CMI Annual Report 2022

The critical hydrogen emission intensity is a benchmark that
can be used to evaluate the impact of hydrogen use, which can
be beneficial or detrimental, on atmospheric methane. Clearly,
this requires detailed estimates of future hydrogen emissions.
Figure 8.2.
Critical hydrogen
emission intensity
(HEI) of green and
blue H 2
(with 0.2,
0.5, 1% CH 4
leak
rates) as a function
of the OH excess,
i.e., the amount of
OH that reacts with
other gases besides
methane. Triangles
mark the critical HEI
for the best estimates.
Dashed (dotted) lines
are obtained for a 20%
increase (decrease) in
the H 2
uptake rate by
soil bacteria.
References
Bertagni, M. B., S.W. Pacala, F. Paulot, and A. Porporato, 2022.
Risk of the hydrogen economy for atmospheric methane.
Nature communications 13(1):7706. (https://doi.org/10.1038/
s41467-022-35419-7).
Ehhalt, D. and F. Rohrer, 2009. The tropospheric cycle of H 2
: a
critical review. Tellus B: Chemical and Physical Meteorology
61(3):500–535.
(https://doi.org/10.1111/j.1600-0889.2009.00416.x).
Saunois, M. et al., 2020. The global methane budget 2000–2017.
Earth System Science Data 12(3):1561-1623. (https://doi.
org/10.5194/essd-12-1561-2020).
Warwick, N. et al., 2022. Atmospheric Implications of
Increased Hydrogen Use. Technical Report (Policy Paper from
UK’s Department for Energy Security and Net Zero and
Department for Business, Energy & Industrial Strategy). (www.
gov.uk/government/publications/atmospheric-implications-ofincreased-hydrogen-use).
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Carbon Mitigation Initiative Twenty-second Year Report 2022