Scientists at the Vienna University of Technology have developed a method of combusting natural gas which allows the resultant carbon dioxide to be separated out without expanding any additional energy.

Currently, when natural gas (methane) is burned, CO2, together with nitrogen, water vapour and other substances, is part of the flue gas mixture. These impurities come from the air in which the methane is burned. In this mixed form, the CO2 cannot be stored nor readily recycled.

In the new combustion method, the natural gas does not come into contact with the air at all.

A granulate made of metal oxide circulates between two chambers. Air is pumped through one chamber in which the granulate particles take up oxygen. The particles then move on to the second chamber, which has natural gas flowing through it. Here the oxygen is released and flameless combustion takes place, producing just CO2 and water vapour.

Having the two chambers means there are two separate flue gas streams – one comprising air with a reduced concentration of oxygen and the other water vapour and CO2. The water vapour can be separated quite easily, leaving almost pure CO2, which can be stored or used in other applications.

The researchers have developed the technology to the stage of being able to begin work on a 10 megawatt demonstration facility. They are also working on a method of burning biomass in a way which will produce just CO2 and water.