Blue hydrogen can be low-carbon, a techno-economic-environmental analysis

• Partial condensation and desublimation CO 2 separation techniques are studied. • Autothermal reforming with low-temperature CO 2 separation shows promising results. • The Levelized Cost of blue hydrogen ranges from 2.4 to 4 €/kg H 2 . • The average carbon footprint is 2.5 kg CO 2 eq/kg H 2 for photovoltaic-powered cases. • Blue H 2 from a low-emission natural gas supply chain is competitive with green H 2 . Hydrogen produced through natural gas reforming with carbon capture and storage (blue H 2 ) is expected to supply up to 30 % of global low-carbon hydrogen by 2030. However, wide variability in reported findings creates uncertainty about its future role. To address this, the present techno-economic-environmental study from a life-cycle perspective evaluates whether blue hydrogen can meet carbon footprint thresholds (3 and 3.4 kg CO 2 eq./kg H 2 ) required to qualify as low-carbon hydrogen. Several configurations of either chemical absorption or low-temperature CO 2 separation techniques integrated with auto-thermal reforming are modeled. Results show that low-temperature separation can achieve comparable or even superior energetic performance to conventional capture methods, with cold gas and overall efficiencies reaching up to 80 % and 78 %, respectively. The economic analysis estimates the levelized cost of blue hydrogen at 3.5–4 €/kg under 2024 EU average non-household consumer natural gas and electricity prices, and 2.4–2.8 €/kg under Italy’s 2024 wholesale prices. From an environmental standpoint, life-cycle assessment indicates an average carbon footprint of 2.5 kg CO 2 eq./kg H 2 , assuming photovoltaic electricity for auxiliary power and excluding more carbon-intensive natural gas supply chains. The findings highlight that partial electrification of the CO 2 separation unit, use of renewable electricity, and maximizing capture rates are key factors essential for producing compliant blue H 2 . Furthermore, adopting ultra-low-emission natural gas supply chains could reduce blue H 2 ′s carbon footprint to the level of green H 2 , suggesting that the introduction of certificate-of-origin schemes for natural gas can guarantee blue H 2 with minimal emissions.