Hi, yes you can use it as a substrate along with a thousand other things, but a few things to consider are:
When a sulcata gets larger and realizes he can eat it, he will. You dont want the substrate to be his main diet.
Is it cost effective to be buying this and cleaning it regulary for a sulcata who is only going to get bigger with bigger messes.
I dont know what the torts are in or where but if its in a open pen or table in your basement or garage I wouldnt want all that mice food laying around all the time!
Topsoil can be purchased any where for less than 1.50 a bag. You can use it dry or moist and even mix some play sand in it for a loamy substrate that works extremely well, very cheap and easy to clean and replace. Just a few thoughts for you. Mike