Jonathan Cullen is a Professor of Sustainable Engineering at the University of Cambridge and a University Lecturer in Energy, Transport and Urban Infrastructure. He leads the Resource Efficiency Collective and has a reputation for top-down studies of resource systems, bringing skills in developing new metrics to reflect both energy and material consequences of materials production. Jonathan studied Petrochemical and Process Engineering in New Zealand and worked as process engineer in the chemical sector for 10 years, before moving to Cambridge, UK to undertake an MPhil in Engineering for Sustainable Development, PhD in Energy Efficiency and a Research Associate position. Jonathan is currently an Investigator on the £5.2m UKFIRES program grant and the £1.25m project “CirPlas: Circular Economy Approaches to Eliminate Plastic Waste”. He is a Lead Author for the IPCC AR6 Industry Chapter, an Expert Adviser to the IEA Technology Roadmaps, and co-authored the book Sustainable Materials: With Both Eyes Open, which pioneered the concept of material efficiency for energy-intensive industries.