Chemical looping: a technology platform for upcycling low-grade industrial resources

Ambitions towards a circular economy are increasingly vocalised across academia, policymaking and industry. The endeavour of realising these ambitions provides major opportunities and challenges in chemical engineering, and requires a tremendous roll-out of new technologies. This perspective highlights the suitability of chemical looping as a technology platform to contribute to the valorisation of material streams that are currently not used to their full potential, termed low-grade resources. Such material streams offer significant opportunities to minimise CO₂ emissions and accelerate towards a circular materials economy. Apart from defining and identifying low-grade streams, both calorific and non-calorific, a non-exhaustive overview of such streams is provided. Based on a selection of case studies focusing on steel mill gases, bauxite residue, pyrite cinder, calcium carbide slag and automotive shredder residue, it is posited that the characteristics and flexibility of the chemical looping approach offer ample possibilities to efficiently reuse low-grade streams and minimise their environmental impact. Finally, an outlook on chemical looping as a technology platform and its possible role in the drive towards circularity is given, with attention for the roles of industrial, academic and governmental stakeholders. In order to assess the suitability of a chemical looping process for valorising low-grade resources, the importance of holistic technology investigations is stressed, taking into account technical, economic, ecological and societal considerations.