German boffins aim to burn natural gas - WITHOUT CO2 emissions

Top boffins based in Germany - including a Nobel Prize laureate - believe they may be able to largely eliminate carbon emissions while nonetheless permitting the human race to use cheap and convenient fossil fuels as much as it likes: and this doesn't involve any tricky and probably expensive capturing of CO₂ which must then be crammed into old gas fields or something.

No, the technology being worked on by the brainboxes of the Karlsruher Flüssigmetalllabor (Karlsruhe Liquid-metal Laboratory, KALLA) and the allied Institute for Advanced Sustainability Studies (IASS) is more cunning than that. They are looking for a way to burn natural gas - and not just in power stations, but potentially powering vehicles, heating etc - without creating any carbon dioxide at all.

They're looking to do that by making methane (CH₄), the main compound in natural gas, into straight hydrogen and carbon. The hydrogen can then be burned as a fuel - in a fuel cell, a combustion engine, a boiler, anything you like - and the resulting exhaust will be harmless water rather than possibly planet-busting CO₂.

There have, of course, been many schemes for a hydrogen powered future. Most have assumed that the necessary large amounts of the gas would be produced using electrical power to split it out of water, a process involving no carbon emissions. Unfortunately that plan requires huge amounts of electricity, amounts which realistically cannot be produced by any likely level of renewable power. One might instead go for nuclear electrcity, but this is often seen as too unpopular.

In reality at the moment, hydrogen is produced industrially by steam reforming of natural gas. This is much cheaper than using 'leccy (and immensely cheaper than using renewable 'leccy) but it does involve creating and emitting CO₂: so much so that hydrogen-powered vehicles or other machines fuelled using this process would often be responsible for more emissions than ones running on fossil fuel.

But the process being worked on in Germany is quite different. KALLA spokespersons describe it like this:

The liquid-metal bubble column reactor [Flüssigmetallblasensäulenreaktor - FLUMBLAR, perhaps] to be built up at KALLA in the next months is a vertical column of about half a meter in height and a few centimeters in diameter. The column is filled with liquid metal that is heated up to 1000°C. Fine methane bubbles enter the column through a porous filling at the bottom. These bubbles rise up to the surface.

“At such high temperatures, the ascending methane bubbles are increasingly decomposed into hydrogen and carbon,” explains Professor Thomas Wetzel of KALLA. “We will study how much hydrogen can be produced."

The Flüssigmetallblasensäulenreaktor is an attempt to solve the problem of carbon buildup. Earlier attempts to break methane up into carbon and hydrogen in a gaseous state were stymied by the way that carbon soot built up on the chamber walls, rapidly clogging the gas channels and bringing the process to a grinding halt.

"The shell of the bubbles assumes the role of the wall,” explains Wetzel. “Only when the bubbles burst at the surface of the liquid metal, is carbon released. The reactor wall is constantly renewed.”

“This is a truly pioneering experiment with the ambition of using fossil fuels without CO₂ emissions,” declared Nobel Prize laureate Professor Carlo Rubbia, during a visit to the facility last month. Rubbia and IASS colleagues carried out the earlier work on the methane-in-gas reaction, and will be collaborating with the KALLA team on the new liquid-metal bubble tech.

Even if successful, the Flüssigmetallblasensäulenreaktor would no doubt face some objections. Hydrogen, though dense with energy compared to other green-energy storage media such as batteries, is nonetheless inconvenient and dangerous (hence, expensive) compared to fossil fuel. Methane itself is a much stronger greenhouse gas than CO₂, and even relatively small leakages of it during natural gas production, refining etc might be seen as a problem. It isn't yet clear how much energy will be used up in the process of turning methane into hydrogen, but this will plainly be non-trivial as metal has to be kept molten for it to happen.

But there is at least some prospect here of powering the human race with very low carbon emissions - not just the few per cent of its needs met by electricity, but just about everything - using potentially abundant natural gas rather than cripplingly expensive, sharply limited renewables or politically contentious nuclear means.

So the Flüssigmetallblasensäulenreaktor is interesting, if nothing else. ®