This research project aims to enhance sargassum through the production of biochars (BCs) and active coals (ACs). The BC/AC produced will be characterised and tested for their ability to sequester organochlorine pesticides (CLD, DDE, Dieldrine, HCH) present in contaminated Caribbean soils. The best BC/CA(s) will be mass-produced to amend contaminated agricultural parcels and secure products from these parcels. The project is structured around 4 complementary sub-projects (WP) allowing (1) the collection, characterisation and decontamination of sargasses, as well as the production of BC/CA at laboratory level, 2) the industrial-scale production of several tonnes of BC/CA via solar energy, 3) the full-scale experiment on contaminated gardens of the role of the selected CB/CA by preventing the transfer of pesticide residues to vegetables or eggs from treated plots, 4) the assessment of the territorial costs and impacts of the collection chain, the production of BC/CA and the practices of modifying contaminated agricultural parcels.