It is not the same blue: A comparative LCA study of blue hydrogen supply network pathways.

Blue hydrogen (H 2) serves as a pivotal initial step towards emissions reduction and a seamless transition to green hydrogen by providing a cleaner alternative to grey hydrogen. Blue H 2 can be obtained through diverse pathways (i.e. , distinct processes and stages) within the hydrogen supply network (HSN), resulting in varying greenhouse gas emission levels. This paper uses the Life Cycle Assessment methodology to compare 18 different blue HSN pathways. Blue hydrogen is produced from three different processes (i.e. , Steam Methane Reforming (SMR), Partial Oxidation of Methane (POM), and Auto-Thermal Reforming (ATR)) that are coupled with carbon capture unit (CCU). Moreover, it can be conditioned to different states or carriers (i.e. , liquefied H 2 , compressed H 2 , ammonia, and methanol), stored using various methods, transported by different means according to its state, and reconditioned to its original state at end-users. The LCA results indicate that the NH 3 pathway has the least environmental impact measuring just 2.12 kgCO 2equ / kgH 2 compared to the other 18 blue HSN pathways. This pathway involves producing hydrogen from ATR process coupled with CCS, and eventually delivering as ammonia to consumers. Additionally, the blue H 2 results of this paper are compared to the green H 2 results discussed in the previous paper. The comparison highlights that integrating renewable energy in the form concentrated photovoltaic collectors produces the lowest emissions compared to all pathways. It reduces the emissions from 45.3% to 67% depending on the pathways, compared to the ATR process coupled with CCU. • SMR, POM, or ATR with carbon capture for blue hydrogen production. • This LCA study compares 18 blue HSN pathways for their environmental performance. • Different pathways within the HSN lead to various levels of GHG emissions. • NH 3 path emits the least emissions (2.12 kgCO 2equ /kgH 2) among blue H 2 paths. • CH 2 path emits the least emissions (0.080 kgCO 2equ /kWh) among all paths. [ABSTRACT FROM AUTHOR]