Industrial ecology aims to highlight a circular functioning of the economy, to save raw materials and energy (substitution synergies) and to pool services between companies (pooling synergies). The analysis of two cases of substitution synergies in Dunkirk, made from a number of interviews with local actors, shows that a common variable - interdependence (economic, technical and intelligence) - structures the relationship between the different actors, and that forms of governance at work can be apprehended from proximities of different natures. The governance of industrial ecology initiatives is divided between operational governance, of a routine nature, based on trust and in which the contract is a political safeguard, and political governance, which is mobilized to arbitrate major conflicts between the parties and which requires intervention of a legitimate third-actor. We show that these two forms of governance rely on the articulation of different forms of proximity between actors involved in industrial ecology approaches.