With the help of the right microbes, hydrogen and carbon dioxide (CO₂) can combine to form methane and water. If we feed this process with CO₂ captured from industrial processes and hydrogen produced on an electrolyser using renewable electricity, we have the means to produce ‘green gas’.

But, why might we want to use hydrogen, which is a combustible and readily transportable gas, to produce methane, which has similar properties?

Part of the answer is quite simply that our gas distribution infrastructure has been built to distribute methane. Methane has a higher heating value than hydrogen per cubic metre – so fair metering and invoicing also comes into the equation.

Furthermore, in many European countries, we must find a reliable way to balance out the seasonal imbalance of renewable electricity generation, which peaks in the summer and the demand for energy, which peaks in the winter. Conversion of hydrogen to methane for long-term underground storage is one way to address that annual supply and demand imbalance.