Decarbonising Transoceanic Cargo Shipping

Why hydrogen is just hot air, electrification won’t work, and biofuels make sense.

Consuming 1.9 billion barrels of oil each year maritime transport is an industry locked into fossil fuels. Emitting over 1 billion tonnes of CO2, transoceanic cargo shipping desperately needs to decarbonise but with assets in service for 20-30 years and at sea for up to 90% of their operational life, it is challenging. The IMO (International Maritime Organisation) however, has big ambitions to drive forward such change. 

Although currently accounting for only 3% of global carbon emissions, the shipping industry is responsible for transporting critical supplies such as food and grains. It is also a growing industry with emissions set to increase to 10% by 2050. International shipping enables 80-90% of global trade and due to supply chain interdependency, any reduction or disruption in this area has a significant impact on all economies. (As witnessed in recent times Ukraine war).  So, if low-carbon fuels are to be successful, they need to be available, reliable and have sufficient supplies in place to support these well-intentioned ambitions. 

Decarbonising Shipping

The targets set by the IMO strive for a 30% reduction in total greenhouse gas (GHG) emissions by 2030 (baseline 2008). At least 70% by 2040 with an uptake of 5%, ideally 10% of the energy used derived from zero-emission technologies/fuels. While member commitment is strong, operators face a massive gap between policy and implementation. Repercussions from reduced sulphur targets are still being felt which resulted in significant diesel price increases and supply chain restrictions.  

So how do operators avoid this encroaching regulatory cliff edge, and meet emission targets without risking stranded assets?

What does the current landscape of choice look like? 

Low Carbon Fuel Options 

Whilst switching to electrification makes sense for passenger and light vehicles, for transoceanic shipping, the numbers just don’t work. Current battery technology would simply be too large and take up valuable goods space. Although recent activity in China demonstrates viable solutions for battery use on boats, these vessels are much smaller and operate in shallow water and through inland shipping routes. 

Capturing energy from the sun or wind would be great but neither method can be guaranteed. Risking operational efficiencies or worse still, stranded assets. Factor in complex ownership business models, where costs are driven to the bone, and any interruption cannot be tolerated. Storage solutions would mitigate some risks but require precious cargo space.  In addition to the volatility in supply, the challenge of using wind power is significant. How do you design sails that are big enough to do the job of moving around 165,000 tons? That doesn’t impede loading and unloading at port or take up valuable space. Especially when you factor in the size and robustness required to provide enough forward thrust.  

There are a couple of companies with interesting designs in this area. Bound4blue are working with Odfjell and Bar Technologies are developing its WindWings system. Time will tell if these solutions are viable in live testing. 

Wind powered ship by Odfjell being tested to see how it impacts shipping efficiencies whilst reducing carbon emissions
Image courtesy of Odfjell

Hydron is Just Hot Air 

A hotly debated subject is hydrogen. Seen by some as the obvious choice due to its theoretical abundance on Earth and lack of carbon in its makeup.  However, extracting the H from H2O (water) or other organic compounds requires significant energy. At present, this means using fossil fuels!  

Electrolysis is the only option at present to produce green hydrogen, but the infrastructure and energy required means costs are still incredibly high. And you need to produce a lot of it because even in its liquid form, the energy density of hydrogen is much lower than bunker fuel. Add in the disruption caused by the necessary fuel cell addition to the vessels (because hydrogen is a feedstock) and costs start to escalate. Changes in supply chain infrastructure, fuel tanks doubling in size, and the energy required to store the liquid at cryogenic temperatures (-252.87°C) it becomes apparent how significant hydrogen investment will be.   

As renewable energy sources increase, forecasts do suggest the cost balance shifting in preference of green hydrogen versus grey sources but only in preferential locations. It will take some time and it’s still not clear if the maths will ever make sense. Michael Barnard has done significant research on the subject which is worth a read. 

What About Methanol and Ammonia? 

Other options include methanol and ammonia, but both have their issues and limitations. Ammonia brings with it significant health risks even in low parts per million. It is highly flammable and needs to be stored at low temperatures (-33 °C). It is also corrosive to equipment and whilst its energy density is better than hydrogen, it is still less than incumbent fuels and carries a high-cost disadvantage.  

Methanol has the advantage that it is sulphur-free and easy to store but like ammonia, requires engine and tank modifications.  Green methanol can reduce CO2 emissions, but supplies are nascent with less than 1% of current methane produced by green methods. Which leaves biofuels. 

At present, hydrocarbons seem to be the only reliable way to carry sufficient energy density for long-haul transportation. Pushing biofuels to the top of the alternate fuel list, especially if engine modifications are not required.  ‘Drop-in’ fuels have the cost and risk advantage not to mention implementation timescale benefits for those who wish to see an immediate reduction in emissions. Switchover can happen rapidly, driving down emissions without affecting efficiencies.    

Big Bets are on Biofuel

The ultimate goal for future biofuel platforms is to use existing waste streams or work in harmony with a sustainable and circular economy. Several pathways are evolving including second-generation biofuels like FAME (Fatty acid methyl ester). These biofuels use waste cooking oil and Maersk is just one of the big names showing interest in the technology.  

Already used as blends in other transportation modes, biofuels are a small but established industry. One which has huge potential in the drive to decarbonise. Fuels derived from crops such as sugar cane, wheatgrass, palm oil or algae, have the additional potential to behave as natural carbon sinks through photosynthesis. Sucking excess CO2 out of the atmosphere and in theory, becoming part of the climate solution.  It is, however, an industry beset with habitat destruction, deforestation and competition. Future growth will require transparency and regulatory control to protect food production, manage land use and avoid incentivising activities such as deforestation as seen with palm oil production.  

Other biofuel solutions include using waste food matter, spent crop material and dung.  What is crucial in these infancy stages is to scrutinise the full life cycle. To understand the impact each pathway has on both the industry and ecosystem. Certainly, for the maritime (and indeed long-haul aviation) industry to meet regulatory demands whilst making the books balance, alternate fuels need to be cost-effective, sufficient in supply and convenient to use. They also need to be genuinely green and not just provide greenwashing. 

A clearing in a rainforest to make way for either agriculture or energy crops
 Deforestation Activities Driven by Palm Oil Production

Decarbonising Transoceanic Cargo Shipping with Algal Biofuel

Although algal-derived bio-oil has fallen from grace in recent years, it has the potential to rise once more. New robust strains, cultivated in enclosed bioreactors have the advantage of utilising barren, unproductive land. Avoiding competition with food crops and thriving on salty wastewater, these sustainable oil farms have the potential to drive climate equity and wealth to the global south. To develop bio economies to support those who are taking the brunt of the climate crisis events.

It is still early days in the shift to low-carbon shipping, but current thinking would suggest that electrifying long-distance transportation may work in some very specific scenarios but it’s unlikely to become the silver bullet.  Wind and solar risks inefficiencies and are cumbersome, whilst hydrogen is too costly.  E-methanol has potential, but the risks associated with ammonia seem too high to have a future which leaves biofuels with the most promising future. 


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