Industrial by-product gypsum, also known as flue gas desulfurization (FGD) gypsum, refers to gypsum produced when calcium oxide reacts with desulfurization and denitrification agents during flue gas desulfurization and denitrification processes. Currently, industrial by-product gypsum mainly originates from flue gas desulfurization and denitrification, as well as waste generation activities in industries such as steel and copper metallurgy, phosphorus chemical industry, and fertilizer production. Unit processes include energy use (especially fuel consumption in sintering), auxiliary material usage, waste treatment, and pollution emissions. The life cycle inventory is formed by consolidating data from multiple sources.