Mario Giampietro is an ICREA Research Professor at ICTA (Institute of Environmental Science and Technology), Department of Chemical Engineering, Universitat Autonoma de Barcelona, Spain. Kozo Mayumi is a Professor at the University of Tokushima, Japan. He is a co-founder and organizer of the Biennial International Workshop ‘Advances in Energy Studies’, which started in 1998. Alevgül H. Şorman is a Researcher in the Integrated Assessment and Societal Metabolism group at ICTA, Universitat Autonoma de Barcelona, Spain.