Page 32 - Materials Chemistry, Second Edition

14 A. Bjørn et al.

2.3 Strengths and Limitations of LCA

A main strength of LCA is its comprehensiveness in terms of its life cycle per-
spective and coverage of environmental issues. This allows the comparison of
environmental impacts of product systems that are made up of hundreds of pro-
cesses, accounting for thousands of resource uses and emissions that are taking
place in different places at different times. However, the comprehensiveness is also
a limitation, as it requires simplifications and generalisations in the modelling of the
product system and the environmental impacts that prevent LCA from calculating
actual environmental impacts. Considering the uncertainties in mapping of resource
uses and emissions and in modelling their impacts and the fact that calculated
impacts are aggregated over time (e.g. tomorrow and in 20 years) and space (e.g.
Germany and China) it is more accurate to say that LCA calculates impact
potentials.
Another strength in the context of comparative assessments is that LCA follows
the “best estimate” principle. This generally allows for unbiased comparisons
because it means that the same level of precaution is applied throughout the impact
assessment modelling. A limitation related to following the “best estimate” prin-
ciple is, however, that LCA models are based on the average performance of the
processes and do not support the consideration of risks of rare but very problematic
events like marine oil spills or accidents at industrial sites. As a consequence,
nuclear power, for example, appears quite environmentally friendly in LCA because
the small risk of a devastating disaster, like the ones that happened in Chernobyl,
the Ukraine or Fukushima, Japan, is not considered.
A final limitation worth keeping in mind is that, while LCA can tell you what
(product system) is better for the environment, it cannot tell you if better is “good
enough”. It is therefore wrong to conclude that a product is environmentally sus-
tainable, in absolute terms, with reference to an LCA showing that the product has a
lower environmental impact than another product. Chapter 5 elaborates on the
relationship between LCA and sustainability.
The above characteristics mean that LCA is suitable for answering some ques-
tions and unsuitable for answering others. Box 2.1 provides examples of questions
that LCA can and cannot answer.

Box 2.1. What LCA can and cannot answer
Examples of questions LCA can answer:

1. Is paper, plastic or textile bags the most environmentally friendly option
for carrying groceries back from the supermarket?
2. From an environmental point of view should we use glass fibre composite
or steel for the car body?
3. How can the overall environmental impact of a refrigerator be minimised
with the least effort?