I have numerous part-used cans of paint in my garage…most of which will lie there until their contents solidify. I suspect that this is a common enough phenomenon.
Today’s invention is a facility to which all such residues could be taken and donated. As well as lessening the chance that this material just gets dumped into a drain, the bank would assess the age and chemical compatibility of deposits.
Many people and local organisations have a need for utility paint -without a strong preference as to colour. The bank would be able to supply them with a large enough volume, by mixing donated paints, at a small enough price, to satisfy their requirements.