In-Use Stocks of Metals: Status and Implications

Abstract

The continued increase in the use of metals over the 20th century has led to the phenomenon of a substantial shift in metal stocks from the lithosphere to the anthroposphere. Such a shift raises social, economic, and environmental issues that cannot be addressed without quantifying the amount of stock of "metal capital" utilized by society. Estimation of the in-use stock of metals has occurred for at least 70 years, with over 70% of the publications occurring after the year 2000. Despite the long history, this is the first critical review to consolidate current findings, critique methods, and discuss future avenues of research. Only aluminum, copper, iron, lead, and zinc have been studied to any extent Nonetheless, it is clear that for the more-developed countries, the typical per capita in-use metal stock is between 10 and 15 t (mostly iron). Comparison of the per capita stocks in more-developed countries with those in less-developed countries suggests that if the total world population were to enjoy the same per capita metal stock levels as the more-developed countries, using a similar suite of technologies, the amount of global in-use metal stocks required would be 3-9 times those existing at present.

In-use product stocks link manufactured capital to natural capital

“…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.…”

Above-Ground Resource Analysis with Spatial Resolution to Support Better Decision Making

“…It also provides useful information to assess current collection and recovery infrastructure and plan new infrastructure. To support decision and policy making in individual companies or organizations such as metal processing, production and recycling industries, public health and environmental agencies, and public policy organizations, above-ground resource analysis should be conducted at a variety of spatial and temporal scales to provide the basis for the development of scenarios of metal demands and discards from stock in use [3]. All these levels of policy and decision making are differentiated on the basis of system boundaries, which are interpreted to be spatial and based on the geographical locations.…”

“…It can be used to support multi-scale above-ground resource analysis based on locational information about metal stocks. There are two methods commonly used for above-ground resource analysis: top-down and bottom-up [3].…”

“…This method takes time series of historical data on metal demands and discards, and calculates in-use stock by adding the annual difference of inflow and outflow over time. Typically, t ranges from 50 to 100 years or longer [3]. Inflow data are usually provided by production, trade, and consumption statistics.…”

“…According to a report on metal stocks in society, published in 2010 by the International Resource Panel hosted by the United Nations Environment Programme (UNEP), during the twentieth century, the variety of metals used in society grew quickly, which leads to expanding metal mining activities, and creating more and more of the world's metal stocks that are above ground in use rather than below ground as unused reserves [1]. The utilization of these growing metal stocks through recycling is expected to be an important source for metal supply in the future [2] [3,4].…”