It combines the advantages of pyrometallurgy and a cheap reductant. For further processing two basic methods are used&colon; pyrometallurgy or electrowinning. Processing techniques that complement hydrometallurgy are pyrometallurgy, vapour metallurgy, and molten salt electrometallurgy. Unit processes are usually broken down into three categories&colon; pyrometallurgy, hydrometallurgy, and electrometallurgy. Pyrometallurgy is a branch of extractive metallurgy. In pyrometallurgy, the metal ore is first oxidized through roasting or smelting.