First in France, MéthaTreil valorizes the CO₂ from its biomethane purification

The MéthaTreil Methanization Unit, photo by agriKomp

By  Frédéric DOUARD · 9 juin 2021 ·

The MéthaTreil project, carried out in Machecoul-Saint-Même near Nantes, is an agricultural methanization unit for biomethane production. What makes it unique is that it is the first installation in France to recover CO2 from biomethane purification for reuse, instead of releasing it into the atmosphere as all other installations do. This renewable and local CO2, which does not impact the greenhouse effect, avoids the production of CO2 from fossil and imported fuels. This virtuous objective led to the creation of MéthaTreil. It includes three farms that provide the inputs for methanization and two market gardeners, one of whom uses the CO2 for the growth of greenhouse crops. These include Erwan Bocquier and Aymeric Egonneau from Gaec du Treil (livestock farmers and respectively president and general manager of the SAS), Dominique Pilet from Earl Pilet (livestock farmer), Jean-François Vinet from Sas Pom’Retz (market gardener), and Charles Vinet from Sas Retz-Charles (market gardener). The investment amounts to €5 million for biomethane production and €1 million for the CO2 part and will be amortized in 9 to 10 years.

A 100% agriKomp Biomethane plant

The choice of agriKomp was made for two reasons: the project promoters were impressed by the Paddelgigant® paddle stirring system, and they also wanted to deal with a single interlocutor to avoid responsibility disputes between suppliers when problems arise. agriKomp offers support from feasibility studies to the drafting of the ICPE file and subsidy applications, and ensures the sizing, construction, and commissioning of methanization and biomethane purification units, which is rare in the market. Maintenance and biological monitoring are also provided by agriKomp through its dedicated subsidiary ServiceUnion. In terms of timing, less than two years were needed between the contract signing and the first biomethane injection on December 18, 2019.

The methanization installation includes a Prémix grinder, a Vielfrass® moving floor introduction hopper of 75 m³, two 1,800 m³ digesters, a 4,500 m³ post-digester, and a Quetschprofi® phase separator. Added to these are infrastructures: a 4,200 m³ storage lagoon, 1,880 m² of flat silos for silage and vegetable waste, a 120 m³ slurry and white water pit, a 60 m³ co-product pit, a 500 m² concrete platform for solid digestate, and an old 1,600 m³ slurry pit now used for liquid digestate.

The amount of inputs is 13,000 tons per year or 35 tons per day. These include 5,650 tons of bovine manure and slurry, 3,650 tons of silage from cover crops, 1,500 tons of maize silage, 1,100 tons of unmarketable potatoes, and 1,100 tons of vegetable waste (tomatoes, cucumbers, salads, and potatoes, vegetable plants, etc.). The SAS has hired a full-time employee to manage these raw materials.

Annually, production exceeds two million m³ of biogas and nearly 12,000 tons of raw digestate. All digestate is processed through the phase separator and spread on the lands of the three associated livestock farmers. This work is carried out by a specialized company working for numerous methanization units in the Pays de Loire region. The company is Efflu’Tec, located in Mortagne-sur-Sèvre in Vendée. It is equipped with practically all existing spreading systems, for both solids and liquids, in trailed, mounted, or cordon form, with simple ramps, injectors, or hoeing, and even with crawler tractors for the least supporting soils.

Biomethane purification is performed in an agriPure® module, the membrane filtration solution offered by agriKomp. The gas separation membranes operate on the principle of selective permeation of the membrane surface: the difference in size and solubility of the molecules present in the biogas leads to different permeation rates (penetration into a solid). While carbon dioxide and water pass through the membranes at high speed, methane is retained. This technology allows purification performance exceeding 99% and offers a flexible and scalable solution thanks to the modular system. The module also includes a compression installation, as filtration is carried out under a pressure of 15 bar, and it is then necessary to ensure the desired injection pressure, here 6.5 bar. Part of the heat produced by this compression is recovered and used to heat the digesters in addition to the dedicated boiler.

In Machecoul, the installation’s capacity is 120 Nm³/h. The biomethane is injected into the GRDF network located six kilometers away. This production represents on average nearly 10% of the municipality’s consumption. However, daily network demand fluctuates between domestic and professional consumption (greenhouses). It is necessary to manage storage in gasometers for nightly demand drops (478 m³ per digester and 1,571 m³ in the post-digester) and anticipate production dynamics for weekend demand drops. The longest low-demand period is from August 1 to 15, during which digestion is slowed to avoid flaring.

In terms of working hours for the SAS, excluding maintenance provided by the equipment supplier and outsourced spreading, operating the installation requires 1.5 FTEs.

A Unique BioCO2 Recovery in France

The SAS purifies and liquefies its CO2 through a cold distillation process named Carboliq. To achieve this, it enlisted the help of VerdeMobil, which manufactures and markets this innovative process in France, developed by the startup CryoCollect.

The process recovers low-grade gas from the agriPure® module and isolates the CO2 in liquid form through a series of thermodynamic and physical operations. This chain of operations even allows the recovery of all residual methane from the membrane filtration, which is then recycled into the agriPure® purification module located right next to it.

The CO2 is then stored in a 60 m³ vertical tank before being transported once or twice a week by a 20 m³ tanker truck to two 30 m³ relay tanks located at the greenhouse site in Saint-Philbert-de-Grand-Lieu, 15 kilometers from Machecoul, which are partly heated by two wood boilers of 3.9 and 5 MW. The annual CO2 production is 1,500 tons and only meets part of the greenhouse farmer’s needs.

Contacts :

• MéthaTreil : Erwan Bocquier
 / +33 626 737 530 – sasmethatreil@gmail.com
• Méthanisation et purification biométhane :
 agriKomp France / +33 254 561 857 
- info@agrikomp.fr – agrikomp.fr
• Purification et liquéfaction CO₂ : CryoCollect 
- Haytham SAYAH / +33 647 56 28 17 – contact@cryocollect.com
 – Verdemobil Biogaz / +33 647 00 21 92 – contact@verdemobil.eu
• Aquasol, étude ICPE : 
www.bureau-etudes-environnement-35.fr
• Maintenance processus et biométhane : ServiceUnion France / +33 245 940 016 – service@serviceunion.fr – serviceunion.fr

Frédéric Douard, reporting from Machecoul

Also read on the same topic: CryoCollect extrait un bioCO₂ de qualité alimentaire des unités d’épuration de biométhane