This article aims to contribute to the analysis of the complex relationship between sustainable development and green economy in mountain areas by focusing on a conflict over the building of a centralized biogas plant to produce renewable energy from livestock manure in an Italian Alpine valley. The case study shows that the project for a large-sized biogas plant promoted by the local political institutions as environmental modernization of local agriculture, and supported by the most important professional organizations, became increasingly controversial at the local community level and was eventually abandoned. By drawing in particular on the literature concerning the social acceptance of renewable energies, the article highlights how this conflict raises issues of distributional justice and procedural justice with regard to the implementation of the green economy model, and it points out the need to embed green economy technologies in the local context and conditions. These concerns should be given primary consideration if the green economy model is to contribute to the sustainable development of marginal areas.