Scrap is a term used to describe steel that has reached the end of its useful life, known as ‘post-consumer scrap’ or has been generated during the manufacture of steel products, known as ‘pre-consumer scrap’. While the term ‘scrap’ may lead one to believe this is a waste product, it is actually a valuable raw material used in every steelmaking process. Due to its inherent magnetism, steel is very easy to separate and recycle, making steel the most recycled material in the world.
Melting steel scrap at the end of its useful life allows us to create new steels, making adjustments to the chemistry and shape of the new product. Almost every steel plant uses scrap as part of its raw materials mix, and therefore almost every steel plant is also a recycling plant.
In blast furnace (BF) steelmaking, each charge of the basic oxygen furnace, in which carbon carbon-rich pig iron is refined into crude steel, typically contains up to 30% scrap.
Scrap acts as a cooling agent, absorbing excess heat from the exothermic decarbonisation process. In some cases, scrap is added directly to the BF as a source of iron units, reducing greenhouse gas emissions. In electric arc furnace (EAF) steelmaking, up to 100% scrap is used to make new steel products.
Around 650 Mt per year of scrap is consumed each year for steel production (compared with a total crude steel production volume of around 1.9 Gt per year), with comparable amounts of scrap used in the primary and secondary routes. This avoids the emission of approximately 975 Mt of CO2 annually and significantly reduces the use of other natural resources use, such as iron ore, coal and limestone.
In theory, all new steel could be made from recycled steel. However, currently, this is not feasible due to the scarcity of scrap. This is because of the long service life of steel products, given steel’s strength and durability.
The average life of steel products ranges from a few weeks for steel packaging to up to 100 years for buildings and infrastructure. The average lifespan of a steel product is 40 years. This means there is a significant delay between steel being produced and being available for recycling. Continued growth in steel demand means that transitioning the industry to entirely scrap-based production is unlikely to be possible during this century.
Steel demand is growing at a faster rate than scrap is being released from the pool of ‘steel in use’. All scrap currently collected is recycled. As such there is only limited scope to increase scrap availability. Any future increase in availability will be drawn from the expected increase of post-consumer scrap availability.