scavenge

Short definition from Wiktionary

Verb

1. 1
   To collect and remove refuse, or to search through refuse, carrion, or abandoned items for useful material.
2. 2
   To remove unwanted material from something, especially to purify molten metal by removing impurities.
3. 3
   To expel the exhaust gases from the cylinder of an internal combustion engine, and draw in air for the next cycle.
4. 4
   To feed on carrion or refuse.