximately 7% while the share of marine diesel oil (MDO) and LNG consumption grew by 6 and 0.9%. Methanolʹs use as a fuel developed during this period and is estimated to be ‘the fourth most significant fuel used’, growing to approximately 130,000 tonnes of consumption in 2018 on voyage-based international routes, or 160,000 tonnes of total consumption.

Average ship sizes across the containership, cruise ship and oil tanker segments have increased, as has the average installed engine power. For each of these three ship types, the average shipʹs fuel consumption has increased over the period, but at a lower rate than the increase in average installed power.

This ‘decoupling’ in the rate of increase in installed power and fuel consumption is attributed to the general and continued trend for slow steaming.

The Studyʹs results suggest that there has been a further reduction of productivity of the fleet over this period, and the Study’s authors noted that: ‘This in turn means that in 2018, relative to 2012, there is an increased risk of a rapid increase in emissions should the latent emissions in the fleet be realised.’

SOx and PM emissions increased over the period in spite of an overall reduction in HFO use and an increase in MDO and LNG use (largely due to the introduction of emission control areas with their restrictions on sulphur content). The explanation for this is that the average sulphur content increase in HFO over the period exceeded the sulphur content reduction associated with the change in fuel use.

Commenting on the Study’s findings in relation to methane emissions, Dr Bryan Comer, who led the review and the revision of the Study’s methodology, said:

‘Methane is not yet regulated by the IMO but it should be because it has a much stronger global warming potential than carbon dioxide.

‘If IMO wants to meet its climate goals, it must take swift action to prevent excess methane emissions from LNG-fueled ships. We expect IMO to include all greenhouse gases, including methane, in the next phase of the EEDI.’

Also responding to the Study, NGO Transport & Environment said the EU must now activate its plans to include maritime emissions in its carbon market and introduce CO2 standards for ships while in operation.

Faïg Abbasov, T&E’s shipping programme manager, said: ‘Shipping’s carbon pollution has grown at an alarming rate and could rise by half by 2050 if real action is not taken. Now is the time for the EU to push ahead with its plan for emissions trading for shipping and also quickly adopt the CO2 standards the European Parliament has called for.

‘Standards will drive the uptake of the hydrogen and ammonia that European shipping needs to decarbonise.’

Lesley Bankes-Hughes

Lesley Bankes-Hughes