Plant Waste Used to Recover Waste Uranium

Professor Lynne Macaskie Sunday presented the group's work to the Society for General Microbiology's meeting at Heriot-Watt University, Edinburgh.

Bacteria, in this case, E. coli, break down a source of inositol phosphate, also called phytic acid, a phosphate storage material in seeds, to free the phosphate molecules.

The phosphate then binds to the uranium, forming a uranium phosphate precipitate on the bacterial cells that can be harvested to recover the uranium.

This process was first described in 1995, but then a more expensive additive was used and that, combined with the then low price of uranium, made the process uneconomic.

The discovery that inositol phosphate is potentially six times more effective as well as being a cheap waste material means that the process becomes economically viable, especially as the world price of uranium is likely to increase as countries move to expand their nuclear technologies in a bid to produce low-carbon energy.

As an example, if pure inositol phosphate, bought from a commercial supplier is used, the cost of this process is $19.30 per gram of uranium recovered. If a cheaper source of inositol phosphate is used such as calcium phytate, the cost reduces to $0.14 for each gram of recovered uranium.

Waste uranium at the the Coeur d’Alene Basin Mine in Idaho (Photo credit unknown)

At 2007 prices, uranium cost $0.34/gram; it is currently $0.14/gram.

These prices make the process economic overall because there is also an environmental protection benefit, says Professor Macaskie.

Use of low-grade inositol phosphate from agricultural wastes would bring the cost down still further and the economic benefit will also increase as the price of uranium is forecast to rise again.

"The UK has no natural uranium reserves, although a significant amount of uranium is produced in nuclear wastes. There is no global shortage of uranium but from the point of view of energy security the EU needs to be able to recover as much uranium as possible from mine run-offs - which in any case pollute the environment - as well as recycling as much uranium as possible from nuclear wastes," said Macaskie.

"By using a cheap feedstock easily obtained from plant wastes," Macaskie said, "we have shown that an economic, scalable process for uranium recovery is possible."

Three European countries are found within the top seven in the world ranking list of uranium producing countries with the highest total production since World War II - Germany, the Czech Republic, and France, which was once by far the largest uranium producer in Western Europe. The last uranium mine in France ceased production in May 2001.

The worldwide production of uranium in 2008 amounted to 43,853 tonnes, of which 20 percent was mined in Canada.

Canada, Kazakhstan, and Australia are the top three producers and together account for 59 percent of world uranium production. Other important uranium producing countries in excess of 1,000 tonnes per year are Namibia, Russia, Niger, Uzbekistan, and the United States. Uranium mining in the United States declined in the 1980s, but has revived since 2001 due to higher uranium prices.

Copyright Environment News Service, ENS, 2009. All rights reserved.