Page 141 - Materials Chemistry, Second Edition

126 A. Bjørn et al.

plastic cup. The processes that change due to a decision may not be the same that a
product ‘sees’ throughout its product life (see Fig. 9.1). The following example
may make this easier to understand.
Assume now for the sake of the example that we have reached the peak in oil
production: we simply cannot economically extract more oil than we are already
doing. This implies that the decision to, say, use this plastic cup will not result in an
increase in the production of oil, as this is already at its maximum. What happens
instead may be that the price of oil will go up due to the increase in demand (which
in this example is going to be extremely small due to the small amount of oil needed
to produce the cup. However, here it is the principle that is of interest). The increase
in price may cause other users of oil to reduce their use, or find a substitute for their
use of oil. In this example we will assume that some oil users will find natural gas a
suitable substitute and these users will therefore increase their demand for natural
gas to compensate for the decreased availability of oil. This implies that, given
these assumptions, an increase in the demand for oil created from the increase in
demand for plastic cups will not result in an increase in the production of oil, but
rather in the production of natural gas. The consequential LCI will therefore not
include an extraction of oil, but rather an increased extraction of natural gas. This
line of thinking obviously does not only relate to the oil used in the production of
the plastic, but to all the inputs used when the plastic cup is produced.
Another very important difference between the attributional and consequential
LCI is that in an attributional LCI the normal procedure is to assume that the
electricity consumed in the production of the plastic cup is produced by all the
suppliers on the market, depending on their market share. In a consequential LCI,
this is different: If we increase the demand for electricity in the market, it is most
likely that not all the suppliers are going to increase their production to meet the
increase in demand. The reason is that the most cost-efficient producers will already
produce at full capacity. This is for example going to be the case for nuclear power
plants. This means that if we increase the demand for electricity, we will not
influence the extent of the production from the nuclear power plants. Rather, we
will influence other types of power plants, for example natural gas power plants,
which are more expensive to operate (per kWh), and which will therefore only
produce during peak load situations (when electricity prices are higher). The same
thinking is applied when studying the effect of increasing or decreasing demands
for other products than electricity. Rather than including an average of the pro-
ducers in the market in the LCI, as is done in the attributional LCI, it is the
‘marginal’ producers, which are included in the consequential LCI. A marginal
producer is a producer who will change its supply due to small changes in demand.
A final important difference between the attributional and consequential LCI lies
in the handling of multifunctional processes (see Sect. 8.5.2). In a consequential
LCI, the multi-output processes are always handled by system expansion (if sub-
division is not possible).
Based on the outline above, there are generally three different tasks in a con-
sequential LCI: