Sustainability reporting is increasingly expected to support governance, not only external commu-nication. This thesis examines how leading sustainability frameworks organise accountability and what this implies for large scientific and research institutions, using CERN as a case study. It com-pares GRI, CSRD/ESRS, EMAS, ISO 14001 and ISO 26000 in a structured matrix and applies the results to CERN’s Environment Reports (2017–2024), complemented by a brief peer institutions benchmark and semi-structured interviews. Findings show that the instruments encode distinct accountability logics (disclosure-oriented, regulatory and management-system based) which shape topic selection, responsibility allocation and credibility. CERN’s reporting is comparatively mature on environmental disclosure, but less integrated across ESG. The thesis argues for functional com-plementarity: retain a strong GRI baseline while selectively adopting mostly CSRD/ESRS connec-tivity and management-system routines to strengthen materiality, governance and performance tracking.