CMI Annual Report 2021

Soil Uptake and Methane Feedback of Atmospheric Hydrogen
PRINCIPAL INVESTIGATOR: AMILCARE PORPORATO
At a Glance
Hydrogen (H 2
) plays a crucial role in global energy scenarios
aimed at achieving net-zero. Because it is not a greenhouse gas,
H 2
has been touted as an alternative to fossil fuels in certain
energy sectors. But the environmental consequences of
perturbing the global hydrogen cycle are still largely unknown.
Specifically, there are concerns around hydrogen interference
with the methane (CH 4
) atmospheric sink by the hydroxyl
radical (OH). To sharpen future H 2
projections, the Porporato
group has been quantitively addressing the major sink of
tropospheric H 2
, namely the soil uptake by bacteria, and the
methane feedback of H 2
fugitive emissions. This research
informs bp’s aims of developing the H 2
economy in a manner
that minimizes adverse climate impacts.
Research Highlight
Hydrogen will play a crucial role in the decarbonization of
energy systems and may provide a cost-effective option to
replace fossil fuels in applications where emission reductions
are difficult, such as in heavy transport. However, large scale
H 2
production with its consequent fugitive emissions may
increase the H 2
atmospheric concentration, which currently
hovers around 530 ppb (Novelli et al., 1999). The
environmental implications of this are not yet clear.
Hydrogen has an indirect global warming effect due to its
interactions with other greenhouse gases (GHG) in the
atmosphere, such as, for example, ozone, water vapor, and
methane. Indirect radiative forcing of H 2
is expected to be
small compared to that of fossil fuels. However, recent global
climate models (Paulot et al., 2021) have raised concerns about
some possible consequences of an increasing concentration of
hydrogen on tropospheric methane (CH 4
), the second most
important GHG.
To improve our understanding of the global hydrogen cycle
and the consequences of its possible perturbation, Porporato’s
research group has refined the modeling of the major sink of
atmospheric H 2
, namely the uptake by soil bacteria, and
quantitatively addressed the methane feedback of H 2
fugitive
emissions.
Carbon Mitigation Initiative Twenty-first Year Report 2021 28