The stove pellets and horse bedding need to be checked for phenol/pine oil before using as litter.

Phenol is absorbed rapidly, either by ingestion or through the skin, then metabolized by the liver. Unfortunately, cats lack the enzyme (glucuronyl transferase) needed to break down phenol. Exposure may lead to serious liver damage, liver failure, and may even be fatal.

Edit: Pine-Sol used to be dangerous to use on floors that cats walk on, due to the pine oil. No idea if it still contains the oil. I've never used the stuff.