Reck, B. K. et al. Challenges in Metal Recycling. Science 10 August 2012 Vol 337 # 6095 pp. 690-695
Bloodworth, A. Track flows to manage technology-metal supply. Recycling cannot meet the demand for rare metals used in digital and green technologies. Nature 2 Jan 2014 Vol 505 pp 19-20
“…modern technology has produced a conundrum: The more intricate the product and the more diverse the materials set it uses, the better it is likely to perform, but the more difficult it is to recycle so as to preserve the resources that were essential to making it work in the first place.”
With infinite amounts of energy, money, and time metals could be recycled. But in the real world it doesn’t happen due to the thermodynamics of separation, poor recycling technologies, product design, and social behavior.
Reck writes in Science: Less than 1% of 34 metals (many of them very rare) are recycled. These metals are essential to microchips, solar PV, consumer electronics — pretty much all high-tech products. It’s thermodynamically impossible to recover many of them. Also it’s very expensive and energy-intensive, since they’re used in such small amounts for extremely precise purposes, and co-mingled with other rare metals.
Bloodworth writes in Nature: “Although recycling is important for managing stocks of common industrial metals, its application to technology metals is more complex. Some materials are impractical or impossible to retrieve after use….Recycling has technical limits. From mobile phones to motor vehicles, technology metals are used in myriad applications. Up to 60 different elements go into the manufacture of microprocessors and circuit boards (Gunn), usually in tiny quantities and often in combinations not found in nature. Metals such as tantalum, gallium, germanium, and rare-earth elements are oxidized and effectively lost in the smelter slag (Hageluken).”
The need to recycle is obvious — only by doing so can the life of these resources be extended to future generations (since ores continue to be of lower and lower grades that need more energy to extract at the same time as oil, coal, and natural gas are diminishing).
Recycling could save as much as a factor of 10 to 20 in energy consumption.
The most commonly recycled metals are also the cheapest and most abundant on the planet, such as steel, aluminum, copper, zinc, lead, and nickel, with rates often over 50%. This high recovery rate is due to their presence in relatively pure form in large amounts in products. But even these are reused 2 or 3 times before being lost to landfills.
Even the valuable precious metals only have a recycling rate of 60%, and there’s only a 50% recovery of platinum, palladium, and rhodium from auto catalytic converters because so many old cars are exported to developing countries that don’t have recovery technology. And for the same reason, when it comes to the platinum group metals in electronics, the rate is even lower, just 5 to 10%.
Many of these metals are highly toxic to plants and animals, yet they’re recycled at very low rates. One of the worst, cadmium, is mainly recycled from nickel-cadmium batteries, but a very low rates. Mercury recovery is at best 10-20% from fluorescent light bulbs. Ecotoxicity from metal-containing nanomaterials is also a problem.
Even when attempts are made to recycle, material is lost all along the way:
Initial collection: a fraction of overall electronic equipment is turned into recycling centers, the percent depends on social and government factors
Recycling centers: much of the electronic waste is sent to countries that have inadequate recycling facilities
Preprocessing & Sorting – some components are too much effort to take apart, so they’re discarded. Nor is there enough material to justify the cost of machine recycling technology.
Recycling technology: Usually just shredding, crushing, magnetic sorting is done. It’s too expensive to recover even more with lasers, near-infrared, or x-ray sorting.
Product design: often makes it hard to separate products out, such as laminated permanent magnets in computers.
Smelter – the easier, larger, most common metals make it to the smelter, i.e. iron, aluminum, etc. Not all material that was collected and could be smelted reaches the smelters, especially if smelters are distant.
Thermodynamics is the ultimate limitation at the final processing stage and can’t be separated out.
Gunn, A. G. In Proc. 12th Bienn. Soc. Geol. Appl. Miner. Depos. Meet (SGA, 2013)
Hageluken, C et al. Precious Materials Handbook, Ch 1. Hanua-Wolfgang, 2012.