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allocates emergy among co-products is not conservative, i.e. the emergy inflow can
be allocated concurrently to all outflows. That said, emergy does address eco-centric
problems that other methodologies are unable to and deserves merit especially for
ecosystem analysis (Sciubba, 2010). Furthermore, the emergy analysis has two
fundamental capabilities that the authors think are required as a scarcity indicator:
1) it is based on the resource's physical characteristics and 2) all resources are
measured with a single unit.
Generally, emergy analysis can be successfully applied for renewable resources.
However, the applicability of this approach is questionable for those mineral re-
sources, where the sun has not played a central role in their creation. For no matter
how much solar energy is received from the sun, the quantity of gold or iron for
instance on Earth, will not change.
2.6.3.3 Heat equivalent of noxious substances
Kümmel and Schüssler (1991) propose the “heat equivalent of noxious substances” as
the waste heat generated in pollution control processes. The idea is that any chemi-
cal contaminant is worse than waste heat, since it is dissipated into the atmosphere
and ultimately into the universe. Therefore, converting any contamination into heat
would be better than dispersing it. In this way, the “heat equivalent” can be used
as an aggregate pollution index in economic modelling.
However, if one actually eliminates a noxious substance with fossil fuels, what
one effectively does is translate the polluting effect from one pollutant to another
type and thus the problem is not solved in reality. It is only solved in the accounting
system. A further consideration is that the combustion of fossil fuels not only
produces heat but also involves GHG emissions that affect the climate.
2.6.3.4 Exergy based methods
Generally, the studies based on exergy and natural resources are focused on cal-
culating the amount of exergy required for the production of a certain commodity.
Probably, the best known is the thermo-ecological cost analysis proposed by Szargut
et al. (Szargut et al., 1988, 2002; Stanek, 2004). The thermo-ecological cost analysis
accounts for the cumulative consumption of non-renewable exergy connected with
the fabrication of a particular product including the additional exergy consump-
tion needed for the compensation of environmental losses caused by the disposal of
harmful substances to the environment. The thermoecological cost is based on the
cummulative exergy consumption (Szargut and Morris, 1987) which is essentially
the same concept of the exergy cost by Valero et al. (1986), explained in Sec. 3.3.2.
A similar approach is also used by Ayres et al. (2006) who applied the exergy con-
cept to accounting for the materials and energy use and waste residuals of five basic
metal industries in the U.S. This allowed for the comparison of systems on a com-
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