Content area
Full Text
Int J Life Cycle Assess (2015) 20:957969 DOI 10.1007/s11367-015-0897-4
LCA METHODOLOGY
Cumulative energy demand in LCA: the energy harvested approach
Rolf Frischknecht1 & Franziska Wyss2 & Sybille Bsser Knpfel1 &
Thomas Ltzkendorf3 & Maria Balouktsi3
Received: 15 October 2014 /Accepted: 29 April 2015 /Published online: 12 May 2015 # Springer-Verlag Berlin Heidelberg 2015
AbstractPurpose Environmental life cycle assessment (LCA) is today an important methodology to quantify the life cycle based environmental impacts of products, services or organisations. Since the very first LCA studies, the cumulative energy demand CED (also called primary energy consumption) has been one of the key indicators being addressed. Despite its popularity, there is no harmonised approach yet and the standards and guidelines define the cumulative energy demand differently. In this paper, an overview of existing and applied life cycle based energy indicators and a unifying approach to establish characterisation factors for the cumulative energy demand indicator are provided. The CED approaches are illustrated in a buildings LCA case study.
Methods The five approaches are classified into two main concepts, namely the energy harvested and the energy harvestable concepts. The two concepts differ by the conversion efficiency of the energy collecting facility. A unifying energy harvested approach is proposed based on four theses, which ensure consistent accounting among renewable and non renewable energy resources.
Results and discussion The indicator proposed is compared to four other CED indicators, differing in the characterisation
factors of fossil and biomass resources (upper or lower heating value), the characterisation factor of uranium and the characterisation factors of renewable energy resources (amount harvested or amount harvestable). The comparison of the five approaches is based on the cumulative energy demand of a newly constructed building of the city of Zrich covering the whole life cycle, including manufacturing and construction, replacement and use phase, and end of life.
The cumulative energy demand of the life cycle of the building differs between 336 MJ oil-eq/m2a (CED uranium low) and 836 MJ oil-eq/m2a (CED energy statistics). The main differences occur in the use phase. The main reason for the large differences in the results are the different concepts to determine the characterisation factors for renewable and nuclear energy resources.
Conclusions The energy harvested approach CED standard is a consistent approach, which quantifies...