A key part of the Biden administration’s climate agenda involves revolutionizing the transportation system. The bipartisan infrastructure bill and the sprawling Democrat-led budget reconciliation package (a.k.a. the Build Back Better Act) include measures that, if included in the final package, will lead to historic investments in electrifying and expanding public transportation, electrifying the nation’s fleet of 60,000 school buses, and expanding the tax credits for people buying electric vehicles—and even electric bikes. 

But it’s not all about electrifying our means of transportation. A key source of toxic air pollution and greenhouse gas emissions that has long been overlooked is also getting some renewed attention: the ports that serve as hubs for the movement of goods.

The air surrounding many ports is a toxic blend of exhaust from burning some of the dirtiest fuels on the planet. Much of the infrastructure at ports runs on diesel—from the ships carrying cargo to the cranes that unload it and the trucks that haul it away. Researchers have long known that the soot and gas belched by diesel engines contain more than 40 cancer-causing substances, including benzene and formaldehyde. They've been linked to asthma, heart disease, and premature death.

“There has been very little regulation focused on making sure that ships aren’t polluting so much,” said Katherine Garcia, the acting director of the Sierra Club’s Clean Transportation for All campaign. “We’ve really been pushing Congress to step up and invest in people’s health.”

Ports are finally having their moment. In September, the House Transportation and Infrastructure Committee outlined its recommendations for the reconciliation bill, setting aside $2.5 billion to reduce the environmental impact of ports. At the same time, the House Energy and Commerce Committee proposed spending $3.5 billion on zero-emission technology at ports—40 percent of which would go to the ones that are not meeting EPA air quality standards.

Cleaning up ports would have ramifications for two of the crises Democrats hope the reconciliation bill can confront: climate change and inequities in health. 

The EPA estimates that about 39 million people live in communities surrounding ports. These communities are predominantly Black and brown, and they’re exposed to such high rates of pollution that physicians have labeled them “diesel death zones.” A 2012 study by researchers at Virginia Commonwealth University found that the average life expectancy in West Oakland, the community adjacent to the Port of Oakland, is 24 years shorter than in wealthier (and whiter) communities in the Oakland Hills, less than five miles away.

“Air pollution discriminates,” said Paul Billings, the national senior vice president of the American Lung Association. “It has a disproportionate impact on these communities. They have greater burdens from air pollution and less access to quality health care, so there is this synergistic effect on individuals who bear the most burden.” 

Diesel isn’t the only fuel that ships burn. The vast majority of oceangoing vessels fuel their main engines with a type of oil called “bunker fuel.” It’s literally the dregs from a barrel of oil—the stuff left over after a refinery has produced everything else (the propane, kerosene, gasoline, and diesel). It’s the cheapest, heaviest, and dirtiest fuel there is. “Refineries appreciate the fact that ships buy it,” said Kenneth Gillingham, a professor of economics at Yale’s School of the Environment, “because no one else will.” 

According to the EPA’s Office of Transportation Air Quality, ships idling their main engines at berth or running diesel generators to provide electricity onboard are responsible for more than half of the particulate matter pollution surrounding ports. 

If you want to reduce emissions at ports, getting rid of the need to run onboard diesel engines is the easiest place to start. In a recent study, Gillingham analyzed the potential environmental and health benefits of a process known as “cold-ironing.” Essentially, cold-ironing is plugging ships into the electricity grid with what amounts to a high-voltage extension cord. 

Gillingham’s analysis found that retrofitting the more than 3,000 port berths capable of serving oceangoing cargo ships in the United States for cold-ironing, along with replacing diesel-burning tugboats with electric ones, would cost a little over $25 billion. Yet, over the next 30 years, it would lead to more than $100 billion in health benefits from decreased pollution. Communities around ports would benefit from cold-ironing almost immediately because the pollution from producing electricity would be emitted at relatively remote power plants, which are now more likely to burn natural gas or generate electricity from renewable energy and nuclear power.

“Natural gas plants outside of cities are far preferable to diesel combustion in these communities,” Gillingham said. “It’s not a panacea. It’s one way to reduce air pollution and help vulnerable populations. But it doesn’t solve climate change by any means.” 

Gillingham did find that cold-ironing every port berth in the country would have an immediate modest impact on the greenhouse gas emissions warming the planet. This finding is similar to research that shows electric cars, even when charged with electricity from fossil-fuel-burning power plants, are better for the environment than gas-guzzlers (one efficient power plant is better than lots of inefficient internal combustion engines). 

But ultimately, further emissions reductions through cold-ironing would depend on decarbonizing the electricity grid.

Cold-ironing and electric tugboats would reduce pollution from ships around ports, but shipping, like climate change, is international in scale. Ships produce somewhere between 2 and 3 percent of global greenhouse gas emissions. According to a recent report by the UN International Maritime Organization, that number could increase to 17 percent by 2050.

Reducing the climate pollution ships emit on the high seas would require an incredible amount of international cooperation and fantastical advances in technology—there are dreams for wind-borne cargo ships with sails taller than sequoias and freighters that run on liquid hydrogen or are powered by the same nuclear reactors as submarines. But this technology is a long way out. “These are all possibilities. None of them are particularly easy. And all of them are far from being off-the-shelf solutions,” Gillingham said.

Nevertheless, Gillingham said a transition to clean energy in the transportation sector could have positive reverberations throughout the economy that eventually help make shipping greener. For example, an increase in the number of electric vehicles would mean fewer car owners buying gas, which might lead refineries to sell that gas to ships in place of dirtier fuels. It’s not the best solution, but in the short term, it would decrease emissions. 

“We may make shipping more efficient. Ships might use different fuels,” Gillingham said. “But shipping is probably going to be one of the last parts of the economy that truly becomes clean.”