The article discusses the problem of the supply of a by-product, which is synthetic gypsum produced as a result of flue gas desulphurization in conventional power plants. The state of production and forecast for the future are presented. Currently, synthetic gypsum is almost entirely used as a raw material in the gypsum products plant located in the immediate vicinity of the power plant. Since the mid-1990s, in Poland, an increase in the production of synthetic gypsum associated with the construction of a flue gas desulphurization installation in Polish conventional power plants has been observed. In the near future, the upward trend will continue in connection with the construction of new coal units in power plants. Significant surpluses of this raw material will appear on the market, which will not be used on an ongoing basis in the production of gypsum components. However, due to the EU’s restrictive policy towards energy based on coal and lignite, within the next few decades, the share of conventional power plants in energy production will be gradually reduced. As a consequence, the supply of synthetic gypsum will also gradually decrease. Therefore, it is advisable to properly store the surplus of this raw material so that it can be used in the future. Taking this into account, it is already necessary to prepare methods for storing the expected surpluses of synthetic gypsum. For this purpose, post-mining open pits are particularly suitable, especially in mines of rock raw materials. The article proposes a legal path enabling the post-mining open pits to be transformed into a anthropogenic gypsum deposit.