The largest amount of input raw materials in the foundry is silica sand, which constitutes more than 90% of the molding mixture, which is necessary for the production of molds necessary for the production of castings. Almost all silica sand that enters the foundry ends its material cycle in a landfill, either after a single use (molding mixture with an organic binder) or after a certain period of time. Three types of waste with a high SiO₂ content are generated in the foundry: dust from handling the molding mixture (preparation of the molding mixture, molding and framing of castings), dust from blasting of castings, the non-magnetic part of which contains a high proportion of SiO₂, and the used molding mixture. The paper proposes methods for treating and utilizing these wastes containing SiO₂ either directly in the foundry or in other industrial sectors. Dust extracted from the molding mixture preparation workplace can be returned to the process in limited quantities without impairing the properties of the molding mixtures. Dust obtained from blasting castings can be separated by magnetic separation into a non-magnetic component containing a high proportion of SiO₂ and can be returned to the process, and the used molding mixture was added as a substitute for building sand in the preparation of concrete.