California can lead the world to reduce emissions from ocean cargo ships, lower climate impacts, and improve air quality around ports

Date: May 23, 2024

Two reports co-released today by Goldman School of Public Policy, University of California Berkeley and Energy & Environmental Research Associates delve into policy changes and technology to decarbonize ocean going vessels. Non-profit Pacific Environment commissioned these reports.

This set of reports seeks to inform stakeholders and policymakers on potential to reduce greenhouse gas (GHG) and other air pollutants from the maritime sector.  These reports describe: 

  1. decarbonization technologies for ships, including low and zero carbon fuels, engine and operational efficiencies; and, 
  2. the policy landscape – what’s happening nationally and internationally, along with recommended policy initiatives for state and federal agencies in the United States.


U.S. national and state governments will need to play a key role in decisions on clean maritime fuel supply chains and infrastructure. California is uniquely influential.  California was the first to require low sulfur fuel and emission controls for ships, action that later inspired international and national emission controls. It can play that catalytic role again by signaling intent to regulate GHG emissions of ships, either:  1) to implement strong international controls;  or, 2) to adopt controls and incentives applicable to shipping and low carbon fuel production in California  if international negotiations fall short.  

For example, California policy leadership could increase momentum for strong regulation by the International Maritime Organization, which is currently debating measures to implement its 2023 zero carbon target for shipping by 2050. In absence of strong IMO action, California can reduce emissions from ships operating in its coastal waters.  Such action would complement and, in effect, extend the geographic scope of recent European Union policies to reduce GHG emissions from ships calling at EU ports.

California can also create financial incentives for production and use of zero or near-zero carbon maritime fuels through Low Carbon Fuel Standards. There is currently no zero carbon fuels suitable for large ships produced on the West Coast of the US.  This fuel supply infrastructure is critical to the success of global voluntary and mandatory commitments to zero carbon ship operations. 


The EERA report provides a technology review of low and zero-greenhouse gas marine fuels and supplemental power systems.  The report describes decarbonization potential, costs, technology parameters, safety, and infrastructure.  The report includes a novel analysis of growth in green fueled fleets and shows the significant potential for sustainable marine fuels. 

Among the report’s findings, the orderbook data for end ofQ4 show that the number of methanol-fueled and methanol-ready vessels is set to increase by 6.8 times, reaching around 285 vessels within the next five years. Ammonia-ready vessels are set to increase by 4.5 times, totaling around 200 vessels over the same time period. Other low-GHG vessel technologies like hydrogen fuel cells, battery power and assist, and solar and wind propulsion are also growing rapidly, indicating a shift towards early uptake of these technologies. 

The report outlines a promising three-stage transition towards net zero emissions in the maritime section, highlighting the role methanol and ammonia may play as hydrogen carriers. While there are sizable gaps between maritime energy demand and projected production, the volumes of low- and zero-GHG fuels are anticipated to increase rapidly, with vessels ready and being built today that can use these fuels. California is uniquely positioned with strong renewable energy generation and regional Hydrogen Hub developments to become a leader in green hydrogen production as demand is likely to sharply increase over the next five to 15 years and shipping moves to zero and near-zero emission fuels by 2040.