There’s no one-size-fits-all path to shipping decarbonisation, a comprehensive review by the World Maritime University has found.
Carried out by academics on behalf of the International Maritime Organization, the snappily-titled report, “Comprehensive impact assessment of the basket of candidate GHG reduction mid-term measures,” noted after a comprehensive literature review that a “wide range of technologies,” could help reducing the GG emissions from ships.
Wind and solar energy could reduce the fuel energy needs, and various energy sources and storage, such as biofuels, hydrogen, methanol, ammonia, synthetic fuel oils, battery electric and even nuclear power “could cover the remaining energy needs,” the Impact Assessment reads.
However, it was noted that none of the studies identified in the literature review, explicitly addressed the quantification of wind or solar energy capture onboard ships as an energy input and their impact on the estimation of the final energy demand of shipping and fuel mixtures. “This is a definite shortcoming of the literature studies reported herein,” the World Maritime University noted. It certainly is, given that there are a wide range of wind-related propulsion devices being tested, and these include (but are not limited to) kites, a multitude of different kinds of sails, and Flettner Rotors.
By 2030, it was predicted, all of the consulted studies predicted that the majority of shipping fuel energy in the year 2030 will be from fossil fuel sources; the percentage of zero or near-zero fuels for that year will be between 10% to 20% of the total fuel energy used, of which biofuels would have the largest market share. By 2040, the consensus forecast begins to greatly split, with an even greater divergence of views as to the energy mix by 2050.
The only scenario to reach net-zero emissions, and even yield negative emissions, was a report from the International Energy Agency in 2023. On that scenario, negative emissions obtained from the use of bioenergy with carbon capture and storage “are likely to prove essential,” for reaching net zero. That’s because, regardless of the alternative fuels or technologies used, the creation and operation of a ship will inevitably involve some greenhouse gas emissions, for example from the production of vessels or the leakage of fuels. “These low-level greenhouse gas emissions will need to be offset somehow, for example, from suitable fuel production methods,” the Impact Assessment reads.
Energy trends
The academics noted that, although the energy demand by international shipping increased from the year 2000 onwards, there has been a stabilisation of energy demand since the year 2008.
“As of today, no clear downward trend in final energy demand is visible, but it can be observed that the world seaborne trade has been steadily increasing… despite a small temporary reduction following the global financial crisis of 2008… [t]he data indicates a clear and consistent downward trend in the energy intensity of international shipping which explains why the total final energy demand of international shipping has remained relatively stable… despite a continuous increase in seaborne trade… [t]his may suggest successful technical and operational implementation of energy efficiency measures in the global fleet,” the impact assessment reads.
Future energy demand
A consensus in the literature was found that the demand for shipping services will grow significantly over the next 25 years or so, with estimates of an increase of between 66% and 125%. Unfortunately, there was a wide range of predictions as to the final energy demand in shipping until 2050. Studies assuming net-zero emissions by about 2050 expect shipping to have a final energy demand ranging from betrween 3.42 exajoules to 11.9 exajoules.
A joule is a measurement of energy and it is defined as the amount of work done by a force of one newton displacing a mass in a direction by one metre. Or, to put it another way, the amount of effort needed to chuck a small apple one metre. One exajoule is an amount of energy that is… considerably bigger. An exajoule is 10 to the power 28 joules. That’s a “1” with 28 zeros after it i.e. this: 10,000,000,000,000,000,000,000,000,000.
That’s a lot of apples.
The website World Population Review puts that into a handy context. In 2023, according to that website, the country of Morocco, which has a population of about 37.5 million, had a total energy consumption of 0.98 exajoules.
Countries in 2023 with roughly 3.42 exajoules include Pakistan (3.37 EJ in 2023) or the Netherlands (3.44 EJ); countries with 11.9 EJ of consumption include Germany (11.41 EJ) or Saudi Arabia (11.6 EJ).
Methodology
The University carried out a systematic literature review by searching for maetrial in databases, on the internet, and a review of literature references; the literature review did not take into account any new literature after 05 January 2024.
