# 21.1: Introduction


Metals have been used for thousands of years. Until the industrial revolution most metal products were recycled, because they were scarce. During the Industrial Revolution recycling was not always a high priority in the shadow of development, as there was a seemingly unending supply of ore and fuel for processing.

In today’s world, the emphasis is shifting away from energy intensive development. This is not because scarcity is once again an issue and ores are running out, but because the energy requirements to extract and process ores into the refined state needed for the high tech industry are ever increasing. There is a drive to reduce emissions from burning hydrocarbons for energy and a decreasing oil supply. This means that recycling is again an economically and environmentally feasible option, since in most cases, the energy required for recycling of metals is much less than the energy required to refine them from ores. Recycling improves the sustainability of metal product systems, by separating resource consumption from economic growth.

It is important to note when looking at recycling statistics that the definition of “% recycled” may differ. Both

$\frac{\text{Amount recycled}}{\text{Amount available for recycling}}$

and

$\frac{\text{ Amount recycled metal}}{\text{Amount metal produced}}$

could be labelled as “% recycled”, although they may have very different values. Ambiguous statistics like this illustrate how background knowledge of the science involved can be useful when assessing the subject of recycling.

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