Computers and Chemical Engineering 23 (1999) 623 – 634 Pollution prevention with chemical process simulators: the generalized waste reduction (WAR) algorithm — full version Heriberto Cabezas *, Jane C. Bare, Subir K. Mallick 1 U.S. Enironmental Protection Agency, National Risk Management Research Laboratory, Sustainable Technology Diision, Systems Analysis Branch, 26 West Martin Luther King Drie, Cincinnati, OH 45268, USA Received 11 February 1998; received in revised form 3 July 1998 Abstract A general theory for the flow and the generation of potential environmental impact through a chemical process has been developed. The theory defines six potential environmental impact indexes that characterize the generation of potential impact within a process, and the output of potential impact from a process. The indexes are used to quantify pollution reduction and to develop pollution reducing changes to process flow sheets using process simulators. The potential environmental impacts are calculated from stream mass flow rates, stream composition, and a relative potential environmental impact score for each chemical present. The chemical impact scores include a comprehensive set of nine effects ranging from ozone depletion potential to human toxicity and ecotoxicity. The resulting waste reduction methodology or WAR algorithm is illustrated with two case studies using the chemical process simulator Chemcad III (Use does not imply USEPA endorsement or approval of Chemcad III). © 1999 Elsevier Science Ltd. All rights reserved. 1. Introduction There is currently a great deal of interest in the development of methods that can be used to prevent or at least minimize the generation of pollution; and there are numerous efforts underway in this area (Lederman & Weaver, 1991; El-Halwagi, El-Halwagi & Manou- siouthakis, 1992; Fonyo, Kurum & Rippen, 1994; Mallick, Cabezas, Bare and Sikdar, 1996; Manou- siouthakis and Allen, 1995; Rossiter, 1995). This inter- est stems from the belief that pollution prevention is likely to lead to the creation of technologies that have a much more benign impact on human health and the environment. Because this technology is inherently less polluting, it is likely to be more robust and economical than simply adding pollution control devices to conven- tional designs. In chemical manufacturing, these pollu- tion prevention methods take the form of an effort to design process plants that generate as little pollution as possible. Since chemical process simulators are widely used in the design and operation of chemical manufac- turing plants, the development of a pollution preven- tion methodology for chemical process simulators is likely to have a significant impact on the pollution generated by the chemical industry. At the National Risk Management Research Laboratory, research ef- forts are underway to develop a methodology for com- mercial chemical process simulators. The research effort is called the waste reduction or WAR algorithm after Hilaly and Sikdar (1994) who performed some of the early work in this area. This paper presents a generalization of the WAR algorithm, discusses the methodology for evaluating potential environmental impacts, and illustrates the use of the method in the design or modification of chemical processes with two case studies. 2. Potential environmental impact theory Potential environmental impact is the unrealized ef- fect or impact that the emission of mass and energy would have on the environment on average. It is, * Corresponding author. Fax: +1-513-5697111. E-mail address: cabezas.herberto@epamail.epa.gov (H. Cabezas) 1 Post Doctoral Research Fellow, Oak Ridge Institute for Science and Education. Present address: Simulation Sciences Inc., 601 South Valencia Avenue, Brea, CA 92621, USA. 0098-0354/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII: S 0 0 9 8 - 1 3 5 4 ( 9 8 ) 0 0 2 9 8 - 1