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METAL EXTRACTION MEETS HIGH-TECH PRACTICES The Talvivaara Mining Company aims to become an internationally significant base metals producer. Its primary focus is on nickel and zinc mining using an environmentally friendly technology known as bioheapleaching. BY SALLA KORPELA PHOTOGRAPH BY TALVIVAARA T he Talvivaara multi-metal deposits are located in the southern part of the Kainuu region in eastern Finland, approximately 30 kilometres south-west of the municipality of Sotkamo. Talvivaara is one of the largest known sulphide nickel deposits in Europe with 336 million tonnes of classified resources. The Talvivaara ore deposits have been extensively studied for more than 20 years. Active development of the deposits by the Talvivaara Mining Company dates back to 2004, when it acquired the mining rights and the rights to use the related geological and bioleaching research data. "Commercial production started in late 2008, and the mine can be operated for a minimum of 24 years with an annual nickel output of approximately 33,000 tonnes. We have the potential to supply roughly 2.3 per cent of the world's current annual production of nickel by 2010. The mine is also expected to produce significant amounts of other metals as by-products of the production process. The annual production of zinc is estimated at 60,000 tonnes, complemented by 10,000 tonnes of copper and 1,200 tonnes of cobalt," says Marja RiekkolaVanhanen, Chief Technology Officer of the Talvivaara Mining Company. "Talvivaara is the first mine in the world to use bioheapleaching in the extraction of nickel," says Marja Riekkola-Vanhanen, Chief Technology Officer of the Talvivaara Mining Company. "The bacteria do the work without pay and without consuming any energy." According to Riekkola-Vanhanen, Talvivaara ore is very low-grade and contains about 8 per cent graphite, which explains why it cannot be concentrated and smelted in the conventional way. The ore is well suited for extraction with the bioheapleaching method, however. Using bacteria to obtain metals The Talvivaara mine uses bacteria and microbial action to obtain base metals out of ore. Leaching involves extracting a substance from a solid by dissolving it in a liquid; bioheapleaching, in turn, is a process where metals are dissolved from ore by certain local live bacteria growing naturally in the ore. "In nature, the process occurs spontaneously in the presence of air and water, but at the Talvivaara mine, this process is accelerated by crushing the ore into smaller particles and then stacking them in an eight-metre heap before treatment. The heap is 800 metres wide and 2,400 metres long the size of 240 football fields," Riekkola-Vanhanen points out. Air is then pumped through the heap and water dripped through it. The solution coming from the heap is collected in a pond and about 10 per cent of it is sent to the metal plant for metal recovery. The remaining solution is diluted with a corresponding amount of clean water, its acidity is adjusted and the solution is circulated back to irrigate the heap. Bioheapleaching technology is widely used elsewhere for recovering copper and gold. 22 FOCUS
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