In the global movement to cut back on greenhouse gas emissions, one sector remains largely overlooked: maritime trade. According to the International Council on Clean Transportation, ocean-going ships carry more than 80% of world trade by volume and are projected to contribute 17% of man-made carbon emissions by 2050. Yet the decarbonization of maritime vessels lags severely behind the electrification of on-road vehicles. 

To address this issue, the International Maritime Organization has set an ambitious target of cutting carbon emissions from ocean shipping by at least 50% by 2050. For any chance of achieving this goal, the shipping sector will need large-scale adoption of alternative energy sources. So far, lithium-ion (Li-ion) batteries have been the most widely used technology for electrifying the world’s cargo ships, but they’re far from a perfect solution. Here’s a look at the potential of battery-hybrid freighters for reducing carbon emissions, and the technological advances the shipping industry will need to achieve decarbonization. 

 The Future Is Battery-Powered 

Of the zero-carbon alternatives to fossil fuels available on the market, battery systems may be the most promising. A 2022 study by the University of California and Lawrence Berkeley National Laboratory found electric power in the transportation sector to be typically five times more energy-efficient than alternative fuels such as green hydrogen and ammonia.  

 The recent electrification of passenger boats and smaller cargo ships gives us a preview of how battery systems can greatly reduce maritime carbon emissions. Denmark’s ferry Ellen offsets 2,000 tons of carbon dioxide a year and transports passengers to their destination 15 minutes faster than her fossil fuel-powered counterpart. 

 Switching to battery technology not only eliminates greenhouse gas emissions, it may also help shipping companies cut costs. Due to rising fossil fuel prices and new carbon taxes on marine shipping, ocean freight will no longer be as cost-effective as it used to be. In contrast, battery-powered ships require less maintenance and fewer engineers on board, reducing operations costs. 

 Maritime battery technology is only set to improve in the coming years. Startups are developing ways to make maintenance even more convenient, like a system for replacing individual battery cells when they die rather than an entire battery pack. Others are making battery systems the size of shipping containers for use on smaller cargo vessels, which not only travel longer and farther on electric power but also can access more ports than full-sized freight ships. In light of these recent advances, shipping companies can expect higher returns than ever when they switch to electric-powered vessels. 

 The Limitations of Lithium-Ion 

 Considering the progress so far, what’s stopping ocean shipping from going green? One major obstacle is the lithium-ion technology used to power a majority of electric ships. While they are the most energy-dense and commercially mature type of battery on the market, lithium-ion batteries pose major risks to maritime applications. 

 Runaway battery fires at sea tend to be catastrophic, even more so than those on land. Before a lithium-ion cell in thermal runaway actually catches on fire, it releases toxic gasses such as hydrogen fluoride and carbon monoxide. These flammable vapors may spread throughout a ship for hours before the point of combustion, culminating in a huge explosion that destroys cargo and puts crew members’ lives at risk. Traditional fire suppression systems are not effective at stopping battery fires, which do not require oxygen to burn and can be exacerbated by seawater. 

 Companies have been working on features to make Li-ion batteries safer — better cooling systems; separation between cells to prevent mass thermal runaway — but lithium-ion batteries have already caused significant damage to the marine shipping industry. According to Allianz Global Corporate & Specialty, fire and explosion accidents were the top cause of loss on marine insurance claims in 2021. AGCS and other insurance experts have identified lithium-ion batteries as a significant source of such fires and a growing risk for maritime shippers’ investments. Meanwhile, the U.S. Coast Guard has issued warnings about transporting lithium-ion batteries at all, let alone using the technology to power shipping. 

 What’s Next: A Better Battery 

 Battery technology will continue to improve over time, but lithium-ion chemistry in particular poses too high a fire risk for large-scale adoption by marine shippers. To reach the International Maritime Organization’s decarbonization targets, shipping companies need a power source just as energy-dense and far safer. The company that develops a non-flammable battery chemistry will turn the tide of maritime carbon emissions. 

Mukesh Chatter is the CEO of Alsym Energy, a technology company developing a low-cost, high-performance rechargeable battery chemistry that is free of lithium and cobalt.