The decomposition temperature of CaSO4 slag is very high. There is no temperature limit to using supercritical carbon dioxide to lift it from the solar field to the decomposing waste reactor. However, the higher the temperature, the more the losses by radiation are. The situation makes the use of solar resources difficult or even impossible. Therefore, a reaction medium containing calcium chloride and some precursors was proposed. Feasibility and products predictions were performed by the thermodynamic studies, the thermogravimetric technique analysis, and the X-ray diffraction verification. Consequently, the pyrometallurgical process based on the treatment of mixtures of CaSO4 with carbon or silica show reacts at temperatures achievable with renewable energies, which are evaluated by thermogravimetric analysis from respectively 500°C and 750°C. On the other hand, the outcomes of XRD analysis give an RIR rate of calcium sulfide (CaS) of about 33% (27% with silica). Therefore, the (CaS) compound leads smoothly to sulfur dioxide used in the electrolysis process. Therefore, sulfuric acid and hydrogen are usual value-added products from Westinghouse electrolysis. Indeed 1/3 of the sulfuric acid produced helps generate H2S, and finally, the elemental sulfur will yield spontaneously.