What does a zero-carbon shipping fleet look like?

Imagining a zero-carbon ship of the future.
Imagining a zero-carbon ship of the future.
Image: Oceanbird/Wallenius Marine
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Nine global retailers, including Amazon, IKEA, Unilever, Patagonia, and Inditex, the fast fashion retailer that owns Zara, announced today (Oct. 19) that they will aim to progressively switch to zero-carbon vessels to ship their goods by 2040.

The companies, who charter cargo space on ships by the millions of tons, were convened by the Aspen Institute nonprofit, and the announcement is intended to galvanize an industry that has so far been moving slowly toward reducing its carbon emissions. Shipping makes up about 3% of the world’s annual global emissions, a substantial share—if the ocean were a country, it would be the sixth largest CO2 emitter in the world.

“It’s an incredibly important signal to the shipping sector that there will be a market for this,” said Johannah Christensen, head of the Global Maritime Forum, a Copenhagen-based think tank for sustainability in shipping.

Resistance in the industry to assume the massive costs and risks, underinvestment in projects to advance technology on zero-carbon ships, and the daunting task of coordinating the global infrastructure—from refueling stations, to clean energy generation, and shipyards building new zero-carbon ships—has meant that the industry is far behind doing its part to meet the Paris Agreement’s goal to keep global warming below 1.5 degrees Celsius.

António Guterres, the United Nations secretary-general recently chastised the International Maritime Organization, a UN agency, for weak regulation and slack targets for the shipping industry that puts it on a track “more consistent with warming way above 3 degrees.”

But the drumbeat to decarbonize is building. In the last year or two, Christensen said, she has seen companies reclassify decarbonization from being side projects in the sustainability department to a “business critical issue” tackled in executive suites, after a realization that “there’s an existential risk involved for them” as vital customers like Amazon and IKEA demand emissions reductions. And while governments, so far, haven’t included shipping emissions in their national plans, some are now considering how to contain these emissions as well.

“There’s a significant development in the perception about what needs to be done,” Christensen said, “and the fact that it’s doable.”

What would a zero-carbon shipping fleet look like?

There are about 50,000 commercial ships in the world, nearly all burning marine fuel oil, a sludgy, noxious byproduct of oil refineries. Decarbonizing the fleet will require a mix of zero-emission fuels, alternative propulsion systems, and design efficiencies, as well as a reduction in demand for international shipping.

  • Fuels: Two fuels being widely explored are ammonia and hydrogen generated from renewable sources (called “green” as opposed to blue, gray, brown, or black versions, in which varying levels of CO2 are emitted during production). Both fuels can be burned in specially-designed internal combustion engines, or used in fuel cells. The Global Maritime Forum estimates that there are more than a hundred zero-emissions projects and demonstration pilots currently underway, with an increasing focus on hydrogen-based fuels. Lower-carbon fuels like methanol and second-generation biofuels from sources like used cooking oil can be used in the transition, though they cannot be scaled sustainably.
  • Propulsion and design: Modern cargo sails, which harness wind, a free, renewable resource, can be used in conjunction with zero-emissions fuels and off-set some of the extra costs. Efficiency measures, like smooth hull coatings, or a layer of bubbles under the ship reduce drag, reducing the amount of fuel required to move a ship across the water.
  • Demand: Reducing global demand for internationally shipped goods, by up to 17% according to a report published last week by the Abu Dhabi-based International Renewable Energy Agency, will be a part of achieving a 1.5 degree Celsius target. This would require a shift in consumer and industrial behavior at odds with current trends—international shipping is booming off the back of record high demand from American shoppers.

What are the challenges to making shipping climate-friendly?

Significant investment is required for technologies to mature and scale. Ammonia and hydrogen fuel cells and combustion engines will have to be developed and tested for commercial vessels that can weigh upwards of 100,000 gross tons and travel tens of thousands of nautical miles. The shipping industry currently uses about 4.5 million barrels of fossil fuels per day, and a sufficient supply of green fuels will need to be produced, for shipping as well as aviation, land-based transport and other industries that are expected to decarbonize using green hydrogen or ammonia.

Both fuels pose unique safety risks that must be mitigated. Ammonia is toxic to humans and can, during combustion, turn into laughing gas, which is worse for the environment than CO2. Hydrogen is highly volatile with a lower flash point than fossil fuels, and will likewise require special equipment and training.

The new fuel systems, which will include additional safety measures, engine changes and increased fuel tank capacity, will mean most of the current fleet would need to be phased out and replaced over the next 30 years. Green fuels are expected to cost 3-5 times more than marine fuel oil, and economic viability will be a factor in adoption of new fuels.

Charles Haskell, manager of the maritime decarbonization hub of Lloyd’s Register, a London-based classification society that ensures ships comply with safety regulations, said “It’s not a technical challenge, it’s an investment and community challenge,” referring to the role of government and industry policies in steering this.

Still, social pressure, from Greta Thunberg’s speeches to the din of companies in other industries announcing their zero-carbon commitments, has advanced the conversation. Other pressures from coalitions like the Sea Cargo Charter, which aims to make the sustainability of shipping lines more transparent to the companies that hire them, have created a demand for greener supply chains, as will Tuesday’s announcement by the Aspen Institute.

How much will cutting shipping’s emissions cost?

The Global Maritime Forum estimates a pathway to shipping’s decarbonization along an S-curve, in which there is a slow run-up to 2030, when 5% of ships should be using commercially-viable zero-carbon technologies, followed by a steep period of quick adoption of zero-carbon technologies by the majority of ships between 2030 and 2045. The final swoop of the curve will be the slow phase-out of the last fossil fuel-burning ships into 2050. Right now, the shipping industry, Christensen said, is on the S-curve, “but on the flat bit.”

According to a study commissioned by the forum, decarbonizing the shipping fleet and building out the land-based port and fuel infrastructure will cost about $1.9 trillion over 20 or 30 years. Another measure, by the Energy Transitions Commission, a London-based think tank, estimates the costs of decarbonization to add about 1% to the final cost of a finished good, the equivalent of adding $1 to the price of a $100 pair of sneakers.

The companies involved with Aspen Institute’s announcement did not lay out specifics of how and how much they will invest in decarbonizing the shipping industry, but signaled that they would work together to use their collective “market power” and “investment capacity” toward the goal.

“Whether or not shipping will decarbonize is no longer a debate. The question is rather how quickly we can get our collective act together, and which supply chain actors and nations will be poised to harness the vast business opportunity this transition represents,” Ingrid Irigoyen, director of the Aspen Institute Shipping Decarbonization Initiative, said in a statement.

The 2040 target is certainly a stretch goal. But if investment and regulatory policy align, it’s not inconceivable that container shipping could be significantly more climate friendly in 2040. Ships running on green hydrogen, and emitting just warm air and water vapor, or green ammonia, could refuel in new, solar-rich hubs like Morocco, or traditional bunkering ports like Singapore, using renewable fuels generated under the sun in Australia. Bulk carriers fitted with modern cargo sails could ply windy, ancient trade routes, and switch to green fuels on windless days or as they pull into port.

For Johannah Christensen, the shipping industry is entering an exciting moment after years of stagnation.

“I think one is always torn between intense optimism and intense pessimism,” she said. “I’m glad to see that the level of ambition in shipping has caught up with the rest of the world, which it now has. I’m terrified at how little time we have to make this happen.”