WASTE REDUCTION AND MINIMIZATION

22.2 WASTE REDUCTION AND MINIMIZATION

The initial sections of this chapter address waste reduction and minimization. During recent years, substantial efforts have been made toward reducing the quantities of wastes and, therefore, the burden of dealing with wastes. Much of this effort has been the result of legislation and regulations restricting wastes, along with the resulting concerns over possible legal actions and lawsuits. In many cases—and ideally in all—minimizing the quantities of wastes produced is simply good bus- iness. Wastes are materials, materials have value and, therefore, all materials should

be used for some beneficial purpose and not discarded as wastes, usually at a high cost for waste disposal. Industrial ecology is all about the efficient use of materials. Therefore, by its nature, a system of industrial ecology is also a system of waste reduction and mini- mization. In reducing quantities of wastes, it is important to take the broadest possible view. This is because dealing with one waste problem in isolation may simply create another. Early efforts to control air and water pollution resulted in

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Manufacturing operation, potential generation of wastes

1 Prevent waste

generation

Wastes generated

Wastes

wastes in secure Sanitary, construction,

Hazardous

4 Wastes

or industrial landfill chemical landfill

treated

Solids

Publicly owned treatment works (POTW) for water

Figure 22.1 Order of effectiveness of waste-treatment management options. The darkened circles indicate the degree of effectiveness from the most desirable (1) to the least (4).

Many hazardous-waste problems can be avoided at early stages by waste reduction (cutting down quantities of wastes from their sources) and waste mini- mization (utilization of treatment processes that reduce the quantities of wastes requiring ultimate disposal). This section outlines basic approaches to waste minimization and reduction.

There are several ways in which quantities of wastes can be reduced, including source reduction, waste separation and concentration, resource recovery, and waste recycling. The most effective approaches to minimizing wastes center around careful control of manufacturing processes, taking into consideration discharges and the potential for waste minimization at every step of manufacturing. Viewing the process as a whole (as outlined for a generalized chemical manufacturing process in

Figure 22.2 ) often enables crucial identification of the source of a waste, such as a raw material impurity, catalyst, or process solvent. Once a source is identified, it is much easier to take measures to eliminate or reduce the waste. The most effective approach to minimizing wastes is to emphasize waste minimization as an integral part of plant design. 2

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Modifications of the manufacturing process can yield substantial waste reduction. Some such modifications are of a chemical nature. Changes in chemical reaction conditions can minimize production of by-product hazardous substances. In some cases, potentially hazardous catalysts, such as those formulated from toxic substances, can be replaced by catalysts that are nonhazardous or that can be recycled rather than discarded. Wastes can be minimized by volume reduction, for example through dewatering and drying sludge.

Reactants Contaminants

(impurities)

Reaction media (water, organic

Atmospheric solvents)

emissions

Manufacturing process

Catalysts Recycle

Products and Discharges that may useful by-products

require treatment

Reclaimed by-products

Wastewater

Solids and sludges

Figure 22.2 Chemical manufacturing process from the viewpoint of discharges and waste minimization.

Many kinds of waste streams are candidates for minimization. As examples, such waste streams identified at U.S. Government federal facilities have included solvents used for cleaning and degreasing, spent motor oil from gasoline and diesel engines, leftover and waste paint thinners, antifreeze/antiboil engine cooling formu-

lations, batteries, inks, exposed photographic film, and pathology wastes. 3 The sources of the wastes are as varied as the waste streams themselves. Motor pool maintenance garages generate used motor oil and spent coolants. Hospitals, clinics, and medical laboratories generate pathology wastes. Aircraft maintenance depots where aircraft are cleaned, chemically stripped of paint and coatings, repainted, and electroplated generate large quantities of effluents, including organic materials. 4 Other facilities generating wastes include equipment- and arms-maintenance facil- ities, photo developing and printing laboratories, paint shops, and arts and crafts shops.

A crucial part of the process for reducing and minimizing wastes is the develop- ment of a material balance, which is an integral part of the practice of industrial ecology. 5 Such a balance addresses various aspects of waste streams, including sources, identification, and quantities of wastes and methods and costs of handling,

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There are encouraging signs of progress in the area of waste minimization. All major companies have initiated programs to minimize quantities of wastes produced.

A typical success story is a 97% reduction of landfill wastes from Mobil’s Torrance petroleum refinery from 1989 to 1993. During the same period, the refinery went from less than 1% waste recycle to more than 70%. One of the technologies used for

waste reduction was the Mobil Oil Sludge Coking Process. 6 Similar success stories in reducing wastes can be cited by a number of concerns in the U.S. and throughout the world.