Life cycle water use and wastewater discharge of steel production based on material-energy-water flows: A case study in China

Abstract

Abstract As a water-intensive industry, iron and steel production has caused serious water resource problems in China. This paper first proposes a material flow analysis-input-output model that considers water use factors and system boundaries for a life cycle water analysis. The life cycle water use and wastewater discharge inventories of different products are quantified, and water flow diagrams of life cycle water withdrawal, consumption and discharge for a steel plant in China are graphically mapped. The results show that the total life cycle water withdrawal, water consumption and water discharge per ton of steel in the case plant were 14.93 t, 5.90 t, and 9.23 t. The steelmaking process constituted the largest fraction, while the cold rolling processes constituted the smallest fraction. By analyzing the direct and indirect water and material-energy-water flow, the indirect water usage in energy and material flows was found to be more important to the water flow in the life cycle water use and discharge for steel production, especially for electricity. However, there were many differences among the subprocesses. In coking and sintering, the main factor was material flow; for ironmaking, water flow; for steelmaking, energy and water flows; and for hot rolling and cold rolling, energy flow.