America’s pandemic shopping haul arrived on dirty cargo ships

A new report assesses the environmental toll of transporting goods for Walmart, Target, Home Depot and other major U.S. retailers in the frenzied year of 2021.
By Maria Gallucci

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Rows of multicolored metal rectangular container boxes lined up at a port
Port of Los Angeles in San Pedro, California, November 2021 (Mario Tama/Getty Images)

Historic amounts of household goods and online impulse buys flooded U.S. ports in 2021, as the pandemic drove a surge in e-commerce sales and spurred more home-improvement projects. Millions of metal containers full of furniture, power tools, cotton sweatpants and weighted blankets sailed to America’s shores on the decks of large container ships — all of which burned fossil fuels as they plied oceans and harbors.

A new report aims to quantify the environmental toll of transporting all of those products by sea. The analysis, released on Wednesday by the Ship It Zero coalition, tracks goods imported by 18 major retailers and consumer brands during that frenzied year. It then estimates the planet-warming emissions and air pollutants associated with each container.

Researchers found that, in 2021, importing 4.7 million containers on more than 1,650 ships generated 3.5 million metric tons of greenhouse gas emissions. That’s roughly equivalent to carbon dioxide emissions from 754,000 typical gas-powered cars in a year. At the same time, ships spewed enough smog-forming nitrogen oxide to equal the annual emissions of seven coal-fired power plants.

Walmart, Target and Home Depot — purveyors of practically everything that fills a home — accounted for the bulk of emissions analyzed in the study. The companies represented the first, second and third largest shares, respectively, of both climate-harming emissions and air pollution from maritime imports.

Many of those goods moved through just a handful of hubs: the Ports of Los Angeles and Long Beach in California, the Port of Houston in Texas and the Port of Savannah in Georgia.

You had this skyrocketing e-commerce demand and, because of that, port communities experienced this enormous wave of pollution,” Madeline Rose, climate campaign director at Pacific Environment and the report’s lead author, told Canary Media. This report is the first of its kind that conducts a deep-dive analysis on retail pollution in specific U.S. ports.”

She said the campaign urges all companies that continue to rely on fossil-fueled ocean freight services to abandon dirty ships now and compete to put their goods on the world’s first zero-emissions vessels.” Such ships could feature marine batteries, fuel cells and wind-harnessing devices — technologies that exist at small scales today — to meet some of their energy needs, while potentially also relying on emerging green” fuels like methanol, hydrogen or ammonia from renewable electricity.

A large ship sails across the ocean with a tethered, rainbow-shaped white kite flying above it
A 2,700-square-foot Seawing is shown flying above the vessel Ville de Bordeaux. A 5,400-square-foot kite is also stowed onboard. (Airseas)

Ship It Zero, of which Pacific Environment is a founding member, commissioned the report’s research from Research Group. The organization provided data including records on individual vessel movements and detailed shipment lists. University Maritime Advisory Services (UMAS), a prominent research consultancy in London, estimated the fuel consumption and emissions for each vessel contained in the study and linked those numbers to specific retailers.

Wednesday’s study was initially envisioned as a follow-up to an earlier analysis of 2019 data, which was itself a first-of-its-kind effort to trace retailers’ shipping-related emissions. However, last summer UMAS researchers realized that a coding mistake had incorrectly inflated the first study’s results. As a result of fixing the code, the emissions numbers in the new analysis are significantly lower by comparison.

James Stewart, a consultant for UMAS, said the error reflects the difficulties of culling data sets from many disparate companies and countries, in varying formats and units, and aligning the numbers to make apples-to-apples comparisons. Because retail giants and cargo carriers don’t report such detailed emissions figures, researchers are left piecing the puzzle together.

We do want [companies] to take responsibility for these emissions calculations themselves,” Stewart said.

It’s really useful to see the scale of the emissions of all these different retailers,” he added. It’s clearly having impacts on local populations, in terms of health, and on climate change globally.”

Assessing the biggest importers — and worst offenders

International shipping accounts for roughly 3 percent of greenhouse gas emissions every year, though experts say it could rise to 17 percent by 2050 if more diesel-burning ships make more voyages, and as other sectors reduce their fossil fuel consumption over time. Vessels are also major sources of air pollution, which tends to concentrate in waterfront communities, threatening people’s health.

Walmart, the world’s largest retail company, represented more than one-fifth of the carbon dioxide emissions generated across the 18 companies in 2021, according to Ship It Zero.

The Bentonville, Arkansas–based retailer, which earned over $611 billion in total revenue last fiscal year, was responsible for 788,000 metric tons of CO2, as well as 14.9 metric tons of the potent greenhouse gas methane. Much of its import-related air pollution accumulated in the Port of Houston, which operates terminals along the Houston Ship Channel — and is already one of the country’s busiest and most polluted waterways.

Walmart says it is working to reduce or avoid 1 billion metric tons of greenhouse gas emissions in the global value chain by 2030. Reducing emissions from ocean carriers is a priority for Walmart, and we work closely with logistics partners, NGOs and suppliers across the retail industry to scale up more sustainable approaches to transporting products,” a representative said by email.

