SMI aims to turn carbon dioxide into fuel

Scientists have already shown that microbes treating wastewater and CO₂ passed through molten carbonates can produce electricity.
Now a team at the Surrey Materials Institute (SMI) hopes to create new technology based on these ideas while reducing their energy usage.

Molten carbonate fuel cells (MCFCs) create a mixture of CO₂ and hydrogen that the Surrey team argues could be used to create hydrocarbon fuel if it can be produced at a lower, more cost-effective temperature.

This would effectively allow the waste CO₂ from existing power stations to be recycled back into fuel.

‘MCFCs operate at a very high temperature, but we think we can do it much lower,’ SMI’s Dr John Varcoe told The Engineer. ‘They may only generate a little electricity but, importantly, they won’t consume any.’

MCFCs are currently being developed by the UK’s Supergen consortium of businesses in the bioenergy sector, funded by the EPSRC.

They work by effectively passing carbon dioxide through a carbonate salt electrolyte at a temperature of around 650°C to create an electric current. The CO₂ then combines with the hydrogen that is also fed into the cell at the other side of the electrolyte.

‘I am proposing low-temperature carbonate fuel cells containing polymer membranes that work in the same way,’ said Varcoe, who is aiming for temperatures between 50 and 100^oC.

SMI also hopes to develop membrane technology to create self-powered desalination systems using microbial fuel cells. These cells rely on microbes to consume the organic material in wastewater, effectively cleaning it while producing an electric charge from protons and electrons that are released.

If salt water is run through the middle of the cell, separated from the two electrodes by exchange membranes, then the positive and negative charges of the cell will pull the salt ions through the membranes and leave the water desalinated.

‘The idea would be to have wastewater and desalination plants next to each other,’ said Varcoe.

‘We need to develop membranes that are resistant to biofouling, where the bacteria effectively clog up the membranes. We have already developed highly conductive membranes and now we need to tailor the chemistry to make them more resistant.’

David Willets, the universities and science minister, used a speech yesterday at the Farnborough International Airshow to award Varcoe a leadership fellowship from the EPSRC in order to continue the work.