Green algae have become a real problem for the Breton coast, especially in the Côtes d'Armor. With the decomposition of algae on beaches and in mudflats, the formation of the toxic H2S gas poses a problem and has accidentally caused the death of animals or humans. A government plan has been put in place for the daily collection of green algae.A solution for the co-composting of green algae with plant waste was finally adopted on the Pleumeur-Bodou site in confined compartments with controlled ventilation in addition to spreading