Remember that locust tree I'd been saving as firewood insurance?  It wasn't what I thought it was.

Black locust is considered to be top-notch firewood because you get 112% as much heat out of a same-sized log compared to red or white oaks.   In contrast, the most common trees Mark and I cut out of our woods give only 75% (box-elder) to 83% (black walnut) as much heat as oak, which means more work for less reward.  Effort aside, oak and locust fires are preferred because they keep going longer into the night and put off more heat in the process.

Unfortunately, I'm reanalyzing that standing dead tree and figuring it might be sycamore, which clocks in at only 80% as good as oak.  I'm not sure why I didn't take the multiple trunks into account before, which is a growth habit common in sycamores but rare in black locusts.  I guess I thought the way the logs were so darn tough to split meant they were locust, but it turns out sycamore has a spiral grain that makes splitting a bear.

The easiest way to guess how many BTUs you'll get out of a log of mystery firewood is to wait until it's totally dry and pick it up.  The lighter the wood, the less heat you're going to enjoy when the wood burns.  Bone-dry box-elder is nearly as light as balsa wood, and our mystery tree isn't much heavier.  Meanwhile, both box-elder and our mystery wood work great as kindling, which is another sign of low BTU --- harder woods are tougher to light, unless they're resinous.

The fact I've been burning light wood all winter would explain why we've been going through it so quickly.  Luckily, the shed's still mostly full, and Mark discovered sycamore isn't terribly hard to split if you wait until it's 20 degrees outside.  If we ever run out of fallen, dead, or in-the-way trees and start managing a woodlot, though, sycamore isn't going to be involved.