AIUI, bottles and cans are sorted easily from paper. Also as the glass/steel/aluminium is going in a furnace some contamination is fine. Contamination the other

AIUI, bottles and cans are sorted easily from paper. Also as the glass/steel/aluminium is going in a furnace some contamination is fine. Contamination the other way is sorted by float-beds; and paper gets shredded and washed anyway as part of the recycling process. Could you expand on what you think the problem is here?