Scavenging

verb (used with object), scavenged, scavenging.
1.
to take or gather (something usable) from discarded material.
2.
to cleanse of filth, as a street.
3.
to expel burnt gases from (the cylinder of an internal-combustion engine).
4.
Metallurgy. to purify (molten metal) by introducing a substance that will combine chemically with impurities.
verb (used without object), scavenged, scavenging.
5.
to act as a scavenger.
6.
(of an engine or cylinder) to become scavenged of burnt gases.
7.
to search, especially for food.
verb
1.
to search for (anything usable) among discarded material
2.
(transitive) to purify (a molten metal) by bubbling a suitable gas through it. The gas may be inert or may react with the impurities
3.
to clean up filth from (streets, etc)
4.
(chem) to act as a scavenger for (atoms, molecules, ions, radicals, etc)