New system can turn green house emissions into fuel

MIT scientists have developed a new system that can convert carbon dioxide and other green house gases into useful fuel for cars and aircraft, as well as chemical raw materials for a wide variety of products.
The system involves a membrane - made of a compound of lanthanum, calcium, and iron oxide - that allows oxygen from a stream of carbon dioxide to migrate through to the other side, leaving carbon monoxide behind.
Carbon monoxide produced during this process can be used as a fuel by itself or combined with hydrogen and/or water to make many other liquid hydrocarbon fuels as well as chemicals including methanol (used as an automotive fuel), syngas, and so on.

The process could become part of the suite of technologies known as carbon capture, utilisation and storage, (CCUS) which, if applied to electricity production, could reduce the impact of fossil fuel use on global warming.
The membrane, with a structure known as perovskite, is "100 per cent selective for oxygen," allowing only those atoms to pass, said Xiao-Yu Wu, from Massachusetts Institute of Technology (MIT) in the US.
The separation is driven by temperatures of up to 990 degrees Celsius, and the key to making the process work is to keep the oxygen that separates from carbon dioxide flowing through the membrane until it reaches the other side.

This could be done by creating a vacuum on side of the membrane opposite the carbon dioxide stream, but that would require a lot of energy to maintain.

In place of a vacuum, researchers use a stream of fuel such as hydrogen or methane. These materials are so readily oxidised that they will actually draw the oxygen atoms through the membrane without requiring a pressure difference.
The membrane also prevents the oxygen from migrating back and recombining with the carbon monoxide, to form carbon dioxide all over again.
Ultimately, and depending on the application, a combination of some vaccum and some fuel can be used to reduce the energy required to drive the process and produce a useful product.

The energy input needed to keep the process going is heat, which could be provided by solar energy or by waste heat, some of which could come from the power plant itself and some from other sources, Wu said.
The method may thus not only cut greenhouse emissions; it could also produce another potential revenue stream to help defray its costs, researchers said.