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Biomining and bleaching of ores

Chile is the world’s first-biggest producer of copper. While in 1990 the production target had been fixed at 2.5 million tons for the year 2000, this figure was superseded in 1995, and the production exceeded 5 million tons in the late 1990s. It has been exploiting copper since the 19th century with the help of local and foreign entrepreneurs, mainly from the USA. In 1971, copper mines were nationalized during the brief socialist episode of Chile’s president Salvador Allende. Since then and despite the liberal economic policies conducted under the dictatorship of Augusto Pinochet and thereafter since 1990 when Chile returned to democracy, there has been no privatization in the mining sector with 80 per cent of the mines still presently owned by the state. Because of the importance of copper

mining and production in Chile’s economy, the country has often been nicknamed the ‘Saudi Arabia of copper’. Copper’s physico-chemical properties and multiple uses, as well as a strong demand for the product from Asia (mainly China) have resulted in a high rise of international prices (London’s stock exchange) during the first half of 2004. Codelco, the National Copper Corporation, created in 1976, controls 20 per cent of the world’s copper reserves and in the late 1990s produced around 2 million tons of the metal, accounting for some 13 per cent of world production. Copper represented 40 per cent of Chilean exports and one-third of Chile’s earnings. According to its director-general, Codelco is planning to raise its annual production up to 3 million tons in 2012 (Lazare, 2004). To illustrate the fast development of copper mining and production in Chile, one could cite the small city of El Salvador, located at an altitude of 2,600 metres and 1,000 km north-west of the capital Santiago; it was created during the 1950s with foreign partners in the middle of a desert area. Nowadays, out of its 10,000 inhabitants, 2,000 are working in copper mining and production. Codelco bears the expenses of housing costs of its workers as well as of the education of their worker’s children. Water recycled from the copper mills is being used for producing vegetables, fruit and flowers, grown in greenhouses, as well as for feeding small livestock (Lazare, 2004).The ore extracted from El Salvador’s mines and containing about 2 per cent of copper is treated in a village in the same region, Llanta, so as to obtain a concentrate with 40 per cent of copper. This concentrate is thereafter treated in the furnaces of Potrerillos (99.5 per cent of copper) and then catalyzed to produce plates of pure copper (99.9 per cent). El Salvador is one of the five main divisions of Codelco. Its annual production only reached 85,000 tons of copper in 2003, but there are many prospects for extension. For instance, El Salvador could follow the model of Chuquicamata – the biggest open-air copper mine in the world, with an annual production of 600,000 tons – which was created at the beginning of the 20th century, partly with funding from US billionaires, including the Guggenheim. Chuquicamata extends over a huge basin 5-km long, 3-km wide and more than 850 m deep. The copper ore is extracted in the middle of the basin and transported in huge trucks to the surface to be treated. Every day, at 5 pm, a new explosion renews the stock of raw material to be processed (Lazare, 2004).At El Teniente, south of El Salvador and another division of Codelco, a gigantic subterranean mine is being dug from the top of a mountain down to the surface level. Explosions are carried out in the heights; rocks are being ground downward, and loaded on a train at surface level. Codelco is not excluding any innovative solution to better exploit the ‘national treasure’ (Lazare, 2004).In its first foray into the world of international corporate takeovers, Codelco and the Canadian company Noranda announced by mid-August 2000 a $1.76-billion bid for Rio Algom, representing a ‘major breakthrough’ in Codelco’s efforts to expand. But the joint bid was quickly topped by Billiton of the United Kingdom, with a $2-billion agreed offer. Noranda and Codelco had to rethink their strategy, maybe with a new bid. Codelco’s expansion plans were boosted in 2000 by a recovery in copper prices from a 12-year low in May 1999, from 60 cents to about 85 cents a pound. It also benefited from a cost-cutting programme forced on it by low copper price and cash costs were down 7 per cent to 41.1 cents a pound in the first half of 2000 .Codelco then partnered with Phelps Dodge of the USA, the world’s second-biggest copper producer, to build the El Abra mine in Chile as well as prospecting alliance with the Mexican Grupo Penoles, the world’s third-biggest producer. It also had a joint venture with Billiton, called Alliance Copper, which pioneered the commercial extraction of copper from low-grade ore using bioleaching. While the Chilean government ruled out selling Codelco, which gave up 10 per cent of its annual revenues to fund military expenses, the debate about privatization was continuing, particularly as large-scale utility sell-offs initiated in the late 1980s were nearing completion. The company nevertheless, seemed to be steadily moving toward a private-sector model. Bioleaching had been used only for