Professor Daniel A. Vallero is an internationally recognized author and expert in environmental science and engineering. He has devoted decades to conducting research, teaching, and mentoring future scientists and engineers. He is currently developing tools and models to predict potential exposures to chemicals in consumer products. He is a full adjunct professor of civil and environmental engineering at Duke University’s Pratt School of Engineering. He has authored 20 environmental textbooks, with the most recent addressing the importance of physical principles in environmental science and engineering. His books have addressed all environmental compartments and media within the earth’s atmosphere, hydrosphere, lithosphere, and biosphere. Professor Trevor Letcher is an Emeritus Professor at the University of KwaZulu-Natal, South Africa, and living in the United Kingdom. He was previously Professor of Chemistry, and Head of Department, at the University of the Witwatersrand, Rhodes University, and Natal, in South Africa (1969-2004). He has published over 300 papers on areas such as chemical thermodynamic and waste from landfill in peer reviewed journals, and 100 papers in popular science and education journals. Prof. Letcher has edited and/or written 32 major books, of which 22 were published by Elsevier, on topics ranging from future energy, climate change, storing energy, waste, tyre waste and recycling, wind energy, solar energy, managing global warming, plastic waste, renewable energy, and environmental disasters. He has been awarded gold medals by the South African Institute of Chemistry and the South African Association for the Advancement of Science, and the Journal of Chemical Thermodynamics honoured him with a Festschrift in 2018. He is a life member of both the Royal Society of Chemistry (London) and the South African Institute of Chemistry. He is on the editorial board of the Journal of Chemical Thermodynamics, and is a Director of the Board of the International Association of Chemical Thermodynamics since 2002.