The Real Cost of the Global Warming Mania — Hydrometallurgy Versus Pyrometallurgy L W John 1 ABSTRACT In the past two decades the global metalliferous mineral industry has trended away from pyrometallurgical (pyromet) and towards hydrometallurgical (hydromet) technologies including biometallurgical (biomet) processes. Pyromet, biomet and hydromet technologies have all developed considerably over this period. New projects have been biased or directed by legislation towards supposedly cleaner and greener hydromet and biomet technologies. The environmental cost and energy cost of pyromet production processes for copper and cobalt are compared with comparable hydromet processes using Life Cycle Assessment (LCA). The ‘real cost’ of the global warming obsession and negative public perception of pyrometallurgy include greater carbon dioxide emissions and energy consumption per unit, associated with current hydromet technologies. Specific examples for copper and cobalt produced via the different routes are provided. The poor science involved with the global warming hypothesis is discussed. The use of LCA with sensitivity analysis as a decision making tool for mineral processing projects and technology developers is discussed. INTRODUCTION In the past two decades the global metalliferous mineral industry has trended away from pyrometallurgical (pyromet) processes and new smelters towards hydrometallurgical (hydromet) technologies including biometallurgical (biomet) processes. This has been the result of several factors, namely: • aging smelters, for example reverberatory furnaces particularly those without SO 2 recovery, have resulted in a poor environmental record and a poor image for pyrometallurgy; • the evolution of a very influential environmental movement which has encouraged a change in many aspects of the mining and minerals industry; • the availability of sulfuric acid produced from smelters retro-fitted with acid plants – the motivation behind the SXEW revolution in Chile; and • international mining companies desperate to be seen as ‘green’ and ‘sustainable’ by a public increasingly influenced by the ‘global warming mania’. Pyromet and hydromet technologies have both developed considerably over this period. Advances in pyrometallurgy include: • semi autogenous to almost fully autogenous smelting of sulfide concentrates allowing production of blister copper in one process with almost zero energy or fuel inputs; • as a result of the use of oxygen and technology developments in flash furnaces, >99 per cent recovery of SO 2 is now the industry norm; and • co-generation of high-grade steam and or electricity from the smelter, and more so from the acid plant (SO 2 → SO 3 ) such as the Monarch® Process by Monsanto. Advances in hydrometallurgy and biometallurgy include: • commercial solvent extraction and electrowinning processes (SXEW) for Cu, Ni, Co, Zn, etc; • bioleaching of almost any sulfide ore is now commercially possible liberating both base and precious metals both as agitated and heap leach operations; • leaching technologies such as ACTIVOX®, BioNic®, BioCOP®, BIOX®, CESL; and • Hydromet technologies that have almost no economies of scale and thus are suited to small, low CAPEX operations. Life Cycle Assessment (LCA) methodologies provide the rational engineer or scientist with a means to determine which mineral processing technology has the least environmental impact and or the lowest energy consumption per unit of production. Regardless of the global warming issues, the minerals industry must aim to minimise its environmental impact if it is to lift its public image. The general directive of any globally competitive industry is also the reduction of costs, including energy consumption per unit produced. Thus sustainability † , the endeavour for a cleaner environment, efficient use of energy and minimised per unit cost are in many ways synergistic objectives. As this paper will show, LCA of mineral process options for sulfide base metal minerals indicates that pyromet or hybrid processes are likely to be more sustainable rather than purely hydromet processes. To further this argument, the global warming hypothesis will be exposed and the ‘real cost’ that this issue has had on energy consumption and carbon dioxide production of the non-ferrous metalliferous mining industry is discussed. LCAs of sulfide mineral processes undertaken by other authors are summarised with the results of this study and discussed along with the usefulness of LCAs in process selection and technology development. The use of both biomet and hydromet technologies does have an important role to play in mineral processing but we must be aware of the real costs of such process options. Future directions in biometallurgy and hydrometallurgy are suggested and discussed. For the purpose of simplicity, in this study, the use of the term ‘hydrometallurgy’ or ‘hydromet’ shall also refer to technologies such as biometallurgy and bioleaching except where stated. THE GREAT GLOBAL WARMING FALLACY The latter half of the last century saw an increase in the commercial, academic and media focus on how humans impact on our immediate environment and on the world as a whole. Generally this focus has been rational and scientific and has resulted in humans and the industry we all depend upon, improving behaviour for the betterment of society. Bac-Min Conference Bendigo, Vic, 8 - 10 November 2004 1 1. MAusIMM, BioMetallurgical, PO Box 1542, Kwekwe, Zimbabwe, E-mail: LWJ@BioMetallurgical.com † ‘Sustainability’ – ‘Meeting the needs of current generations, without compromising the ability of future generations to meet their own needs.’ This is the generally accepted definition of ‘Sustainable Development’ from the report of the World Commission on Environment and Development, which was led by former Norwegian prime minister Gro Harlem Brundtland. It is the definition used by the United Nations and most other international bodies to describe this complex topic.