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5 Alternative Fuels to Effectively Lower Shipping Emissions

Emily Heaslip

Progress toward decarbonization in the shipping industry will take a multi-pronged approach. The UN International Maritime Organization has set an ambitious goal to cut the maritime shipping industry’s greenhouse gas emissions by at least half by 2050; most experts agree that no single solution will help the industry reach that target. It will require a combination of technological measures, fleet-related measures, market-based approaches, and decision support models. 

Among those technological measures is the process of switching to alternative fuels to lower shipping emissions. One study estimates that around 95% of the global fleet is reported to run on diesel, also known as bunker oil. Shipping bunker oil is not only much cheaper than that used in road transport, but it is also much lower quality. “Bunker oil results in high emissions per power output, even when the most modern marine engines are used,” wrote the study authors.

Luckily, researchers have identified alternative fuels that can lower carbon emissions in the shipping industry. Here are a few of the most promising options so far that can help the sector reach decarbonization goals. 


Biofuels are a category of alternative fuels that include bio-oil; renewable diesel made from wood waste or fats such as used cooking oil; as well as mixtures of these biobased feedstocks with petroleum-based feedstocks including petroleum, natural gas and coal. One study from the Department of Energy and the Department of Transportation compared biofuels with conventional heavy fuel oil. Biomass-based fuel could reduce greenhouse gas emissions between 40 and 93%.

“Across the board, the biofuels lowered emissions of greenhouse gases, sulfur oxides and particulate matter — and at costs that could be competitive with heavy fuel oil, after considering incentives such as California’s Low Carbon Fuel Standard. Due to the low sulfur content of the biobased feedstocks, the biofuels analyzed reduced sulfur oxides emissions by 97% or more; particulate matter emissions came down between 84 and 90%,” wrote the Argonne National Laboratory.

However, there are some skeptics in the maritime industry as to whether biofuels are the best alternative fuel option. The main challenge to the adoption of biofuels on a large scale is the difficulty in securing the necessary production volume to meet all major shipping routes

Renewable energy

Wind and solar energy are being considered as options for reducing emissions along some shipping routes. Early analysis shows that solar energy can reduce CO2 by up to 12%, while onboard wind-solar hybrid systems can lead to up to 40% fuel savings

Few shipping routes are able to be fully navigated while using renewable energy. The shift from fossil fuels to wind or solar energy is still a long way off; however, promising developments such as the use of kites can reduce fuel consumption and emissions. Kites that capture the wind have been shown to be both more powerful than a traditional sail and more powerful than a traditional wind turbine, according to CNBC. It’s also a very low-cost solution: a win-win for the shipping industry. 

Electrification and batteries

Full-electric and hybrid solutions are being explored for all different types of shipping vessels. In 2019, more than 320 hybrid ships were reported to be in operation or on order, with more expansion planned due to the cost-effectiveness of battery technology. Short shipping routes are those that are most suited to fully-electric ships; shorter distances can make electric or hybrid propulsion systems more efficient than traditional ones. 

“Conversely, deep-sea shipping looks unlikely to use a significant level of onshore power shortly but can already install batteries for energy optimization,” wrote one study. “The potential of electrification to reduce GHG emissions depends heavily on the source of electricity. According to DNV GL forecast, 30% of all global electricity production will come from wind energy by 2050—12% from offshore wind and 18% from onshore wind. Today’s levels are 0.2% and 4.1%, respectively, of global electricity production.” 

Some shipping routes are investigating the use of hydrogen cells to fuel engines. But, there are still safety, storage, and transport obstacles to be overcome in order to make this a viable alternative fuel source. 

Liquified natural gas (LNG)

Liquified natural gas is one of the most promising alternatives to bunker fuel: LNG reduces CO2 emissions by around 20–30% and contributes to the almost complete removal of SOx and PM emissions and a reduction of NOx emission of up to 85%. LNG becomes virtually sulfur-free during its production process; the removal of sulfur from exhaust results in better air quality.

The use of liquified natural gas as an alternative fuel is already well underway. By the end of 2020, up to 600 commercial merchant ships were expected to be using LNG as a fuel. Even cruise companies are exploring the use of LNG as an alternative fuel source to lower emissions. 

Unfortunately, storage concerns and slippage make LNG an imperfect solution. “Slippage occurs as a result of not all the fuel being burned in the combustion process of the engine or gas lost during transfer,” explained one analyst. “A great deal of benefit of the lower CO2 release of this fuel when used as a fuel can be lost because of slippage.” 

Nevertheless, improvements into LNG technology continue to make this a promising option for lowering shipping emissions. 

Clean ammonia

Maersk and Lloyds Register identified ammonia as one of the most promising alternative fuels for the future in a 2019 study conducted by the industry giant. 

“​​Ammonia is truly carbon-free and can be produced from renewable electricity. The energy conversion rate of this system is higher than that of biomaterial-based systems, but the production pathway cannot tap into potential energy sources as e.g. waste biomass,” wrote Maersk. “The main challenge for ammonia is that it is highly toxic and even small accidents can create major risks to the crew and the environment. The transition from current to future applications is also a huge challenge for ammonia.” 

While ammonia is promising, it also brings safety and storage concerns that will be difficult to overcome. Ammonia is difficult to store and use; it is highly toxic and corrosive, requiring stainless steel and Teflon sealed fuel storage and transfer systems. 

What’s next for marine fuels?


Image source

This image from a survey conducted in May 2021 shows what ship operators believe will be the most important alternative fuels in years to come. LNG and biofuels are among the most compelling options for reaching decarbonization efforts; but the shipping industry is exploring other options as well.

With proactive route optimization tools like Wayfinder, ship operators can work with seafaring captains from shore to ensure efficient fuel use and cost gains on every voyage. Given historical noon reports, speed targets, and the vessel’s intended path, Wayfinder recommends the safest, fastest route, drawing upon the latest weather forecasts from one of the largest distributed marine sensing networks by density.

To learn more about decarbonizing the shipping industry, check out our blog on Sofar Ocean.

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