Page 181 - Design for Environment A Guide to Sustainable Product Development

160 Cha pte r Ei g h t

Advanced Resource Recovery
Resource Cascading
One approach to Design for Environment that seeks to maximize
the utility of resource usage is based on the theory of resource cascad-
ing [10]. The aim of this approach, illustrated in Figure 8.10, is to
find a sequence of resource uses that extracts as much economic
value as possible from a given resource as it evolves from higher-
quality to lower-quality forms. Resource cascading incorporates many
elements of the above guidelines, including dematerialization and
revalorization.
For example, a batch of solvent used for degreasing in electronics
manufacturing could, after a single use, be transferred to a metal
cleaning operation. It could then be used in repeated cycles, until
eventually being relegated to its lowest quality use, as a paint solvent.
Finally, through purification and recycling, the spent solvent could
again be shifted back up the cascade chain to a higher-quality use.
Similarly, in a closed-loop cascading approach, plastic materials
can be used first for cosmetic parts, secondly for internal structural
parts, and finally for base parts in a particular manufacturing pro-
cess, before being recycled into a commingled stream. By the laws of
thermodynamics, all materials and energy reach an equilibrium state
of maximum entropy, but resource cascading enables us to capture as
much economic value as possible during this decline.

FIGURE 8.10 Illustration of resource cascading and relinking.