Assessment of the Environmental Impact of Residual and Critical Elements in Steel:Removal, Recovery and Substitution

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SUSTAIN (www.sustainsteel.ac.uk) is an exciting £35M collaborative project between the Universities of Swansea, Warwick and Sheffield working in partnership with the UK steel industry. This project will link to the first grand challenge in the SUSTAIN Hub of 'Zero Waste, Carbon Neutral Steel and Ironmaking' with the aim of decarbonizing iron and steel manufacturing, and so aligns to the Advanced Metallics DTC.Significantly increasing the use of steel scrap in steel production has become a strategic decision for the UK steel industry. This is driven by the government compulsory target of reducing CO2 emissions by 80% before 2050 for industry and is motivated by the current over-supply of steel scrap and its projected growth in quantity over the next decade. There are a number of challenges associated with this approach. The first challenge for the increased use of scrap is the impurities (residual elements) inherited from the steel scrap that can strongly influence the processing of the steel and the in-service properties of steel products. This means that a lot of current scrap recycled steel is down-cycled to lower grade steel products. Scrap can also cause problems when it is mixed with other materials, and its chemical composition can vary depending on its origin and the degree of previous processing. Mechanisms for removal of residual elements do exist, but these can be energy intensive. New removal mechanisms are being proposed, but the environmental impact of these are uncertain.The second important issue arising from the use of scrap in the steelmaking process (although this problem is not unique to electric steelmaking practices) is the recovery of key elements from a product at the end of its life, or during the manufacturing process. This issue becomes even more important from a resource efficiency, supply chain and cost perspective if the element is classed as critical or strategically important. Finally, replacement or substitution of these critical or strategically important elements in steel products is something that will be required for a number of supply-chain, economic and ethical reasons. There are potential replacements and alternatives for many steel products, but quantifying the environmental impact of using these replacements is vital before fully informed decisions can be made. The principal aims of this project therefore are to assess (i) the economically feasible removal mechanisms and limits for key residual elements such as tin, lead, nickel, zinc and copper(ii) the environmental impact of recovery mechanisms for residual and or critical elements such as niobium(iii) the environmental impact of substituting residual and/or critical elements in steel productsThe most widely used and accepted technique to assess this type of impact is Life Cycle Assessment (LCA). An LCA is a systematic technique used to analyse the environmental aspects and potential impacts associated with a product at all stages across the life cycle chain. Using LCA methodologies, this study will assess strategies for removing residual elements, assess strategies for keeping alloying elements 'in the loop' through the life-cycle of steel, by for example better segregation of scrap and the adoption of technical advances to improve the yield / recovery of key resources during the recycling process, and assessing their potential in a resource efficiency context, and finally will assess the impact of substituting or replacing critical elements in a number of steel products. The collection of data e.g. on current (and predicted) recycling rates of steel products will be an important element of the project and a full life cycle approach will be adopted in reaching conclusions that are practical and can make a positive contribution to the performance of a resource efficient steel industry.