Methane from megafires: More spew than we knew
Novel detection technique raises pollution policy questions

Date:
April 17, 2023
Source:
University of California - Riverside
Summary:
Using a new detection method, scientists found a massive amount of
methane, a super-potent greenhouse gas, coming from wildfires --
a source not currently being accounted for by California state
air quality managers.


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FULL STORY ========================================================================== Using a new detection method, UC Riverside scientists found a massive
amount of methane, a super-potent greenhouse gas, coming from wildfires --
a source not currently being accounted for by state air quality managers.


========================================================================== Methane warms the planet 86 times more powerfully than carbon dioxide
over the course of 20 years, and it will be difficult for the state to
reach its required cleaner air and climate goals without accounting for
this source, the researchers said.

Wildfires emitting methane is not new. But the amount of methane from
the top 20 fires in 2020 was more than seven times the average from
wildfires in the previous 19 years, according to the new UCR study.

"Fires are getting bigger and more intense, and correspondingly,
more emissions are coming from them," said UCR environmental sciences
professor and study co- author Francesca Hopkins. "The fires in 2020
emitted what would have been 14 percent of the state's methane budget
if it was being tracked." The state does not track natural sources of
methane, like those that come from wildfires. But for 2020, wildfires
would have been the third biggest source of methane in the state.

"Typically, these sources have been hard to measure, and it's questionable whether they're under our control. But we have to try," Hopkins
said. "They're offsetting what we're trying to reduce." Traditionally, scientists measure emissions by analyzing wildfire air samples obtained
via aircraft. This older method is costly and complicated to deploy.

To measure emissions from 2020's Sequoia Lightning Fire Complex in the
Sierra Nevadas, the UCR research team used a remote sensing technique,
which is both safer for scientists and likely more accurate since it
captures an integrated plume from the fire that includes different
burning phases.

The technique, detailed in the journal Atmospheric Chemistry and Physics, allowed the lead author, UCR environmental sciences Ph.D. student Isis
Frausto- Vicencio to safely measure an entire plume of the Sequoia
Lightning Fire Complex gas and debris from 40 miles away.

"The plume, or atmospheric column, is like a mixed signal of the whole
fire, capturing the active as well as the smoldering phases," Hopkins
said. "That makes these measurements unique." Rather than using a
laser, as some instruments do, this technique uses the sun as a light
source. Gases in the plume absorb and then emit the sun's heat energy,
allowing insight into the quantity of aerosols as well as carbon and
methane that are present.

Using the remote technique, the researchers found nearly 20 gigagrams of methane emitted by the Sequoia Lightning Fire Complex. One gigagram is
1,000 metric tons. An elephant weighs around one metric ton. For context,
the fire therefore contained roughly 20,000 elephants' worth of the gas.

This data matches measurements that came from European space agency
satellite data, which took a more sweeping, global view of the burned
areas, but are not yet capable of measuring methane in these conditions.

If included in the California Air Resources Board methane budget,
wildfires would be a bigger source than residential and commercial
buildings, power generation or transportation, but behind agriculture
and industry. While 2020 was exceptional in terms of methane emissions, scientists expect more megafire years going forward with climate change.

In 2015, the state first established a target of 40 percent reduction in methane, refrigerants and other air pollutants contributing to global
warming by 2030. The following year, in 2016, Gov. Jerry Brown signed
SB 1383, codifying those reduction targets into law.

The reductions are meant to come from regulations that capture methane
produced from manure on dairy farms, eliminate food waste in landfills,
require oil and gas producers to minimize leaks, ban certain gases in
new refrigerators and air conditioners, and other measures.

"California has been way ahead on this issue," Hopkins said. 'We're
really hoping the state can limit the methane emissions under our control
to reduce short-term global warming and its worst effects, despite the
extra emissions coming from these fires."
* RELATED_TOPICS
o Earth_&_Climate
# Wildfires # Climate # Global_Warming #
Environmental_Issues
o Science_&_Society
# Environmental_Policies # Energy_Issues # STEM_Education
# Resource_Shortage
* RELATED_TERMS
o Greenhouse_gas o Natural_gas o Methane o Air_pollution
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Sulfur_hexafluoride o Greenhouse_effect

========================================================================== Story Source: Materials provided by
University_of_California_-_Riverside. Original written by Jules
Bernstein. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Isis Frausto-Vicencio, Sajjan Heerah, Aaron G. Meyer, Harrison
A. Parker,
Manvendra Dubey, Francesca M. Hopkins. Ground solar absorption
observations of total column CO, CO2, CH4, and aerosol
optical depth from California's Sequoia Lightning Complex Fire:
emission factors and modified combustion efficiency at regional
scales. Atmospheric Chemistry and Physics, 2023; 23 (7): 4521 DOI:
10.5194/acp-23-4521-2023 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/04/230417142508.htm

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