In addition to iron pellets, other sources of iron for steel production are sinter and recycled scrap. Recycled iron and steel scrap comes from mill processes and post-consumer scrap, such as automobiles and construction debris. Metallurgical-grade coal is transformed into coke at a steel mill or a coke plant. Before being processed into coke, the coal taken directly from a coal mine is crushed, sorted, washed, dried, and blended to achieve the desired size and composition. Calcination removes some of the carbon dioxide by treatment with heat.
Lime reacts more rapidly than limestone and thus is preferable for most steel making applications.
Input Pollution Prevention Options Selecting inputs with more desirable characteristics is a pollution prevention strategy. Using scrap with low lead, cadmium, zinc, and volatile organic compound content reduces toxic air and water pollution. Similarly, using low sulfur coal reduces sulfur dioxide generation, which can produce acid rain. Recycling scrap into new steel is cheaper and more energy-efficient than virgin steel production.