Slow steaming reduces carbon emissions, but making ocean shipping less attractive could do more harm than good.
Slow steaming reduces carbon emissions, but making ocean shipping less attractive could do more harm than good.
M arc Levinson, an economist and historian who has written extensively about the development of containerized shipping, warned about “the cost of slow” in a recent blog post. He writes:
A few days ago, I chatted with a shipping executive who made a bold prediction. The future of ocean shipping, he told me, is slow: the maritime industry faces great pressure to reduce its greenhouse gas emissions, he said, and steaming at lower speeds is the only way to do it. If my friend is right, he has identified an additional drag that will depress the growth of goods trade in the years ahead.
The International Maritime Organization, a United Nations agency, has prioritized reducing greenhouse-gas emissions from international shipping. The IMO estimates that shipping accounts for 2.89 percent of total anthropogenic carbon-dioxide emissions. The IMO’s goal is to reach “peak GHG emissions from international shipping as soon as possible and to reduce the total annual GHG emissions by at least 50% by 2050 compared to 2008.” These are all part of the U.N.’s overall climate goals.
Cargo ships are powered by bunker fuel. There are a few different blends of it, but it’s nasty stuff, thick like tar and containing higher levels of sulfur than other forms of fuel such as gasoline. Port areas often suffer from poor air quality (think Los Angeles smog), and governments in regions with lots of shipping make policies to protect air quality. Those policies can be reasonable, and it’s not a bad thing to strive to make ships more fuel efficient and pollute less.
But when zoomed out to the entire world, and guided by the environmentalist zealots at the U.N., pollution reduction could cause serious problems.
Rather than looking at shipping’s proportion of global carbon emissions, it’s more helpful to think of the rate of pollution per unit of freight. There is no more fuel-efficient and environmentally friendly way to transport one ton of freight over long distances than by water. Airplanes and trucks use much more fuel per ton of freight. Cargo ships benefit from massive economies of scale since their capacity is so much higher than any other mode of transportation, and the physical properties of water make things easier as well, requiring less energy to move the same amount of stuff.
Thinking of the rate of pollution, not the total, matters because ocean shipping has substitutes. It is true that slow steaming (the industry term for traveling at reduced speed) would reduce pollution, but it can add a week to a transoceanic journey, which would also make ocean shipping less attractive to shippers who handle time-sensitive freight. They aren’t just going to not ship their goods if ocean shipping doesn’t meet their needs. They’re going to put their goods on planes, trains, and trucks instead, which is worse for the environment.
Slow steaming is already a common practice to save money when oil prices rise. It’s also a way for carriers to adjust capacity to meet demand. Rather than canceling a sailing when demand goes down, which is very costly and throws off schedules around the world, carriers can run the same route at a slower speed, which reduces capacity in a less disruptive way.
But mandating slow steaming all the time as an environmental measure would take away that flexibility from carriers to meet market conditions, and it would increase costs to everyone involved. As Levinson points out, longer voyages mean more days to pay crews and other operational costs for carriers and longer container leases for shippers. Interest rates come into play as well, as he writes:
In recent years, with interest rates near zero, the shippers who own the goods aboard those vessels queuing for a berth at major ports haven’t faced much of a financial penalty due to longer transit times. But interest rates aren’t zero any more, and the cost of owning goods during longer trips across the seas is no longer negligible.
There are also diminishing returns to the environmental benefits. Cargo ships are generally designed to run at around 24 knots (nautical miles per hour). Slow steaming is defined as around 18–20 knots, which saves lots of fuel, but is also pretty common already. Extra slow steaming is 15–18 knots, but that is only commercially viable over short distances. Anything lower isn’t commercially viable at all (transit times would nearly double), and wouldn’t save much fuel, either, because the engine would approach the lower bound of idling.
Instead of trying to squeeze the last knot out of shipping speeds, it would be better for the environment to make ocean shipping a more attractive mode of transportation relative to land or air. In the U.S., that means repealing the Jones Act to bring down the costs of coastwise shipping and allow it to become a viable alternative to long-haul trucking and freight rail. Globally, that means giving ocean carriers more flexibility to meet shippers’ needs, not chastising them over 2.89 percent of the world’s man-made carbon emissions.