Carnegie Mellon University,
Summary:The basic reaction used to reduce iron ore has remained the same since the start of the iron age: carbon is the main reductant. While modern ironmaking is highly efficient and optimized, the high production rate of steel results in the steel industry being a large emitter of carbon dioxide. Full decarbonization would require fundamental changes in ironmaking and steelmaking, but existing technologies already give much lower-carbon steel production. These include scrap-based electric arc furnace steelmaking using renewable electricity, direct reduction using natural gas, and the use of metallic feed in blast furnaces. The carbon intensities of these alternatives have been quantified. In the longer term, electrochemical approaches hold promise, pending their demonstration at industrial scale.