I cut down a few sumac trees (not poison Sumac) at work about 8 months ago. Veteren woodburners I know told me it wouldn't burn hot or last and just to use it as a filler with hardwood. I have found that it burns pretty hot and is good for starting a fire and building a good bed of coals for my locust, cherry, maple and oak. It does burn up fast. My question is, does it leave alot of creosote, or is it safe to burn a lot of it?