Some scrap yards will buy metal powder and metal cuttings while other scrap yards may not buy it.
Different scrap yards have their own list of things that they will buy and want to deal in so you'd have to call up your individual scrap yard locations and ask them directly for a definite answer on whether the particular scrap yard will purchase metal powder or metal cuttings.
Most scrap yards will buy the metal powder or metal cuttings but some may not.
Just like here one scrap yard will buy steel wire and wire fencing while another one will not buy the steel wire or wire fencing.