4. Select materials with ecological factors in mind. Of importance here are the
known availability in nature of the required raw materials, processing energy requirements,
processing pollution problems (air, water, land, thermal, and noise),
and recyclability. Ideally, all these factors would be appropriately reflected
within the pricing structure, and this will more likely happen in the future than it
has in the past.
Another factor to be considered is the relative durability of alternative materials
for use in a perishable part. For example, consider the great reduction in the
number of razor blades required (and in the number of scrap razor blades) made
by changing the material to stainless steel. (But would it be better, overall, to devise
a convenient and effective way to resharpen the blades rather than throwing
them away?)
The engineer should also consider the compatibility of materials with respect
to recycling. For example, zinc die castings deteriorate the quality of the
scrap obtained when present junked cars are melted.