Meta-analysis of climate impact reduction potential of hydrogen usage in 9 Power-to-X pathways

Owing to the ongoing energy crisis, increasing shares of renewables, and climate mitigation targets, a green hydrogen economy through water electrolysis has gained interest. Hydrogen can be directly utilised or converted via different Power-to-X pathways to produce fossil-free substitutable products; therefore, their life-cycle emissions were studied to determine whether these solutions could provide sustainable alternatives. Thus, understanding which Power-to-X solution can provide the greatest greenhouse gas emission reduction is crucial. This study provides nine meta-analyses of different pathways to compare climate emissions reductions based on the literature. The minimum, maximum, and average values were estimated for each investigated Power-to-X pathway. The direct use of hydrogen or its service to produce steel, biogas upgrading, protein, or ammonia resulted in over 10 kgCO2 kgH2−1 reductions on average while using low-carbon energy sources. Co-electrolysis can potentially provide higher emission savings owing to lower electricity consumption compared with low-temperature electrolysers. In addition, the possibility of integrating electrochemical synthesis with hydrogen production has great potential, but the usability depends on the advancement of the technology in the future. Selections of carbon dioxide sources, substitutable products, and other assumptions of the investigated studies significantly impact the reduction potential. Low-emission-factor electric grid mixes containing fossil sources can result in emission savings in many Power-to-X systems. However, using grid mixes that result in emission savings is system-dependent, and the largest emission savings are achieved through renewables or nuclear energy.