Other retailers have set more specific targets for addressing shipping emissions. Target has pledged to move its products off of fossil-burning ocean freighters by 2040. In late September, the Minneapolis-based company joined Cargo Owners for Zero Emission Vessels, an initiative of the Aspen Institute that includes other giant companies such as Amazon, Ikea, Unilever and Michelin.

The retailer produced an estimated 544,000 metric tons of CO2 emissions and 10 metric tons of ultra-warming methane from its U.S. imports in 2021, the report states.

Target made its clean-shipping commitment just weeks after the Minneapolis City Council unanimously passed a Ship It Zero resolution, which urges retailers to make all imports on 100% zero-emission ships” by 2030, and to disclose their maritime greenhouse gas emissions in public annual reports. The cities of Los Angeles and Long Beach, home to the nation’s largest port complex, also adopted the resolution.

Of all the retailers surveyed, Target imported the most goods through the Southern California hub, which itself represented the largest share — some 35 percent — of the total carbon emissions in 2021. That same year, the region also saw a dramatic spike in nitrogen oxide emissions and carcinogenic particulate matter from ships idling their engines as they waited to enter crowded ports.

Satellite imagery shows dozens of cargo ships idling off the coast of Los Angeles and Long Beach in California.
Cargo ships idle at sea on Oct. 10, 2021 due to congestion at the Los Angeles and Long Beach ports. (NASA Earth Observatory)

Our big takeaway is that Los Angeles–Long Beach, which is still managing the lion’s share of these imports, has the responsibility to move fastest and set the course for a zero-emission future for U.S. ports,” Rose said. For their part, the ports are working on converting cargo-handling equipment to zero-emissions technologies by 2030 while also partnering with authorities in Shanghai and Singapore to establish green-fuel hubs.

The No. 3 polluter on Ship It Zero’s list, Home Depot, was responsible for nearly 420,000 metric tons of carbon emissions and 8 metric tons of methane in 2021. The Atlanta-based retailer’s preferred port, in Savannah, is also one of the nation’s fastest-growing hubs, with plans to expand its container-handling capacity by 60 percent in the next few years.

A spokesperson for Home Depot said the home-improvement giant works with its strategic partners to identify opportunities and encourage sustainable shipping solutions as they’re available. For example, one of our largest carriers, Maersk, recently announced a commitment to net-zero emissions by 2040.”

Zero-emissions container ships have yet to hit the water 

As environmental groups push major retail importers and ship operators to ditch fossil fuels, it’s not entirely clear which fuels and technologies the companies will use instead.

Nearly two dozen vessels now use sails, kites, suction wings and other forms of wind-assisted propulsion, a number that’s expected to reach 50 ships by the end of 2023. Hundreds of ships now use batteries to power onboard equipment or drive electric motors. A handful of vessels, including a ferry coming soon to the San Francisco Bay, are powered by hydrogen fuel cells.

But those technologies aren’t expected to fully replace the massive diesel engines that power today’s enormous oceangoing vessels. Experts say ammonia — a pungent, carbonless compound — could become the leading fuel source for the world’s giant cargo ships by 2050. However, engineers are still developing the engines and fuel cells that will be able to use ammonia, and only tiny amounts of the fuel are produced today using renewable electricity.

An illustration of a large aqua cargo ship stacked with white containers. The name "Maersk" is in red letters on the ship.
A rendering shows a future Maersk container ship powered by green methanol, which can be made by combining hydrogen with carbon dioxide. (Maersk)

In the near term, more ships may come to burn methanol. While not entirely carbon-free, the chemical can be made using electricity (e-methanol) or be produced from plant biomass (bio-methanol). Crucially, it can work as a drop-in” replacement for oil-based fuels with relatively minor adjustments to a ship’s engine and fuel system.

Maersk, one of the world’s largest container carriers, has ordered 19 vessels with engines capable of running on methanol. The Danish shipping giant also signed agreements with six fuel producers with the goal of sourcing at least 730,000 metric tons of green” methanol per year by the end of 2025. Other shipping companies have ordered a couple dozen more vessels, though, as is the case with green ammonia, demand for renewably produced methanol currently far outpaces the actual supply.

The methanol engine is there; the ammonia engine is being developed but is not there,” Johan Byskov Svendsen, program manager for the Maersk McKinney Møller Center for Zero Carbon Shipping, said in a January webinar. If someone is decarbonizing and has a very, very short timeframe…they will have to choose methanol.”

Rose, of Pacific Environment, said Maersk’s methanol push shows how major companies, including U.S. retailers, can use their clout to help transform the global shipping industry. There’s no excuse for them not to make these [clean-shipping] commitments and begin to extend their climate commitments to the seas,” she said.

Maria Gallucci is a senior reporter at Canary Media. She covers emerging clean energy technologies and efforts to electrify transportation and decarbonize heavy industry.