Imagine a scenario where a greenhouse gas with more than 80 times the heat-trapping potential of carbon dioxide is allowed to be freely released into the atmosphere from ships with little to no consequences.
While this may sound unthinkable, this is the reality that the global shipping sector is experiencing every time methane leaks into the air – allowing fleets to sail on scot-free.
Compounding the issue is the maritime industry, which is alone responsible for roughly 3 per cent of global anthropogenic methane emissions. Estimates note that the increase in methane emissions is responsible for up to 30 per cent of the global temperature rise since the Industrial Revolution.
There is growing evidence that ships that transport or run on liquefied natural gas (LNG) in particular are responsible for a bulk of methane emissions due to methane leaking or “slipping out” from their engines during the combustion process.
LNG is natural gas that has been cooled down to liquid form to reduce its volume for ease of transportation and storage. While it emits lower carbon emissions and particulate matter compared to traditional marine fuels like heavy fuel oil, LNG produces significant methane emissions throughout its lifecycle via unintentional leaks.
This is deeply concerning, and why growing methane emissions from LNG carrier fleets as well as the uptake of LNG as propulsion fuel must be curbed in the near term to achieve net zero by 2050, said Panos Spiliotis, senior manager of EU transport and global shipping lead at the Environmental Defense Fund (EDF), a global non-profit organisation focused on tackling climate change and environmental issues.
Without additional policy action, shipping’s greenhouse gas (GHG) emissions are projected to increase by 16 per cent from 2018 to 2030 and by 50 per cent by 2050.
The International Maritime Organisation’s (IMO) Fourth Greenhouse Gas Study 2020 found that methane emissions from ships have ballooned in the last decade, increasing by 150 per cent between 2012 and 2018 due to the rapid growth in the use of LNG as a marine fuel. The IMO is a specialised agency of the United Nations responsible for regulating international shipping.
One of the main reasons for this is that methane is not regulated by the IMO compared to other individual pollutants like sulfur oxides, nitrogen oxides, and carbon dioxide.
“Regulations on these pollutants propelled the uptake of LNG – which are mostly methane – as a marine fuel. This is because it contains no sulfur, can achieve low nitrogen oxide emissions, and emits about 25 per less carbon dioxide than conventional marine fuels,” said Bryan Comer, marine programme director of the International Council on Clean Transportation (ICCT), a non-profit research organisation focused on improving the environmental performance and energy efficiency of road, marine, and air transportation.
Methane emissions from ships, Comer added, must be reduced because they are 80 times more potent than carbon dioxide with a 20-year global warming potential.
“Methane is responsible for about 30 per cent of the global rise in temperature. Reducing it is one of the most effective ways to limit near-term climate warming and is central to the efforts to limit global warming to 1.5°C.”
LNG and its effects
Reducing methane emissions from ships is crucial to achieving net zero with shipping industry emissions growing, especially via methane slip.
Methane slip is a process where unburned methane is unintentionally released into the atmosphere during the production, transportation, and use of natural gas.
The ICCT’s Fugitive and Unburned Methane Emissions from Ships (FUMES) study shows that the rate of methane slip from the most common LNG marine engine is 6.4 per cent on average. This is more than double that of European Union estimates of 3.1 per cent and almost twice as high as IMO approximations of 3.5 per cent.
The ICCT also traced fugitive methane emissions along the LNG supply chain, measuring between 24 to 40 kilogrammes of methane emissions emitted per hour when large LNG carriers offloaded their cargo at a European LNG terminal, with the ships’ LNG engines alone emitting 8 kgs of methane per hour.
“While the amount of methane released from these ships as a percentage of the cargo unloaded may be small, the methane emissions rates from the unloading operations are greater than those from the highest-emitting marine engines,” Comer said.
Within Asia, there are also concerns that growing LNG hubs in the region may significantly add to existing emissions, with nations such as Thailand, Vietnam, and the Philippines expanding LNG import capacity in recent years.
Another nation that has seen growth is Singapore, which traded about US$240 billion worth of LNG in 2022, with imports increasing by 35 per cent the following year.
LNG constitutes about half of Singapore’s gas imports, according to Lu Ming Pang, Gas and LNG research senior analyst at Rystad Energy, an independent energy research and business intelligence company.
“Singapore consumes about 13 billion cubic metres of gas, coming into the country by way of pipeline natural gas or LNG. It imported about 5.8 million tonnes of LNG in 2023, or equivalent to 7.8 billion cubic metres of natural gas,” Pang said.
Singapore LNG, the city-state’s largest LNG terminal, supplies roughly 9 million tonnes per annum (MTPA) of LNG, with a peak capacity of 11 MTPA, he added.
While these numbers may be concerning from a methane emissions standpoint, Pang pointed out that methane leaks generally stem from older carriers, which use low-pressure engines. The high methane-emitting carriers identified in the ICCT’s FUMES study, for instance, all use low-pressure, dual-fuel 4-stroke engines. They are also the most common LNG engines globally.
