In metals industry Mass Flow Analysis (MFA) has a long tradition.
Combined with scenario calculation this method can for example
be used to estimate the future development of scrap availability
and metal composition. Despite the unknown inaccuracy of
such calculations what regional distribution of material, lifetime
or growth rates concerns highly valuable information can be
generated to support the industrial business strategy.
When particular products or metal applications in functional
units become the scope of such calculations besides mass
flow often energy consumption and emissions appear on the
agenda. And, unfortunately, metals are recycled (of course
only from a methodological and not from a resource point of
view). At that point MFA crosses the border from being a static
snapshot of an existing system towards a time depending life
cycle approach. Besides volume, quality, and location time is
introduced as a fourth dimension and the dilemma starts. In
the past one approach was to develop depreciation models
to allocate the expenditures of mining and primary metal
production of Copper and Aluminium according to the recycled
content. But latter is even more disputable since metal recycling
cannot be treated as an alternative production route achieving
the original properties and chemical composition. And, as a
result of its electrochemical behavior, each metal cycle looks
completely different compared to any other. Consequently
the general acceptance of the existing allocation methods for
recycling in life cycle models is still low.
In case of Aluminium the historic primary metal production
cumulates to an amount of almost 900 million tons worldwide.
With the aid of recycling 75% of this material could be conserved
in the current inventory in use. As this stock significantly contributes
to todays and future's raw material supply the following question
arises: Can metallic materials have a defined history and
therewith an ecological hereditary debt, which will be reduced
by further recycling cycles? If the answer would be yes, on
a highly aggregated level, another more practical question
would be whether such a credit should be based on the historic
expenditures of primary production or better considering the
future recycling potential of the inventory in use. In these cases
recycling credits are either overestimated or underestimated
depending on the lifetime and herewith the deviation from
current End of Life recycling practices.