If i have a machining session on oak or cherry the sawdust & shavings get bagged up & given to a mate with a smoker. If theres mdf or other treated stuff & it goes on the bonfire, mixed or hardwood goes in the compost or on the garden.
Used to work at a coachbuilders in the 60s and there was a big sawdust burner that was the apprentices job to light first thing in winter. After filling the inner drum and removing the central tube it was normally enough to put a couple of pages of newspaper underneath and put a match to it. One day he had no joy so decided to pour a jar of what he thought was dirty turps in to help it along. He put the lid on and put a light Into the bottom. Unfortunately it was thinners not turps and the 3ft diameter lid hit the roof with an almighty bang.