Reach for the stars (and stripes): Raising the U.S. ambition to lower shipping pollution


Welcome back to the table, America; your commitment to addressing the climate crisis is needed once again. The new Biden Administration is already showing they are up to the task, having started their term with bold moves, such as rejoining the Paris Agreement, issuing an executive order addressing climate, and revoking the permitting on the Keystone XL pipeline. These actions manifest hope for all realms of greening society.

One area in need of attention is the maritime shipping sector, which was responsible for emitting about 1 billion metric tons of carbon dioxide in 2018, or nearly 3% of anthropogenic emissions. Shipping pollution can fall between the regulatory cracks, as shipping isn’t directly included in the Paris Climate Agreement. Instead, all international regulations fall onto the shoulders of the International Maritime Organization (IMO). Domestically, shipping can also get lost in the U.S. government agency alphabet soup—EPA, DOT, DOC, and USCG—although important state actions are emerging in California and Washington.

However, there’s ample room for U.S. leadership from this administration concerning marine emissions. Climate Envoy John Kerry recently stressed the role of zero-emission vessels (ZEVs) in protecting oceans, and there has been increased emphasis on ocean climate solutions from international bodies.

To align with the Paris agreement goals and reinstate their leadership, the Biden administration should consider the three actions described below to decarbonize the shipping sector.


Include shipping in the U.S. nationally determined contribution to the Paris Agreement

Let’s start with what the Biden Administration can do sooner rather than later. This month, the United States is hosting 40 world leaders for a Leaders Summit on Climate. Headlining this high-level Earth Day summit is the reintroduction of the U.S. Nationally Determined Contribution (NDC), which will outline how the United States plans to follow the Paris Agreement objective to limit global warming to well below 2°C, preferably to 1.5°C. To show bold leadership, the Biden Administration should include shipping in their NDC. This would immediately set the United States apart from the rest of the international community, where the majority of countries left shipping policy for IMO.

The IMO has presented a sluggish pathway to reduce GHGs by at least 50% by 2050 from 2008 levels. This timeline is not adequate based on what the Paris Agreement has set forth to maintain global temperatures below 2°C–1.5°C. With the current policy, IMO’s emission trajectory would overshoot a 1.75°C pathway between 65% and 150%. According to the draft EPA inventory of U.S. GHG emissions and sinks from 1990 to 2019, U.S. domestic shipping was responsible for 33.8 million tonnes of carbon dioxide equivalent (CO2e) in 2019, or about 0.5% of annual U.S. GHG emissions. International shipping emissions could also be included in the U.S. NDC by considering all or a portion of emissions from ships calling on U.S. ports. This would require the United States to establish an emissions Monitoring, Reporting, and Verification (MRV) scheme similar to the European Union’s.

Tackling air and water pollution: Ban scrubbers

The United States could also take action to reduce coastal air pollution and water pollution by banning the use of exhaust gas scrubbers in national waters. More than 4,300 vessels have taken advantage of IMO rules that allow for them to use scrubbers instead of burning lower sulfur, but more expensive fuel. The technology is meant to “clean” the exhaust after burning heavy fuel oil (HFO). However, we found that while using scrubbers can substantially reduce sulfur dioxide emissions, carbon dioxide, particulate matter, and black carbon emissions were actually higher when using HFO with a scrubber than using marine gas oil (MGO).

In addition to emitting more air pollution than MGO, scrubbers also generate water pollution in the form of “washwater” that is sprayed onto the exhaust. Washwater discharged overboard is acidic and contains nitrates, polycyclic aromatic hydrocarbons, and heavy metals, all of which can negatively affect water quality and marine life. States like California and Connecticut have already banned scrubbers; the United States should do the same for its full coastline.

A future of green shipping corridors with allies

In the long-term, U.S. leadership in green shipping could come by establishing zero-emission shipping corridors between the United States and trade partners like Canada, Mexico, and China supplied by zero-emission vessels (ZEV) using renewable fuels. Between Mexico and Canada, a Green Marine Highway could be built on existing initiatives at MARAD. In addition, to strengthen diplomatic relationships with two of America’s most important allies, such a move could send critical market signals across the industry. The shipping route between the United States and China is also ripe for the establishment of a green corridor. We recently completed two ZEV feasibility studies on the Transpacific shipping corridor indicating potential refueling locations for liquid hydrogen. One notable refueling hub found was the Aleutian Islands, located at a halfway point between China and the United States, which could provide fuel for more than one quarter of the voyages that would require an additional refueling stop to complete the long transpacific voyage. San Pedro Bay, the location of the U.S.’s top container ports, could also support significant hydrogen demand.

There’s hope for a green future with the new Administration. Prioritizing low carbon shipping will set the United States apart as a problem solver of our climate crisis. It’s time to regain ground and push ahead with high ambition and solid policies to decarbonize our shipping and clean our waterways.