This paper presents the utilization of the multi-agent platform Geamas through the Biomas application for the collective management of animal wastes. The complexity of the scenarios under study gives rise to many unpredictable behavioral schemas whose analyses necessitate a simulation approach. In the present article we describe the whole set of concepts in use in multi-agent systems modeling and we demonstrate how these concepts are implemented in the Biomas application. We put the emphasis on the representation of agents, roles and on their operational environment. Simulation outputs of a realistic scenario of negotiation between agents are discussed and we demonstrate the importance of a well-adapted user interface.