scavenging >> /ˈskavɪn(d)ʒ/
Definition: [verb] Search for and collect (anything usable) from discarded waste.
Example: people sell junk scavenged from the garbage
Definition: [verb] Remove (combustion products) from an internal combustion engine cylinder on the return stroke of the piston.
Definition: [verb] Combine with and remove (molecules, groups, etc.) from a particular medium.
Example: chlorine molecules can scavenge ozone at a very fast rate