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Life cycle assessment applied to recycled aggregate concrete 233

9.3.2 Inventory analysis

The necessary information can be obtained directly from the industries involved using
detailed questionnaires or from publicly available annual environmental reports (ERs)
and environmental product declarations (EPDs). Obviously, data from questionnaires
will result in a more reliable LCI because ERs and EPDs will always hold a certain
risk of misinterpretation and double counting. However, first-hand data are not
always provided by the companies because of confidentiality issues. As a conse-
quence, the larger part of the LCIs is based on data from ERs, EPDs and LCA related
journals. Therefore, it is understandable that ISO. ISO 14044 (2006) requires detailed
documentation referencing for all public sources used. A sensitivity analysis is also
very useful. For instance, Josa et al. (2004) made an extensive comparative analysis
of the available life cycle inventories of cement in the EU to obtain a general trend in
CO 2 ,NO x ,SO x and dust emissions. LCA databases [e.g., Ecoinvent (Frischknecht
and Jungbluth, 2007)] are seen as another important data source.
Since LCA relies heavily on the quality of the inventory data, several authors
have compared the accuracy of some of the existing LCA databases applied to the
construction sector (Islam et al., 2015; Martı ´nez-Rocamora et al., 2016; Seto et al.,
2017; Takano et al., 2014). Ecoinvent and GaBi database were praised as the most
complete, the former being especially suitable for the European context.
Nevertheless, the common practice among researches is to create CDW and
recycled aggregates related units based on industrial information which is then ana-
lysed in a software of choice.

9.3.3 Impact analysis
The main aim of the impact analysis is to connect each LCI result to the corre-
sponding environmental impacts. Usually, this approach results in a classification
of impact categories, each with a category indicator. Two main schools of methods
can be distinguished (Jolliet et al., 2003).
1. The first school comprises classical life cycle impact assessment (LCIA). Its category
indicator is located right in between the LCI results and the category end points (where
the environmental effect or damage occurs). The corresponding methods restrict quantita-
tive modelling to relatively early stages in the cause effect chain to limit uncertainties
and group LCI results related to a certain environmental problem, into midpoint catego-
ries. Therefore, these methods [e.g., CML 1992 2002 (Heijungs et al., 1992)] are consid-
ered to be problem oriented. For example, a material’s impact on climate change can be
expressed in kilograms CO 2 equivalents. Obviously, this is merely a quantification of an
emission that contributes to the problem of climate change and not a quantification of the
actual environmental damage.
2. The second school focuses much more on the actual effect. So-called damage-oriented
impact methods [e.g., Eco-indicator 99 (Goedkoop and Spriensma, 1999)] try to model
the cause effect chain up to the endpoint, or the actual environmental damage, some-
times with high uncertainties. With respect to climate change, the damage on human
health is quantified in terms of disability adjusted life years. This unit counts as a measure
for the years lived disabled and the years of life lost due to this damage.