Page 97 - Materials Chemistry, Second Edition

3.2 Energy Analysis 81

Table 3.3 Worldwide extraction of fossil energy sources. 58)

9
−1 a
Source of energy (10 ta ) (min–max) Lower heating value (LHV)
Lignite 0.9–1.3 (1980–1993) 10.9 MJ kg −1
Hard coal 3.2–3.6 (1985–1993) 29.3 (26.8–35.4) MJ kg −1b
Oil (crude oil) 2.7–3.0 (1980–1992) 42.5 (38–46) MJ kg −1
Natural gas Approximately 1.4 36.0 (32–38) MJ m −3
Sum 8.2–9.3

a The tonne [t] is according to ISO 1000 a recognized designation for the megagram (Mg); 10 9
3
6
Mg = 10 Gg = 10 Tg = 1 Pg Mills et al. (1988) and ISO (1981).
b Water and ash-free; by definition, 1 kgce = 29.3 MJ kg .
−1
alternative concept to the one proposed in VDI 4600. It is consistent, but eliminates
most efficiencies of energy transformation (biomass, photovoltaics). There are open
questions related to the use of hard coal and lignite. Most questions with regard
to efficiency would vanish, if the waste heat was used consistently. Because this is
not the case, the more efficient processes should have an advantage, as scarce raw
materials should be protected (fossil fuels) or less area should be used (photovoltaic,
wind).
From the point of view of LCA, every specification must keep an eye on system-
thinking and the awareness that the goal is not ‘art pour l’art’ but aims to achieve
an economic management and a lifestyle closer to the required sustainability.
3.2.3
Energy Content of Inflammable Materials

3.2.3.1 Fossil Fuels
Fossil fuels are still the most important primary energy carriers. Estimated annual
9
extractions are of the order of magnitude of some 10 metric tonnes (1 t = 1Mg),
compared to the annual production of mass chemicals which ‘only’ amounts to
6
some million (10 ) tonnes. Table 3.3 lists annual extractions of the most important
fossil energy sources.
3.2.3.2 Quantification
Energy carriers are quantified either as mass or volume (standard cubic meter in
the case of gases). For energy assessment and also from the practical view of quality,
energy units are, however, more meaningful. Therefore a measure is necessary for
the chemical energy content (more precisely: enthalpy) of the energy source. For
this purpose, the lower heating value (LHV) 59) is usually chosen in technology. In
reactions of hydrocarbons of the general formula C H , it is related to the energy
n
m
58) Hulpke, Koch and Wagner, 1993; Falbe and Reglitz, 1995; ¨ Osterreisches Statistisches Zentralamt,
1995.
59) Synonyms are: net caloriferic and lower caloriferic value.