Page 49 - Materials Chemistry, Second Edition

2.2 Scope 33

Inputs specified in Figure 2.4 originate ‘from the earth’ (+ air + water) or are
directly or indirectly made available by solar power. The following inputs from the
environment are to be considered:

• All processes necessary for the extraction of raw materials (mining industry, oil
production, forestry, etc.) belong to the investigated system (‘exploitation of raw
materials’).
• In addition, inputs which, due to the cut-off criteria, are not traced over their entire
life cycle must be considered (‘miscellaneous’). These inputs may be pre-products,
ancillary material or lubricant produced in the remainder of technosphere not
included into the system under study.
• The entry ‘energy’ on the input side should actually be named ‘energy raw
materials’, because the energy is produced from fossil, nuclear and regenerating
raw materials. Exceptions are solar energy, potential energy of water (hydro
power) and kinetic energy of wind (wind power). The energy supply, for example,
in power stations, is within the system boundary.
Outputs, such as usable products and releases into the environment, are delivered
to the system’s surrounding. The investigated product in the centre of the system
remains within the system boundary.

• ‘Usable products’ are the product under study, co-products and secondary raw
materials (see below), which remain in the technosphere.
• Material emissions are delivered into the ecosphere by waste water and exhaust
air. The plants for waste water treatment and exhaust air purification are within
the system boundary.
• The allocation of solid wastes (landfill) has in former times occasionally been
rated as ‘releases into soil’, which means they would leave the system. Today,
controlled landfills are regarded as part of the technosphere and thus lie within
the system boundaries. Only degassing and contamination of the groundwater
due to leaky landfills are regarded as outputs into the environment. For waste
incineration, analogous considerations apply. In the early days of LCA (‘proto-
LCAs’), 15) the sum of solid wastes has been an important aggregated parameter
of the inventory. 16)
• ‘Other emissions’ can be radiation, biological releases, noise and similar non-
chemical emissions.

The handling of co-products and secondary raw materials requires special attention
during the definition of the system boundary.
2.2.2.2.1 Co-products During a chemical synthesis (or any other production
process), besides the desired output within the examined product system, further
useful products, materials or substances may be generated and covered by the
generic term co-products. 17) In particular, co-products are frequently formed in the

15) Kl¨ opffer (2006).
16) BUWAL (1991).
17) Riebel (1955).