Disclosed is an intermediate part forming a wadding cup to be placed in the case of a cartridge for separating the explosive charge and the shot. It includes a cylindrical sleeve of outer diameter suitable for being inserted slidingly into the case, the sleeve having a front portion the end of which is open, suitable for containing the shot, and a rear portion including a cylindrical wad flush with the end of the rear portion, the intermediate part being formed of at least 95% by weight of biodegradable or decomposable materials, such as cardboard and cork. Also disclosed is a biodegradable cartridge with cup and wadding, complying with environmental rules.