In the photo above, see the unsightly holes in the seat of the Adirondack chair, made by the deck screws? My classmates taught me to fill those inconvenient cavities with a mixture of sawdust and wood glue. You just mix it up with your fingers and jam it down into the holes. Or you can squirt wood glue into the holes and shove dust on top.
When the sawdust paste dries, you hit it with the palm sander, and the filled holes are much less obvious.
To be fair, it’s not exactly a re-use for ALL the sawdust, but rather for a very small percentage. For example, imagine all the sawdust you could sweep up and put into a 2006 Honda Odyssey minivan, then remove, say, a Starbucks venti cup worth of shavings from the car. Then remove from the cup an amount of sawdust equal to the amount of coffee you would pour into the Starbucks trashcan if you needed room to add half & half to your coffee. That ratio–sawdust remaining in van to sawdust poured in Starbucks trash–is about the same ratio of sawdust thrown away to sawdust up-cycled on any given day in the shop.
But it’s a start.