No escape for methane

The benefits of LNG as a fuel are undisputed, but the emission of methane in the course of combustion could cancel out its positive climate impact. A key issue for the future that presents challenges for MAN Energy Solutions too.

Liquefied Natural Gas – LNG for short – is supposed to clean up shipping, not to mention power plant operation, with its lower carbon emissions, zero sulfur emissions and zero particle emissions. Perfect, you might think, were it not for a small but serious shortcoming that needs to be dealt with urgently. We are talking about methane, which makes up 85 – 95 percent of LNG. When LNG is burned, small amounts of methane (CH₄) that become significant when added together can escape into the atmosphere, where they prove to be several times more harmful to the climate than carbon dioxide (CO₂). The more LNG is used as fuel, the higher the methane emissions and the greater the potential threat to our atmosphere. This issue is currently worrying manufacturers of large engines. How is MAN Energy Solutions tackling the challenge presented by methane slip?  

“We are putting a lot of resources into minimizing the amount of methane that escapes into the atmosphere,” says Gunnar Stiesch, Head of Engineering. “This includes looking at the issue in its entirety. The whole natural gas supply chain needs to be made ‘escape-proof’, so to speak.”

Gunnar Stiesch

There is already a solution for two-stroke engines. In ­ME-GI dual-fuel engines, LNG is injected straight into the combustion chamber just after a liquid pilot gas has initiated ignition – the same principle as for diesel. This technique minimizes unburned residues, enabling MAN to guarantee very low methane slip of 0.2 to 0.3 g/kWh throughout the load range of ME-GI engines.  

In the case of four-stroke dual-fuel engines, methane slip has already been halved in the past decade, with the result that combined CO₂ and CH₄ pollution is now well below the corresponding value for diesel engines running on liquid fuels. Our technical department is energetically pursuing several avenues with a view to further minimizing methane slip from four-stroke gas engines in the next few years.

The whole natural gas supply chain needs to be made ‘escape-proof’, so to speak

“We want to make it possible for our customers to continue enjoying the financial and environmental benefits of gas engines,” says Stiesch. Besides, LNG is the first step towards complete climate neutrality. Using liquefied natural gas lays the groundwork for the future use of synthetically produced fuels, making it a key element in the Maritime Energy Transition.