René Kleijn is an assistant professor and project manager at the Department of Industrial Ecology at the Institute of Environmental Sciences, Leiden University. He has over 20 years of experience in scientific research with a focus on substance and material flow analysis, lifecycle assessment and resource scarcity. Currently, within the institute, he is working on the development of more dynamic and comprehensive tools that can be used to study the effects of large scale transitions i.e. Life Cycle Sustainability Analysis. He applied these different tools in many domains, including energy systems. In recent years, he studied the apparent new epoch of material scarcity and has performed a series of case studies in which the material constraints for different fossil fuel based and renewable energy technologies have been studied. René Kleijn has co-authored over 30 peer reviewed scientific journal papers as well as many research reports, conference papers and columns. He has been a subject-editor of the Journal of Industrial Ecology and a member of the Council of the Society for Industrial Ecology. He has been involved in over 10 large European research projects on topics such as Material Flow Analysis, Eco-innovation and Life Cycle Assessment. He is also member of the consortia that are involved in two major European research projects that are related to the flagship initiative Resource Efficient Europe