Methane at sea: In search of the invisible climate killers, so-called “green” (LNG) ships

T&E’s Methane at Sea survey of so-called “green” ships fueled with liquefied natural gas (LNG) reveals significant amounts of invisible methane being released into the atmosphere.

On a clear Monday morning in the port of Rotterdam, the ecodeltaa dredger, sets out to scrape the seabed, clearing the way for the gigantic cargo ships that pass through one of the world’s busiest ports.

That ecodelta is part of a new trend towards supposedly clean gas-powered ships. The names contain words like “eco” and are often painted green. But their green credentials end there.

Shipping is a huge source of CO2 emissions and the transition to clean fuels is slow. Traditional marine (bunker) oil is the dirtiest fuel there is, and shipping is responsible for about the same amount of global emissions as flying.

The shipping industry alongside oil and gas companies and many European politicians are pushing for liquefied natural gas (LNG) as a ‘clean’ alternative to traditional fuels.

On paper, LNG-powered ships emit less. There is no dark smog. But invisible to the naked eye, they have a dirty secret: methane. In fact, around 80% of the European LNG used by ships today is worse for the climate than the fuels they replace, due to the release of this powerful gas that is over 80 times more heating than carbon dioxide.

A major problem is that unburned methane leaks throughout the gas supply chain and enters the atmosphere, warming the planet faster.

In a first-of-its-kind investigation, T&E, with the support of hydrocarbon experts, went to sea to investigate methane leaks from ships.

The investigation found that significant amounts of unburned methane were being released into the atmosphere, with alarming effects on the climate.

These images show heat and gas emissions from the exhaust stack of ship engines. The bright light near the exhaust stack indicates a heat source. As the plume moves away from the heated exhaust stack, we can observe unburned hydrocarbon emissions.

Find the invisible

T&E conducted the survey on a clear November day in the port of Rotterdam – Europe’s largest.

Using a state-of-the-art infrared camera with a special filter to detect hydrocarbon gases, the T&E team embarked on a boat to track down known LNG vessels in the area.

According to an independent peer review of the images conducted by TCHD Consulting, an optical gas imaging consultancy, the images are from the ecodelta and a giant container ship owned by France-based CMA CGM Louvre is evidence that intense unburned hydrocarbon emissions were released into the atmosphere.

While the bright red flames indicate the heat source, the plumes escaping in the background are evidence of unburned hydrocarbon emissions. Although the combustion of hydrocarbon gases can result in different components, LNG typically contains over 90% methane. Therefore, the hydrocarbon emissions observed in this study consist mainly of methane.


The “Methane at Sea” survey of “green” ships using liquefied natural gas (LNG) uncovers significant amounts of invisible methane being released into the atmosphere.

According to CMA CGM, its LNG vessels enable a significant reduction in CO2 emissions per container and the company is investing heavily in LNG. According to its website, “LNG is the best solution currently available to reduce the environmental impact of shipping.”

None of his communications mention methane or how much methane typically slips from his vessels. Either the company is guilty of blatant greenwashing or, more worryingly, it is unaware of the climate damage it is causing.


CMA CGM includes LNG on its website under “Environmental Services” with statements such as “having a positive impact on public health and the environment with CLEANER ENERGY LNG”. There is no mention anywhere of methane emissions.

Europe’s dirty secret at sea: how the EU is promoting LNG

Shipowners commissioned more gas-powered ships in 2021 than in the previous four years combined, with LNG-powered ships being promoted as a clean alternative to traditional fuels.

Last year, the EU proposed carbon intensity targets for marine fuels that would force shipowners to move away from residual fuel oil, the most commonly used marine fuel today.

However, T&E has warned that without sustainability guarantees, this will simply lock in LNG as the cheapest alternative. Recent analysis by T&E shows that by 2025 more than two-thirds of new ships could be powered by LNG. This would increase the share of fossil LNGs from an estimated 6% today to over a fifth of all marine fuels in Europe by 2030, securing fossil fuel use for decades.

There are clean alternatives

LNG is a fossil fuel. Cleaning up one of the dirtiest sectors in the world is not the solution. The imminent threat of climate change means we can no longer release warming gases into the atmosphere.

To avoid this, the EU must adopt stricter greenhouse gas reduction targets for all ships calling and leaving European ports, so that the sector is emission-free by 2050 at the latest.

There are clean fuels. Green hydrogen-based fuels can massively reduce the climate impact of shipping, but they are currently expensive. If policymakers set binding targets and incentives for these fuels now, it would stimulate supply and demand and make them widely available at much lower costs.

Fossil gas does not play a role in the future of green shipping. Europe must end its dirty secret at sea now.

What is natural gas?

Natural gas/methane/LNG is a fossil fuel extracted from underground. It consists mainly of methane molecules, which produce CO2 when completely burned. Methane is much more potent than carbon dioxide, but it stays in the atmosphere for much less time. Methane is therefore 29.8 times more warming than CO2 over 100 years and 82.5 times more warming over 20 years, according to the IPCC 6th Assessment Report.

Natural gas is “gaseous” at normal temperature and atmospheric pressure. To facilitate transportation and storage, it is often liquefied at freezing temperatures, creating Liquified Natural Gas (LNG). Natural gas is used by many sectors, including households for heating in boilers and cooking in kitchens, but also by power plants to generate electricity. Increasingly, it is used for shipping.

Why is methane so bad?

Leaks and glitches occur throughout the natural gas supply chain. The use of LNG as a marine fuel is particularly problematic, since slippage occurs in marine engines. According to the International Maritime Organization (IMO), depending on the engine, between 0.2% and over 3% of the fossil gas escapes the combustion process and ends up directly in the atmosphere.

Because of this, about 80% of the LNG burned in shipping today is used in engines (low-pressure four-stroke engines), which have overall worse greenhouse gas emissions than conventional engines that run on dirty fuel oil. This is an estimate based on the fuel consumption of LNG-powered ships from the European data reporting system MRV and fleet characteristics from shipowners’ order books.


These images show heat and gas emissions from the exhaust stack of ship engines. The bright light near the exhaust stack indicates a heat source. As the plume moves away from the heated exhaust stack, we can observe unburned hydrocarbon emissions. Image courtesy of Transport & Environment

Delphine Gozillon, Maritime Officer at T&E, said: “Europe has a dirty secret at sea. By promoting LNG ships, European politicians are locking us into a fossil gas future. The ships may be painted green, but beneath the surface the truth is that most LNG ships on the market today are more harmful to the climate than the fossil fuel ships they are designed to replace.”

Originally published by Traffic & Environment.

Press Release: Methane Leaks from ‘Green’ Gas-Powered Ships Fueling Climate Crisis – Investigation.


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Jane Marczewski

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