How much sawdust do you need to dry up spilled oil?

I don't know.

During the clean up operations, there was many suggestions of mopping up oil using sponges, mats made of hair, and maybe sawdust. Any absorbing material should be able to remove some oil from water. Small spills of oil or other pollutants in calm water, may be more effectively cleaned up using these mats. Material or mats that absorbs oil must then be picked up and creates a very large disposal problem. Skimmers seemed to work best.