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Upgrading biogas
to biomethane

The Pot-au-Pin Énergie initiative

For the first time in France, the entire biomethane value chain is represented at a single site. Discover the Pot-au-Pin Énergie site located in Cestas, near Bordeaux.

The incredible potential of biomass

In Cestas, the Planète Végétal commercial farm grows and sells carrots and leaks for large grocery store chains and wholesalers. In order to enrich the soil between two vegetable plantings, the company has decided to introduce intermediate energy crops, with a particular focus on rye. This biomass has considerable potential as a renewable energy.

Planète Végétal and Air Liquide have teamed up to create Pot-au-Pin Énergie and thus upgrade this biomass in order to produce biomethane.

From rye to biomethane

Rye is one of the organic materials of agricultural origin used for the production of biomethane. It is harvested before it is fully mature and stored in silo at the Pot-au-Pin Énergie biomethane production unit. It can be stored for several months. This material feeds the methanizer throughout the year.

It is in the methanizer that the process of methanation takes place. Micro-organisms break down the material in an anaerobic environment. At the end of this process, digestate and biogas are produced.

  • Digestate is a liquid residue that is stored in lagoons before being used as a natural fertilizer in the fields.
  • The biogas is routed to the purification unit operated by Air Liquide as soon as it comes out of the methanizer.

Purification of biogas

Initially, the biogas is processed in order to remove all impurities. Then, using a membrane-based process, 99.5% of the methane contained in the biogas is extracted in the form of biomethane. The purification units designed by Air Liquide allow for the processing of biogas at speeds ranging from a hundred to several thousand cubic meters an hour. The biomethane is then odorized, its composition is measured, and its volume is counted.

Only then is it ready to be injected into the natural gas distribution network operated by GRDF, which supplies the city of Cestas.

An alternative for cleaner transportation

This same network supplies Air Liquide’s multi-energy station, located 3 kilometers from the production site. This station distributes the biomethane (bio-NGV), an alternative to fossil fuels, to carriers. Present in compressed form, biomethane offers delivery trucks an extended range capacity of up to 800 kilometers. Biomethane also reduces particulate matter emissions by 85% and reduces carbon dioxide emissions by 90%. It also cuts down on vehicle noise by up to 50% compared with diesel engines.

Open non-stop, the multi-energy station is already meeting the daily needs of 100 trucks. Soon, it will provide liquid nitrogen to cold storage trucks using Air Liquide’s cryogenic solution blueeze™ for their cold production. Associated to bio-GNV, Air Liquide’s clean and silent solution based on liquid nitrogen blueeze™ is a real asset for deliveries.

What the Pot-au-Pin Énergie initiative shows is that the biomethane value chain contributes to the development of the circular economy by bringing together local players who are working together to make the energy transition happen.

Biomethane reduces particulate matter emissions by 85%