After all, around 90% of world trade is carried by sea – at an average of 1.5 tonnes per person each year. This is largely because shipping is the cheapest way to move raw materials and goods across large distances. It contributes just 0.3p to a £2.50 cup of coffee, for example. Or $5 to a $100 pair of shoes. It is without doubt one of the most important enablers of globalisation.

Shipping’s environmental impact

But all this consumer choice and ready availability comes at a growing environmental cost. The majority of container ships run on cheap ‘bunker’ fuel which emits more carbon dioxide per gallon than other transport fuels. And with more and more goods travelling greater distances, the problem is becoming more acute. Shipping is now responsible for almost 3% of global CO₂ emissions. If left unchecked, that could rise to a massive 17% by 2050.

The problem is that shipping is considered one of the hardest industries to decarbonise. Moving thousands of tonnes of cargo across the ocean requires huge amounts of energy: one large container vessel uses the same amount of energy each day as 50,000 homes. Right now, alternative propulsion methods like electricity or hydrogen are either too unsafe, too expensive or simply not as effective as bunker fuel.

It’s not that shipping hasn’t cleaned up its act at all. Incremental improvements to aspects like fuel efficiency meant CO2 emissions in 2018 were 7% lower than ten years previously, despite a 40% rise in maritime trade. But in the long run, this won’t be anywhere near enough.

Sustainable shipping targets

In 2018, the International Maritime Organization’s (IMO) Marine Environment Protection Committee set targets to cut shipping’s carbon emissions by at least 40% by 2030 as well as halve greenhouse gas emissions by 2050 from 2008 levels.

The industry’s biggest player, Maersk, has called for further action. CEO Soren Skou has said consumers could pay a little more for their goods to fund greener shipping technologies. He has also suggested the IMO should introduce a global carbon tax in the next few years. The EU, as part of it’s Green Deal, recently proposed adding shipping to its carbon trading market. This would mean ship operators would have to pay for their emissions when using EU ports.

Cleaner propulsion options

Funding for greener technologies will certainly be needed. There are a variety of exciting solutions under exploration, but decarbonising shipping is likely to cost more than $1 trillion.

Just like on land, electricity could have a vital role to play, and the world’s first electric container ship is set to launch later in 2021. The 80-metre-long Yara Birkeland will have enough batteries on board to produce 9 megawatts of energy – the same as 90 Tesla Model S batteries. But as a sign of how far electric shipping still has to go, its cargo capacity will be just 120 TEU (20-foot equivalent units), compared to the 20,000-plus TEU capacities offered by the world’s largest container vessels.

Could hydrogen provide the answer? Some members of the shipping sector are certainly optimistic and there are already pilot projects underway, mostly involving ferries.

Here, too, there are major hurdles to overcome, though. Liquid hydrogen storage takes up vast amounts of space – a crucial factor for cargo ships. And then there’s the problem of production. Hydrogen fuel cells may be emission-free, but 99 per cent of hydrogen itself is currently produced using fossil fuel methane. So-called ‘green’ hydrogen can be made via renewable energy, but this remains prohibitively expensive and energy inefficient.

One potential compromise is ammonia – a mixture of hydrogen and nitrogen that has nearly twice the energy density of liquid hydrogen. MAN Energy Solutions plans to deliver ammonia-powered ship engines by 2024. However, the problem of turning ‘grey’ hydrogen into green hydrogen remains.

Long journey ahead

In reality, there is no single solution to the sustainable shipping puzzle. Seriously reducing emissions will require a combination of low- and zero-carbon propulsion systems.

Other technologies, like increasingly ‘intelligent’ AI-powered control systems, will also play a part in improving fuel efficiency for existing vessels. This is important: revolutionising an entire industry is a slow process. Ships typically stay in service for around 25 years. Approximately 80% of the 56,000 cargo vessels in service today will still be carrying your electronics, clothes, furniture and more in 2030.