DAVID T. ALLEN, PhD, is the Beckman Professor in Chemical Engineering at The University of Texas at Austin. He is the recipient of numerous awards and is the author of several books. The authors' previous collaborations have resulted in numerous publications, including a widely used collection of course modules entitled Pollution Prevention: Homework and Design Problems for Engineering Curricula. KIRSTEN SINCLAIR ROSSELOT is the owner of Process Profiles, a consulting firm that specializes in environmental planning and management tools for pollution prevention.