In outermost islands the current increase of imported agricultural input costs questions the viability of farms and of the whole agricultural sector. The need, for these territories, to be less dependent and to mobilize local resources in a circular way is rising. Nevertheless, technical and organizational lock-in makes changes difficult to achieve. From 2017 to 2020, a Research and Development project has been caried out on Reunion Island to implement a territorial approach of biomass in agriculture based on circular economy. Five case-studies were undertaken with development, agricultural training and research actors and policy makers for the co-conception of organizational biomass scenarios. This project bas created a strong momentun and the co-construction of solutions. However, as in many prospective works with actors, the implementation - which is then delegated to stakeholders - is rarely applied. To overcome this pitfall, we built a new project with some of the previous actors, on the territory of a municipality, starting from the insights of two case-studies (the levers to lower man ure spreading constraints and the evaluation of the interest of composting manure with green waste). After a first diagnostic phase of the territory, we carried out two kinds of actions. We first organized focus-groups with local actors to conceive an agroecological transition for the territory. Second, we set up on-farm experiments with 5 farmers to develop composting of manure mixed with green waste and to test the compost on meadows and market gardening. The transition scenario confirms the need to improve biomass management to reduce inputs, jointly with the transformation of systems toward more agroecological ones. The development of farm composts a long with their use on crops and meadows were successful. But, if the project allows the production of references and learnings, we observed within the project period various dynamics of actors, more or less competing, for treat