Project Name: SEVADEC
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Project Description:

The centralised biogas plant in Calais was built in 2005 to reduce the amount of household organic waste going to landfill. Fermentation takes place in one digester of a volume of 3100 m3. The digester uses the VALORGA process, working in thermophile mode (55°C) with 25-30% dry matter content (“dry digestion”). The outcoming digestate is dehydrated in two drying tunnels for 20h at 17 500 Nm3/h airflow.

The biogas is collected in the upper part of the digestor for drying and filtering. The biogas is then compressed in 2 compressors and a double-envelope tarpaulin allows for stocking the gas at 25 mbar. A booster allows for raising the pressure to 100 mbar. Surplus and substandard quality gas is torched. The gas mainly feeds two generators (installed electrical power of 940 kW and 500kW repectively) and the electricity produced is sold to the public grid.

Technology at a glance

  • Biogas production: 3.171.024 Nm3/a
  • Installed power: 1.440 kW
  • Digester type and volume (m3): 3.100 (15m x 18m) (dry digestion)
  • Type of waste used: food oils, green clippings, other residential waste
  • Amount of waste/raw material used as substrate (t/year): 26.994 t/a of which 1.478 t/a food oils, 2.323 t/a other residential waste, 22.194 t/a fermentable waste and green clippings

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