A recent scientific report from the United Nations Environment Program emphasizes some of the challenges of our voracious appetite for metals:
- Mining can cause environmental and health problems due to leaching of toxic substances into the ground- and surface water. Mining can also cause ecosystem degradation. Accidents, e. g. related to tailings dam breaches, can be the cause of severe local surface water pollution.
- Mining and especially refining of metals is very energy intensive and presently uses about 8 % of the total global energy supply,
- An increasing share of metal emissions to the environment comes from non-metal sources such as fossil fuels and phosphate fertilizer. For some metals this is presently the major source. Especially in agriculture, closed loop accumulation can lead to high concentrations of metals in soils.
- For certain metals, a reduced demand leads to an oversupply due to their chemical/geological/designed linkage to valuable carrier metals or other materials. Oversupply also occurs for metals with a former high level of use, where old stocks entering the waste stage form a potential but no longer wanted source of secondary material. But even for metals with rising demand, thermodynamics dictate that cycles can never be completely closed. Those final waste streams need to be immobilized in order to prevent them from being emitted to the environment.
The report states that recycling is an option that can mitigate three out of four of these areas, and that is specifically relevant for metals: metals can be recycled almost indefinitely, with little loss in their technical attributes regardless of the number of times recycled. It reduces the need for primary production with all related impacts of mining and refining. It slows down the need for exploiting low grade ores. Secondary production, including collection and transport, is much less energy intensive and therefore can reduce energy requirements significantly.
The report seeks to define a sustainable metals management strategy. Suggested elements include:
- Metals have an important function in new energy systems, thus contributing to a reduction of GHG emissions. It should be kept in mind, however, that implementing these technologies at pages scale will probably lead to a reduced availability of high quality ores. Hence the production of these metals will become more increasingly energy intensive, which in turn reduces resource productivity.
- Substitution of metals by other materials could be an option to consider. However, side-effects must then be considered as well: these substitutes are not without their own environmental and supply issues, and an assessment should be made of the benefits of such a substitution in all cases. Moreover, the use of metals in new technologies is often essential, and therefore substitution will come at the expense of either resource efficiency losses or functionality.
- Dematerialisation, in the context of a sustainable metals management, would mean using less metals in the product to fulfill the same functions. This would reduce potential life cycle impacts accordingly. Again, one has to be aware of potential side-effects.
- Recycling rates for many metals are at present low, but rising. System optimization and design for recycling can help much to further increase recycling rates. Secondary production in general takes much less energy than primary production, therefore, increasing the share of secondary production in the total supply would reduce energy use substantially.
The 162 page highly readable report, with the cumbersome title Environmental Risks and Challenges of Anthropogenic Metals Flows and Cycles, is available at http://www.unep.org/resourcepanel/Publications/EnvironmentalChallengesMetals/tabid/106142/default.aspx