This article considers the analysis of upgrading strategies, focusing at the level of subordinate firms themselves. This approach develops the concept of "strategic upgrading". We study the institutional environment of subordinate firms, and we analyze subordinate firms' strategies through concepts from industrial economics, such as differentiation, diversification, and specialization. We thus reexamine the category of inter-chain upgrading, i.e., the improvement of the position of actors of a GVC by integrating a new GVC. We confront this proposal with a territorialized case study on the development of biogas production by farmers in the Ardennes. We observe that these farmers are part of the emerging GVC of biomass energy based on their experience as "captive" actors in the agro-industrial GVC. In particular, they have sized their biogas production units to be autonomous regarding agro-industry. This new activity also has feedback effects on their positioning in the agro-industrial GVC.