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

Hydrogen produced through natural gas reforming with carbon capture and storage (blue H2) 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 CO2 eq./ kg H2) required to qualify as low-carbon hydrogen. Several configurations of either chemical absorption or low-temperature CO2 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 CO2 eq./ kg H2, assuming photovoltaic electricity for auxiliary power and excluding more carbon-intensive natural gas supply chains. The findings highlight that partial electrification of the CO2 separation unit, use of renewable electricity, and maximizing capture rates are key factors essential for producing compliant blue H2. Furthermore, adopting ultra-low-emission natural gas supply chains could reduce blue H2 ' s carbon footprint to the level of green H2, suggesting that the introduction of certificate-of-origin schemes for natural gas can guarantee blue H2 with minimal emissions.