One of the main sinks of energy in the “developed” world is the creation
of stuff. In its natural life cycle, stuff passes through three stages. First, a
new-born stuff is displayed in shiny packaging on a shelf in a shop. At this
stage, stuff is called “goods.” As soon as the stuff is taken home and sheds
its packaging, it undergoes a transformation from “goods” to its second
form, “clutter.” The clutter lives with its owner for a period of months
or years. During this period, the clutter is largely ignored by its owner,
who is off at the shops buying more goods. Eventually, by a miracle of
modern alchemy, the clutter is transformed into its final form, rubbish. To
the untrained eye, it can be difficult to distinguish this “rubbish” from the
highly desirable “good” that it used to be. Nonetheless, at this stage the
discerning owner pays the dustman to transport the stuff away.
Let’s say we want to understand the full energy-cost of a stuff, perhaps
with a view to designing better stuff. This is called life-cycle analysis. It’s
conventional to chop the energy-cost of anything from a hair-dryer to a
cruise-ship into four chunks:
Phase R: Making raw materials. This phase involves digging minerals out
of the ground, melting them, purifying them, and modifying them
into manufacturers’ lego: plastics, glasses, metals, and ceramics, for
example. The energy costs of this phase include the transportation
costs of trundling the raw materials to their next destination.
Phase P: Production. In this phase, the raw materials are processed into
a manufactured product. The factory where the hair-dryer’s coils
are wound, its graceful lines moulded, and its components carefully
snapped together, uses heat and light. The energy costs of this phase
include packaging and more transportation.
Phase U: Use. Hair-dryers and cruise-ships both guzzle energy when
they’re used as intended.
Phase D: Disposal. This phase includes the energy cost of putting the
stuff back in a hole in the ground (landfill), or of turning the stuff
back into raw materials (recycling); and of cleaning up all the pollution
associated with the stuff.
To understand how much energy a stuff’s life requires, we should estimate
the energy costs of all four phases and add them up. Usually one of
these four phases dominates the total energy cost, so to get a reasonable
estimate of the total energy cost we need accurate estimates only of the
cost of that dominant phase. If we wish to redesign a stuff so as to reduce
its total energy cost, we should usually focus on reducing the cost of
the dominant phase, while making sure that energy-savings in that phase
(kWh per kg)