A multi-model assessment of the Global Warming Potential of hydrogen

Abstract

With increasing global interest in molecular hydrogen to replace fossil fuels, more attention is being paid to potential leakages of hydrogen into the atmosphere and its environmental consequences. Hydrogen is not directly a greenhouse gas, but its chemical reactions change the abundances of the greenhouse gases methane, ozone, and stratospheric water vapor, as well as aerosols. Here, we use a model ensemble of five global atmospheric chemistry models to estimate the 100-year time-horizon Global Warming Potential (GWP100) of hydrogen. We estimate a hydrogen GWP100 of 11.6 ± 2.8 (one standard deviation). The uncertainty range covers soil uptake, photochemical production of hydrogen, the lifetimes of hydrogen and methane, and the hydroxyl radical feedback on methane and hydrogen. The hydrogen-induced changes are robust across the different models. It will be important to keep hydrogen leakages at a minimum to accomplish the benefits of switching to a hydrogen economy.

Climate Impacts of Hydrogen and Methane Emissions Can Considerably Reduce the Climate Benefits across Key Hydrogen Use Cases and Time Scales

“…Our analysis builds upon previous studies that show how hydrogen emissions can considerably reduce the climate benefits of hydrogen systems by quantitatively evaluating how hydrogen emissions affect the climate impacts of individual use cases. − , The inclusion of hydrogen emissions increases the warming effects of all hydrogen pathways analyzed, especially in the near and medium term because hydrogen’s warming effects are short-lived. , Hydrogen emissions have been omitted from analysis of the benefit of deploying hydrogen as a decarbonization strategy as it is not included in the list of GHGs considered under the Kyoto Protocol, and until recently, there was a low level of awareness of its atmospheric warming effects. However, this assessment makes it clear that ignoring hydrogen emissions can considerably overestimate the decarbonization benefits of hydrogen systems.…”

“…Currently, conventional hydrogen technology assessments lack consideration of hydrogen emissions and their warming effects, − ,− yet hydrogen is a leak-prone gas with a potent indirect warming effect in the near term due to the fact that its chemical oxidation in the atmosphere increases the levels of other short-lived greenhouse gases (GHGs) in the atmosphere (methane, tropospheric ozone, and stratospheric water vapor). − This needs to be considered to fully understand the implications of deploying hydrogen at scale. Hydrogen’s indirect warming effects have been documented over the past several decades, − with a consensus emerging that hydrogen’s global warming potential (GWP) is approximately 12 over a 100-year period and approximately 35–40 over a 20-year period. − The largest uncertainties in hydrogen’s GWP are associated with the removal of atmospheric hydrogen by soil and potential future changes in the atmospheric concentrations of other GHGs such as methane. − …”

Subsidizing Grid-Based Electrolytic Hydrogen Will Increase Greenhouse Gas Emissions in Coal Dominated Power Systems

“…This increases the infrared radiative capacity of the stratosphere and results in an overall warming effect on the climate. 10,11,36 Hydrogen is a small volatile molecule that can easily leak from pipelines and transport vessels. 37,38 To estimate potential hydrogen leakage through the hydrogen life cycle of production, compression, storage, and transport, we conduct a sensitivity analysis of hydrogen leakage emissions based on prior studies.…”

“…However, minimizing leakage is crucial since hydrogen is an indirect GHG. 10,11 As hydrogen demand increases, pipeline transport becomes the most cost-effective option. 12 Using existing natural gas pipelines can reduce transmission costs by over 60% compared to building new pipelines.…”

Fundamental tools for managing sustainability

“…Hydrogen does not directly affect the climate, but its presence does increase the lifetime of methane, create changes in ozone, increase stratospheric water vapour and change the production of certain aerosols. Recent LCA studies on the global warming potential (GWP) of hydrogen give it a GWP100 of 11.6 CO 2 e. 9 However, because it is so short lived in the atmosphere (current best estimate is 2.4 years) it has a GWP20 of 37.3 CO 2 e. Projected hydrogen usage by 2050 by the International Energy Agency net zero scenario is production of 528 million tonnes of hydrogen. 10 If indeed the estimates being discussed are correct for leakage rates, this would give a GWP100 of over 360 million tonnes per annum which is not captured in the “zero emission vehicle” descriptions often ascribed to hydrogen vehicles.…”