Late last month, Long Beach, California, signed onto a historic effort to clean up the shipping industry when city council members unanimously passed a resolution to reach 100 percent zero-emissions shipping by 2030.
The move comes just months after a similar declaration from Los Angeles, whose port abuts Long Beach’s to make up the San Pedro Bay Port Complex — the U.S.’s largest port, handling more than 275 million metric tons of furniture, car parts, clothes, food and other cargo every year. Together, the two cities’ resolutions represent one of the world’s most aggressive shipping decarbonization targets and reflect a growing desire among policymakers and environmental advocates to drive down the industry’s emissions.
"We need major shipping companies to lead the way to a cleaner future and ship their goods using only the best available technologies," Long Beach City Councilmember Cindy Allen said in a statement.
But getting to net-zero shipping is a monumental task that will require significant technological advancement and investments in alternative fuels — in addition to ambitious pronouncements from policymakers. Although some zero-emissions solutions already exist, experts say they need to be refined, scaled up and supported by government policies to facilitate industry-wide decarbonization.
According to Jing Sun, a marine engineering professor at the University of Michigan, more work is needed to create viable clean fueling systems before they can be rolled out en masse. "It’s not just a technology deployment issue," she said.
Zero-emission technologies that are powering a rapid energy transition in other sectors fall short when it comes to global shipping.
At any given time, more than 50,000 ships are zipping around the world’s oceans, carrying about 90 percent of all globally traded goods from port to port. Virtually all of these ships run on fossil fuels — either sludge-like heavy fuel oils, diesel, or liquefied natural gas, all of which release planet-warming greenhouse gas emissions when burned. Altogether, the global shipping industry is responsible for nearly 3 percent of all human-caused climate pollution, and international regulators say emissions could continue rising without urgent action.
But how do you propel a massive cargo ship — which can weigh hundreds of millions of pounds when fully loaded — across the ocean without using fossil fuels? Zero-emission technologies that are powering a rapid energy transition in other sectors fall short when it comes to global shipping. Batteries, for example, are much too heavy to push cargo ships across the oceans. Onboard solar panels take up too much space, and nuclear power creates safety and environmental concerns. Many companies have plans to launch or have already launched ships powered by biofuels — fuels produced from plant crops, algae, or animal fats — but experts expect them to play a limited role in the future of decarbonized shipping due to scalability constraints and high demand from other sectors. The nonprofit Pacific Environment has criticized biofuel as a "dead end" fuel that is only in some instances carbon neutral.
Only two kinds of alternative fuels are widely considered to be viable candidates for decarbonized shipping: green hydrogen and green ammonia. Both can be produced with clean electricity and burned in an internal combustion engine or a fuel cell — a versatile technology that converts chemical energy into electricity — where they produce no greenhouse gas emissions.
Green hydrogen is still too expensive to be made in the kinds of quantities that could power a global shipping fleet.
However, these fuels aren’t quite ready for prime time, in part because their supply is so limited. Green hydrogen, produced by splitting a water molecule using renewable energy, is still too expensive to be made in the kinds of quantities that could power a global shipping fleet. The supply chain for ammonia — produced by combining hydrogen with nitrogen that’s extracted from the air — is more established, as ammonia is widely used as an agricultural fertilizer. But to make ammonia green, the hydrogen input has to be green hydrogen. This, along with costly storage requirements, makes green ammonia about as expensive as green hydrogen.
"There are definitely going to be some challenges along the road" to scaling green hydrogen and ammonia up, said Dan Hubbell, shipping emissions campaign manager for the nonprofit Ocean Conservancy.
Ships also need to be configured differently to run on greener fuels. Although some pilot projects have developed small hydrogen-powered vessels, it’s another question to expand hydrogen and ammonia compatibility to all ships globally. According to Sun, at the University of Michigan, researchers are still grappling with many design and safety questions, like how best to fit alternative fuels — which are less energy-dense than oil and gas — onto a ship, or how to safely contain ammonia, which can release hazardous nitrogen oxide or unspent fuel when combusted.
"We need to, as a research community, take a holistic approach and explore the whole space. I don’t think that has happened," Sun said, calling for more government investment to make that exploration possible. She and other experts also want the International Maritime Organization, or IMO — a unique United Nations agency that can set legally binding regulations — to unify the industry behind a stronger decarbonization goal. The IMO’s current target is nonbinding: to achieve only a 50 percent reduction in emissions by 2050, relative to a 2008 baseline. Hubbell called the goal "abysmal."
The IMO’s current target is nonbinding: to achieve only a 50% reduction in emissions by 2050, relative to a 2008 baseline.
Still, the IMO isn’t the only government body capable of pushing the shipping industry. Madeline Rose, climate campaign director for Pacific Environment, noted that regulators such as the California Air Resources Board or the federal Environmental Protection Agency could mandate emissions standards for all ships entering California ports, or all U.S.-owned ships, respectively. These policies could potentially spread outside the U.S., as California’s 2007 standard for sulfur emissions eventually did when the IMO adopted a similar — albeit weaker — standard in 2020. They can also help drive down prices for green technologies, allowing them to permeate throughout the shipping industry, by artificially increasing demand.
And even smaller jurisdictions such as the Long Beach City Council can also make waves, helping to foster the conditions necessary for decarbonization. An ambitious commitment is one way to do that. "Having a port take a clear stance now … is a key enabler of the technology demonstration and wider regulation that is necessary to drive the switch away from fossil fuels," said Tristan Smith, a lecturer at University College London’s Energy Institute. Other actions ports can take include prohibiting polluting ships from using their docks, giving docking preference to zero-emissions ships, or installing "shore power," which allows ships to plug into electricity while docked so they don’t have to keep burning fuel. Both LA and Long Beach already provide shore power, and groups such as Pacific Environment are pushing for them to adopt the other policies as well.
Although Smith called Long Beach’s 2030 target "entirely appropriate," Sun was more cautious. She said that many shorter routes or routes along so-called "green corridors" with supportive infrastructure for alternative fuels could feasibly go net-zero by the end of the decade, but that decarbonizing long-haul voyages across the oceans by then might be overambitious.
"The Long Beach initiative is great," she said, because it puts greater pressure on lawmakers and industry to get to net-zero. But she called for more research and development to ensure that alternative fuels and the engines that run them are safe, effective and reliable. "And then once we get that, then how do we scale them?"