Not all types of glues used in hot glue guns are biodegradable.
Glue used in Hot Glue Guns can be referred to as Hot Melt Adhesive. These are made using different chemicals or synthetically produced base materials. Biodegradability of such adhesives largely depends on the base materials which are used to develop them.
Most commonly used base materials used to make these glues are :
Polymers – (Most polymers are not biodegradable)
Resins – (Most polymers are not biodegradable)
Plasticizers- (Not biodegradable)
However, now-a-days, there are biodegradable hot melt adhesives also available.