I've had this idea for a while. A roving machine that slowly and autonomously eats through commingled landfills, like a giant industrial shredder on tires. Take in everything, refrigerators, catalytic converters, electronics, toys, couches, nylon clothing, diapers. Separate everything with some combination of magnets, eddy current metal detectors, centrifuges, machine vision and other means. The metals can surely be sorted in many ways, aluminium, steel, rare earths, the odd radioactive extracted, others melted down and separated. Glass and recyclable plastics cut to pellets. Everything not recyclable but with some chemical energy in it sent to a incinerator (with a high-efficiency electrostatic filter) for power generation. Things like cinder blocks would be left over. This would also reclaim land and eliminating huge eyesores.