Waste recycling continues to be an urgent problem for the much-demanded production of phosphate fertilizers, without which maintaining soil fertility and, as a result, solving the problem of food supply is becoming increasingly difficult. These wastes contain calcium and silicon compounds in their composition and are an industrially important source of raw materials for solving a wide range of problems in various fields of science and technology. The basics of hydrothermal synthesis in the recycling process developed jointly with scientists of the Institute of Inorganic Chemistry RAS under the leadership of Academician A.I. Holkin can attract the attention of a wide range of specialists recycling waste products of ferrous metallurgy, chemical industry and power industry, containing calcium and silicon compounds.