Jonathan Cullen is the Professor of Sustainable Engineering at the University of Cambridge. He leads the Resource Efficiency Collective (www.refficiency.org) and has a reputation for top-down studies of resource systems, bringing skills in developing new metrics to reflect both energy and emissions consequences of materials production. Jonathan's research interests span energy and material systems, efficiency limits, circularity and zero carbon transition pathways. He currently leads C-THRU: carbon clarity in the global petrochemical supply chain (c-thru.org), and is a co-investigator on: CCG, TransFIRe: Foundation Industries Research and Innovation Hub (transfire-hub.org), S2uPPlant: Smart Sustainable Plastic Packaging from Plants (UKRI), and UK FIRES: Locating Resource Efficiency at the heart of Future Industrial Strategy (ukfires.org). He is a Lead Author for the IPCC AR6 Industry Chapter and co-authored the book "Sustainable Materials: with both eyes open", which pioneered the concept of material efficiency for energy-intensive industries. (www.refficiency.org/publications/smwbeo/).