Page 182 - Design for Environment A Guide to Sustainable Product Development

Design Rules and Guidelines 161

There are four basic principles associated with resource cascading:

1. Appropriate fit—reserve the highest quality resources for the
most demanding uses.
2. Augmentation—increase the utility of a resource by extend-
ing utilization time or counteracting the decline of resource
quality (e.g., through regeneration).
3. Relinking—at each consecutive link in the cascade chain,
consider shifting the resource to a secondary cascade chain
where its utility may be greater (e.g., by using waste or by-
products as feedstocks for other processes).
4. Sustainability—ensure that the rate of resource consump-
tion is balanced with the rate of resource regeneration.

Note that augmentation and relinking invariably involve some
expenditure of resources, so that decisions about alternative path-
ways should take into account the associated net utility. Examples of
resource utility maximization efforts include:
• Impeding quality decline (e.g., adding preservatives)
• Supplementing quality losses (e.g., chemical replenishment)
• Increasing use intensity (e.g., sharing among multiple
processes)
• Improving durability (e.g., protective coatings)
• Separation of a substance into basic resources (e.g., solvent
filtration)
• Recollection of dispersed material (e.g., cadmium reclama-
tion from batteries)
• Regeneration of quality (e.g., thermal transformation).
While inorganic substances, such as metals, can often be relinked
to the highest quality level through physical processes, organic mate-
rials must eventually be allowed to cascade through biochemical de -
composition to the bottom of the chain, where they are regenerated
into new life forms through solar energy.
The principles of resource cascading have already been applied in
diverse areas, for example:
• Reuse of agricultural biomass to produce biofuels such
as ethanol
• Repeated use of chlorinated solvents for degreasing
operations
• Recovery of wood products for particleboard and pulp
production
• Recycling of plastic materials used for packaging into
textiles or roofing materials
• Energy cascading in multistep alcohol distillation.