The contemporary anthropogenic chromium cycle

Chromium is an essential engineering metal used in stainless and alloy steels, chemicals, and refractory products. Using material flow analysis, all major anthropogenic chromium flows are characterized for the year 2000, from mining through discard, on three spatial levels: fifty-four countries, nine world regions, and the planet. Included is the first detailed quantification of chromium in internationally traded finished products and diverse waste streams. Findings include (1) 78% of chromium flow entering final use is added as a net addition to stock on the global level; most countries are close to this figure; (2) the majority of mining occurs in Africa (2400 Gg Cr/yr) and the Commonwealth of Independent States (1090 Gg Cr/yr), while the major end-users are Asia, Europe, and North America at 1150, 1140, and 751 Gg Cr/yr, respectively; (3) waste flows of chromium are the greatest in Europe (420 Gg Cr/yr), Asia (370 Gg Cr/yr), and North America (290 Gg Cr/yr), but the composition of these waste flows varies greatly among the world regions; (4) releases of chromium by the global system, which total 2630 Gg Cr/yr, are nearly evenly divided among tailings, ferrochromium slag, downgraded scrap, and post-consumer losses; (5) many countries have a heavy foreign dependence on chromium in the all forms, as is demonstrated for the United States. The findings relating to in-use stock changes and finished product trade are relevant to industry, allowing for more accurate planning for future scrap availability. The quantification of releases due to discards and dissipation hold environmental and human health relevance, while the full life cycle international trade assessment addresses local scarcity.