Initiative #9 : The Ekovore composter (Nantes, France)

Biowaste represents a significant source of CO2. Did you know that a third of the content of the French residual waste bin is made up of bio-waste? On a national scale, the total amount of biowaste thrown away is distributed rather evenly between households and restaurants/schools. The household part alone represents more than 60 million tons per year, which are just waiting to be composted.

When I was in Nantes, I met Victor, who works for the company Faltazi. They are developing a number of projects, including one in particular called Les Ekovores. These are circular, local and resilient systems to provide for the city. Victor introduced me to an Ekovore composter (one of the very first to be installed) near the Malakoff district in Nantes.

It was installed here as a demonstration and experimentation object on a neighbourhood scale. The design brief called for the adaptation of the know-how of the Compostri association, which was composting in family gardens (on natural soil), into an all-asphalt solution, available in urban areas and on artificial soil.

This ekovore is very large, because the specifications proposed by the Nantes metropolis required imposing dimensions for this composter which would be placed in the middle of high-rise buildings.

Soil on top of soil

This composter contains a base in which there is a supply of soil, which "recreates" the soil. So even after emptying, there is still a volume of worms and bacteria to seed the next vat.

A water-collecting roof

The canopy allows the apprentice composters to protect themselves from any rain and to collect it in a 2m³ tank, for watering the compost.

A composter separated into three different silos

The composter contains 3 silos: two small input silos and a large maturing silo. The composting process takes between 4 and 5 months.

In the first step, a first input silo is filled, and a wall is built with wooden laths for easy filling. This area fills up in 5 weeks. Once this silo is full, the second input silo, which has prematurely matured during this time, is emptied into the maturing silo. The two feed silos are then filled alternately.

Here, the volume was calculated and adjusted according to the estimated quantity of waste for 40 to 50 families, in order to respect the compost production cycle, which requires turning after 10 weeks.

The problem of turning

The problem with any neighbourhood compost today is its management and turning. Indeed, citizens are willing to put their waste in the compost bin, but they often do not take care of the tedious task of turning it over. In this case, it is companies that come and take care of it. The idea here was to find a system that would make turning over simple and easy, so that anyone could do it!

Winch and crank to lift the compost up

The team therefore decided to design its system with a winch and crank (one for each input silo), which allows the silo to be raised. All you have to do then is catch up with the compost as you go along, turn it over and drop it into the maturing silo. Simple, isn't it?

Dry matter, an essential ingredient for quality compost

To make good compost, you need to mix your bio-waste with dry matter. That is why next to the composter there is a container of about 1m³ of wood shavings, which the participants mix with their bio-waste. This dry matter forms a sort of "millefeuille" which allows enough oxygen to pass through for the material to degrade properly, without creating any juice due to maceration. Compostri replenishes this dry matter bin every three months.

The problem of rodents

These little creatures love compost! To prevent them from making a mess, grids are placed under and over the silos. Very effective!

Des ateliers de démonstration avec les écoles

Une fois par an, des écoles viennent voir le compost et découvrir son fonctionnement. Trois ateliers sont alors réalisés :

• Quoi mettre dans mon seau à biodéchets à la maison?

• Faire fonctionner le composteur et retourner le compost

• Maturation et observation des bebettes à la loupe

How to compost? Poster made by Compostri

The ekovore maturation tank is emptied twice a year. The quantity is then shared between all families. 5 tons of waste in the silo will give 1.5 tons of compost at the end of the maturation process. Each family thus recovers the equivalent of a 60 litre bag of compost per year! Plus the satisfaction of having done their bit...

A nice energy saving

Thanks to compost, each family reduces its residual waste and also reduces the number of trucks that have to come and collect it. Moreover, bio-waste is difficult to incinerate because it is full of water. The incinerators therefore consume less energy if they have less recalcitrant waste...

This ekovore is still the only one in Nantes, but a public contract has been launched to install 4 or 5 others.

Other models, slightly redesigned (square rather than curved doors, 500 litres of water rather than 2m³) have been installed in Angers. It is also one of the doors of the composter that acts as a canopy against the rain.

The ekovores are not open 24 hours a day, and the opening slots allow for more exchange between the different inhabitants of the neighbourhood who come to meet for a coffee. They call it "compost aperos". A great way to create social links!

A French experimental production

These products remain quite expensive but are produced (still pre-industrially) in France and seek to meet the most complete specifications possible. A certain economy of scale can be applied as soon as several composters are purchased, and the depreciation is done over 6 to 8 years.

Ekovores also include other systems, such as uritrottoirs, uritonoirs (to be planted in straw bales for festivals), glass collectors, and water recuperators (in facades for urban areas, or integrated in public benches for family gardens outside the water network)

Great perspectives to come to create more circularity in our cities!

Thanks to Victor for his explanations and his great motivation.

Learn more about the ekovore composter: https://www.ekovore.com/

Learn more about Faltazi: https://www.faltazi.com/