Sawdust is a material added by Thermal Expansion. It is a common byproduct of processing wooden items in a Sawmill. Sawdust is also produced when Wood logs are smashed by a Pulverizer. A variant of the material, Compressed Sawdust, can be produced by crafting multiple piles of Sawdust together.
Regular Sawdust can be used to craft Paper, Phyto-Gro, Sponges or Florbs. Compressed Sawdust only has one use: it can be smelted into Charcoal. However, this is very useful, as it makes processing Wood logs in a Sawmill even more efficient.