Dirty diesel ships can start decarbonizing now. Here’s how

With the IMO’s new emissions-reduction goals set last week, cargo shipping companies are under more pressure than ever to slash CO2 emissions.
By Maria Gallucci

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A large cargo ship piled high with colorful metal containers and spewing exhaust travels on the water
(Costfoto/NurPhoto/Getty Images)

As the world races to electrify passenger cars, school buses and big-rig trucks, efforts to clean up another essential vehicle — the cargo ship — have lagged behind. 

Now, cargo-shipping companies are under increasing pressure to decarbonize the world’s merchant fleet.

Last week, the International Maritime Organization (IMO), the United Nations agency that governs global shipping, set new targets that call for reaching net-zero” emissions as close to 2050 as possible. Member countries also agreed to have 5 to 10 percent of shipping’s energy use come from​“zero or near-zero” emissions fuels and technologies by 2030.

Critics say the IMO’s strategy doesn’t align with limiting global temperature rise to 1.5 degrees Celsius above preindustrial levels. Still, meeting the latest emissions-reduction goals will require companies to make dramatic changes in how they operate and fuel their fleets.

Oceangoing freighters move staggering volumes of clothing, electronics, foods and other materials necessary to our daily lives. To do so, they burn hundreds of millions of tons of fossil fuels every year, spewing greenhouse gases into the sky and enshrouding ports in smog. International shipping contributes around 3 percent of the world’s greenhouse gas emissions every year, and the sector’s planet-warming pollution is rising as more vessels hit the water to carry more stuff.

To decarbonize the tens of thousands of merchant ships that fuel our modern economy, the world will need to spend roughly a trillion dollars over the next two decades — an undertaking that includes building more renewable energy projects to enable the production of low- or zero-carbon marine fuels.

If the task feels herculean, a few strategies are already available or developing rapidly to help reduce ships’ reliance on dirty diesel fuel.

A recent study by the consultancy CE Delft found that shipping companies could slash their CO2 emissions by 36 to 47 percent within the next seven years without going bankrupt or upending global trade flows. The report, which was commissioned by four U.S. and European environmental groups, was released at the outset of the IMO negotiations in late June.

To achieve the highest CO2 reductions, analysts envisioned that all of the world’s fleet will incorporate at least some form of wind-powered technology by 2030. Cargo ships will all reduce their average speeds, and thus fuel use, by 30 percent relative to 2018 speeds. And 10 percent of vessels’ energy will come from zero-GHG fuels” — which this report defined as ammonia made from renewable energy.

Here’s a closer look at these three solutions that freighters and tankers could start adopting today for cleaner shipping.

A return to wind power

For thousands of years, merchant sailors harnessed the wind to propel their canoes, caravels, schooners and brigantines across rivers and oceans. Then came the diesel engine, which made it possible to transport larger volumes of cargo around the world in less time, and with greater ease, than sailing ships and even coal-burning steamers. By the early 20th century, the number of vessels powered by canvas and mast began declining precipitously.

Now, the modern shipping industry is clawing its way back to wind power. A handful of scrappy ventures are building sailing cargo ships to haul modest batches of coffee, cacao, rum and wine between Europe and the Americas. Major shipping companies and their multinational customers, including Airbus and mining giant BHP, are installing high-tech wind devices to reduce vessels’ fuel consumption — and associated emissions — by anywhere from 5 to 20 percent per voyage.

Two white cylindrical tubes rise from the red deck of an oil tanker
Two Norsepower rotor sails rise from the deck of the Maersk Pelican tanker. (Maersk)

Wind is going to be essential in the short term if we’re going to get the emissions reductions we need to stay at 1.5 degrees,” said John Maggs, shipping director for Seas at Risk, one of the organizations that commissioned the CE Delft report.

An industry like shipping that is uniquely placed to use wind really should be going to wind first,” he added.

Around two dozen large ships have installed wind-assisted propulsion systems” — such as spinning rotor sails, towing kites and automated wing sails — to lessen the demand on their diesel engines. The number of hybrid vessels is projected to double by the end of this year, according to the International Windship Association. While that represents only a tiny fraction of the world’s merchant fleet, it still reflects significant growth for the emerging field.

This year and 2024 could be breakout years” for planning and ordering wind-harnessing devices on ships as the industry faces more pressure to reduce emissions, Panos Koutsourakis of the American Bureau of Shipping previously told the shipping news site Splash Extra.

Smarter, slower ships 

Another seemingly straightforward way for ships to curb their fuel consumption — and the emissions that come with it — is to sail at slower speeds. As a rule of thumb, a 10 percent drop in speed will reduce a vessel’s power demand by nearly 30 percent.

A growing number of startups has emerged in recent years to help vessels chart more fuel-efficient voyages. Companies combine data from satellites and onboard sensors with machine-learning tools to help ship operators set fuel-saving speeds, devise shorter routes, and avoid unfavorable wind conditions and time arrivals so that ships don’t wind up idling their diesel engines in congested ports.

