Profitable approach to
cleaning the air
Date:
May 20, 2019
Source:
Stanford University
Summary:
A seemingly counterintuitive
approach -- converting one greenhouse gas into another -- holds promise for
returning the atmosphere to pre-industrial concentrations of methane, a
powerful driver of global warming.
A relatively simple process
could help turn the tide of climate change while also turning a healthy profit.
That's one of the hopeful visions outlined in a new Stanford-led paper that
highlights a seemingly counterintuitive solution: converting one greenhouse gas
into another.
The study, published in Nature
Sustainability on May 20, describes a potential process for converting the
extremely potent greenhouse gas methane into carbon dioxide, which is a much
less potent driver of global warming. The idea of intentionally releasing
carbon dioxide into the atmosphere may seem surprising, but the authors argue
that swapping methane for carbon dioxide is a significant net benefit for the
climate.
"If perfected, this
technology could return the atmosphere to pre-industrial concentrations of
methane and other gases," said lead author Rob Jackson, the Michelle and
Kevin Douglas Provostial Professor in Earth System Science in Stanford's School
of Earth, Energy & Environmental Sciences.
The basic idea is that some
sources of methane emissions -- from rice cultivation or cattle, for example --
may be very difficult or expensive to eliminate. "An alternative is to
offset these emissions via methane removal, so there is no net effect on
warming the atmosphere," said study coauthor Chris Field, the Perry L.
McCarty Director of the Stanford Woods Institute for the Environment.
A problem and a possible
solution
In 2018, methane -- about 60
percent of which is generated by humans -- reached atmospheric concentrations
two and a half times greater than pre-industrial levels. Although the amount of
carbon dioxide in the atmosphere is much greater, methane is 84 times more
potent in terms of warming the climate system over the first 20 years after its
release.
Most scenarios for stabilizing
average global temperatures at 2 degrees Celsius above pre-industrial levels
depend on strategies for both reducing the overall amount of carbon dioxide
entering the atmosphere and removing what's already in the atmosphere through
approaches such as tree planting or underground sequestration. However,
removing other greenhouse gases, particularly methane, could provide a
complementary approach, according to the study's authors, who point to the
gas's outsized influence on the climate.
Most scenarios for removing
carbon dioxide typically assume hundreds of billions of tons removed over
decades and do not restore the atmosphere to pre-industrial levels. In
contrast, methane concentrations could be restored to pre-industrial levels by
removing about 3.2 billion tons of the gas from the atmosphere and converting
it into an amount of carbon dioxide equivalent to a few months of global
industrial emissions, according to the researchers. If successful, the approach
would eliminate approximately one-sixth of all causes of global warming to
date.
Methane is challenging to
capture from air because its concentration is so low. However, the authors
point out that zeolite, a crystalline material that consists primarily of
aluminum, silicon and oxygen, could act essentially as a sponge to soak up
methane. "The porous molecular structure, relatively large surface area
and ability to host copper and iron in zeolites make them promising catalysts
for capturing methane and other gases," said Ed Solomon, the Monroe E.
Spaght Professor of Chemistry in the School of Humanities and Sciences.
The whole process might take
the form of a giant contraption with electric fans forcing air through tumbling
chambers or reactors full of powdered or pelletized zeolites and other
catalysts. The trapped methane could then be heated to form and release carbon
dioxide, the authors suggest.
A profitable future
The process of converting
methane to carbon dioxide could be profitable with a price on carbon emissions
or an appropriate policy. If market prices for carbon offsets rise to $500 or
more per ton this century, as predicted by most relevant assessment models,
each ton of methane removed from the atmosphere could be worth more than
$12,000.
A zeolite array about the size
of a football field could generate millions of dollars a year in income while
removing harmful methane from the air. In principle, the researchers argue that
the approach of converting a more harmful greenhouse gas to one that's less
potent could also apply to other greenhouse gases.
While reducing greenhouse
gases in the atmosphere to pre-industrial levels may seem unlikely in the near
future, the researchers argue that it could be possible with strategies like
these.
Story Source:
Materials provided
by Stanford University.
Original written by Rob Jordan, Stanford Woods Institute for the
Environment. Note: Content may be edited for style and length.
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