[Podcast] Shipping: If I Got a Cent Every Time…

Darren Hau
Published in
3 min readJun 27, 2022


Okay! We’re venturing outside the realm of my expertise. In the coming episodes, the landlubber tries to swim and we talk with industry experts and startup founders to try to figure out how the shipping industry will decarbonize. In our first two episodes, we spoke with Maria Gallucci, a clean energy reporter at Canary Media, and Bryan Comer at the International Council on Clean Transportation (ICCT).

This post is part of a Climate Now podcast series on the intersection of transportation and energy. I encourage you to listen to the full episodes yourself, as well as Climate Now’s other content. It’s chock full of science and data and nitty gritty stuff that often gets glossed over.

For a sense of scale, shipping moves 11 billion tons of goods each year, which is almost 300 times as much as the goods transported by air. While ships are far less carbon intensive than aircraft, the sheer volume of stuff means maritime shipping is responsible for 3% of global emissions. Container ships comprise ~25% of these emissions, bulk carriers (i.e. grain, coal) comprise ~20%, and oil tankers contribute another ~16%. As a matter of fact, fossil fuels alone make up 40% of those 11 billion tons moved by sea!

So how do we start tackling this issue? The easiest thing to do is to slow down the ships, since there’s a cubic relationship between a ship’s speed and the fuel it consumes. However, some industry structures and incentives make it difficult to fully leverage this trick. For example, under most charter agreements, the party contracting the ship will specify when it should leave one port and arrive at another, and the captain will determine the course and speed. When ports are as backed up as they are today, this could lead to ships arriving at port and waiting days to actually unload — time that could have been spent traveling more slowly. In other words, “hurry up and wait!”

There are a variety of technologies being proposed to reduce or eliminate carbon emissions, such as liquified natural gas, methanol, hydrogen, wind energy (rotary sails or kites), batteries, or even carbon capture. Each of these could deserve its own post, but based on her reporting Maria believes ammonia is emerging as the long-term solution.

On the positive side, ammonia produces zero carbon emissions (there are no carbon atoms), it’s more energy dense than hydrogen or batteries, and there’s already robust infrastructure for producing ammonia.

On the negative side, most ammonia today is made with fossil fuels, and it produces NOx emissions that contribute to air pollution. As a matter of fact, nitrous oxide (N2O) is itself a greenhouse gas with a warming potential almost 300 times as strong as CO2 over a 100 year period, and we don’t know how much will be emitted in a combustion engine. (This issue can be mitigated if ammonia is used in a fuel cell instead of a combustion engine.)

Furthermore, there are plenty of infrastructure challenges even though production facilities already exist. Ammonia refueling would require pipelines, storage, and other bunkering infrastructure. Ships would have to be redesigned — for example, including double-walled fuel pipes to reduce the probability that this toxic fuel leaks.

Finally, green ammonia is currently sitting at $500 per metric ton — 3x the cost of conventional fossil fuel-based ammonia. But if we take a step back, the shipping industry can theoretically absorb a lot of cost. If you double the cost of shipping, it would increase the price of a flat TV by less than a dollar.

In summary, ammonia’s certainly not a near term solution. A few ammonia-powered ships may be sailing within a few years but rolling them out at scale will require one or two decades. In future episodes, we’ll highlight some complementary solutions that could accelerate maritime decarbonization.