Trompetter, W.J.; Fleming, L.; Gupta, P.S.; Griffin, A.G. 2025 Does the growing hydrogen economy pose a risk to the environment?. Lower Hutt, NZ.: Earth Sciences New Zealand. GNS Science report 2024/20. 18 p.; doi: 10.21420/14RE-R927
Abstract
In recent years, there have been growing concerns by climate scientists that green hydrogen (H2) emissions may undermine the climate benefits of reducing carbon dioxide (CO2) emissions. This is because hydrogen is an indirect greenhouse gas due to its reaction with the hydroxyl (OH) radical in the atmosphere. This reaction has a number of impacts, including a reduction in the amount of OH available to remove methane (CH4) from the atmosphere. The literature review undertaken as part of this study conjects that green H2 will mitigate climate impact even for worst-case leakage rates of 10%, while 1% H2 leaks could yield a near elimination of the climate impact compared with fossil-fuel CO2 emissions. On the other hand, other forms of hydrogen generation (blue/grey/brown/black hydrogen) have increasing amounts of additional emissions, primarily CO2and CH4, from their hydrogen-production processes, which undermine their climate benefits. In addition, hydrogen emissions are detrimental to safety and the economy. A literature review of H2 losses and leakage rate show that these are currently 2.0–5.6%. However, as technology develops and production scales increase, these rates are expected to decrease. Going forward, key opportunities identified are to (1) explore H2 monitoring at both clean-air sites for background concentrations and H2 industry sites for local emissions and (2) to develop technologies with industry to mitigate losses and leakages from H2 industry processes (auths)
