Big cargo ships, big pollution

The world runs on unsustainable maritime shipping

Alex Hureau
Age of Awareness
Published in
6 min readFeb 8, 2021


Blue cargo ship filled with containers.
Photo by Ian Taylor on Unsplash

Have you ever asked yourself how things get to where you are?

Bananas from Ecuador? No problem. A computer from China? It’s waiting for you. Clothes from Bangladesh? Of course.

Sure, there’s a lot of buzz going around about Amazon’s supply chain, but that’s usually the end of the journey for a given product. Before it gets to the merchant or the warehouse that will dispatch it to you, it has to be grown or manufactured. And, since many products originate from abroad, it has to be shipped.

Often overlooked, the shipping industry serves as the bloodstream of our modern, globalized world. It also represents 10% of all global transport GHG emissions, a number which could rise by up to 250% by 2050. In addition, a single cargo ship may cause the same health issues as 50 million cars due to the use of low-quality bunker fuel. This is in addition to other issues such as the movement of species through the ballast water (pumped to keep the ships more stable), and the occasional oil spill or loss of cargo.

Despite this, the industry has managed to continue operating with very little oversight, having been left out of international treaties such as the Paris Agreement. To this day, even though the public and governments are starting to demand change, there is very little public information about what the world’s largest shipping companies are up to when it comes to the environment. The shipping industry is in need of reform and innovation, and this change needs to happen now.

Cargo ship near a dock at night.
Photo by Julius Silver from Pexels

Cargo ships are big

It’s hard to imagine how large cargo ships are because most of us don’t hang around cargo ports on a regular basis. Common factors that dictate the maximum size of a ship include Suezmax and New Panamax. These are essentially standards dictating the maximum size a ship can have and still cross the Suez Canal and the Panama Canal. The former has a limit of 400 meters long, while the latter stops at 366 meters. Unsurprisingly, many ships aim for these upper limits, allowing them to transport vast amounts of cargo while reducing transit time as much as possible.

Of course, these extremely large ships need extremely large engines to power them, and as the size of freighters continues to expand, so does the size of their powertrain. It’s not uncommon to find engines that stand multiple stories tall and can deliver over 100,000 horsepower. As you might expect, the fuel consumption that goes along with it is equally impressive. A somewhat efficient engine may consume as much as 1,660 gallons (7,547 litres) of bunker fuel per hour.

Now imagine the cumulative impact of these ships going around the world.

Cargo ship under cranes.
Photo by David Dibert from Pexels

Emissions are also big

The thing is, bunker fuel is nothing like the oil you use in your car. Most commonly, it is diesel of such low quality that it is almost a waste when looking at oil refining. Of course, along with making it extremely cheap to run, it also makes it extremely polluting. While the global warming impact is certainly high, the other pollutants emitted by cargo ships are also very alarming. A study estimated that global maritime shipping was responsible for up to 250,000 deaths annually due to air pollution, and up to 6.4 million childhood asthma cases.

While there are restrictions when close to shore, these ships spend most of their time in international water, where there is little supervision and the level of enforcement is low. In fact, penalties for non-compliance with environmental rules have been a large point of debate in the creation of international agreements. The maritime industry is slow to adopt new environmental standards on its own, and as all is tradition in international affairs, governments have a hard time coming to an enforceable agreement.

Sinking rusty cargo ship.
Photo by Jason Blackeye on Unsplash

There are other environmental impacts

Of course, air pollution is but one negative environmental impact that maritime shipping has. It would take a very long time to cover them all, but these include the aforementioned movement of species through water ballasts and the spills that periodically occur.

Ships the size of those found in the maritime shipping industry often carry large amounts of water as ballast which they collect near the coast of one country and dump near another. In turn, they carry animals and plants from one place to the next, potentially introducing invasive species. A convention was adopted in 2004 to try and deal with this problem, but many countries still haven’t signed on, including large actors such as the United States. Fun fact, the International Maritime Organization apparently doesn’t have a page for the convention either.

Spills and cargo losses need no introduction. Every few years, a large oil spill makes the news, but only if it’s large enough. Meanwhile, some beaches have become famous for the peculiar things that wash up on them because of cargo that was lost at sea.

3D render of a futuristic cargo ship with sails.
Image by Oceanbird

Cool tech and innovation

Thankfully, the world is not completely asleep when it comes to the future of the maritime industry, and there is a constant flux of innovation that has been happening over the past few years. Though whether or not some of these reach a large enough scale to make an impact will likely depend on the price of oil and pressure from investors and governments.

Some of these innovations involve going back to previous technologies. Cargill, for instance, wants to add large sails to its cargo ships in a bid to reduce their emissions by up to 30%. There is also at least one company that aims to use modern technologies to make highly efficient cargo ships powered by sails, though at a much smaller scale than used in the current industry.

There is also a lot of research happening to find alternative energy sources. Ranging from biofuels to synthetically produced fuels powered by renewable energy, there are many options out there. The problem remains that these will only truly be adopted if they have an economic benefit for the shipping companies, or if they are incentivized or forced to innovate.

Sunset over a cargo ship in the distance.
Photo by Roger Hoyles on Unsplash

Most of the things in your life have been shipped by cargo — from the food you eat, to the clothes you wear. Even if a product is manufactured locally, the odds are that parts and materials were shipped. Our globalized world trives on this interconnectedness, and, for better or worse, the maritime industry will keep getting bigger to meet the growing demand. The pressure is mounting for change to happen, but it’s still too slow. We need people to start demanding stricter environmental regulation, governments to get on board existing regulations while pushing for new ones, and companies to step up and bring innovation to a sector that is so desperately in need of it.