If all ships made these changes, the industry could potentially eliminate 15 to 20 percent of its greenhouse gas emissions without disrupting global trade, according to industry studies.

Several workers stand in front of an array of electronic displays in the bridge of a cargo ship overlooking the ocean
The bridge of a cargo ship crossing the Indian Ocean (Camille Delbos/Art In All of Us/Corbis/Getty Images)

However, shipping companies historically haven’t been motivated to adopt such techniques, especially when the price of fuel is cheap. Often, they don’t have much choice to slow down. Contracts between a shipowner and the charterer” — the firm that hires the ship to move containers of T-shirts or piles of iron ore — can require the vessel to reach its destination as quickly as possible, even if that means burning more fuel at higher speeds.

That mindset is starting to shift, in part because fuel has become more expensive in recent years, and because companies are facing more pressure to decarbonize. As of January, shipowners are now required to reduce their carbon-intensity — a measure of a ship’s CO2 emissions, linked to the amount of cargo carried over a voyage — and will be graded on their performance under the IMO’s new rating system.

Some shipowners are adding virtual arrival” clauses to their contracts with charters. If it becomes clear during a vessel’s voyage that a berth won’t be available when it reaches port, the ship is then free to shift into slower gear. Singapore-based BW LPG, which hauls liquefied petroleum gas, said it avoided burning more than 500 metric tons of fuel last year by using this strategy, Bloomberg reported.

Nautilus Labs, a startup in New York City, recently launched a product that uses data analytics to update the industry’s decades-old ways of drafting legal agreements. To help companies determine the most efficient and profitable course vessels can take, Nautilus builds virtual replicas of cargo ships to simulate performance and operational outcomes — data that shipowners can use to define the parameters of more carbon-conscious contracts.

Matt Heider, CEO of Nautilus Labs, said his startup has seen more demand for its smart-planning technology since the start of this year. Hundreds of cargo ships use the company’s software platform to monitor and optimize their voyages, according to Nautilus.

What we’ve seen is that carbon-intensity [rules] drive behavioral change,” he told Canary Media.

Ditching diesel for cleaner fuels 

While windblown devices and fuel-saving software can help reduce shipping emissions immediately, the largest CO2 reductions are expected to come from replacing fossil fuels with cleaner alternatives.

Nearly all of the world’s cargo ships still burn heavy fuel oil and other petroleum products to ply the oceans. A small but rising number of ships run on liquefied natural gas. Of the 330 million metric tons (87 billion gallons) of marine fuels that the shipping industry consumes each year, practically none of it comes from low- and zero-carbon sources.

That’s now beginning to change — the only question is how rapidly it will happen.

A laboratory with industrial testing equipment
A Wärtsilä engineer performs early combustion tests using ammonia fuel blends. (Wärstilä Marine Power)

Maersk expects to launch its first methanol-burning container vessel in early 2024. Methanol is a common chemical (CH3OH) that’s primarily made today using fossil gas. But if produced using renewables, methanol can curb carbon dioxide emissions and eliminate harmful particulate matter when used as a marine fuel. The Danish shipping giant has 18 other methanol-powered ships in the works. Another major carrier, France’s CMA CGM, expects to have 24 such vessels in service by 2027.

Major manufacturers and startups are also racing to develop the world’s first ammonia-powered ships. Like methanol, today’s ammonia supplies are primarily made using fossil fuels in energy-intensive processes, but the chemical can be made in other ways. Ammonia doesn’t produce CO2 emissions when burned, and it’s considered a top candidate for replacing diesel in ocean-crossing vessels — despite it being a highly toxic and corrosive compound.

Later this year, the Finnish manufacturer Wärtsilä will start selling a marine combustion engine that’s capable of using a fuel blend of ammonia and a low-sulfur petroleum product. Wärtsilä is also partnering with Norwegian shipping firm Eidesvik Offshore to retrofit a small vessel with an ammonia combustion engine by late 2025. The two companies are part of a separate initiative in Norway to install a 2-megawatt fuel-cell system on a supply vessel, which is set to begin operating on ammonia in 2024.

Meanwhile, in the United States, the Brooklyn-based startup Amogy is converting a 65-year-old tugboat to use its ammonia-to-power system, potentially later this year.

The industry is still a far cry away from getting 10 percent of its energy from ammonia-fueled engines, as envisioned in the CE Delft analysis. But the first-of-a-kind projects now under development are expected to be the first of many vessels to come, enabling sweeping reductions in shipping industry emissions over the next few decades.

To preserve the possibility of keeping warming below 1.5 degrees, it’s no good delaying,” Maggs of Seas at Risk said of shipping’s clean-energy transition. Cuts have to happen immediately.”

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