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estimate refers to the quantity of resources that is ultimately available, estimated by
multiplying the average natural concentration of the resources in the earth’s crust by
the mass of the crust. Lately, the extractable geologic resource, also called ultimate
recoverable resource and ultimately extractable reserves, has also been adopted by
a few LCIA methods. This reserve type is the amount of a given metal in ore in the
upper earth’s crust that is judged to be extractable over the long term, e.g. 0.01%
(UNEP International Panel on Sustainable Resource Management 2011).
Each reserve estimate has pros and cons. Reserves are known and economically
viable to extract, but this amount can fluctuate considerably with changes in prices
and discoveries of new deposits. Reserve base has not been reported by the US
Geological Survey since 2009 because its size also increases and decreases based
on technological advances, economic fluctuations and new discoveries, etc.
Consequently, basing the characterisation factoron reserves or reserve base has the
problem that it changes with time. Ultimate reserves are calculated on basis of the
average concentration of metals in the earth’s crust so they are more stable but this
is not a good indicator of the quantity of the resource that can realistically be
exploited. Finally, the extractable geologic resource seems to be a quite certain
reserve estimate but authors are still debating how to quantify it (Schneider et al.
2015).
From the category 2 methods, CML-IA and EDIP are the most widely used. The
CML-IA method for characterisation of abiotic stock resources defines an Abiotic
Depletion Potential, ADP with a characterisation factor based on the annual
extraction rate and the reserve estimates. In Guinée et al. (2002) only the ultimate
reserves are included, but Oers et al. (2002)defined additional characterisation
factors on the basis of reserves and reserve base estimates. CML-IA using reserve
base estimates is the method recommended in the ILCD Handbook for LCIA in the
European context (EC-JRC 2011).
An alternative approach inspired by the EDIP method (Hauschild and Wenzel
1998) bases the assessment for the abiotic stock resources on the reserve base and
defines the characterisation as the inverse person reserve, i.e. the amount of reserve
base per person in the world. For renewable resources, the EDIP inspired charac-
terisation is based on the difference between the extraction rate and the regeneration
rate. If the regeneration rate exceeds the extraction rate, it is considered that there is
no resource availability issue, and the characterisation factor is given the value 0.
Further, down the impact pathway, category 3 methods have been developed
expressing the future consequences of current resource consumption. Some meth-
ods quantify these consequences as additional energy requirements: Eco-Indicator
99, IMPACT 2002+; some methods quantify this effort as additional costs: ReCiPe
and Surplus Cost Potential on basis of relationships between extraction and cost
increase (Ponsioen et al. 2014; Vieira et al. 2016b), EPS 2000 and the Stepwise
method based on willingness to pay; and some methods quantify this effort as
additional ore material that has to be dealt with: Ore Requirement Indicator ORI
(Swart and Dewulf 2013) and Surplus Ore Potential SOP (Vieira et al. 2016a) used
in the LC-IMPACT LCIA method. These methods suffer from a strong dependency
on rather uncertain assumptions about the future efficiencies and energy needs of