P. Aarne Vesilind received his undergraduate degree in civil engineering from Lehigh University and his Ph.D. in environmental engineering from the University of North Carolina. He spent a post-doctoral year with the Norwegian Institute for Water Research in Oslo and a year as a research engineer with Bird Machine Company. He joined the faculty of Duke University in 1970 where he served as chair of the Department of Civil and Environmental Engineering. In 1999, he was appointed to the R. L. Rooke Chair of the Historical and Societal Context of Engineering at Bucknell University. He served in this capacity until his retirement in 2006. William A. Worrell received a B.S. and M.S. in Civil Engineering from Duke University in 1976 and 1978, respectively. His master's thesis involved evaluating the separation efficiencies of various air classifiers. In 1989 he attended Harvard University's John F. Kennedy School of Government Summer Program for Senior Executives in State and Local Government. Mr. Worrell has published and/or presented 56 professional papers in the United States, England, Switzerland, Japan, Hong Kong, Peru, and China. He is a registered professional engineer in California, Georgia, and Florida. Christian Ludwig received his master's degree (1990) and Ph.D. (1993) from the Chemistry Department at the University of Berne, Switzerland. Post-doctoral years were spent at the Department of Land, Air, and Water Resources (LAWR), UC Davis, CA (1994-1995) and at the Swiss Federal Institute for Environmental Science and Technology EAWAG (1995-1997). Since 1997, he has worked at the General Energy Research Department of Paul Scherrer Institute (PSI). In 2005 he was appointed adjunct professor at the Swiss Federal Institute of Technology Lausanne (EPFL) in the field of Solid Waste Treatment. He has (co-)chaired several large international conferences focusing on Resources and Waste Management, such as REWAS and World Resources Forum.