Reducing carbon emissions from transportation has become one of the primary fronts in the battle against greenhouse gas emissions. The effort involves much more than just transitioning to electric vehicles.
Transportation is a vast sector of commerce that includes many industries, such as air travel, railroads, and vehicle fleets. All of them are undergoing changes to incorporate cleaner fuels and reduce carbon emissions.
The decarbonization effort has even reached the high seas, with many factors driving changes in cargo shipping. Adoption of new fuels is accelerating to reduce emissions and steer the industry onto a “greener” course.
Currents of Change
According to the Center for Climate and Energy Solutions, the transportation sector is one of the world's biggest contributors of greenhouse emissions, at 15% of the total. That is second only to electricity and heat, which account for 31%.
Within the transportation sector, international shipping accounts for 2% to 3% of global energy-related CO2 emissions, and it is facing pressure on numerous fronts to reduce its output of greenhouse gases.
In addition to popular pressure and regulations from individual countries, the International Maritime Organization (IMO), the UN agency that is responsible for the shipping industry, has adopted new strategies and standards that are regulating the industry.
Using 2008 emissions as a baseline, the [International Maritime Organization’s] new regulations call for a reduction of at least 20%, but striving for 30%, by the year 2030.
Using 2008 emissions as a baseline, the new regulations call for a reduction of at least 20%, but striving for 30%, by the year 2030. Similarly, the regulations call for a reduction of at least 70%, but striving for 80%, by the year 2040.
Green Fuels and the Shipping Industry
Each industry within the travel sector, including cars, trains, and airplanes, must navigate a different path to become green. Each of these paths is defined by the unique characteristics and limitations of the industries themselves.
In the shipping industry, several factors including the size of the vessels, the power needed to propel them, and the paths they travel, make a transition to electric-powered ships impractical.
According to a white paper from the market research firm, DNV, the primary challenge facing the maritime industry is its inability to easily electrify propulsion. In deep-sea shipping, “batteries alone are not an adequate substitute for combustible energy sources.” In other words, there aren’t going to be fleets of electrified shipping vessels any time soon. To cut carbon emissions, a more practical option for the industry will be transitioning to alternative fuels.
DNV projects the shipping industry to meet the IMO’s target through a combination of measures. It will require a shift to low- and zero-carbon fuels. These include liquified natural gas (LNG), liquified petroleum gas (LPG), methanol, hydrogen, ammonia, and biofuel.
LNG, liquified natural gas, consisting mainly of methane and some ethane, is considered a less polluting alternative to fossil fuels, and is gaining acceptance.
At the top of the list, LNG, consisting mainly of methane and some ethane, is considered a less polluting alternative to fossil fuels, and is gaining acceptance. Trailing behind but gaining traction, methane and ammonia are even less polluting alternatives, but they face their own challenges related to availability and safety.
New Builds Going Green
Transitioning to cleaner burning fuels will require a major change in the industry because most ships are not equipped to run on alternative fuels.
The World Resources Institute (WRI) notes that most commercial shipping vessels currently run on heavy fuel oil. It is well-suited to the industry because the fuel is inexpensive and its high energy density sustains ships for long distances across the ocean, but it raises concern of sulfur oxide and nitrogen oxide emissions.
50% of new ships ordered in 2023 included alternative fuel capacity, compared with only 7% of ships currently operating in the industry.
To decarbonize, the industry appears to be embracing the challenge of transitioning away from this polluting fuel. The number of orders for new ships to be built with alternative fuel burning technology is rising. DNV notes in its white paper that 50% of new ships ordered in 2023 included alternative fuel capacity, compared with only 7% of ships currently operating in the industry.
The types of vessels that are being built reveal which fuels are emerging as the most promising to help the industry’s transition to zero emissions.
For example, in January of this year, the global shipping giant, Maersk, announced it had built “the world's first large methanol-enabled container vessel.” The “Ane Maersk,” named after Ane Mærsk Mc-Kinney Uggla, a prominent member of the Maersk family, is the first in a series of 18 large methanol-enabled vessels that the company will deliver between 2024 and 2025.
Methanol is not the only option. Last year, Finnish maritime technology developer Wartsila announced commercial production of its Wartsila 25 Ammonia, that the company describes as the world's “first 4-stroke ammonia powered engine.”
While methanol and ammonia are still in the early stages of adoption, LNG remains the leading alternative to fossil fuels in the shipping industry. According to the maritime services company, Lloyd’s Register, new orders in 2023 are projected to increase the fleet of LNG-fueled ships by 90% to 1,938 vessels.