the recovery of copper from wastes until the mid 1980’s. The process was upgraded thanks to multidisciplinary and multi institutional research efforts by several universities, research institutes and the productive sector, with the support of the Chilean government, the United Nations Development Programme (UNDP) and the United Nations Industrial Development Organization (UNIDO). In 2000, there were over five mines using bacterial bioleaching, and there were several projects to expand the use of this technology in the future, so as to raise its contribution to national copper production over 8 per cent to 10 per cent. The 5 million tons of copper produced in the late 1990s were the result of processing 400 million tons of ore, including 40 million tons treated via bioleaching . Back in Chile, the country had been exploring ways and means for applying bioleaching to gold production. Following the duplication of gold production in the country during the 1990s and the prospects for a 50 per cent increase in production during the three-year period 2000- In July 2001, Chile’s ministry of economy, the National Committee for Science and Technology Research (CONICYT) and the National Development Corporation (CORFO), in the presence of Chile’s president, R. Lagos, entrusted the company BioSigma S.A. with pursuing a leadership in biotechnology applied to copper mining. This attracted a Japanese corporation, Nippon Mining & Metals Co. Ltd., to join BioSigma S.A., to establish leadership in biotechnologies involved in copper mining and in about one year the new company was created. Codelco’s contribution was 66.6 per cent of the company’s equity, while that of Nippon Mining & Metals Co. Ltd. amounted to one-third of equity. The Japanese corporation’s contribution was not only financial, but it also opened the doors of for advanced technology and industry transfers among the countries involved. BioSigma S.A. was the first example of an alliance between two major mining groups and a government which allocates competitive funds to attract research groups from Chilean and foreign universities to help industry transform basic knowledge into innovative products and services. Consequently, BioSigma S.A. elaborated a plan of technological development, which included the identification of specific microorganisms, technologies for the production of biomass of these microorganisms as well as the identification of specific genes encoding proteins that facilitate the bioleaching of copper sulfurated ores. It was estimated that a minimum of one thousand genes would be identified in every microorganism. The expected outcome of the plan included technologies aimed at improving the current biomining processes, as well as more advanced solutions relating to the cloning or designing bacteria that increase bioleaching efficiency. BioSigma S.A.’s business plan set up short, medium and long-term tasks, and it was foreseen that BioSigma S.A. would recoup earnings from technology sale in 2005.A major challenge for copper mining in Chile is the high concentration of arsenium and chloride in copper ores as well as the necessity to keep the mining wastes on the site and not to remove and dump them near urban settlements, e.g. around the city of Calama in the extreme north of the country. It was therefore necessary to design a safer and cheaper bioleaching process by arsenium-resistant and chloride-tolerant microorganisms, to be applied not only to new mining sites, but also to mining wastes from which the maximum amount of residual copper would be extracted. Nippon Mining & Metals Co. Ltd., which is also a shareholder of several copper mines in Chile, including the well-known huge mine named La Escondida, has built a $150-million pilot plant, in association with Codelco, to test the applicability of the bioleaching process named BioCop and developed in South Africa by the BHP consortium; in this pilot plant, tests included the use of chloride-tolerant hyperthermophilic micro-organisms. The University of Antofagasta which has set up a Centre of Biotechnology and Molecular Biology dealing with industrial and environmental biotechnology, has signed a biomining programme research contract with BioSigma S.A. Codelco, Nippon Mining and CONICYT have contributed $2 million, $2 million and $1 million, respectively, to the biomining programme, which is part of CONICYT’s Genomics Chile – the national genomics programme devoted to mining on the one hand and to agriculture and food on the other. The allocated budget allowed the building of BioSigma S.A.’s new reference laboratory in Santiago, the maintenance of the company’s head office also in Santiago and the funding of four research projects – three Chilean and one Japanese. Three of the four projects were funded for the three-year period 2004-2006, and the fourth one was an innovative, exploratory research project to be carried out by the University of Antofagasta. The latter aimed at developing innovative bioremediation treatment of toxic mine effluents, i.e. transforming toxic metallic compounds into harmless substances. The three other research projects focused on sequencing the genomes of bioleaching microbes, cloning them to improve the bioleaching process, and on bioinformatics.



 

 


Date: 2015-04-20; view: 1133


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