FAIT DU SOIR In Greater Avignon, anaerobic digestion turns waste into biogas
The anaerobic digestion unit of the Avignon Courtine wastewater treatment plant, which treats wastewater from Avignon, Le Pontet from the Gard municipalities of Villeneuve and Les Angles, was taken this Friday morning.
The principle is simple: recover the sludge from wastewater treatment (we are not drawing you a picture) by the station, which treats the equivalent of 177,000 inhabitants for 29 million cubic meters annually, to make biogas, green and local energy. If the principle is simple, the process a little less.
“The sludge will arrive in a digester, which works like a stomachexplains Véolia’s director of Provence operations Lydiane Riff. Bacteria will feed on the sludge, which will ferment and produce biogas”, stored in a large sphere, the gasometer. After 25 days in the digester, heated to 37 degrees by heat pumps powered by the calories released by water treatment, the volume of sludge will have decreased, after “digestion”, by 40%. To make the 60% digested biomethane usable, it must still be passed through a treatment unit with a membrane to recover biomethane “90% pure”says Lydiane Riff.
This biogas is then odorized, ie GRDF will add its characteristic odor to it for safety reasons, and fed into the network of Avignon and the surrounding municipalities. “Since April, we have been injecting enough to produce electricity for 1,300 homes”, owner Véolia, i.e. 5,400 MWh per year. As for the remaining 40% of sludge, it ends up in compost about fifteen kilometers away, in Tarascon (Bouches-du-Rhône). Previously, all the sludge was dewatered and ended up in compost, transported by two to three trucks a day.
A plus for energy independence
The anaerobic digestion unit represents an investment of 9 million euros, appointed to Véolia and supported by the Sud Paca Region, Ademe and the Rhône Méditerranée Corse Water Agency. The price to transform what is basically smelly waste into clean, local energy. “The local resource is full of future”, launches the general manager of Véolia France Jean-François Nogrette. And there is potential: “in France, only 12% of large wastewater treatment plants are equipped with a biogas production system”he recalls.
Or, biogas has solid arguments, in a context of exploding energy prices and especially gas. “It makes it possible to replace fossil gases and therefore reduce the ecological footprint of energy, it replaces imported gas with locally produced gas, which is important for France’s energy independence, and it develops energy “circular economy”, summarizes Philippe Rechinac, the territorial director of GRDF for Vaucluse. And the same to affirm it: biogas is developing at high speed. “Today, 480 installations inject biogas into the network in France, with 115 commissioning of new installations since the beginning of the year.” Enough to represent at this stage 8.4 TWh of production, i.e. heating for more than 2 million homes. The objective is to “20% of gas consumption produced in biomethane by 2030”adds Philippe Rechinac.
“An inspiring example”
For Greater Avignon, this biogas unit represents “a major step for the environment and the energy transition”, underlines the vice-president of the Agglomeration Jacques Demanse. The Greater Avignon aims to triple the volume of renewable energies produced locally by 2030. It “responds to the challenges of recycling waste through the small water cycle”underlines the director of the Provence Mediterranean Corsica delegation of the Water Agency Annick Mièvre.
“It’s a good example of a project that works well”emphasizes South Paca Regional Councilor Violaine Richard, “an inspiring example”, for the secretary general of the prefecture of Vaucluse Christian Guyard. An example that will undoubtedly spread: several projects have already been launched in the area.
Thierry Allard