The invention relates to a plant complex for steel production comprising a blast furnace for producing pig iron, a converter steel mill for producing crude steel, a gas-conducting system for gases that occur in the production of pig iron and/or in the production of crude steel, and a power-generating plant for electricity generation. The power-generating plant is operated with a gas that comprises at least a partial amount of the blast-furnace top gas that occurs in the production of pig iron and/or a partial amount of the converter gas. According to the invention, a chemical or biotechnological plant is provided and connected to the gas-conducting system and arranged in parallel with the power-generating plant with respect to the gas supply. Externally obtained electricity and power-generating plant electricity are used to cover the electricity demand of the plant complex.