Wouldn't there be massive amounts of copper in landfills? Might be hard to separate from the rest of the waste, but perhaps not harder than regular mining?
A quick bit of googling suggests that copper ore is between 0.4% and 12% copper [1]. Just guessing, but I'd be surprised if there was anything like that much copper in a generic landfill site which makes me think it'd be pretty uneconomical to extract copper from landfill at the moment. I suspect the price of copper would need to be a few orders of magnitude higher before it became feasible.
The US produces 200 million tonnes of municipal solid waste (MSW) per year, ignoring the parts recycled or composted. Most copper production is not from recycled metal (< 10% is recycled from post consumer waste). US copper consumption is about 1.7 million tonnes per year. So, if all the copper used ends up in MSW (which is likely an exaggeration), the landfills would be nearly 1% copper.
I think the salient point is that construction & demolition debris is not included in MSW. So copper that ends up in that waste stream is not necessarily going to MSW landfills.
The US produces 600 million tonnes of C&D debris each year.
It's probably one of the easier things to recover from eg used PCBs. It's not like plastic resins which decompose into carbon when you do something wrong.
Also manufactures probably throw a ton of copper (chloride?) out which they could recover copper from.
