Can we reduce the carbon footprint of maritime freight?

In 2018, the ship­ping sec­tor emit­ted just over one bil­lion tonnes of CO₂ into the atmo­sphere. This rep­res­ents 2.89% of glob­al anthro­po­gen­ic CO₂ emis­sions accord­ing to the latest glob­al estim­ate ¹. The main con­trib­ut­or to these cli­mate change emis­sions? Sea freight. It includes the trans­port of vehicles, pas­sen­gers or refri­ger­ated goods, but also sec­tors of activ­ity that weigh more heav­ily in the car­bon foot­print by their num­ber of units and the ton­nages involved. Con­tain­er ships, bulk car­ri­ers, oil tankers, chem­ic­al tankers, cargo ships and gas tankers account for 86.5% of emis­sions from inter­na­tion­al mari­time trans­port. “It should be noted that these fig­ures only rep­res­ent fuel con­sump­tion: they do not take into account all emis­sions, from the man­u­fac­ture of ships to the post-trans­port­a­tion of goods,” emphas­ises Éric Foulquier. 

The total green­house gases (GHG) emit­ted by mari­time trans­port – CO₂, meth­ane (CH₄) and nitrous oxide (N₂O) – amoun­ted to 1,076 mil­lion tonnes in 2018, up by almost 10% com­pared to 2012. The sector’s car­bon foot­print is pre­dom­in­antly due to CO₂, but in recent years some changes have been observed. Because of a decrease in sul­phur con­tent lim­it in fuels, the pro­por­tion of heavy fuel oil con­sumed is fall­ing (-7% between 2012 and 2018), to the bene­fit of mari­time dies­el (+6%) and lique­fied nat­ur­al gas (+0.9%). As a res­ult, CO₂ emis­sions are sta­bil­ising while CH₄ emis­sions are increas­ing (see art­icle 2).

Mari­time freight plays a major role in world trade and eco­nom­ic devel­op­ment. In 2020, the world’s mari­time fleet numbered 99,800 ships, includ­ing almost 54,000 mer­chant ships ² car­ry­ing more than 80% – or even more for the most developed coun­tries – of the goods traded around the world ³. “As of 2015, at least 10 bil­lion tonnes of goods are loaded annu­ally in the world’s ports. It is inter­est­ing to note that since 2013, coun­tries con­sidered to be devel­op­ing have been unload­ing more than they load,” adds Éric Foulquier. “This undoubtedly cor­res­ponds to the emer­gence of a middle class in these coun­tries, in line with the devel­op­ment tra­ject­ory they are on.” 

In terms of its cli­mate foot­print, is mari­time freight an effi­cient mode of trans­port? A con­tain­er ship emits 3 grams of CO₂ equi­val­ent per tonne per kilo­metre, com­pared to 80 for a truck or 437 for a cargo plane ⁴. “Com­par­ing modes of trans­port accord­ing to this indic­at­or min­im­ises the impact of mari­time freight, but it is more real­ist­ic to express it in abso­lute terms,” says Éric Foulquier. “It makes no sense to com­pare these modes of trans­port: the sec­tors are dif­fer­ent, and they often com­ple­ment each oth­er in terms of glob­al eco­nom­ic circulation.”

So how can we decar­bon­ise this vital sec­tor? The car­bon intens­ity of ships – the amount of CO₂ emit­ted per tonne of cargo per kilo­metre – has already been reduced by 20–30% between 2008 and 2019 ⁵. This has been achieved through the replace­ment of older ships, the pur­chase of lar­ger ships, but also through tech­nic­al and oper­a­tion­al meas­ures. Since the fin­an­cial crisis of 2008, a major­ity of shipown­ers have adop­ted slow steam­ing, redu­cing their speed by 20–30% between 2008 and 2015 ⁶. A stable fig­ure since then. While it was not con­sidered at all before 2009, energy con­sump­tion is now the second envir­on­ment­al pri­or­ity of the European Sea Ports Organ­isa­tion ⁷, behind air qual­ity. It is also a fin­an­cial con­cern: if you double the speed of a ship, its fuel con­sump­tion quadruples. 

How­ever, these efforts are being under­mined by the increase in freight flows: GHG emis­sions from mari­time trans­port have increased by 30% since 1990 ⁸. The capa­city of mari­time freight has increased from 1 to 2 bil­lion between 2006 and today ⁹ and is expec­ted to reach 3 bil­lion by 2030 ¹⁰. “Mari­time trans­port is only one response to the needs of our soci­ety, we must act on the flows”, states Éric Foulquier. By 2050, the Inter­na­tion­al Energy Agency estim­ates that CO₂ emis­sions linked to freight should increase by 135% com­pared to 2018 levels ¹¹, while the Inter­na­tion­al Mari­time Organ­isa­tion (IMO) estim­ates this at +250% by 2035. “The mas­sific­a­tion in which we find ourselves must be pro­foundly recon­sidered in favour of the demas­sific­a­tion of the com­mer­cial world, which is neces­sary if we are to imple­ment a trans­ition,” the research­er argues. It implies short­er cir­cuits, the mobil­isa­tion of small ports organ­ised around medi­um-sized urb­an centres.

Driv­en by the glob­al object­ives of car­bon neut­ral­ity, the reg­u­lat­ory con­text is also chan­ging.  By 2050, the IMO is aim­ing for a 50% reduc­tion in the sector’s GHG emis­sions com­pared to 2008. The European Uni­on has a much stronger com­mit­ment to achiev­ing car­bon neut­ral­ity by 2050, after an ini­tial 50% reduc­tion in emis­sions by 2040 com­pared to 1990. In 2020, the European Par­lia­ment voted to include mari­time trans­port in the EU’s emis­sions trad­ing scheme. The meas­ure should be effect­ive by the end of 2022. How­ever, the Inter­na­tion­al Mon­et­ary Fund estim­ates that “a tax of US$75/tonne by 2030 would pro­mote a reduc­tion of only 15% of cur­rent emissions.”

The ship­ping sec­tor can choose to rely on many levers to reduce its CO₂ emis­sions. Oper­a­tion­al meas­ures – speed reduc­tion in the first instance, but also weath­er rout­ing or over­all energy effi­ciency meas­ures – have the poten­tial to reduce GHG emis­sions by up to a third [4]. Finally, a sig­ni­fic­ant poten­tial for decar­bon­isa­tion lies in tech­no­lo­gic­al solu­tions: modi­fic­a­tion of ship design, improve­ment of machinery, but also the integ­ra­tion of renew­able ener­gies (altern­at­ive fuels or propul­sion) into the energy mix.

Interview by Anaïs Marechal