Exploring the engine of anthropogenic iron cycles

Abstract

Stocks of products in use are the pivotal engines that drive anthropogenic metal cycles: They support the lives of people by providing services to them; they are sources for future secondary resources (scrap); and demand for in-use stocks generates demand for metals. Despite their great importance and their impacts on other parts of the metal cycles and the environment, the study of in-use stocks has heretofore been widely neglected. Here we investigate anthropogenic and geogenic iron stocks in the United States (U.S.) by analyzing the iron cycle over the period 1900 -2004. Our results show the following. (i) Over the last century, the U.S. iron stock in use increased to 3,200 Tg (million metric tons), which is the same order of magnitude as the remaining U.S. iron stock in identified ores. On a global scale, anthropogenic iron stocks are less significant compared with natural ores, but their relative importance is increasing. (ii) With a perfect recycling system, the U.S. could substitute scrap utilization for domestic mining. (iii) The per-capita in-use iron stock reached saturation at 11-12 metric tons in Ϸ1980. This last finding, if applicable to other economies as well, could allow a significant improvement of long-term forecasting of steel demand and scrap availability in emerging market economies and therefore has major implications for resource sustainability, recycling technology, and industrial and governmental policy.dematerialization ͉ material flow analysis ͉ resource management ͉ secondary resource exploration ͉ ferrous scrap recycling I n 1969, the urbanist Jane Jacobs referred to cities as ''the mines of the future'' (1). Her perspective was that resources that have been mined, processed, and fabricated into products constituted a material stock that could eventually supplant in-ground ore. Almost 4 decades later, and with still limited knowledge of these urban mines, we recognize significant differences between urban and traditional mines. First, whereas mineral ores change very slowly over time, anthropogenic stocks change rapidly and therefore require better monitoring. Second, mining production of mineral ores can readily be adjusted to changes in demand, provided that necessary reserves, capital, and labor are available, whereas urban mining faces physical limitations because it is restricted to products in use becoming obsolete. Third, the material in urban mines is generally of higher quality than mineral ores (2), because already processed and purified material often requires less energy and technology to re-employ. Fourth, there is extensive knowledge about the size and chemical and physical properties of geological ores, but there is very little understanding of anthropogenic material stocks and their dynamics.The lack of knowledge about in-use stocks not only limits our insights into future resources, but it also confines our understanding of entire mineral cycles. Comprehending in-use stocks is therefore essential for measuring and improving overall resource utilization.The study of a...

China's Growing CO2 EmissionsA Race between Increasing Consumption and Efficiency Gains

“…Since the importance of construction decreases as a country develops (52), it is likely that the environmental impacts associated with the construction sector will decrease as well. There is recent evidence for this observation in the global iron cycle (54). On the other hand, infrastructure may lead to increased usephase emissions.…”

In-use product stocks link manufactured capital to natural capital

“…(iii) The growth of in-use product stocks results in the growth of in-use metal stocks, and therefore also for metal flows, although for metals such as iron and aluminum, the saturation of product stocks may result in the saturation of metal stocks (13,16).These phenomena reveal that manufactured capital in the United States has increasingly relied on the use of more and more types of materials and on the growing magnitude of use of most of them.…”

“…1). In this sense, in-use stocks of products play the role of driving anthropogenic material cycles (16) and linking these cycles with manufactured capital, as well as functions and services demanded by modern society (15). (iv) When integrated with price information, in-use stocks of products can be used to estimate or to be compared with net stocks of products.…”

“…Extensive determinations of in-use stocks have only appeared in the last two decades (12)(13)(14)(15)(16), and, unfortunately, almost all in-use stock studies focus on materials rather than products. We argue that the determination of in-use stocks and relevant flows of products has its own special importance.…”

Prediction Model of Global Demand for Iron Source by Utility of Stock Hypothesis—Verification of Predictive Power and Outlook for Demand to 2050—

“…4,[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] This study uses total world figures, which has advantages as follows. Although it is difficult to make a reliable estimation of the consumption of metals by country because of indirect trade of metal containing final goods such as automobile, it is easier to estimate the world consumption.…”