MagmaS is a multi-agents system aiming at modelling animal wastes production, use, and transfers at the farmer community level, and enabling one to test various scenarios to help wastes management in the case of the Reunion Island. The system is composed by both an hybrid dynamical system modelling wastes production and uses, and an agent based model of wastes transfers between farms. This model was used to study how transfers can help to avoid wastes surpluses, and how the nature of relationships among farmers can rule transfers of wastes between them.