Process Substitution

Processes that create major environmental impact should be replaced with more benign ones. This simple approach to impact reduction can be effective. For example, copper sheeting for electronic products was previously cleaned with ammonium persulfate, phosphoric acid, and sulfuric acid at one large American company's facility. The solvent system was replaced by a mechanical process that cleaned the sheeting with rotating brushes and pumice. The new process produces a nonhazardous residue that is disposed in a municipal solid waste landfill.

A large American chemical and consumer products company switched from organic solvent-based systems for coating pharmaceutical pills to a water-based system. The substitution was motivated by the need to comply with regulations limiting emissions of VOCs. To prevent the pills from becoming soggy, a new sprayer system was designed to precisely control the amount of coating dispensed. A dryer was installed as an additional process step. The heating requirements increased when the water-based coatings were used. However, for a total cost of $60,000, the new system saved $15,000 in solvent costs annually and avoided the expense of $180,000 in end-of-the-pipe emission controls that would have been required if the old solvent system had been retained (Binger 1988).

Process redesign directed toward plant employees can also yield health and safety benefits, as well as reduce cost. In addition, through certain process changes, a facility can reduce its resource demands to a range where closing the loop or completely eliminating waste discharges from the facility is economically feasible. Unless a company fine tunes each process first, however, the waste volume may overwhelm the equipment's capacity to recycle or reuse it. For example, an electroplating process that does not have an optimized rinsing operation must purchase metal re covery equipment with a capacity of five to ten times that needed under optimal rinsing conditions.

The EPA has published several pollution prevention manuals for specific industries. Each manual reviews strategies for waste reduction and provides a checklist.

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