Cheaper butanol production method

Engineers at Ohio State University have found a way to double the production of the biofuel butanol, which might someday replace petrol in cars.

The process improves on the conventional method for brewing butanol in a bacterial fermentation tank.

Normally, bacteria can only produce a certain amount of butanol - perhaps 15g of the chemical for every litre of water in the tank - before the tank would become too toxic for the bacteria to survive, according to Shang-Tian Yang, professor of chemical and biomolecular engineering at Ohio State University.

Yang and his colleagues developed a mutant strain of the bacterium Clostridium beijerinckii in a bioreactor containing bundles of polyester fibres. In that environment, the mutant bacteria produced up to 30g of butanol per litre.

Today, butanol is mainly used as a solvent or in industrial processes that make other chemicals. However, experts believe that this form of alcohol holds potential as a biofuel.

Once developed as a fuel, it could potentially be used in cars in place of petrol, while producing more energy than another alternative fuel, ethanol.

Yang said that this use of his patented fibrous-bed bioreactor would ultimately save money too.

'Today, the recovery and purification of butanol account for about 40 per cent of the total production cost,' he said. 'Because we are able to create butanol at higher concentrations, we believe we can lower those recovery and purification costs and make biofuel production more economical.'

Currently, a gallon of butanol costs approximately $3 (£1.80) - a little more than the current price for a gallon of petrol in the US.

The engineers are applying for a patent on the mutant bacterium and the butanol production methodology and will work with industry to develop the technology.

Their research is funded by the Ohio Department of Development.