Backed-up container ships filled cities with pollution

As the pandemic snagged global supply chains, causing a backlog of cargo ships in seaports around the world, consumers  felt the impacts in the form of delivery delays and rising prices. But for people living near ports, they also felt the impacts in other invisible ways: a rise in shipping-related emissions at those clogged up ports.

When ports are full, ships idle offshore, running their diesel engines, which releases pollutants including carbon dioxide, sulphur oxide, nitrogen oxide, particulate matter, carbon monoxide, and methane. Supply chain snags during the pandemic often left dozens of ships awaiting entry—at times, between 40 and 60 ships waiting to enter the ports of Los Angeles and Long Beach alone.

All that idling added up: Emissions at that Los Angeles port were modeled to have increased by 100% during the period of July 1, 2020 to July 30, 2021, according to researchers at the Nanyang Technological University in Singapore. In a recent study published in the journal Environmental Research, researchers looked at the effect the pandemic has had on emissions at four major seaports: Los Angeles, Long Beach, Singapore, and Hamburg.

Using what they call the “pandemic period” of July 2020 to 2021, and comparing that to 2019 emission levels, the researchers found that ship emissions increased by an average of 79% across those four ports. The Singapore port—the world’s busiest container hub, which handled 626.2 million tonnes of cargo in 2019—saw the highest increase, at 123%. At Long Beach, emissions increased by 65%, and at the Hamburg port, by 27%.

Though ships do anchor while they wait to enter these ports, they do so with their auxiliary engines still running. “When the ship undertakes the berthing activity, it mainly relies on the auxiliary engines and boilers rather than the main engines, which are more efficient,” Adrian Law, an engineering professor at NTU who led the study, and Jiahui Liu, doctoral student and first author, said over email. “Therefore, more emissions are occurring due to the port congestion.”

To calculate these increases, the team used ship movement data from the Automatic Identification System, which transmits continuously from ship vessels. Using engine power and speed data from the system, the researchers calculated fuel consumption and pollutant emissions.

The researchers also created models for what pollution could look like going forward, from August 2021 to August 2022. In the first, they assume COVID-related congestion at ports is solved and turnaround time goes back to pre-pandemic levels. In that case, there’s a high likelihood (more than 50% probability) that emissions drop by at least 34% compared to the pandemic period they studied. The second forecasted scenario assumes port congestion continues in the same way, at these four major ports. If so, pollutant emissions will also keep rising—for Singapore, a projected 6% higher than the July 2020 to July 2021 levels, for a total 137% increase in emissions compared to 2019 levels.

There could be a way to reduce these emissions in the future, by using electrical power rather than diesel auxiliary engines, with ships connecting to the grid to power lights, pumps, refrigeration, and so on. Called shore power, some studies say this could cut emissions at berth (when the vessel is moored at a port) by 95%. California is experimenting with implementing this technique, with a new mandate that vessels run on shore power at berth by 2023. But the NTU researchers note that berthing time is still a small portion of the entire time ships are waiting at ports, so ships also need new, cleaner engines and carbon-neutral marine fuels.

“We believe the most important finding from our study is that the current port congestion not only increases the business costs but also has an environmental footprint,” they said. But shipping is necessary: “It is really difficult to imagine how we can live through this period without shipping, when air and road traffics had literally stopped completely across borders.” Average consumers should be appreciative of the maritime industry, which has continued to operate throughout the pandemic, but it’s up to policy makers, they add, who should plan ways to mitigate the impacts. “Hopefully, the finding can further justify the need to return to pre-pandemic normalcy as well as accelerate the pace of greening innovation in the post-pandemic world.”