One method of treating incinerated waste comprises: size separating at least some of the incinerated waste into a first undersize fraction comprising particles smaller than the first separation size and into a first oversize fraction comprising particles larger than the first separation size; size reducing at least some of the first oversize fraction; size separating at least some of the size-reduced first oversize fraction into a second undersize fraction comprising particles smaller than the second separation size and into a second oversize fraction comprising particles larger than the second separation size; combining at least some of the first undersize fraction and at least some of the second undersize fraction into a fine fraction; and extracting metal from at least some of the fine fraction. Another method of treating incinerated waste comprises extracting metal by froth flotation from at least some of the incinerated waste. Systems are also disclosed.