A five-indicator methodology for early-stage sustainable selection of metal scraps and raw materials: Application in the steel industry

Abstract

This work proposes a straightforward methodology for integrating the environmental, economic, social, criticality and circularity dimensions as normalised indicators into a single equation, yielding a sustainability index, and demonstrates its applicability in the context of the steelmaking industry. This new approach, designed for early development stages and based on the elemental composition of the input materials (metal scraps and raw materials), allows the identification of those within a dataset that are of greatest concern according to their sustainability index and facilitates decision-making regarding their use in alloy production. A sensitivity analysis, with 11 studied scenarios, was conducted to evaluate the influence of the five indicators on the outcome, assigning different weights to them. The developed strategy, compatible with the Safe and Sustainable by Design framework, was successfully applied to a family of 207 materials of varying qualities. A set of raw materials, including both ferroalloys and pure elements, was identified as the most worrying group from the sustainability viewpoint, in line with previous works (e.g., ferroniobium, ferrotungsten, pure cobalt and pure copper), thereby validating the described framework. However, metal scraps should, whenever feasible, be prioritised, as their recovery would reduce the reliance on mineral resources. Consequently, a number of them are presented as alternatives to the least sustainable raw materials according to their sustainability indexes. The application of this methodology provides a holistic view of sustainability and enables rapid decisions regarding which products from a given set are more suitable for use, based on their index values and stakeholder needs.