Fertile substrate created on-site in the Bois de Vincennes, Paris

20 August 2020

A responsible solution for greening the city

The on-site production of a fertile substrate or growing medium is an environmentally-friendly solution, making it possible to extend “nature in the city”, a major environmental factor for the cities of tomorrow. This growing medium is a local and sustainable alternative to importing of topsoil, which is a natural resource that should be left intact.

For 10 days, ECT has been creating a fertile substrate on site. This growing medium, which is essential for restoring vegetation to the Esplanade Saint-Louis, is an application of ‘circular economics’; the fertile substrate comes from recycling inert soil together with composted plant/vegetable waste.

A recycling plant on a landmark site

The purpose of the works is to landscape the traffic junction next to the Château. The requirement was to produce a recycled growing medium to re-green the Esplanade to a particular contractual specification, because the grassed area will be for public use for open-air events.

On-site creation of a fertile ‘technosol’ is one of a line of experiments already carried out in conjunction with the City of Paris. These experiments have been carried out within the Bois de Vincennes, in the context of a call for proposals by Paris Région Lab.

« The concept of fertility is integral to ECT’s business. We use a high-grade material in the form of inert soils from the construction & public works sector, to recreate fertile soils and to offer communities and local authorities a base for planting that is environmentally friendly, recycled and locally produced. And without falling back on topsoil stripped from the land hundreds of miles away. » Laurent Mogno, président d’ECT. 

The fertile substrate for reconstructing soil, and its agro-ecological qualities

2,800 cubic metres of fertile substrate have already been produced in this way. The process for making this substrate can be modified to meet a particular contractual specification. A range of soils and aggregates can be used. These materials are levelled out on site, before being covered with a layer of vegetable compost. Once this “layer cake” has been created, the substrate is given a full-thickness blending to produce a consistent texture. The growing medium is now ready to be planted by a landscaping business.

The ‘circular economics’ of soil excavated for “Vert en Ville” or greening the city

This site represents another advance in the deployment of a ‘circular economy’ of excavated soil at the service of communities and local authorities. A circular economy involves maximum recycling with the minimum addition of raw materials, water and energy, as opposed to the extraction-manufacture-consumption-disposal model of linear economics. The re-use of inert soils represents a striking opportunity for the creation of natural, agricultural and leisure spaces. It’s an important issue, given that 63% of town-dwellers in France say they would like to see more green spaces created in their neighbourhood (study carried out for ECT by IFOP in February 2020).

The production of a fertile substrate that’s suitable for planting in an urban environment has been the subject of several years of R&D by ECT, culminating in 2019 with the creation of Urbafertil, a branded substrate with a composition that varies for each project but always meets the French standard NF U 44-551 (growing media).


    On-site fabrication of a fertile substrate by ECT © Pierre Charlier / ECT