Miniature miners making it big
What is “biomining” – a sustainable new method for one of our oldest professions, or just business as usual under a new name? The most common variation on the theme is currently a process known as bioleaching. In general, the term refers to situations where the target metals in an ore are solubilised during bioprocessing. Up to 15% of the world’s copper is extracted in this way. In gold mining – the second most important biomining industry, with 5% of total output produced using biotech methods – experts speak of “bio-oxidation”. In this process, microorganisms are used to remove minerals that occlude target metals. After this biological pre-treatment, the gold is extracted chemically.
Mining can be a dirty business
New biomining ventures like the Vuonos talc processing site and the Talvivaara nickel mine, both in Eastern Finland, are growing more common, since compared to traditional pyrometallurgical methods, bioleaching consumes less energy and produces almost no pollutants (such as sulphur dioxide) or greenhouse gases (like carbon dioxide). In Vuonos, Dutch talc producer Mondo Minerals plans to extract nickel and cobalt from a by-product. The technology comes from South Africa’s state-owned Council for Mineral Technology (Mintek). Currently under construction, the bioleach plant will start up in summer.
Only a few years years old, but already long in the tooth is Talvivaara. In environmental terms, this surface mining operation turned into a nightmare. The mine in Sotkamo, which has been operational since 2008, employs a technique known as “heap leaching” to extract nickel, as well as zinc, copper and cobalt. In it, piles of ore that have been blasted and ground are pushed into mounds up to 10 metres high. The heaps are aerated so that the microbes receive enough oxygen and carbon dioxide.
In the past, heap leaching relied on naturally occuring microorganisms to take care of the job, but inoculation with the desired bacteria has now grown increasingly common. The most significant environmental issue is the accumulation of wastewater containing sulphuric acid, which has to undergo special treatment. And that’s where Talvivaara’s problems began, after it became public knowledge that several wastewater spills from the facility had acidified nearby lakes. The Finnish online magazine Long Play revealed last autumn that the mining company’s management was also likely aware of the problems as early as 2009, but ignored them completely. Talvivaara CEO and founder Pekka Perä is now under investigation for aggravated environmental crimes. In addition to – or because of – those legal and environmental difficulties, mine operator Talvivaara Sotkamo filed for bankruptcy last autumn after reporting huge financial losses. Under a restructuring plan that’s on the table, creditors might lose up to 97% of their investment.
Read the full background on biomining in our print magazine!
- The European players in biomining
- Talvivaara’s heap bioleaching design
- More on the German-French biomining project Ecometals
- More on the EU bioleaching project BioMOre