Tell us about yourself!
I think you mean BTU, or British thermal unit. How much energy it takes to raise 1 gallon of water 1 degree, The higher the BTU, more heat is created depending on fuel. Wood or any Fuel like it are impossible to assign a BTU. How dry is the wood, where was it grown, etc. If this isn't what you were talking about, sorry for taking up your time.
Back in the 70's you stuff over the counter in your local drug store. It Came in tins that were between 1oz to 1lb over the counter. You could restock your average chemistry set. Of course other than a small candy counter, that was all they sold. I recently asked at my local store of I could still order it, unfortunately they were all to young to remember what a drug store was before all the food and toys. But if all you want is Balckpowder, you can get it without a license at Walmart.