major project at La Grange David for better energy management

At La Riche, the Grange David is a site that brings together 5 waste-related infrastructures:
– the recycling centre;
– the deposit of collection trucks;
– the household waste transfer centre;
– the waste sorting center, an essential step between sorting by the inhabitants and recycling;
– the wastewater treatment plant.
Major works (to the tune of €5 million 300,000) are underway on what is currently one of the largest wastewater treatment plants in France, in order to optimize its energy operation. Indeed, as explained to us by Bertrand Ritouret, Vice-President of the Métropole in charge of the water cycle, the activity of a wastewater treatment plant is very energy-intensive, it is the largest energy consumer in a city. It is therefore interesting to try to limit the energy consumption of this station while valuing that which was produced on the site but lost. The conclusion was ultimately simple. By decomposing, under the action of bacteria, at a temperature of 37°C in the “minute cookers” or digesters (see photo), the waste produces methane, a biogas, which until now was burned, and therefore wasted. In addition, this gas is very polluting, more so than CO2. It was therefore necessary to find the means to enhance it so that it contributes to the operation of the site and even better, that it produces more than it spends. With almost 1 million euros per year in electricity consumption bills, this building is the most energy-intensive in the metropolis. The long-term objective, as Vincent Soulard, Director of the water cycle at Tours Métropole Val de Loire, tells us, is for the wastewater treatment plant to produce more energy than it consumes for the end. of the year 2022. Limiting energy consumption on the site and increasing the injection of biogas into the GRDF network by 50% are the conditions for becoming the “expected positive energy station”.