## 3 Factsage in the Environmental Sector
### Application in the Field of Solid Waste  
Factsage is widely employed in the field of solid waste treatment to investigate the physical and chemical properties of solid waste, conduct thermodynamic analyses of heat treatment processes for solid waste, optimize metal waste resource recovery processes, and address other solid waste treatment concerns [119; 120; 121]. Some of the study cases are shown in Table 8. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Case Descriptions** & **Related Modules** & **Reference** \\ \hline Used phase diagrams to analyze the sintering mechanism for the preparation of porous ceramics from fly ash. & Phase Diagram & [122] \\ \hline Calculated the reduction thermodynamics of copper slag and determined the process conditions for recovering metal elements from copper slag. & Phase Diagram & [123] \\ \hline Studied the thermodynamic properties of the CaO-SiO\({}_{2}\)-FeOx-MgO quaternary oxide system to provide a basis for the slaging treatment of incineration bottom ash. & Phase Diagram & [124] \\ \hline Used various analytical tools to study the chemical and mineral compositions of ash from burning corn stalks, wheat straw, and poplar wood at different temperatures. & Reaction Phase Diagram & [125] \\ \hline Used phase diagrams to analyze the melting behavior and mechanisms of co-melting for municipal solid waste incineration fly ash and fly ash. & Phase Diagram & [87] \\ \hline Used a metallurgical shaft furnace reactor to process municipal solid waste incineration fly ash and analyzed the physical phase changes during the melting process of the fly ash. & Equilib Viscosity & [126] \\ \hline Performed thermodynamic calculations and simulations on the evolution of iron and sulfur compounds during the co-combustion of coal and sludge. & Equilib & [127] \\ \hline Studied and analyzed the changes in the chemical forms of heavy metals during sludge incineration. & Equilib & [128] \\ \hline Studied the reduction smelting process of red mud and calculated the composition of the resulting metal and slag phases. & Equilib Viscosity & [129] \\ \hline Performed a thermodynamic analysis of the carbothermic chlorination process for extracting aluminum from fly ash to determine its feasibility. & Phase Diagram Equilib & [130] \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Application study of the field of solid waste of Factsage software. Factsage is a valuable tool in studying the physicochemical properties of solid wastes and can provide essential data for determining the appropriate treatment and disposal technology for these wastes. For instance, [PERSON] et al. [124] investigated the thermodynamic properties of the CaO-SiO\({}_{2}\)-FeO\({}_{\mathrm{x}}\)-MgO quaternary oxide system and calculated the effects of temperature and oxygen partial pressure on the phase equilibrium in the liquid phase region and the high FeO\({}_{\mathrm{x}}\) region of this oxide system. The obtained thermodynamic data provide crucial information for studying incineration waste bottom slagging treatment, ensuring the formation of a glassy phase in incineration waste bottom slagging and low leaching of heavy metals. [PERSON] et al. [125] also used the Reaction module to predict the chemical and mineralogical composition of post-combustion ash from corn straw, wheat straw, and aspen, contributing to better utilization of these biomass ashes and avoiding their negative effects through a comprehensive understanding of their chemical composition and thermodynamic properties. Factsage is a versatile tool that can be utilized not only for studying the physicochemical properties of solid waste but also for developing treatment and disposal technologies for specific solid wastes, such as heat treatment and metal resource recovery technologies [122; 131].