Page 140 - Materials Chemistry, Second Edition

124 3 Life Cycle Inventory Analysis

Table 3.6 Operational data for the unit process ‘Punching of Steel Sheets’ (fictitious data).
INPUT Quantity Unit Factor Quantity Unit Per piece Unit
Electric energy 5 × 10 5 kWh a −1 3.6 MJ kWh −1 1.8 × 10 6 MJ a −1 1.5 MJ
el el
• For a procurement of primary data to defined unit processes, usually a question-
naire will be handed out to the company where inputs and output are registered
(see Figure 3.26; also appendix A in ISO 14044 lists examples of data acquisition
sheets). If the processes are well known to the data surveyors, the questionnaire
can be refined more specifically, which usually increases the data. An important
step in LCI is consequently a description as precise as possible of all processes
for which primary data shall be gathered.
• Even if the data situation is better than those in the example above, the conveyed
data usually have to be converted. For further use of the data in LCA it is common
practice to convert those data to 1 kg of the product of the appropriate unit process
or to a multiple of the reference flow according to the fU. In the above example
not the mass of the product P but the number of pieces is indicated. Therefore
the energy consumption in Table 3.6 relates to the number of pieces.
• The environmental loads due to the energy supply of the 1.5 MJ /piece must be
el
assigned to the unit process ‘Punching of Steel Sheets’. It is important to know
the country of origin or provider of the electricity. In Germany, for example,
‘Strommix Deutschland 135) ’ (‘electricity mix’: the average primary energy mix
used for producing electricity) can be used (see Section 3.2.4).
• In many data bases and publications the generic data record to the electricity
mix is available. It lists all environmental loads from raw material extraction
to electricity supply at the customers site. Table 3.7 shows this data record on
the left. Appendix B lists the complete standard report sheet to current mixes
in Germany related to 1 kJ of electrical energy. 136) In some countries, as in the
USA, no single electricity net exists. In such cases it should be known where the
electricity is used so that the regional net can be identified and used; alternatively,
a weighted average of the energy mix in such countries can be used. In Europe
often the EU-mix is used.
• For a calculation of the unit process data ‘Punching of Steel Sheets’ the energy
demand procured in the operational inventory (transformed in units of MJ )is
el
multiplied with the electricity mix generic data record. The result is shown in
Table 3.7 on the right.
If appropriate data are available upstream processes can thus be included,
according to the principle of inclusion of an upstream electricity mix generic
dataset. Unit processes can be seamlessly linked to one another with suitable
software (see Section 3.4.3.3).

135) See Section 3.2.4.
136) UBA, 2000, Materialsammlung S. 179 ff.