My cat wants to play fetch this morning (when she's not attacking my feet). Both of the partial Russian Blue cats I've had have loved to play fetch.
Most particle board and pressure treat has cchemicals in it that will give off fumes when you burn it. I wouldn't advise using it for a campfire. Maybe you can stick it on the curb with a FREE sign?
Anyways, have fun camping and don't burn the state down.
I have no idea what the regulations are where you live. Are you camping in a park where there might be a Mr. Randy Ranger to ask?
You should never burn anything with "glue" in an indoor fireplace, such as press board or plywood, but I'm not sure about outside. If you do, don't breath the fumes.
I would say just break up the shelf unit (if it's press board that wouldn't be that hard to do) and use something else for your campfire. Just an opinion.
Edited to add: I cross-posted with kayleamay. I didn't mean to duplicate her reply.