A new study explores how electrifying the U.S. domestic shipping fleet could drastically reduce greenhouse gas emissions, bringing us closer to a cleaner, more sustainable future on the water. By retrofitting small to mid-sized vessels under 1,000 tons with battery-electric systems, researchers estimate that the United States could reduce its domestic shipping emissions by up to 73% by 2035. This electrification could also become cost-effective compared to traditional internal combustion engines, paving the way for a large-scale shift toward battery-powered ships that are both economically viable and environmentally friendly.
The Environmental Impact of Battery Electric Ships
The shipping sector is a major contributor to carbon emissions, and in the U.S., domestic vessels alone produced over 21 million metric tons of CO₂ equivalents in 2021. As part of ambitious climate goals, the U.S. aims to cut greenhouse gas emissions by 52% by 2030 and reach net-zero emissions by 2050. For shipping, these targets mean finding clean alternatives to fossil fuels.
Battery electric ships (BESs) are one promising solution. The study estimates that if around 6,300 small and mid-sized ships are converted to battery power, it could make a meaningful dent in emissions, potentially achieving a 73% reduction by 2035. These benefits would depend on charging these ships using electricity from a low-carbon grid, which could reduce operational emissions while also ensuring that ship retrofitting aligns with broader decarbonization efforts.
Advances in Battery Technology Are Key
One of the main challenges of converting ships to battery power is the size and weight of batteries needed for long journeys. Recent advances in battery technology, such as lithium nickel manganese cobalt oxide (Li-NMC) cells, have led to increased energy density, allowing batteries to store more power in smaller spaces. Programs from the U.S. Department of Energy’s are driving this innovation, targeting energy densities as high as 500 watt-hours per kilogram (Wh/kg). These breakthroughs are making it possible to envision batteries that can handle the energy demands of maritime travel without excessively weighing down ships or reducing cargo capacity.
The study outlines different capacity tiers for battery-powered ships based on the percentage of historical trips they can complete. For instance, a BES with enough battery power to handle 99% of historical trips requires a significantly smaller battery than one designed to cover 100% of trips, lowering costs and making retrofitting more feasible. By slightly reducing battery capacity, BES weight can be cut by up to two-thirds, making electrification a practical option for most U.S. vessels under a 1,000 tons.
Health and Cost Benefits of Battery-Powered Shipping
Switching to BESs offers significant health benefits as well. Traditional internal combustion engines contribute to air pollution in ports, affecting nearby communities. By reducing pollutants, battery-powered ships could improve air quality and reduce respiratory issues among residents near major shipping hubs.
On the economic front, battery electric ships are poised to become cost-effective in the coming years. As battery prices continue to decline and the costs of fossil fuels rise, BESs could reach price parity with conventional ships by 2035, especially under policies that account for the social cost of carbon emissions. The study found that BES retrofits could be viable for up to 85% of the U.S. shipping fleet by this time, making battery-powered shipping a financially sound option as well as a green one.
Challenges and the Path Forward
While BESs are promising, their success depends on building the necessary infrastructure for charging at ports and ensuring that the grid can support the additional demand. The study estimates that most of the electricity demand from electrifying ships could be concentrated at 20 major U.S. ports, reducing the need for widespread grid upgrades. Installing renewable energy-based microgrids at these ports could help meet demand while keeping emissions low.
Battery life and maintenance are also key considerations. The study suggests that battery systems could have a second life in stationary energy storage applications once they reach the end of their maritime lifespan, helping to extend the environmental and economic value of each battery. Additionally, as the market for battery electric ships grows, innovations in charging technology and modular ship design could further enhance the scalability of battery-powered shipping.
The Future of Clean Shipping
The findings of this study represent a roadmap for a cleaner shipping sector. By transitioning to battery electric ships, the U.S. could significantly reduce its shipping emissions, improve air quality, and make strides toward national climate goals. If implemented, this shift could make the maritime industry a leader in sustainability, transforming how goods are transported on the seas.
As climate targets become more urgent, the potential of battery-powered shipping offers a compelling vision of the future - a future where U.S. waters are cleaner, communities are healthier, and shipping is part of the solution rather than the problem.
