Liquified natural gas (methane) is the cleanest fossil fuel: it emits no particulates, significantly less carbon dioxide than oil, almost no nitrogen oxide, and zero sulphur dioxide. It also has an energy density some 600 times greater than gaseous methane. If produced in a carbon-neutral way, it makes an ideal alternative fuel for shipping, heavy goods vehicles and to replace heating oil.

Back in 2020, the Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) began a project to demonstrate an end-to-end process chain for producing synthetic, carbon-neutral liquefied natural gas (eLNG), with the goal of developing industrial use concepts for the fuel. The project “eLNG from air” was funded by the Baden-Württemberg Ministry of Economics.

The production technology used by ZSW included an apparatus for extracting CO2 from air, an electrolyser for generating green hydrogen (H2) powered by renewable energy, and a new technology for synthesising and liquifying the regenerative methane. After the project’s successful completion, the technology can now be transferred to industry.

Dr Marc-Simon Löffler, head of the ZSW’s Department of Renewable Energy Sources and Processes, describes the ‘Eureka’ moment when the liquid methane first trickled into the receptacle: "The amount of liquid methane was still small, but the proof of concept had been provided," he says in a press release. The laboratory is only capable of producing small quantities – a maximum of one kilogram per hour – but the scientists have developed scaling concepts and believe the process could be optimised to achieve an efficiency of 55 percent.

"The plant concept opens up opportunities for companies in different sectors. In particular, the technology for extracting CO2 from air is not only an important component of the eLNG process chain, but also promises great development prospects beyond that in the global market for climate protection measures," summarises Maike Schmidt, who heads the Systems Analysis Department at ZSW.