Risø DTU Investigating Production of Synthetic Transportation Fuel from Renewable Electricity and CO2

. Nørskov from DTU Physics.

The Fuel Cells and Solid State Chemistry Division is working with two electrolyte types. One is a mesoporous ceramic material, which can absorb liquid electrolytes in their nanopores and retain them. The second type is low-temperature proton-conducting materials which uses a solid ceramic electrolyte.

Limestone from the Danish subsoil can be used to produce sustainable synthetic fuels. Source: Risø. Click to enlarge.

Limestone in the production of sustainable synthetic fuels. It is hard and costly to directly separate CO₂ from the atmosphere. Professor Mogens Mogensen therefore envisages the necessary CO₂ coming from other sources such as breweries and second-generation bioalcohol plants, where fermentation produces large volumes of CO₂. Another local possibility is using Denmark’s most widespread raw material, limestone (calcium carbonate). Heating limestone liberates CO₂, leaving quicklime (calcium oxide). Water is mixed—or ‘slaked’—with quicklime, producing slaked lime (calcium hydroxide), whereby most of the heat which was used is again released.

Slaked lime reabsorbs CO₂ from the air relatively quickly. Slaked lime mixed with sand is called mortar, which has traditionally been used as a binding paste in masonry. The wet mortar between the bricks absorbs CO₂ from the air and hardens through the formation of lime to a stone-hard substance that binds the bricks together.

In other words, the lime is part of a carbon cycle. The CO₂ which is released when the lime is burnt is absorbed again when the slaked lime absorbs CO₂ and is thereby converted back to lime. This cycle can be used to manufacture synthetic CO₂-neutral fuel, Mogensen suggests.