Page 30 - Materials Chemistry, Second Edition

12 A. Bjørn et al.

2.2.1 Takes a Life Cycle Perspective

The life cycle metaphor is borrowed from the field of biology. For example, the life
cycle of a butterfly starts with an egg, which bursts and lets a caterpillar out that
turns into a pupa from which a butterfly emerges that eventually dies after laying
eggs for the cycle to be repeated. In much the same way a man-made object starts
its lifecycle by the harvesting and extraction of resources, followed by production,
use and eventually management of the object as waste, which marks the end of the
life cycle. Recycling or reuse can be seen as “new eggs” for the life cycles of other
man-made objects. The objects studied in LCA are often physical products and the
term “product system” signals that a life cycle perspective is taken, i.e. that all the
processes required to deliver the function of the product are considered. For
example, the function of a car fuel is to propel a car. As illustrated in the case
above, the delivery of this function requires a number of industrial and agricultural
processes that can be conceptually organised in stages of the life cycle of a biofuel
(see Fig. 2.1). The core reason for taking a life cycle perspective is that it allows
identifying and preventing the burden shifting between life cycle stages or pro-
cesses that happens if efforts for lowering environmental impacts in one process or
life cycle stage unintentionally create (possibly larger) environmental impacts in
other processes or life cycle stages. As shown above, the substitution of fossil fuels
with biofuels reduces impacts on climate change from the use stage but increases
climate change impacts from the harvest and extraction stage. Although LCA is
mostly used to study product systems, it can also be used to study more complex
man-made objects, such as companies (see Chap. 22), energy-, transport- or waste
management systems (see Chaps. 26, 27 and 35) and infrastructure and cities (see
Chap. 28). In all applications the assessment takes a life cycle perspective having
the function of the studied entity as focal point.

2.2.2 Covers a Broad Range of Environmental Issues

In LCA, the comprehensive coverage of processes over the life cycle is comple-
mented by a comprehensive coverage of environmental issues. Rather than focusing
exclusively on, say, climate change, which generally receives most attention these
days, LCA covers a broad range of environmental issues, typically around fifteen
(see Chap. 10). These issues include climate change, freshwater use, land occu-
pation and transformation, aquatic eutrophication, toxic impacts on human health,
depletion of non-renewable resources and eco-toxic effects from metals and syn-
thetic organic chemicals. The core reason for considering multiple environmental
issues is to avoid burden shifting, which is also why a life cycle perspective is
taken. Here burden shifting happens if efforts for lowering one type of environ-
mental impact unintentionally increase other types of environmental impacts.