Lifecycle energy analysis of metallic recycling, composite recovery, and additive manufacturing as circular economy strategies in aerospace manufacturing

Aerospace materials are highly energy-intensive: titanium mill products require 420–700 MJ kg −1 , virgin CFRP 300–500 MJ kg −1 , and primary aluminium 170–210 MJ kg −1 . With buy-to-fly ratios of 12–25:1 in conventional machining, the embodied energy per finished titanium part can exceed 14,000 MJ. This study analyses three circular economy interventions, closed-loop metal recycling, composite fibre recovery, and additive manufacturing, on a cradle-to-gate-plus-end-of-life boundary excluding the use phase. Aluminium remelting achieves 93%–95% savings, titanium vacuum arc remelting yields 61%–73%, and CFRP pyrolysis reduces embodied energy by 83%–92%; titanium additive manufacturing with recycled feedstock cuts cradle-to-gate energy by up to 94%. A 50,000-iteration Monte Carlo simulation, with stratified buy-to-fly ratios for forged, wrought, and fastener titanium sub-pools and triangular distributions on parameters with literature central tendencies, yields a median lifecycle energy saving of 47% (90% CI: 38%–55%) for a representative wide-body aircraft, with a median GWP reduction of 44% (90% CI: 35%–53%). Under the assumed scenario (mass-weighted titanium BTF ≈ 7 . 7 , AM-suitability fraction 0.20–0.60), titanium accounts for approximately 60% of manufacturing embodied energy and 85% of achievable savings despite constituting only 15% of airframe structural mass, driven by its forged-fitting sub-pool; the CFRP recycled-content rate is bounded to its secondary-structure sub-pool, reflecting the continuous-fibre requirement of primary CFRP airframe components. The titanium-dominance finding is directional but its precise share is regime-dependent.