Amit Kapur

The Multilevel Cycle of Anthropogenic Zinc

Summary A comprehensive annual cycle for stocks and flows of zinc, based on data from circa 1994 and incorporating information on extraction, processing, fabrication, use, discard, recycling, and landfilling, was carried out at three discrete governmental unit levels—54 countries and 1 country group (which together comprise essentially all global anthropogenic zinc stocks and flows), nine world regions, and the planet as a whole. All of these cycles are available in an electronic supplement to this article, which thus provides a metadata set on zinc flows for the use of industrial ecology researchers. A “best estimate” global zinc cycle was constructed to resolve aggregation discrepancies. Among the most interesting results are the following: (1) The accumulation ratio, that is, addition to in-use stock as a function of zinc entering use, is positive and large (2/3 of zinc entering use is added to stock) (country, regional, and global levels); (2) secondary input ratios (fractions of input to fabrication that are from recycled zinc) and domestic recycling percentages (fractions of discarded zinc that are recycled) differ among regions by as much as a factor of six (regional level); (3) worldwide, about 40% of the zinc that was discarded in various forms was recovered and reused or recycled (global level); (4) zinc cycles can usefully be characterized by a set of ratios, including, notably, the utilization efficiency (the ratio of manufacturing waste to manufacturing output: 0.090) and the prompt scrap ratio (new scrap as a fraction of manufacturing input: 0.070) (global level). Because capturable discards are a significant fraction of primary zinc inputs, if a larger proportion of discards were recaptured, extraction requirements would decrease significantly (global level). The results provide a framework for complementary studies in resource stocks, industrial resource utilization, energy consumption, waste management, industrial economics, and environmental impacts.

The future of the red metal: discards, energy, water, residues, and depletion

Estimates for mine tailings, smelter slag, mine overburden, stock buildup, loss of copper discards to the landfills, and energy and water use requirements have been presented based upon scenario analysis results of three alternative copper futures. The resource availability concerns emerge to be the most critical. Globally, the copper resource availability barrier might potentially emerge during 2035–2060, with more likelihood of appearing in a highly technological and affluent world scenario first. Cumulatively, the amount of copper in mine tailings generated by 2050 will equal the amount of contemporary in-use copper stock. Such large amounts of production residues can serve as future sources of high-grade copper, as copper ore grades will continue to decline over time. Should we wish to mine the remaining low grade copper still, the amount of energy required will be equivalent to present global energy use. Unrealistically large amount of water would also seem to be required.

Water auditing – tracking unaccounted-for water in Delhi, India

Unaccounted-for water losses average approximately 30 per cent of supply in developing country cities. The methods of water auditing described here can identify where losses are occurring.

Towards a global freshwater convention: challenges ahead

The imminent freshwater crisis affects all forms of development. Freshwater concerns are multi-scale, diverse and complex in nature, and management options may either call for action by local stakeholders or require transboundary/regional agreements. Unlike other global environmental issues, the international community is yet to formulate a global water convention. The progress over two decades from Marl del Plata to Rio to Hague to Bonn has been significant. Institutionalisation of global water think tanks and networks has paved the way to structure a World Water Vision and a Framework for Action. Yet, immense barriers persist for an international protocol on water.