By Blaine Friedlander at Cornell Chronicle|
August 12, 2021 – “Blue” hydrogen – an energy
source that involves a process for making hydrogen by using methane in natural
gas – is being lauded by many as a clean, green energy to help reduce global
warming. But Cornell and Stanford University researchers believe it may harm
the climate more than burning fossil fuel.
The carbon footprint to create blue
hydrogen is more than 20% greater than using either natural gas or coal
directly for heat, or about 60% greater than using diesel oil for heat,
according to new research published Aug. 12 in Energy Science &
Engineering.
“Most of the hydrogen in the U.S. and
Europe comes from natural gas, using steam and pressure to convert the methane
from natural gas into a so-called ‘gray’ hydrogen and carbon dioxide,” said Robert
Howarth, the David R. Atkinson Professor of Ecology and Environmental
Biology in the College of Agriculture and Life Sciences. Howarth, together with
Mark Z. Jacobson, Stanford professor of civil and environmental engineering,
authored “How Green is Blue Hydrogen?”
Blue hydrogen starts with converting
methane to hydrogen and carbon dioxide by using heat, steam and pressure, or
gray hydrogen, but goes further to capture some of the carbon dioxide. Once the
byproduct carbon dioxide and the other impurities are sequestered, it becomes
blue hydrogen, according to the U.S. Department of Energy.
The process to make blue hydrogen takes
a large amount of energy, according to the researchers, which is generally
provided by burning more natural gas.
“In the past, no effort was made to
capture the carbon dioxide byproduct of gray hydrogen, and the greenhouse gas
emissions have been huge,” Howarth said. “Now the industry promotes blue
hydrogen as a solution, an approach that still uses the methane from natural
gas, while attempting to capture the byproduct carbon dioxide. Unfortunately,
emissions remain very large.”
Methane is a powerful greenhouse gas,
Howarth said. It is more than 100 times stronger as an atmospheric warming
agent than carbon dioxide when first emitted. The United Nations’
Intergovernmental Panel on Climate Change released on August 9 shows that
cumulatively to date over the past century, methane has contributed about
two-thirds as much to global warming as carbon dioxide has, he said.
Considering both the uncaptured carbon
dioxide and the large emissions of unburned, so-called “fugitive” methane
emissions inherent in using natural gas, the carbon footprint to create blue
hydrogen is more than 20% greater than burning either natural gas or coal
directly for heat, or about 60% greater than using diesel oil for heat,
according to the new paper.
Emissions of blue hydrogen are less than
for gray hydrogen, but not greatly so: perhaps surprisingly, only by about 9%
to 12%.
“Blue hydrogen is hardly emissions
free,” wrote the researchers. “Blue hydrogen as a strategy only works to the
extent it is possible to store carbon dioxide long-term indefinitely into the
future without leakage back to the atmosphere.”
An ecologically friendly “green”
hydrogen does exist, but it remains a small sector and it has not been
commercially realized. Green hydrogen is achieved when water goes through
electrolysis (with electricity supplied by solar, wind or hydroelectric power)
and the water is separated into hydrogen and oxygen.
On Aug. 10, the U.S. Senate passed its
version of the $1 trillion Infrastructure Investment and Jobs Act, which
includes several billion dollars to develop, subsidize and strengthen hydrogen
technology and its industry.
“Political forces may not have caught up
with the science yet,” Howarth said. “Even progressive politicians may not
understand for what they’re voting. Blue hydrogen sounds good, sounds modern
and sounds like a path to our energy future. It is not.”
Said Howarth: “The best hydrogen, the
green hydrogen derived from electrolysis – if used wisely and efficiently – can
be that path to a sustainable future. Blue hydrogen is totally different.”
This research was supported by a grant
from the Park Foundation. Howarth is a fellow at the Cornell Atkinson Center
for Sustainability.
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