Page 100 - Materials Chemistry, Second Edition

84 3 Life Cycle Inventory Analysis

Exercise: Calculation of emissions based on final energy

Coal is declared as ‘CO -loaded’ and natural gas as ‘less CO -loaded’. Justify this
2 2
statement by showing in an arithmetical example of how much CO emissions
2
result from the production of 100 MJ usable energy from coal and natural gas.
(Basis LHV; with an implied efficiency in both cases of 35%.) Use the data in
Table 3.4 as well as the following additional information:
• C-content natural gas: 75% (w/w)
• C-content hard coal: 80% (w/w).

3.2.3.3 Infrastructure
The inclusion of the construction of plants (infrastructure, capital goods, etc.) with
energy-intensive goods and processes is not uniformly handled in LCA. Usually
these CEDs relating to construction of power plants, factories, and roads are cut-off
because they contribute less than 1% to the total energy. The energy necessary to
build a power plant is of the order of 1 ppm of the energy the plant will provide
during its 30–50 years’ life time. This can be illustrated by the following rough
calculation:
6
The production of electricity of a large 1000 MW (10 kW) power plant with a
60% average capacity factor and 50 years working time results in (1 kWh ≡ 3.6 MJ):
= 10 [kW]× 50[a]× 365[da ]× 24[hd ]× 0.6[–]
6
−1
−1
11
17
11
= 2.628 × 10 kWh = 9.46 × 10 MJ = 9.46 × 10 J
≈ 1 ( )
This energy is not yet the final usable energy, but corresponds to the electric
energy provided without transmission and distribution losses (thus starting from
the power station). If the energy for the construction of a power plant is, for
simplification, set equal to the steel and concrete applied, the following power
supply is required (average value for a nuclear power station, or a coal power station
of comparable size):
CED(plant)≈ 10 J(= 0.001EJ)
15
Comparison of these rough estimations shows that only 1 per mil of the provided
energy is necessary for the two most important building materials. Mauch and
Schaefer 64) indicate a range of 0.1–0.2%. Although in this case the neglect is not
relevant for the final result, this will not always be the case. For the first time
in the history of LCA, the so-called ETH data 65) included infrastructure data. On
the basis of the ecoinvent data that can be used either with or without capital
goods, it was shown that a neglect of these data is not always acceptable. 66)

64) Mauch and Schaefer, 1996.
65) See query Section 1: this tradition is maintained in the Swiss data base ecoinvent, ecoinvent 1,
2004a; Frischknecht et al., 2005.
66) Frischknecht et al., 2007a.