3203
Comparative Life Cycle Assessment of Geosynthetics versus Conventional filter
layer
Analyse de cycle de vie comparative d’une couche de filtre géotextile et conventionnelle
Frischknecht R., Büsser-Knöpfel S., Itten R.
Treeze Ltd., Kanzleistrasse 4, 8610 Uster, Switzerland
Stucki M.
Zurich University of Applied Sciences, Institute of Natural Resource Sciences, Campus Grüental, 8820 Wädenswil
Switzerland
Wallbaum H.
Chalmers University of Technology, Civil and Environmental Engineering, 412 96 Göteborg, Sweden
ABSTRACT: Geosynthetics made from plastics can replace filter layers made of gravel. In this article goal and scope, basic data and
the results of a comparative life cycle assessment of gravel and geosynthetics based filter layers are described. The filter layers of a
road made of 30 cm gravel and a filter geosynthetic, respectively, form the basis for the comparison. The filter layers have the same
technical performance and the same life time of 30 years. The product system includes the supply of the raw materials, the
manufacture of the geotextiles and the extraction of mineral resources, the construction of the road filter, its use and its end of life
phase. The life cycle assessment reveals that the geosynthetics based filter layer causes lower environmental impacts per square
metre. The cumulative greenhouse gas emissions amount to 7.8 kg CO
2
-eq (mineral filter) and to 0.81 kg CO
2
-eq (geosynthetic filter).
The variation of the thickness of the gravel based filter layer confirms the lower environmental impacts of a geosynthetics based filter
layer. Environmental impacts of the geosynthetic production are dominated by the raw material provision (plastic granulate) and
electricity consumption during manufacturing.
RÉSUMÉ : Les géotextiles sont utilisés pour remplacer le gravier dans les couches de filtres. Cet article contient une description de la
définition de l’objectif et du champ d’étude, de l’analyse de l’inventaire et des résultats d’un analyse de cycle de vie comparative
d’une couche de filtre géotextile et conventionnelle. La couche de filtre d’une rue est construite avec 30 cm de gravier ou avec une
couche géotextile. Les deux couches de filtres ont les mêmes propriétés techniques et la même durée de vie de 30 ans. Les systèmes
contiennent la provision des matériaux, la fabrication des filtres géotextiles et l’extraction du gravier, la construction, l’utilisation et
l’évacuation de la couche de filtre. L’analyse de cycle de vie démontre qu’un mètre carré d’une couche de filtre géotextile cause
moins d’impacts environnementaux qu’un mètre carré d’une couche de filtre gravier. Une couche de filtre gravier entraîne 7.8 kg
CO
2
-eq, celle de filtre géotextile 0.81 kg CO
2
-eq des émissions des gaz à effet de serre par mètre carré. La variance de l’épaisseur de
la couche de gravier n’influe pas sur la séquence environnementale des deux couches. La provision des matériaux et l’électricité
utilisé dans la fabrication de la couche de filtre géotextile sont des facteurs primordiaux en ce qui concerne les impacts
environnementaux de la couche de filtre géotextile.
KEYWORDS: filter layer, geosynthetics, gravel, life cycle assessment, LCA
MOTS-CLÉS : couche de filtre, géotextile, gravier, analyse de cycle de vie, ACV
1 INTRODUCTION
Geosynthetic materials are used in many different ap-
plications in civil and underground engineering, such as in
road construction, in foundation stabilisation, in landfill
construction and in slope retention. In most cases they are
used instead of minerals based materials such as concrete,
gravel or lime.
Environmental aspects get more and more relevant in the
construction sector. That is why the environmental
performance of technical solutions in the civil and
underground engineering sector gets more and more attention.
The
European
Association
for
Geosynthetic
Manufacturers (E.A.G.M.) commissioned ETH Zürich and
Rolf Frischknecht (formerly working at ESU-services Ltd.) to
quantify the environmental performance of commonly
applied construction materials (such as concrete, cement, lime
or gravel) versus geosynthetics (Stucki et al. 2011).
In this article, the results of a comparative Life Cycle
Assessment (LCA) of a filter function in road construction are
described. The filtration function is either provided by a
gravel or a geosynthetic filter layer.
The environmental performance is assessed with eight
impact category indicators. These are Cumulative Energy
Demand (CED, Frischknecht et al. 2007), Climate Change
(Global Warming Potential, GWP 100, Solomon et al. 2007),
Photochemical Ozone Formation (Guinée et al. 2001a; b),
Particulate Formation (Goedkoop et al. 2009), Acidification
(Guinée et al. 2001a; b), Eutrophication (effects of nitrate and
phosphate accumulation on aquatic systems, Guinée et al.
2001a; b), Land competition (Guinée et al. 2001a; b), and
Water use (indicator developed by the authors). The
calculations are performed with the software SimaPro (PRé
Consultants 2012).
2 GEOSYNTHETIC FILTER VERSUS MINERAL
FILTER
Filters systems in road construction assure that the base soil is
retained with unimpeded water flow. In this article, the case
of a geosynthetic filter layer is compared to the case of a
mineral filter layer.
Polypropylene granules are used as basic material for the
geosynthetic layer. They need to be UV stabilised to meet the
requirements. The average weight of the polymer is 175 g/m
2
.
