Frequently asked questions on biohydrometallurgy

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These are questions from non-professional people about bioleaching. Maybe you are the right person to answer them.


Microbes and minerals - microbes as geological agents

Formation of minerals (or of the earth surface) - does that involve microbes? Does it involve bioleaching microbes?

Have minerals close to the surface already been leached? Can it be said that bioleaching is only speeding up conventional natural oxidizing processes?

Can one always know what type of microbe is doing what in a mineral extraction process? Is it really important to know?

If bioleaching bacteria have existed for many millions of years and so have rocks and mountains – why is not all possible bioleaching already done and the bacteria starved to death?


Bioleaching in general

Is there a good example for something that resembles bioleaching: Yeast for bread-baking? Garden waste compost heap? Wine or beer making?

I have heard about bioleaching for copper and gold, but what about other metals? In which cases is bioleaching most economical to use?

  • Although to date (2007?) bioleaching has only been applied commercially toward the recovery of gold, uranium, copper, and nickel, it has also been suggested as a route to effective heap leaching of low grade zinc ores. However, to follow this route further advances are required in the solvent extraction of zinc from iron-contaminated liquids. Electrowinning of zinc, while more complex than is the case for copper, is technically feasible (Grant, 1994).

When is bioleaching preferable to conventional methods?

Does bioleaching save energy compared to alternatives?

Bioleaching microbes

Are bioleaching microbes (microorganisms) and bioleaching bacteria synonymous?

Where do these peculiar extremophile, bioleaching microbes come from?

Do scientists search for new bioleaching microbes with special characteristics to optimize processes like metal extraction, or do scientists think that they already know the most important types?

Are bacteria cloned and genetically manipulated in laboratories in order to improve bacterial processes like bioleaching? If so, how dangerous is that?

When a bacterium is forced to accommodate more and more extreme conditions (heat, pH, etc) and faster processes – isn’t there a risk for mutations with unknown consequences?

I know that microbes die when it becomes too hot, but what if it becomes too cold? Or too wet – do they drown or just not work as well?

Wouldn’t it be a good idea to use a reasonable mix of bacteria to see which one will work on my ore or concentrate?

Where can I buy this bacterium x? How is it delivered? How can it be stored and kept alive waiting for a heap or a tank to be ready? How is it dispersed? How much is needed?

Is it good for a bioleaching process when the bioleaching microbes are multiplying very fast?

How do the microbes in mining environments differ from microbes in treatment plants for metal-rich wastewater?

Environment and risks

Is bioleaching an environmentally friendly process compared to alternatives?

It is wonderful when processes work as planned, but how often do bioleaching processes fail? Are they as reliable as the alternatives?

When should bioleaching not be used, even though it is possible?

Can some microbes be dangerous outside a heap or tank if they escape?

Is it true that all geo-bacteria are resistant to antibiotics? Why? Is it a risk to use such bacteria among people?

Is bioleaching a good future way of treating old problematic waste dumps around our cities?

In-situ leaching, one of several leaching methods, seems as a very ideal situation for metal extraction, just drilling holes and letting the microorganisms bring up the metal? – Why is it not more commonly used? Open pits are ugly!

  • The main release from in-situ mining is contaminated water which may contain a wide range of dissolved species from the ore (similar to acid mine drainage) and chemical species added to the leaching solution. Although there are other technical limitations to the use of in-situ mining, the major unresolved issue is the question of losses of metal-laden leachate and subsequent contamination of groundwater resources.

As bioleaching microbes consume CO2 wouldn’t bioleaching operations be a good way to reduce the greenhouse-effect?

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