Energy Security in Transition: Multi-Scale Risks, Metrics, and Circular Bio-Resources from Europe to Bavarian region of Germany

This article reviews how energy security is being reconceptualised and practiced in the context of Europe’s low-carbon transition, with a particular focus on Germany and the state of Bavaria, and on the role of circular bio-resources converted by thermo-chemical-conversion technologies. A targeted review of recent peer-reviewed work was undertaken using major bibliographic databases, complemented by a critical appraisal of widely used indicator frameworks and composite indices, and by a spatially explicit assessment of bio-waste and sewage-sludge conversion potential in Bavaria using Thermo-Catalytic Reforming (TCR®) as an illustrative technology. The synthesis shows that the dominant understanding of energy security has shifted from narrow fuel-supply concerns to broader socio-technical concepts that link security to sustainability, risk, equity and digitalisation. However, prevailing indices remain strongly supply- and price-oriented, rely on overlapping indicators and weakly justified weights, and only partially capture environmental, social and technological dimensions. At the European level, diversification of energy mixes, improvements in energy and carbon intensity, and expansion of renewables have improved several aspects of security, yet high import dependence and new vulnerabilities associated with gas trade, critical materials and concentrated low-carbon technology supply chains persist. Germany’s Energiewende has raised the share of renewables and reduced coal use, but the simultaneous nuclear phase-out and former reliance on Russian pipeline gas have created a complex risk profile in which system flexibility, storage, hydrogen and bioenergy become central levers. The Bavarian case underlines that energy security is strongly region-specific: high industrial demand, heterogeneous renewable resources, land-use and biodiversity constraints, water stress and local acceptance shape feasible pathways. Across all scales, the growing use of digital platforms and artificial intelligence offers powerful capabilities for forecasting, clustering and operational security, but also introduces cyber and governance risks. Overall, the review argues for explicitly risk-oriented, multi-scale energy-security metrics and scenarios that embed climate-neutrality, justice and water-energy-food nexus constraints; for systematic integration of circular bio-resource and thermo-chemical pathways into regional and national planning; and for treating digitalisation and ’Artificial Intelligence’ (AI) as core dimensions of energy security rather than neutral enablers.