Pyro-hydrometallurgical methods are described to economically and environmentally recover a target metal from iron slag or steel slag. For instance, the method can enable subjecting an iron or steel slag feed to acid-baking with an acid to produce a dried mixture comprising at least one soluble metal salts, then subjecting the dried mixture to water leaching to an aqueous solution comprising an aqueous leachate rich in said target metal and solid residues and subsequently separating the aqueous leachate rich in said target metal from the solid residues. This acid-baking water-leaching method facilitates efficient recovery of target metal compared to conventional methods.

A slag foaming system for an electric arc furnace utilizing algae is described. The algae may be dried algae in particle form that is injected into the electric arc furnace through a solids injector and may be directed into the slag. Other slag foaming compositions may also be injected into a furnace as a function of furnace parameters to create slag foam while maintaining a high yield of slag without excess iron oxide and reduced carbon and carbon dioxide emission. The algae and slag foaming composition may be used in combination for slag formation and control.

A slag foaming system for an electric arc furnace utilizing algae is described. The algae may be dried algae in particle form that is injected into the electric arc furnace through a solids injector and may be directed into the slag. Other slag foaming compositions may also be injected into a furnace as a function of furnace parameters to create slag foam while maintaining a high yield of slag without excess iron oxide and reduced carbon and carbon dioxide emission. The algae and slag foaming composition may be used in combination for slag formation and control.