Because material selection is a fundamental part of design, it offers many opportunities for reducing environmental impact. In life cycle design, designers begin material selection by identifying the nature and source of raw materials. Then, they estimate the environmental impact caused by resource acquisition, processing, use, and retirement. The depth of the analysis and the number of life cycle stages varies with the project scope. Finally, they compare the proposed materials to determine the best choices.
Minimizing the use of virgin material means maximizing the incorporation of recycled material. Sources of recycled feedstock include in-house process scrap, waste material from another industry, or reclaimed postconsumer material.
The quality of incoming material determines the amount of unusable feedstock and the amount of time required to prepare the material. Therefore, product design dimensions should closely match incoming feedstock dimensions to minimize machining, milling, and scrap generation.
Material substitutions can be made for product as well as process materials, such as solvents and catalysts. For example, water-based solvents or coatings can sometimes be substituted for high-VOC alternatives during processing. Also, materials that do not require coating, such as some metals or polymers, can be substituted in the product.
For example, an American company replaced its five-layer finish on some products with a new three-layer substitute. The original finish contained nickel (first layer), cadmium, copper, nickel, and black organic paint (final layer). The new finish contains nickel, a zinc-nickel alloy, and black organic paint. This substitution eliminates cadmium, a toxic heavy metal, and the use of a cyanide bath solution for plating the cadmium. The new finish is equally corrosion resistant. It is also cheaper to produce, saving the company 25% in operating costs (U.S. EPA 1991b).
A large textile dye house in Chelsea, Massachusetts, complied with local sewer limits by working with its imported fabric suppliers and clients to select only those fabrics with the lowest zinc content. The company thus avoided installing a $150,000 treatment plant. (Kennedy 1993).
Finally, reducing the use of toxic chemicals results in fewer regulatory concerns associated with handling and disposing hazardous material and less exposure to corporate liability and worker health risks. For example, a water-based machining coolant can reduce the quantity of petroleum oils generated onsite and allow parts to be cleaned more effectively using a non-chlorinated or water-based solvent.
Reformulation is an appropriate strategy when a high degree of continuity must be maintained with the original product. Rather than replacing one material with another, the designer alters the percentages to achieve the same result. Some material may be added or deleted if the original product characteristics are preserved.
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