Recycling of metals is in principle easy since metal in its ground state will not change. However, the recirculation is restricted by impurities and contaminations. The composition of steel can vary and the surface of the steel can be protected with different metallic and/or organic coatings. However, these coatings give rise to major problems in the recovery of scrap such as the creation of undesired by-products like dust containing zinc, lead and cadmium and the creation of harmful or toxic air emissions in the off gas. These problems can be avoided if the coatings are removed prior to the steelmaking stage, e.g. through a separate surface cleaning processing step.
Also, zinc removal is promoted by the presence of chlorine, which can be introduced by using plastics from shredded vehicles (“fluff") as energy source in the preheating step. This ensures that a by-product from vehicle shredding, usually destined for landfill, may become a key ingredient for the recycling of steel scrap.