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              Pollution Prevention from Chemical Processes                                                595

              companies and whole industry associations or sectors, the
              policy of priority for pollution prevention took shape in
              the United States. The outcome has been impressive, not
              necessarily uniform, but achieving a philosophical shift
              to cleaner manufacturing. These events are even more im-
              pressive when it is recognized that virtually all of the indi-
              vidual changes to manufacturing have been cost-effective
              (a  generally  held  rule  of  a  2-year  payback  on  capital
              investment).
                Use of the term pollution prevention is common in the
              United States, but is actually one of many nearly synony-
              mous terms, which include the following:

              Waste minimization
              Cleaner production
              Waste reduction
              Clean technology
              Source reduction
                                                                           FIGURE 2  Plant with pollution.
              Environmentally benign synthesis
              Environmentally conscious manufacturing
              Green chemistry                                   materials to make the saleable products(s) and energy. The
              Technology for a sustainable environment          only significant outputs are saleable products.
              Sustainability
              Green engineering
                                                                IV.  HOW DOES ONE DEFINE
              Use of a particular terminology usually is linked to the  POLLUTION PREVENTION?
              forum in which the debate is occurring and hence these
              terms have subtle differences, but share the major empha-  We define pollution prevention fairly broadly, in keeping
              sis on prevention. That is, all of these descriptors refer to  with the actual practices widely utilized by industry. This
              the intuitive perspective that it is advantageous to manage  definition is any cost-effect technique aimed at reducing
              chemical losses or wastes generated from the top of a hier-  chemical or energy-related emissions that would subse-
              archy for waste minimization. In addition, there is a certain  quently have to be treated. In keeping with the generally
              trend to reinvent terms with new government initiatives.  voluntary nature of U.S. pollution prevention activities,
                                                                the double hurdle of technical and economic feasibility
                                                                are met in a pollution prevention option (Fig. 4).
              III.  WASTE AS POLLUTION                            This definition manifests itself in the form of the pollu-
                                                                tionpreventionhierarchyshowninFig.5.Inthishierarchy,
              An industrial waste is defined as an unwanted by-product  safe disposal forms the base of the pyramid, and minimiz-
              or damaged, defective, or superfluous material of a manu-  ing the generation of waste at the source is at the peak.
              facturing process. Most often, it has or is perceived to have  The U.S. Environmental Protection Agency (EPA) def-
              no value. It may or may not be harmful or toxic if released  inition of pollution prevention recognizes actions which
              to the environment. Pollution is any release of waste to  encompass the upper three levels in the hierarchy: min-
              the environment (i.e., any routine or accidental emission,  imize generation to segregate and reuse. The U.S. EPA
              effluent, spill, discharge, or disposal to the air, land, or
              water) that contaminates or degrades the environment.
                Figure 2 depicts a typical manufacturing facility. In-
              puts to the facility include raw materials to produce the
              saleable product(s), water, air, solvents, catalysts, energy,
              etc. Outputs from the facility are the saleable product(s),
              waste energy, and gaseous, liquid, water, and solid wastes.
              In contrast, a manufacturing facility with an absolute min-
              imum (but not zero) amount of waste being generated is
              shown in Fig. 3. Inputs to the facility include only the raw  FIGURE 3 Absolute minimum waste generation facility.
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