Évaluer les impacts des recherches en agriculture sur la société : outils, méthodes, études de cas. Abstract -Innovating in the agri-food processing sector in West Africa. Based on the ImpresS method developed by CIRAD, the article analyzes the innovation processes driven by the users of the fonio (Digitaria exilis Stapf) dehuller in West Africa. The characterization of the actors system and the chronological narrative of the innovation process were mobilized to characterize the mechanisms and conditions explaining the success of this innovation. They highlight the decisive role of building a partnership around shared objectives between several stakeholders (researchers, processors and equipment manufacturers) and the importance of mobilizing a capital of knowledge among these stakeholders to solve a societal problem: the drudgery of hulling fonio. Formal and informal cross learning between stakeholders were essential in solving problems encountered during the process.