Page 93 - Materials Chemistry, Second Edition

78 A. Bjørn et al.

as the elementary flow bauxite which contains different minerals, some of which,
e.g. Al(OH) 3 , are sources of aluminium) or cover a group of individual substances
(such as the elementary flow VOCs, volatile organic compounds).
What makes resource flows differently from material and energy flows is that
they have been “drawn from the ecosphere without previous human transforma-
tion”. This means that resource flows are not outputs from other unit processes. In
the steel sheet example of Fig. 8.1, the resource flow “water” may be sourced
directly from a river close to the location of the steel sheet rolling process (i.e. no
previous human transformation), whereas unalloyed steel (a material flow) is the
product flow of another unit process and acts as a material flow to the steel sheet
rolling unit process. Also, in the example of a unit process composed of an entire
slaughterhouse, solar influx may be harvested directly in photovoltaic panels on the
roof of the slaughterhouse to produce electricity and the solar influx is then a
resource flow to the unit process because it has not undergone a previous human
transformation. If the slaughterhouse instead was purchasing electricity from the
grid, this electricity would be an energy flow to the slaughterhouse unit process
because it has undergone previous human transformation, meaning that it is a
product flow of another unit process (e.g. a coal-fired power plant). Similarly, what
makes emission flows differently from waste flows is that they are “released into the
ecosphere without subsequent human transformation”. This means that emissions
are not inputs to other unit processes. In the steel sheet example shown in Fig. 8.1,
particulates (emission flow) are emitted directly into the air, whereas mineral oil
will go through treatment, i.e. be a material input for another unit process. Chapter 9
will further explain how these concepts are used to model an LCI.

8.2.2 The Technosphere and the Ecosphere

LCA divides the world into a technosphere and an ecosphere, see Fig. 8.2.
The technosphere can be understood as everything that is intentionally “man-
made” and also includes processes that are natural in origin, but manipulated by
humans, such as photosynthesis when part of an agricultural system. All unit
processes of an LCI model belong to the technosphere.
The ecosphere is sometimes referred to as “the environment” or “nature” in
layman’s terms and can be understood as everything which is not intentionally
“man-made”. In the ecosphere reside those qualities that LCA has been designed to
protect, i.e. ecosystems, human health and resource availability. These qualities are
called Areas of Protection or damage categories in the field of LCA (see Chap. 10).
Changes to the ecosphere can be considered unintentional “man-made” conse-
quences of activities in the technosphere. Note that the ecosphere also undergoes
natural changes, for example, via ice age cycles or natural ecological successions,
which means that it can be difficult to choose an appropriate natural reference state
against which human impacts should be measured, see Chap. 10.