Waste not, want not! Convert CO2 back into fuel

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ELCAT
With the levels of carbon dioxide (CO2) in the atmosphere increasing inexorably, scientists are urgently looking for ways to reduce emissions. At the same time, rising energy prices are escalating the need to find alternative fuel sources.

But what if we could kill two birds with one stone by capturing the CO2 and converting some of it back into fuel? The EU-funded ELCAT (Electrocatalytic Gas-Phase Conversion of CO2 in Confined Catalysts) project has proven the feasibility of a technique which could do exactly that. Although the technology is still in the early phases of development, the project partners hope it will be ready for application in around 10 years, when it could help to cut global CO2 emissions by 5 %. This would give a significant boost to EU targets to cut CO2 emissions by 20 % by 2020.

Meanwhile, ELCAT is already attracting interest from around the world, and the technology it is using is one of just 10 technologies to have been nominated for the USD 25 million (EUR 15.7 million) Virgin Earth Challenge award. Set up by former US Vice President Al Gore and British entrepreneur Richard Branson, the prize will go to the first scientists to come up with ‘a commercially viable design which results in the removal of anthropogenic, atmospheric greenhouse gases so as to contribute materially to the stability of Earth’s climate’.

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An idea is born

The project evolved from an idea to an EU-funded consortium through a virtual laboratory created seven years ago by French, German and Italian scientists to generate ideas and hold discussions. During one of the sessions, ideas were swapped on how CO2 can be addressed in an unconventional way, and from this grew the idea for ELCAT.

Scientists from the University of Messina in Italy, who were involved in the virtual laboratory, observed an electrocatalytic reaction, in which a catalyst was used to convert carbon dioxide into hydrocarbons and alcohols at room temperature and atmospheric pressure.

The products of the reaction were similar to those produced by the so-called Fischer-Tropsch (FT) process, in which carbon monoxide (CO) is converted into hydrocarbons and water. The FT process is widely viewed as a potential source of fuels and raw materials, and some countries are already using it to produce substitutes for diesel. However, it is not without drawbacks: it requires high temperatures and pressures to work, and it is difficult to control which hydro carbons are released and in what proportions.

The scientists at the University of Messina immediately saw the potential of a process which could reproduce the results of the FT process at lower temperatures and pressures. The new reaction also had the advantage of using a major pollutant, carbon dioxide, as its raw material. The CO2 could be extracted from exhaust or emission gases using the technologies developed for carbon capture and storage initiatives*.

However, the reaction originally observed by the Messina scientists did not work perfectly: the catalyst was quickly deactivated and the productivity of the reaction was relatively poor – it only converted about 1 % of the CO2. Another difficulty was the fact that most work on electrocatalysis had focused on liquid-phase electrocatalysis, and the new process involved gas-phase electrocatalysis.

The challenge for the ELCAT team was to overcome these hurdles and demonstrate that the process is a feasible option for recycling carbon dioxide from burning fossil fuels and turning it back into fuel, using apparatus that could be integrated into conventional technologies for carbon capture.

Proving the concept

The project’s main achievement was to prove that it is indeed possible to work in the gas phase and use nanoconfined electrocatalysts to form long chain hydrocarbons and alcohols at room temperature and atmospheric pressure.

Meanwhile, the part of the process studied by the ELCAT project involved trapping the carbon dioxide inside the pores of a carbon nanomembrane along with a catalyst in the form of nanoclusters of noble metals such as platinum. The system diffuses the hydrogen ions from the first stage of the process through a membrane where they combine with the CO2 to form hydrocarbons. The scientists found that by increasing the temperature they could improve productivity by one to two orders of magnitude.

The researchers emphasise that the technology is still very much in its early stages, but even so, the research has already resulted in advances in other fields. For example, the partners’ nanostructured electrodes could improve the performance of fuel cells, and one of the project partners developed a better system for lithium batteries. Furthermore, the project also has applications in fields as diverse as the production of nanoconfined carbon-based matter and the use of nanocarbon materials for energy storage.

From ‘carbon capture and storage’ to ‘carbon capture and re-use’

The project’s results will also be of great interest to industries, which until now have seen carbon dioxide as a negative cost. Thanks to the new technologies developed by ELCAT, they may now start to look at it as a raw material which can be converted into other, more useful chemicals or fuels.

The scientists even speculate that their technology could prove useful for an eventual trip to Mars. Currently, a major challenge facing those considering such a journey is the question of how to produce, on the red planet, the fuel for the return trip to Earth. CO2 makes up a large part of Mars’ atmosphere and there is also water and sunlight. With the new technology, astronauts would be able to generate fuel onsite. Several studies have already been financed by NASA to search for solutions, including one to research the possibility of using an apparatus to produce carbon monoxide and water on Mars, followed by water electrolysis to produce oxygen and hydrogen.


*Another EU-funded project, CASTOR, covers this subject.