Waste and Minimization

Some industrial wastes result because it is cheaper to buy new material than to reclaim the used material. Some catalysts fall in this category. The 1996 American Chemical Society National Chemical Technician Award went to a technician at Eastman Chemical who set up a program for recovering cobalt, copper, and nickel from spent catalysts for use by the steel industry.194 This process for avoiding landfill disposal gave Eastman significant savings. Some 

Mixed solvents can be difficult to recover. If they are kept separate, they can be reclaimed by distillation on site. The capital investment required is paid back by the reduced need to buy new solvent. In Germany completely enclosed vapor cleaners give 99% reduction in solvent emissions.198 After cleaning and draining, the air-tight chamber is evacuated, the solvent vapors are captured by chilling and adsorption on carbon. When a sensor shows that the solvent is down to 1 g/m3 the vacuum is released so that the lid can be opened. 

In some cases the amount of waste may be considered too small to justify the research needed to find a use for it or to improve the process to eliminate it. The staff may also be so busy with potentially profitable new ventures that it hesitates to take time to devise a new process for a mature product made in an established plant. This may be particularly true in the current period of downsizing and restructuring. 

Improved process design can minimize waste. Deborah Luper suggests asking the following questions 199 

Are you using raw materials that are the target of compound-specific regulations  

---

Isolation of radioactive wastes for long periods to allow adequate decay is sought by the use of multiple barriers. These include the waste form itself, the primary containers made of resistant materials, overpacks as secondary layers, buffer materials, concrete vaults, and finally the host rock or sod. Barriers limit water access to the waste and minimize contamination of water suppHes. The length of time wastes must remain secure is dependent on the regulatory limit of the maximum radiation exposure of individuals in the vicinity of the disposal site. 

Are measures taken to simplify, optimize designs, reduce waste, and minimize risks ... 

Green chemistry (Chapter 11 Focus On) The design and implementation of chemical products and processes that reduce waste and minimize or eliminate the generation of hazardous substances. 

As the example in Fig. 3.18 shows, apart from achieving selectivity, biocatalysis also renders steps such as protection, deprotection, or activation redundant, thereby increasing atom-efficiency, reducing waste, and minimizing energy requirements. 

Precision forging near-net shape generation through the use of precision dies. Reduces waste and minimizes or eliminates machining. 

Reactor temperature and pressure. If there is a significant difierence between the effect of temperature or pressure on primary and byproduct reactions, then temperature and pressure should be manipulated to improve selectivity and minimize the waste generated by byproduct formation. d. Catalysts. Catalysts cam have a major influence on selectivity. Changing the catalyst can change the relative influence on the primary and byproduct reactions. 

The catalytic vapor-phase oxidation of propylene is generally carried out in a fixed-bed multitube reactor at near atmospheric pressures and elevated temperatures (ca 350°C) molten salt is used for temperature control. Air is commonly used as the oxygen source and steam is added to suppress the formation of flammable gas mixtures. Operation can be single pass or a recycle stream may be employed. Recent interest has focused on improving process efficiency and minimizing process wastes by defining process improvements that use recycle of process gas streams and/or use of new reaction diluents (20-24). 

Reduced Emissions and Waste Minimization. Reducing harmful emissions and minimizing wastes within a process by inclusion of additional reaction and separation steps and catalyst modification may be substantially better than end-of-pipe cleanup or even simply improving maintenance, housekeeping, and process control practices. SO2 and NO reduction to their elemental products in fluid catalytic cracking units exemplifies the use of such a strategy (11). 

The main purpose of pesticide formulation is to manufacture a product that has optimum biological efficiency, is convenient to use, and minimizes environmental impacts. The active ingredients are mixed with solvents, adjuvants (boosters), and fillers as necessary to achieve the desired formulation. The types of formulations include wettable powders, soluble concentrates, emulsion concentrates, oil-in-water emulsions, suspension concentrates, suspoemulsions, water-dispersible granules, dry granules, and controlled release, in which the active ingredient is released into the environment from a polymeric carrier, binder, absorbent, or encapsulant at a slow and effective rate. The formulation steps may generate air emissions, liquid effluents, and solid wastes. 

You should use the material balance information to identify the major sources of waste and pollution, to look for deviations from the norm in waste production, to identify areas of unexplained losses, and to pinpoint operations that contribute to flows that exceed national-, local-, or site-discharge regulations. Also, a good thing to remember is that, from a practical standpoint, process ciency is synonymous with waste minimization. 

Information provided in Part III. Section 8. of Form R is optional. In this section, you may identify waste minimization efforts relating to the reported toxic chemical. Waste minimization reduces the amount of the toxic chemicai in wastes by reducing waste generation or by recycling. This can be accomplished by equipment changes, process modifications, product reformulation, chemical substitutions, or other techniques. Waste minimization refers exclusively to practices which prevent the generation of wastes. Treatment or disposal does not minimize waste and should not be reported In this section. Recycling or reuse of a toxic chemical is considered waste minimization. Waste minimization applies to air emissions and wastewater, as well as to liquid or solid mate-... 

The volume represents the initial fulfillment of a series, and is aimed at assisting process engineers, plant managers, environmental consultants, water treatment plant operators, and students. Subsequent volumes are intended to cover air pollution controls, and solid waste management and minimization. 

The requirements of the automotive industry are more demanding than some other industries. Automotive products have to be safe, reliable, and maintainable, protect the occupants, and have minimal impact on the environment in their manufacture, use, and disposal. The automotive sector is a very competitive market and as a consequence costs have to be optimized. There is little margin for excessive variation, as variation causes waste and waste costs money and time. Therefore several methods have evolved to reduce variation. Among them are SPC, FMEA, MSA, and many other techniques The automotive industry believes that the more their suppliers adopt such variation reduction techniques the more likely it will be that the resultant product will be brought to the market more quickly and its production process be more efficient. 

The key to efficient destruction of liquid hazardous wastes lies in minimizing unevaporated droplets and unrcacted vapors. Just as for the rotary kiln, temperature, residence time, and turbulence may be optimized to increase destruction efficiencies. Typical combustion chamber residence time and temperature ranges arc 0.5-2 s and 1300-3000°F. Liquid injection incinerators vary in dimensions and have feed rates up to 1500 gal/h of organic wastes and 4000 gal/h of aqueous waste. 

Use less hazardous processes. Synthetic methods should use reactants and generate wastes with minimal toxicity to health and the environment. 

---