Page 142 - Materials Chemistry, Second Edition

9 Life Cycle Inventory Analysis 127
1. To identify whether an increase or decrease in demand for a product will
actually lead to corresponding increases or decreases in supply for that product.
As illustrated with the oil and gas example above, this is not necessarily the
case.
2. To identify which production technology will be affected by the change in
supply of products. This is most likely not going to be an average of the
production technologies on the market, but rather one or a few operating on the
margin.
3. To identify which product substitutes which. This is relevant when changing
demands for a product whose production is constrained, such as oil in the
example above. It is also relevant for the handling of multi-output processes,
where it involves identifying the product that will be affected (substitute or be
substituted) by a co-product from a multi-output process.

From the discussion above, it can be seen that if we want to perform an attri-
butional LCI, we can do so simply on the basis of knowledge about the product and
the parts that it includes: we need to know about how plastic cups are made, used
and discarded. However, if we want to perform a consequential LCI, besides the
technical knowledge about how the plastic cup is produced, used and discarded, we
also need knowledge about how the market reacts to an increase (or decrease) in
demand and supply.
As can be imagined, answering how the market reacts is easier said than done.
What will actually happen if I increase the demand for this or that? Modelling the
reactions of the market is a very complex task—just ask any stockbroker! Outlining
what will happen is therefore necessarily somewhat uncertain, especially if the
assessment addresses decisions in the more distant future. However, to ease the
answering of these questions we will in this chapter outline a range of ‘rules of
thumb’ developed for identifying the processes that are likely to change due to a
decision.
As outlined above, the goal of the consequential LCA is to answer questions of
the type: “What are the environmental consequences if …?”. As the environmental
consequences that are considered arise from changes in production of products, this
overall question answered in the consequential LCA can basically be translated to
“What changes in the production of goods if we demand/supply more/less of X(, Y,
Z, …)?”. We continue asking this question until we have covered all induced
changes. For example, in the case where we want to assess what happens if we use a
plastic cup, we basically want to increase the demand for plastic cups. We therefore
start by asking: “What will happen if I increase the demand for plastic cups?” If
what happens most likely turns out to be that additional cups will be produced, then
the follow-up question will be: “What will happen if we produce additional plastic
cups?” The overall approach of identifying processes to include in a consequential
modelling of the product system is to repeatedly ask this question for each step
upstream and downstream from the reference flow (see Sect. 9.2.1) until all changes
have been covered.