Bacteria `reducing carbon emissions`

A species of bacteria is saving mining industry millions of dollars.

Updated: Jul 24, 2010, 13:31 PM IST

Melbourne: A previously unknown species of bacteria is saving the mining industry millions of dollars, and reducing its carbon emissions, scientists have found.

A team, led by Naomi McSweeney of University of Western Australia, discovered the naturally occurring bacteria break down and remove sodium oxalate, an organic impurity produced during refining of low-grade bauxite into alumina.

At a typical refinery, sodium oxalate forms by the tonne during the production of alumina. It can affect colour and the quality of the final product.

"Oxalate can be removed by combustion, but this process releases excess carbon dioxide. The impurity may also be stored but this represents a major cost to refineries so treatment is a preferred option," McSweeney said.

Alcoa designed and installed an innovative large-scale bioreactor which has the capability to remove about 40 tonnes a day of sodium oxalate produced at its Kwinana refinery.

"Using bacteria to break down and remove oxalate is a better, more sustainable alternative. The bacterial process breaks down the sodium oxalate and produces significantly less carbon dioxide while avoiding the need to store the impurity," McSweeney said.

The scientists used DNA fingerprinting techniques to pick out the key players. What they found was a potentially new genus of Proteobacteria and a new species of the known genus Halomonas which are able to use the carbon in the oxalate to grow.

"Oxalates, and bacteria that feed on them, are common in nature -- for example in our food, in our guts and in the root systems of plants such as rhubarb. "However, these oxalate-degrading microorganisms were not the ones we found in the bioreactor. The bacteria doing most of the work in the bioreactor have never been found before," she said.