Every year millions of tons of earth are excavated in the main metropolises of the world. We extract soil, a very valuable material, and dispose of it as rubble, or store it under roads, landscaped areas, etc.
What if we started to recognize that excavated soil is a resource, and used it to build? In Paris, this is already a reality. The Cycle Terre Project, launched in 2018, provides a possible answer to a very hot question: how to apply the principle of the circular economy in construction.
The Grand Paris construction: 400 million tons of earth
In the French capital, the management of excavation land will represent a major problem in the next decade due to the Grand Paris Express, a project to expand the Paris metro network and its metropolitan area, with the extension of some underground lines and the creation of four new ones.
The amounts of waste or resources at stake are impressive: forecasts for earth excavations are between 20 and 35 million tons per year, for a total volume of 400 million tons generated before 2030 .
Panels, blocks and plasters from the excavation soil
Launched in 2018 thanks to the European Actions Innovatrices Urbaines program, aimed at implementing innovative solutions for cities, the Cycle Terre Project faces the challenges of managing excavated land, giving it a new life.
Uncontaminated excavated soils are collected in Sevran, a commune of 50,000 inhabitants in the Paris metropolitan area, near the main construction sites.
Here, a construction materials factory was built, with a mixed structure and wall fillings of compressed earth blocks, designed by the architects Joly + Loiret.
Starting in October, the factory will be managed by a cooperative society, and it will produce three ranges of earth materials for construction: a range of earth and vegetable fiber boards (an ecological alternative to plasterboard), one of compressed earth blocks and one of earthen mortars and plasters. The medium-term goal is 25,000 m3 of earth reused each year.
The construction materials produced in Sevran will be used at zero kilometers, in public and private construction sites within the Paris metropolitan area. Schools, cultural centers and above all the new complex of housing, offices and other activities in Ivry-sur-Seine, a complex of 60,000 m2. Delivery is scheduled for 2024, and it was designed by Joly+Loiret architects together with Chinese architect Wang Shu, winner of the 2012 Pritzker Prize, the «Nobel Prize for Architecture».
An opportunity to spread the use of unstabilized earth
«We will work with natural earth from excavated material, uncontaminated,» insists Silvia Devescovi, the person in charge of the project at the Sevran town hall. The reused raw material will be mixed with sand and vegetable fibers of different types, such as chopped straw, cellulose wadding and hemp. Only a small part of the production of compressed earth blocks, intended for the most exposed parts of buildings, will contain a percentage of cement.
Currently, almost all the compressed earth blocks marketed in the world are stabilized with cement or lime, mainly to make them more resistant to impacts during transport and to contact with water throughout the life of the building. Explains Paul-Emmanuel Loiret, architect and president of the cooperative society that manages the factory:
«Most of the blocks will be made without cement or lime, which will constitute a major challenge to disseminate construction with unstabilized earth as an ecological alternative.»
Within the framework of the project, Cycle Terre has financed the certification of the construction process of the earth block walls, and has chosen to publish and disseminate it, which will allow this construction technique to be replicated in different works without the need for new certifications or tests.
Silvia Devescovi explains:
«Our goal is to create a base to make construction with earth a common technique.»
An example for Iberian cities?
The project budget is 6.1 million euros, of which 4.9 million were financed by the European call Actions Innovatrices Urbaines. For Silvia Devesconi, the reflection now focuses on the possibility of replicating this first experience in other French and European cities, which is one of the objectives of the project.
A presentation of the project is currently being organized in the metropolitan area of Barcelona, to assess its replication potential.
We hope that this will be the occasion to assess the possibilities of the earth for the transition towards a circular architecture and at zero kilometers, which does not need to exploit new resources and can give a new life to the materials.
 (Fuente: PREDEC)