1979
Comparative Life Cycle Assessment of Geosynthetics versus Concrete Retaining
Wall
Analyse de cycle de vie comparative d’un épaulement géotextile et conventionnel
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: Geogrids made of geosynthetics can replace conventional building materials like concrete. In this article, goal and
scope, basic data and the results of a comparative life cycle assessment of concrete reinforced retaining walls (CRRW) and
geosynthetics reinforced retaining walls (GRRW) are described. One running meter of a three meters high retaining wall forms the
basis for comparison. The two walls have the same technical performance and an equal life time of 100 years. The GRRW has a lower
demand of steel and concrete compared to the CRRW. The product system includes the supply of the raw materials, the manufacture
of the geotextiles and the concrete, the construction of the wall, its use and its end of life. The life cycle assessment reveals that the
GRRW causes lower environmental impacts. The cumulative greenhouse gas emissions of 300 m CRRW are 400 t and 70 t in case of
GRRW. The use of an environmentally friendlier lorry in a sensitivity analysis and monte carlo simulation confirm the lower
environmental impacts caused by the construction of a GRRW compared to a CRRW. More than 70 % of the environmental impacts
of the geogrids production are caused by the raw material provision (plastic granulate) and the electricity demand in manufacturing.
RÉSUMÉ : Géogrids peuvent remplacer les matériaux conventionnels comme le béton. 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’un
épaulement géotextile et conventionnel. La comparaison est faite sur un mètre courant d’un épaulement de trois mètre d’hauteur. Les
deux alternatives ont les mêmes propriétés techniques et la même durée de vie de 100 ans. Les systèmes contiennent la provision des
matériaux, la fabrication des géotextiles et du béton, la construction, l’utilisation et l’évacuation de l’épaulement. L’analyse de cycle
de vie démontre qu’un mètre courant d’un épaulement géotextile cause moins d’impacts environnementaux qu’un mètre courant d’un
épaulement de béton. 300 mètres d’un épaulement de béton entraînes 400 t CO
2
-eq, celui de géotextile 70 t CO
2
-eq des émissions des
gaz à effet de serre. L’utilisation des camions aves les émissions réduites ne change pas les résultats. Une simulation « monte carlo »
confirme la stabilité des résultats. La provision des matériaux et l’électricité utilisé dans la fabrication de la couche de filtre géotextile
sont des facteurs primordiaux (plus que 70 %) en ce qui concerne les impacts environnementaux du géogrid utilisé dans l’épaulement
géotextile.
KEYWORDS: retaining wall, slope retention, geosynthetics, concrete, geogrid, life cycle assessment, LCA
MOTS CLÉS : épaulement, géotextile, géogrid, béton, 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 Manu-
facturers (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 slope retention are described. The slope
retention is either provided by a concrete reinforced retaining
wall (CRRW) or a geosynthetics reinforced retaining wall
(GRRW).
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, GWP100, 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 VERSUS CONCRETE RETAINING
WALL
It may be necessary in some cases, especially in the
construction of traffic infrastructure, to build-up very steep
walls. For such walls, supporting structures are necessary.
The retaining walls need to meet defined tensile and shear
