I was born unto a sawmill and grew up with the offal that never disappointed... I even bought my first car, using sawdust as a down payment, and then a load every week for the summer at the local race track (horses), and I'd be the new owner of a 1947 DeSoto!
As for using it as firewood, it burns too quickly to be practical, in my useless opinion. It isn't compacted, has air throughout, so with the two you get a good deal of heat for a limited time, and then it is converted to ash, which is an insulation, so when it dies, it dies quickly... depending on the type wood, also in my opinion.
I always keep a big can of clean sawdust for using on outside spills of all sorts (oil, anti-freeze/brake fluid/etc.) and even dog eggs benefit from a cup of sawdust and quickly become part of the lawn without blowing off your foot as you traverse your dogs favorite poop spot.
I also use it when turning wet/green raw branches/lumber. You rough down/clean off surface imperfections until you have a clean blank. Write what is is/date/type on the piece and bury it in the very dry (from years of protection) sawdust and it will draw out all the moisture w/i days, week at the most. You can then rough in whatever you choose to make, stick it back in the dust for another week for good measure, and then machine to your heart's content!
It works well on the new/spring plants to hold in the initial watering, and repeat as needed. Great for starting poultry, as well as keeping it in the bottom of the coop to absorb those droppings as well... simply add a cup of lime for smell, DE to kill bugs/mosquitoes, or Sevin dust for mites and such. The birds will dust bath in it, controlling their own parasites.
Personally, I use all my sawdust today on my small farm, and just can't imagine having enough to burn... as a child, we could go through a big mountain of sawdust every week, but selling it was just as good, since we always had plenty at the mill.
Good luck regardless!