Newer LNG carriers, he noted, are more likely to be fitted with high-pressure engines allowing for less methane slip. “The bulk of LNG-capable new-builds will employ new high-pressure engines that will significantly reduce methane slip, allowing emission intensity levels that are lower than conventional bunker fuels,” Pang said.
But until LNG carriers that run using high-pressure engines are more prevalent, the city-state will have to find ways of managing emissions as its LNG hub grows. Singapore should nonetheless stick to LNG in the long term for its “benefits” as an alternative fuel, he added.
“As Singapore positions itself as an LNG bunkering hub with higher standards of emissions monitoring, the shift towards cleaner alternative fuels such as using LNG with the right engine, bio-LNG, E-LNG, methanol, or ammonia, is [still] the right step to take,” Pang said.
The IMO has been working to regulate other greenhouse gases like methane as a result of increased GHG emissions, added Comer, following a revision of its 2018 GHG strategy in 2023.
“We expect the first IMO methane regulations to be agreed in 2025 and enter into force in 2027. These measures will include a GHG fuel standard and some form of GHG pricing.”
Alternative fuel solutions and operational changes
While shipping has traditionally been seen as a difficult sector to green, much can be done to decarbonise at present – for example, through switching to cleaner fuels or maximising fuel efficiency through operational changes.
Fully transitioning shipping to zero emissions will require large-scale industrial transformation to green hydrogen-based fuels.
Green hydrogen is produced using renewable energy to split water into hydrogen and oxygen. Unlike hydrogen from fossil fuels, it does not produce carbon emissions during production.
“The fastest way to decarbonise is to implement a set of ‘quick win’ energy efficiency measures that can reduce emissions substantially in the next few years and kickstart shipping’s energy transition,” said Spiliotis, adding that measures include wind-assisted propulsion, reducing frictional drag on ships through air lubrication, and the use of batteries – all of which can reduce fuel consumption.
“Combined, these can deliver substantial emissions reductions in the next few years and help kickstart shipping’s energy transition,” he added.
Aoife O’Leary, the founder and chief executive of Opportunity Green shares a similar view. Her company is a non-profit that uses legal, economic and policy knowledge to advise on climate issues.
Half of the shipping emissions alone, O’Leary says, can be reduced through operational changes such as regularly cleaning the hull, ensuring propeller efficiency, and optimising the speed of ships when travelling.
Despite these solutions, policies remain rigid, with the shipping industry failing to factor emissions into existing operations and journeys.
“While the industry will say that fuel is one of their biggest costs, they fail to optimise their operations to reduce these costs,” she said.
More sustainable fuels such as methanol made from sources like waste biomass or from direct air capture, or renewable hydrogen, can achieve the same emission reductions without methane slip.
Scaling wider use, however, will require significant global investments in vessels and infrastructure.
“On the energy side, fuel production for shipping will draw on the limited production capacity of green hydrogen, ammonia, and methanol, all of which also have competing downstream applications,” added Spiliotis.
“To access and expand green fuel capacity, the shipping sector needs to provide credible demand signals so that investments in green fuel plants are ramped up,” he said, noting that while the EU’s FuelEU Maritime and upcoming IMO equivalent will take the industry part of the way there, market barriers could still impede capital flow.
Key policies and regulations
More stringent regulations will be key to driving down shipping industry emissions.
Regional regulations such as the Emissions Trading System (ETS) – the EU’s flagship cap-and-trade scheme – have already extended coverage of carbon emissions from all large ships (of 5,000 gross tonnage and above) entering EU ports in January 2024.
The system, which covers emissions from voyages starting or ending outside the EU, as well as emissions between and within EU ports, will expand to cover methane in 2026 and penalise ships that use high-methane-slip engines and offer an economic incentive to reduce their emissions.
Spiliotis said the ETS is already helping to cut the price gap between heavy fuel oil and green fuels, such as biodiesel in Asian bunkering hubs like Singapore.
“By effectively raising fuel cost, it is, along with other IMO measures, also incentivising the adoption of energy efficiency, though with a limited effect,” he explained.
“The EU ETS in its current set up will not be able to significantly reduce shipping emissions, as buying allowances will generally be more economical for shipowners and operators than reducing fuel burn.”
O’Leary agrees, noting that while no one policy is sufficient enough to decarbonise the shipping industry, the extended coverage of the ETS signals some progress as it will tax the shipping sector and could potentially generate revenue to produce cleaner fuels.
“There has been a real push from climate-vulnerable countries in the IMO to have a levy on shipping with some of that revenue supporting those who are affected by the climate crisis.”
“The shipping industry must address climate change. Even if [the ETS] doesn’t engage shipping emissions, it should as a carbon price,” she said. The shipping industry will ultimately fail to decarbonise without international regulations, concludes Comer, calling for quicker action from the IMO in developing effective policies.
While the IMO aims to achieve net zero GHG emissions by or around 2050 under its 2023 GHG Strategy, Comer adds, these goals are not legally binding – but the regulations that are developed to achieve these goals will be.
“It’s important that the IMO move swiftly, but it’s equally important that the IMO develops effective regulations that have reasonable assumptions for the baseline GHG emissions from ships. This is so that we don’t end up with only on-paper reductions in GHGs.”
