This paper presents a systematic comparative analysis of energy efficiency and carbon footprint of welded, adhesive, and hybrid (weld-bonding) joining processes for metallic components, within the framework of the circular economy and Extended Producer Responsibility (EPR). With global welding energy consumption estimated at over 400 TWh annually, the identification of lower-energy joining alternatives is a critical step toward industrial decarbonization aligned with Paris Agreement targets and EU climate neutrality goals for 2050. The study integrates quantitative energy balances, Life Cycle Assessment (LCA) data, and experimental results on surface preparation effects on adhesive joint performance. Results demonstrate that adhesive bonding requires up to 6000× less direct process energy than MIG/MAG welding for equivalent joints, and generates 3-50× lower CO2 emissions per meter of joint. Hybrid joining reduces energy consumption by approximately 30% compared to pure spot welding while improving fatigue strength by 60-70%. The circular economy implications of each technology - including repairability, disassembly, and end-of-life recyclability - are examined, and a conceptual decision framework for joining technology selection is proposed, based on lifecycle performance indicators and EPR compliance.