So eventually when the cost of finding/creating new materials makes recycling economically feasible we "mine" old landfills and use the materials. The landfill materials become the new raw material for manufacture.

...except that they distribute the material so thinly, its unlikely it'll ever be economical to mine. Even the 'original' mines e.g. copper, iron, need very high mineral densities to make them worthwhile. Landfills are orders of magnitude less dense.

There is more gold in a ton of garbage electronics than there is in a ton of gold ore.

http://pubs.usgs.gov/fs/fs060-01/fs060-01.pdf http://europa.eu/rapid/press-release_SPEECH-14-527_en.htm http://www.bbc.com/news/blogs-magazine-monitor-28802646

Cool! If only electronics were concentrated somehow in a landfill, instead of thinly spread around.

What? Why would the material be distributed thinly? It's not like they rake it all over the desert. It's extremely concentrated.

Concentrated ore is essentially solid material of a single nature. Nothing resembling that occurs in landfills. Its a big pile of 'stuff' with pellets of interesting materials every few meters. That's many orders of magnitude too sparse to be worth mechanically mining.

Of course landfills decompose, that's an absurd assertion. If they're treated not to decompose, then they were put in the wrong place obviously.

Clearly some things in the landfill don't decompose, but like others have pointed out, they will someday become profitable to mine if they're full of so much concentrated stuff.

Read up on landfills. There's little or no effort to make them decompose. Impermeable soil layers are deposited to expressly prevent mixing and mulching, since that would allow contaminated water to travel from layer to layer.