I am not so sure about this. Do you have any sources? I think I read that it's difficult due to the abundance of very different aluminium alloys.
Ignoring gold, platinum, and silver, copper comes in quite high, followed by aluminum and then at the bottom is steel and iron.
Most places will pay you over the CRV for aluminum cans, and they will usually also pay for bulk aluminum, more than they'd pay for steel or cast iron.
https://international-aluminium.org/new-iai-study-reveals-en...
To quote wikipedia:
> Recycling scrap aluminium requires only 5% of the energy used to make new aluminium from the raw ore
https://en.wikipedia.org/wiki/Aluminium_recycling
Which cites this article from The Economist: https://www.economist.com/leaders/2007/06/07/the-price-of-vi...
"Since the demand for recycled aluminum continues to increase, the discarded aircraft provide a large source of valuable metal. However cost-effective recycling of aircraft alloys is complex because aircraft alloys are: (a) typically relatively high in alloying elements and (b) contain very low levels of impurities to optimize toughness and other performance characteristics."
https://www.totalmateria.com/page.aspx?ID=CheckArticle&site=...
Also
"The separation of scrap into specific aluminum alloy groups can be checked by Laser Induced Breakdown Spectroscopy (LIBS) or color sorting, but economic and technological challenges limit the use of these processes (Capuzzi and Timelli 2018; Gaustad et al., 2012). All sorting methods offer less than 100 % efficiency. This leads to significant contamination of the aluminum, in particular with iron and copper"
https://www.sciencedirect.com/science/article/pii/S092134492...
I can maybe shed some light, however I’m not 100% positive. And you very well might know all this:
My read here is that “aircraft grade” alloys, probably like 2000 and 7000 series, are relatively harder to recycle. They are less used and more expensive, I cba to look up stats on raw production estimates, if they exist publicly.
This is separate from recycled Aluminum being treated as a separate product(green aluminum), with effort made to bring it to parity with traditional Aluminum.[1]
Again I don’t know for sure, but I suspect a lot of it comes down to Aluminum cans being the highest single use of Aluminum globally and being efficient to recycle and make with recycled aluminum.
[1] https://www.sciencedirect.com/science/article/pii/S007964252...