By default you have one scavenger who sorts 100 pieces of scrap every 60 minutes. He works while there's enough scrap to produce car parts and enough free space in storage.
You can recruit additional scavengers to increase the amount of scrap that can be sorted in the same time period. For every recruited scavenger you get 6 additional slots in storage.
You can also recruit a Taskmaster. The Taskmaster makes the storage limitless and scavengers work without breaks under his management.