The Undertow of Alternative Fuels
If shipping companies appear to be embracing a future with alternative fuels, it remains to be seen which of these fuels will emerge as the best choice.
Each has its own benefits and limitations.
At this stage, LNG appears to have the strongest competitive advantage. According to DNV, about 90% of ships in the current global fleet powered by alternative fuels are powered by LNG. Its share of new ships on order is slightly less, meaning that other fuels are gaining ground, but it still represents an overwhelmingly dominant share of the total, at about 78%.
The disadvantages for LNG are methane leakages during production, transportation, and storage, because the gas has an even greater warming effect than carbon dioxide (CO2).
The disadvantages for LNG are methane leakages during production, transportation, and storage, because the gas has an even greater warming effect than carbon dioxide (CO2). The WRI notes that when accounting for leakages from LNG burning engines, this can cancel out, and in some cases even exceed, the carbon reductions achieved by LNG that make it an attractive alternative in the first place.
Methanol faces a different set of challenges. According to Lloyd's Register, the biggest challenge facing the widespread adoption of this fuel in the shipping industry is the lack of sufficient storage space. Because it has a lower energy density than other fuels, it requires more fuel to generate the same amount of power. This necessitates larger space to store enough fuel to supply shipping vessels on their long journeys. Additionally, some methods of generating methanol, such as those using natural gas, are not considered green because they also can leak methane, a harmful heat-trapping gas.
Other green methods do exist. For example, methanol can be generated through a process that combines electricity from renewable power, electrolysis of water to create hydrogen, and a catalytic reaction with captured carbon dioxide. However, these greener methods are expensive and have not been developed to a scale that can fully power the shipping industry.
Ammonia may emerge as the leading fuel source for the shipping industry. It produces no carbon emissions from combustion.
Finally, ammonia may emerge as the leading fuel source for the shipping industry. It produces no carbon emissions from combustion. When renewable energy is used to create the necessary elements for ammonia, hydrogen and nitrogen, the entire cycle is completely green, or carbon-free.
As is the case with all other fuels, there is a drawback. Ammonia's main disadvantage is its high toxicity. The chemical is dangerous to humans and to marine life, and spills, leaks, and exposure can be hazardous. For it to become a practical alternative fuel for shipping, the industry will need to develop the proper technology and protocols to address these safety concerns. NOx emissions from combustion are also a concern.
Sailing into Headwinds
Another challenge facing the use of clean fuel alternatives is the adaptability of the world's existing fleet of ships. According to DNV, “only a small part of the existing fleet is currently able to run on alternative fuels.”
Most ships are not equipped to burn alternative fuels, so they will have to be retrofitted or replaced by newly built ships with the proper technology. This will require major investments.
The good news, DNV reports, is that “a rapidly increasing proportion of new ships are being ordered with alternative fuels.”
As noted above, most of these are for LNG, but DNV says many shipowners are “keeping their options open” by ordering vessels ready to be retrofitted to alternative fuels, such as "methanol ready" or "ammonia ready."
Many considerations go into the design of new ships or the retrofit of existing ships to burn on alternative fuels. These considerations span the entire supply chain, beginning with the sourcing and production of the fuel; its transport; ground-based fuel storage in bunkers; storage in tanks on board the vessels; the type of engine that can run on a particular fuel; plus, emissions, leaks, spills, and other safety factors.
The shipping industry does have even more options. For example, carbon capture and storage (CCS) is an evolving technology that captures the CO2 emissions from the combustion of fossil fuels and stores it for other uses. CCS is being developed for various land-based applications and can be used on board maritime vessels. CCS will enable shipping to continue using fossil fuels while reducing its carbon emissions. It is being applied as a temporary “transitional technology” to help shipping reduce its carbon footprint while the industry makes the transition to long-term solutions involving alternative fuels.
However, like alternative fuels, CCS is a developing technology that involves a significant expense, it also competes for usable space on maritime vessels; an area dedicated to a CCS installation is an area that can’t be used for the cargo that generates revenue for the ship's operator.
The Slow Turning Gears of Decarbonization
International shipping is doing its part to reduce carbon emissions. The process is long, slow, and expensive. Ship owners are responding to expectations that they decarbonize by retrofitting existing ships and ordering new builds that can run on alternative fuels.
Many promising alternatives could help power the industry into a zero-carbon future. However, none of these is ready to transform the industry by itself or in the near term. For now, change will come incrementally and through a mixed bag of solutions working together to help shipping transition away from carbon-emitting fossil fuels.
*Rick Laezman is a freelance writer in Los Angeles, California, US. He has a passion for energy efficiency and innovation. He has covered renewable power and other related subjects for over ten years.