Shipping lines must comply with new global emissions controls. Ian Taylor reports

All ships over 400 tonnes became subject to International Maritime Organisation (IMO) limits on sulphur emissions from January 1.

These cut the permissible sulphur content in ship fuel outside designated emission control areas (ECAs) from 3.5% to 0.5%. The limit remains 0.1% in these control areas – the Baltic Sea, the North Sea, North American coastal waters and the ‘US Caribbean’.

The cruise industry accounts for just 1% of the shipping and 2% of global outbound travel but claims to be at the forefront of cutting emissions.

However, the shipping sector has moved painfully slowly. The January limit on emissions of sulphur oxide – a toxic by-product of heavy fuel oil – was agreed in 2008.

Cruise association Clia announced last year that its members were “well on the way to full compliance”.

However, the IMO warned of “price volatility” until “supply and demand find a balance” with the marine oil required to replace the heavy fuel oil commonly used by ships costing up to 50% more.

There are concerns about supply and about inconsistent enforcement, given the IMO limit is policed by ports and ‘flag states’ – the countries where ships are registered.

Broadly, there are three ways of complying – switching to marine fuel oil, investing in liquified natural gas (LNG) technology or installing exhaust cleaning systems.

There are serious issues with all three.

Switching to marine diesel cuts the sulphur content but the fuel still contains many times more pollutants than vehicle diesel. Ships must also beware of mixing fuels which can be unsafe.

Using LNG cuts sulphur emissions almost entirely and nitrogen oxide by 85%. Clia suggests 25 ships or about 12% of the global total could be using LNG by 2025. But the primary component of LNG is methane, an accelerant of global warming.

There are also limits to LNG infrastructure, with fuelling stations only slowly being established in Europe.

Exhaust cleaning systems or scrubbers enable ships to continue using heavy fuel oil by removing the sulphur – dissolving it in seawater which is returned to the ocean as sulphuric acid or held on the ship to be disposed of on land.

Royal Caribbean Cruises vice-chairman Adam Goldstein has said: “You inject tremendous amounts of water into the exhaust and it takes the sulphur away. That is our principal strategy.”

Clia reported in September that more than 68% of global capacity would utilise scrubbers. But China, Hong Kong, Singapore and some Caribbean islands have banned the release of water from scrubbers and there is a call for a worldwide ban.

Cruise lines also try to cut emissions in port by using shore-side power. But only 16 ports offer this – and only three outside North America.

Shipping sector leaders agreed in December to establish a $5 billion fund for research and development into cutting emissions, with the aim of developing zero-carbon emission ships by the 2030s.

Companies would make a $2 contribution for every tonne of marine fuel they purchase from 2023 if governments back the proposal at a meeting in London in March.