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Confronting Climate Change

Taking the ocean into account is critical for successfully addressing climate change, and addressing climate change is critical for the future of the ocean

Exploring the Pathways to Zero-Emission Shipping

This is a deep dive into pathways to zero-emission shipping—if you would like to read a general overview on shipping, please check out our shipping page here.

Getting to zero-emission shipping is complicated. There are a number of components that need to be addressed in order to reduce shipping’s gigatonne of CO2 equivalent emissions each year. To put that in perspective, that is roughly equal to the emissions of the entire country of Japan. Without the sector’s full-scale decarbonization by 2040, fulfilling the goals of the Paris Agreement and limiting warming to 1.5 degrees Celsius above pre-industrial levels or reaching economy wide targets of net-zero by 2050 will be impossible.

The industry must transition quickly. New zero-emission fuels need to be produced at scale. We need vessels and propulsion technologies that maximize efficiency and can run on these fuels, and we need ports that can refuel and service these vessels, while cutting their own emissions. To accelerate a clean shipping transition, policy and investment pathways are powerful. In particular, we must establish domestic and international standards that will push the sector as a whole to decarbonize.

Learn more about our work towards zero-emission shipping with the pathways listed below:


Global shipping’s large carbon footprint is due mainly to the industry’s reliance on cheap and dirty heavy fuel oil (HFO) and other fossil fuels. The Global Maritime Forum (GMF) and other experts argue that if zero-emission fuels can make up 5% of the global shipping fuel mix by 2030, the goals of the Paris Agreement will be in reach. There are a number of options on the table that can become the zero-emission shipping fuel of the future.

The most promising are “green” hydrogen and hydrogen-derived fuels like ammonia. If the hydrogen is produced through electrolysis using 100% renewable energy, the resulting “green” hydrogen and ammonia can be true low- and zero-emission fuels. In contrast, other options, such as methanol, rely on carbon dioxide for production, so it would depend on a mostly theoretical carbon recapture to reach zero. And while biofuels have already been used in some ships effectively, depending on the source their use on a large scale raises greater questions about potential deforestation and land use.

Liquified natural gas (LNG) has been seen as a potential “transition” shipping fuel, as it produces less CO2 than HFO and minimal air pollution. However, full lifecycle greenhouse gas emissions analyses show that the methane released during LNG production, transport and use eliminates any climate benefits. To stay on track to eliminate shipping emissions, we need to transition without an intermediary stop in LNG.

Initially, all of these fuels will be more expensive than HFO in terms of upfront expenses, and early producers face risks of market uncertainty and weak production supply chains. But this is an industry that has transitioned fuels and ships before, and, when pressed for time, can do so fairly quickly.


In order to transition to electrofuels (i.e., green hydrogen and ammonia), we need to build or retrofit ships to run on these fuels. Yet the long operational lifespans of ships means that 2040 is just one lifetime away—the next generation fleet needed to achieve global climate goals is being designed and built now. Investing in vessel design and providing incentives or mandates for replacing older polluting vessels with new builds or retrofitting vessels to run on alternative fuels is necessary for this transition.

We also need to maximize energy efficiency through operational measures and energy efficiency technologies such as wind assistance on applicable vessels to ratchet down emissions and extend the fuel efficiency of vessels. Replacing diesel-powered short transit vessels like ferries with hybrid or electric ships can not only eliminate emission from this sector of ships but can also help further develop the technology for the future. These technologies have started to be used in pilot programs in the United States and beyond, but more widespread adoption of these technologies will be needed throughout the world for them to make an impact.

In looking at the United States, more than half of the domestic commercial fleet is more than 15 years old, with vessels using less efficient technologies that are higher emitting than those found in newer vessels. With many of these vessels nearing the end of their useful lives, there is an opportunity for the United States to replace these vessels and integrate new technologies into their builds. The United States can make a big impact as a first mover to new technologies and remove barriers for other countries to do the same.

Green Ports

We need to build out the necessary port infrastructure to serve these vessels while also reducing port emissions and pollution. Busy maritime ports are the heart of shipping but are also often fossil-fueled pollution hotspots. Belching carbon dioxide and other noxious chemicals, heavy equipment and trucks service vessels and transport cargo, and vessels idle at berth to refuel or while waiting to dock.

Green ports are essential to reducing emissions from the shipping industry. Green ports are those that take steps to invest in environmentally friendly and sustainable operations, including port electrification, installing renewable energy microgrids and providing portside charging infrastructure for ships to plug into while at berth, called “cold ironing.” Infrastructure also will be needed to offer refueling of low and zero emission fuels, and ports can set zero emissions deadlines for all ships calling at their port as well.

Ocean Conservancy has partnered with several technical and policy experts on research and analysis that identifies promising decarbonization technologies and the infrastructure to support industry uptake.

Policy and Other Investment Drivers

Establishing domestic and international standards via policy provides regulatory certainty and incentives for action across the sector. Without policy intervention, things will continue on status-quo and the shipping industry will continue to prioritize profit over the environment and health of communities.

Shipping is a truly global industry, so strong action at the international level to set global shipping decarbonization targets is critical. In July 2023, the International Maritime Organization (IMO) will adopt a revised strategy to reduce greenhouse gas (GHG) emissions from shipping. This new GHG strategy will govern the sector worldwide. In order to align with the Paris Agreement goal of keeping global warming under 1.5 degrees Celsius compared to pre-industrial levels, the strategy must set a target for shipping to reach zero emissions by 2040 and absolutely no later than 2050, with ambitious interim targets for 2030.

In addition to IMO action, there are a number of policy and investment pathways that can help accelerate the uptake of low-carbon fuels, the transition of vessels and fleets, and the greening of maritime ports.

These can include:

As the planet continues to warm and we face record shattering wildfires, hurricane seasons and ever thinner Arctic sea ice, the need for climate action has never been more urgent. Join us as we use these pathways to zero-emission shipping completely by 2040, for the future of our ocean and the planet.

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