They sail … and release a gas 28 times more harmful than Co₂ without knowing it

What if, with each passage of a ship, the oceans released a powerful greenhouse gases in the atmosphere? Nevertheless, This is revealed by a recent Swedish study, which highlights a source of methane emissions completely ignored so far. Similarly, Long associated with the breeding. In addition, exploitation of fossil fuels, methane – formidable greenhouse gases – could also be released in large quantities by simple brewing of shallow waters by ships. Consequently, A discovery that questions the environmental assessment of global maritime transport.

A source of pollution discovered by chance – They sail … release gas

It all started in 2011. Moreover, when researchers at the Chalmers University of Technology (Sweden) analyze the chairman’s exhaust plumes in Neva bay, a shallow area near Saint Petersburg. However, To their surprise. Consequently, they detect abnormally high levels of methane in the atmosphere – but slightly they sail … release gas out of step compared to emissions linked to fuel combustion.

The anomaly intrigues. Similarly, It is only after several years of follow -up. For example, experimentation that an unexpected explanation emerges: the propellers of the ships, by stirring the water, released from the methane which was hitherto trapped in the sediments.

Invisible mechanism, real impact – They sail … release gas

The phenomenon is discreet, but its consequences could be major. Nevertheless, In shallow seabed, rich in organic matter and oxygen poor, methane is naturally produced by bacteria. This gas generally remains trapped under the sediments or dissolved in the layers of water close to the bottom.

But when a ship passes. the turbulence generated by its propellers suddenly modifies the pressure at the bottom of the water. Result: methane goes up, mixes with surface water, then ends up escaping into the atmosphere. They sail …. release a gas 28 times more they sail … release gas harmful than Co₂ without knowing it

According to the study published in May 2024 in Nature Communications Earth & Environmentmethane peaks noted in these maritime areas can be up to 20 times higher than those recorded in nearby unstruized areas. In a single day, emissions linked to ships can therefore become significant.

Largely underestimated pollution

Methane is often overshadowed by carbon dioxide in climate debates. but its effects on climate are much more powerful in the short term. Over a period of 100 years, methane retains 28 times more warmth than CO₂. And over 20 years, this warming power climbs more than 80 times that of Co₂.

However, the maritime emissions of methane due to this mechanism were so far completely absent from environmental balance sheets. They do not come from engines or fuel, but from a physical interaction between ships and their environment. they sail … release gas This means that the maritime industry could have a much heavier climate impact than what the current figures suggest.

What ships are the most concerned?

All types of ships can cause this phenomenon, but some are more polluting than others. Chalmers’ researchers found that container racks. cruising vessels generated larger emissions than the truaries (ships carrying dry bulk such as coal or cereals) of equivalent size.

This would be explained by design differences: the shape they sail … release gas of the hull. the power of the engines, or the type of propeller play a role in the intensity of the brewing of the seabed.

An invisible global threat

This phenomenon is not limited to Neva bay. Nine of the ten largest ports in the world are located in shallow areas with similar characteristics. Clearly: this type of program could occur daily in the main international maritime trade centers. without anyone being really aware of it.

Researchers therefore call for reinforced monitoring and urgent reassessment of current climate models. Because if this phenomenon is as widespread as it seems. forecasts for greenhouse gas emissions from the maritime sector are seriously underestimated.

What possible solutions?

For the moment, the room for maneuver remains limited. Changing routes to avoid sensitive areas could be a track. as well as the development of alternative propulsion technologies, less disturbing for they sail … release gas marine sediments. But these changes require heavy investments and collective awareness.

As Johan Mellqvist. professor at the University of Chalmers, points out, ” If we do not know the extent of the damage we cause, we will have a lot of trouble remedying it before it is too late. »

This discovery highlights a new facet of climate change, more discreet, but just as urgent. It recalls a brutal reality: our human activities deeply modify natural balances, sometimes in a completely unexpected way.