Page 80 - Materials Chemistry, Second Edition

64 3 Life Cycle Inventory Analysis

3. Increase of entropy (second principle of thermodynamics)
Relevant for the explicit examination of chemical reactions (very frequent in
LCI analyses, among others for the production and transformation of chemicals
and, for example, the determination of CO loads by incineration of fossil fuels)
2
4. Principles of stoichiometry (basis for all chemical reactions)
Transitions of mass into energy and vice versa are only relevant in nuclear
reactions, thus providing an exception to the first and second principle.
2
5. E = mc (equivalence of mass (m) and energy (E) according to Einstein). 4)
These principles (1–5) belong to the scientifically best proved laws and thus provide
a solid framework for processes analysed within LCIs. 5)
These principles can be used as estimations for what quantity of a product can
maximally be formed, how much energy can maximally be released or is necessary
as a minimum amount for a chemical reaction to occur, how much usable (‘free’)
energy can be produced from combustion heat, and so on. Technically attainable
yields, efficiencies, and so on, are usually lower than those theoretically predicted,
never higher. In the praxis of LCI this means that in the absence of specific,
that is, measured data, respective estimations canalsobemadebythe useof
6)
technical handbooks and manuals or by technical information from the Internet. 7)
This is often suited for the estimation of main flows (mass, energy) but fails,
however, with trace emissions, which often stem from uncontrolled side reactions.
The database in the centre of the inventory with the most important mass and
energy flows is usually much more extensive than the data converted into impact
categories (classification) in life cycle impact assessment (LCIA, see Section 3.7
and Chapter 4).
The laws of conservation of mass and energy can be used for a strict balance 8)
(input = output), which, however, most LCAs do not use; for example, oxygen as
a seemingly inexhaustible resource on the input side is mostly not assessed and
waste heat on the output side is practically not quantitatively recorded.
3.1.2
Literature on Fundamentals of the Inventory Analysis

Fundamentals of a method are often better described in older texts than in newer
ones, where much is already assumed to be known. Classical descriptions of LCA
have been given by, for example, William Franklin, Robert Hunt and co-workers, 9)

4) The use of Einstein’s equation in LCA as a basis for an estimation of energy equivalence has also
been discussed (Heijungs and Frischknecht, 1998).
5) Hunt, Sellers and Franklin (1992) and Hau, Yi and Bakshi (2007).
6) Boustead and Hancock (1979).
7) Greatest care is to be taken to ensure legitimacy of data.
8) Ecobalance (in German ‘‘ ¨ Okobilanz’’ is still the correct translation of LCA) was used prior to
the term life cycle assessment. It is derived from the Italian expression bilancio; a reference to
economical balance is straightforward.
9) Hunt et al. (1992), Janzen (1995) and Boguski et al. (1996).