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Global ship emissions keep on rising

By: Christer Ågren

Greenhouse gas (GHG) emissions – including carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O), expressed as CO₂-equivalents – from all shipping activities around the world increased by nearly ten per cent between 2012 and 2018, according to a recent study for the International Maritime Organization (IMO).

As a result, shipping emissions’ share of global anthropogenic emissions of the main GHG carbon dioxide, increased from 2.76 per cent in 2012 to 2.89 per cent in 2018.

Estimates of ships’ fuel consumption and emissions vary depending on the methodology applied, and the study used both bottom-up (fleet activity data) and top-down (bunker sales data) methods for its estimates. By using data from the Automatic Identification System (AIS), the study has produced new emission inventories that distinguish domestic shipping from international emissions on a voyage basis.

This distinction is of some importance, since only voyages between ports in different countries are counted as international shipping. However, even though IMO formally has responsibility only for international shipping emissions, its regulations can be applied to both international and domestic emissions.

According to the study, annual fuel consumption for all shipping activities was approximately 330 million tonnes in 2018, resulting in CO₂ emissions of 1056 million tonnes.

When using the new voyage-based method and focussing only on international shipping (i.e. excluding domestic shipping and fishing vessels), the CO₂ emissions were estimated to amount to 740 million tonnes in 2018.

A breakdown of the overall GHG emissions in 2018 by species type for voyage-based international shipping emissions, shows that the contribution from each of the GHG emission species (CO₂, CH₄, N₂O) to overall CO₂-equivalent emissions is 98, 0.5 and 1.5 per cent respectively.

If emissions of Black Carbon (BC) are also included in the calculation of CO₂-equivalents (using a 100-year Global Warming Potential of 900), then the shares for CO₂, CH₄, N₂O and BC become 91.3, 0.5, 1.4 and 6.8 per cent respectively. In both accounting methods, CO₂ emissions continue, as observed in the Third IMO GHG Study 2014, to dominate international shipping’s GHG emissions.

Annual emissions from international shipping of the air pollutants nitrogen oxides (NOx), sulphur dioxide (SO₂) and fine particulate matter (PM2.5) increased slightly during the seven-year time period 2012–2018, despite the introduction of stricter emission requirements. In 2018, these emissions were estimated to amount to 17.1, 9.6 and 1.4 tonnes, respectively. (See Table 1.)

Table 1: Annual emissions from international shipping 2012 and 2018 (thousand tonnes).

  2012 2012 2018 2018
  Vessel-based Voyage-based Vessel-based Voyage-based
CO₂ 848,000 701,000 919,000 740,000
CH₄ 59 55 148 140
N₂O 47 39 51 41
SO₂ 10,800 9,100 11,400 9,600
NOx 19,700 16,900 20,200 17,100
PM2.5 1,527 1,304 1,589 1,351
BC 73 59 79 62
NMVOC 790 674 861 725
CO 742 628 829 692

Note: The “vessel-based” method for emission inventory is consistent with the one used in the Third IMO GHG Study from 2014, and is based upon vessel type and size, not on a route basis. This new study applied an important new approach, called ”voyage-based”, which uses the identification of port stops to estimate discrete voyages.

Heavy fuel oil (HFO) dominates the fuel consumed by international shipping, with a share of approximately 79 per cent in 2018, down from 86 per cent in 2012. This decrease coincides with an increase in consumption of lower-sulphur marine distillate oil (MDO) after the entry into force in January 2015 of the 0.1% sulphur limit in the Sulphur Emission Control Areas in northern Europe and North America.

According to the IMO’s global sulphur monitoring reports, the worldwide average fuel sulphur content in 2018 was 2.59 per cent for heavy fuel oil and 0.07 per cent for marine distillates.

Three types of ship – container ships, bulk carriers and oil tankers – dominate ship fuel consumption and consequently emissions. In combination with chemical tankers, general cargo ships and liquefied gas tankers, these ship types constitute 86.5 per cent of international shipping’s total emissions.

It is expected that global demand for shipping will keep growing over the next few decades, resulting in a rise in fuel use and emissions. According to the study, CO₂ emissions from shipping are projected to increase by up to 50 per cent above 2018 levels by 2050 if no additional actions are taken.

The authors note that “emissions could be higher (lower) than projected when economic growth rates are higher (lower) than assumed in the study or when the reduction in GHG emissions from land-based sectors is less (more) than would be required to limit the global temperature increase to well below 2 degrees centigrade.”

The International Council on Clean Transport (ICCT), which was involved in preparing the study, concludes that much work lies ahead if the sector is to meet IMO’s goal of cutting GHG emissions from international shipping by at least 50 per cent from 2008 levels by 2050. They referred among other things to the fact that over the study period demand for shipping grew twice as quickly as fuel efficiency improved.

“It’s notable that improvements in fuel efficiency have slowed since 2015, with annual improvements of only 1 to 2 per cent,” said Dr. Dan Rutherford, ICCT’s marine programme director. “Policies are needed to accelerate innovative fuel efficiency technologies like wind-assist and hull air lubrication, along with new, low-emission and zero-emission fuels.”

Green group Transport & Environment (T&E) 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. T&E also pointed to one of the findings of the study, namely that shipping’s methane emissions had increased by 150 per cent in the last six years because of the increased deployment of liquified natural gas (LNG) as a ship fuel.

“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,” said Faig Abbasov, T&E’s shipping programme manager.

The report will be presented first to the IMO’s Intersessional Working Group on reduction of GHG emissions from ships in mid-October, and then to the IMO’s Marine Environment Protection Committee (MEPC 75) to be held in London in mid-November, where it is intended to feed into the ongoing discussions about how to best address GHG emissions from the shipping sector.

Christer Ågren

The report: Fourth IMO GHG Study 2020. International Maritime Organization (IMO) MEPC 57/7/15, 29 July 2020. IMO website: www.imo.org

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