I know nothing about Box Elder, but I am burning a lot of "Punky" oak this year. It was from standing dead trees I took down as a favor to a neighbor. The sap wood is soft and will not split, comes off in chunks, but the heart wood is still good and I can get the sap wood to stay together if I split a little heart wood off with each piece of sap wood. At first I thought I was wasting my time and threw a lot of it away, but then I discovered what Husky J reported . It burns slowly, with a lot of ash, but adequate for a cool spring evening or morning or a bonfire on a night that is not too cold. Slow burning is not all bad, since it means fewer trips to the wood pile to replenish the fire, but on a big bonfire one night it threw so much white ash into the air it looked like it was snowing. Actually, kinda fun for those of us in SE Louisiana.