Mulberry, Hickory, Osage Orange, Locust and Oak are all very high btu dense woods and would render good lump. The Hickory for me is too rare and valuable as smoking wood, same as mulberry. I've read that osage and locust are not good smoking woods - leave a bad taste to food, so I worry about them as charcoal. Since Oak is ubiquitous around here it gets the nod. If Hickory is readily available I'd consider using it, too. Stick with dense, high btu hardwoods and be sure they are properly seasoned or charcoal burn will take 12 hrs or more.