My guess is not at all useful. Iron ore is mined at such a massive level that it is hard to imagine a bio based process could be cost effective or even possible.

For example bioremediation and bleaching can be considered for valuable ores, but the amount of gold ore mined across the world is a few thousand tons annually. Whereas with iron ore it is a hundreds of millions of tons.

Bioleaching is considered to be an environmentally friendly alternative to traditional pyrometallurgical methods, as it does not generate as much waste and reduces the energy requirements for metal extraction.

Therefore, it is worth pursuing further studies in bioleaching as it has the potential to revolutionize the iron ore extraction industry. I would like to invite you to read my recent article on this subject, which provides some latest insights into the latest developments in this field.

Article Development of a Model to Estimate the Thermodynamic Stabili...

We already have been using bacteria for refractory gold ore beneficiation on large scale, the technology is being used for more than 20 years now. Using sulfuric acid-producing microbes is a well-established area to remove sulfide from the surface of sulfidic ores to help have better oxidization of our desired metal. While Prof. Benedik is right about the scale of the process we need to take into account the huge environmental impact of steel making industry and the increasing cost of tightened environmental regulation which can motivate these companies to integrate alternative low-impact bio-based processes such as biobenefication into their process. And with the right motivation, I believe we can expand the capacity for bioleaching of iron ores easily.

https://www.youtube.com/watch?v=165QVbDgocc

https://www.mogroup.com/portfolio/biox-process/

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Article Bio-beneficiation of australian iron ores - Potential applic...