This article compares how visions for integrating environmental issues into the union agenda are articulated from two different positions in the Swedish Trade Union Confederation (LO). The article is based on an analysis of ‘life history interviews’ and directs attention to the biographical circumstances under which individuals are able to work with environmental issues in unions. The analysis shows that the conditions for integrating environmental issues are weakened by the hierarchical culture of the organisation and by high levels of institutionalisation. LO furthermore lacks routines for mobilising the interests of environmental enthusiasts, and being positioned at headquarters hampers the abilities of union officials to mobilise environmental interests among members. Comparing the experiences from Sweden with the case of Comisiones Obreras (CCOO) in Spain shows that success depends on a relationship between individual engagement and political. Union transformation is contingent on developing issues that connect the immediate interests of workers with their long-term interests as citizens, such that a new workers’ identity can develop and lead to practices that overcome the ‘metabolic rift’.