Search finds super-emitters of methane and hydrocarbons | Chemical & Engineering News
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Web Date: April 25, 2016

Search finds super-emitters of methane and hydrocarbons

Aerial surveys identify leakage from oil and gas storage tanks and their hatches as major culprits
Department: Science & Technology
News Channels: Environmental SCENE
Keywords: greenhouse gases, climate change, methane loss, oil and natural gas production
Aerial surveys of oil and gas fields identify methane and hydrocarbon super-emitters.
Credit: Shutterstock
Photo of oil well.
Aerial surveys of oil and gas fields identify methane and hydrocarbon super-emitters.
Credit: Shutterstock

Certain oil and natural gas sites are known super-emitters of methane and hydrocarbons. Now, using helicopters and infrared cameras, researchers have better characterized these sites and pinpointed the major source of their emissions: leakage from field storage tanks and their hatches (Environ. Sci. Technol. 2016, DOI: 10.1021/acs.est.6b00705). These leaks could be easily controlled with the appropriate equipment, the researchers say.

Methane is a powerful greenhouse gas, 25 times more potent than carbon dioxide over a 100-year time span, according to the Environmental Protection Agency. Controlling methane emissions is critical to curbing climate change. About 30% of U.S. methane emissions come from the oil and gas sector, according to the EPA.

In the new study, a team headed by scientists at the Environmental Defense Fund, a nonprofit advocacy group, hired a firm to survey more than 8,000 oil and gas well pads in seven regions of the U.S., using helicopters equipped with IR gas-imaging instruments to detect methane and hydrocarbon leakage. These IR cameras can detect gas plumes emanating from individual pieces of equipment at the facilities, such as tanks and pipes.

By matching IR-observed gas plumes at field sites with IR images of controlled releases of known size and duration, the scientists were able to determine leak rate and the exact location of leaking equipment at the well pads. They found that more than 90% of some 500 detected leakage sources were the tanks that hold, separate, and further process oil and natural gas in the field, as well as hatches allowing access to the tanks. Tanks are a somewhat surprising source, notes David R. Lyon, lead study author. In the past, he adds, more attention fell on leakage from other stages of the process, such as drilling, production, transmission, and distribution.

“Most of the tank sites had control devices that appear to be not working, ineffective, or undersized,” notes Lyon. He recommends more frequent inspections and a greater emphasis on eliminating tank emissions.

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Dennis Malpass (April 27, 2016 1:29 PM)
What were the sources of the other 70% of methane emissions?
Edgar Mueller (April 28, 2016 6:48 AM)
Dear Sir, Dear Madam,

As a scientist, I cannot adhere to the EPA statement that methane is a powerful greenhouse gas, 25 times more potent than carbon dioxide.

Methane is constantly produced by natural processes, but also degraded in the earth atmosphere (its half-life is about 8.4 years), hence no important concentrations may build up on a long term; the actual concentration is a dynamic steady-state concentration.

Methane displays only two electromagnetically active spectral bands at about 3 and 7 micrometers wavelength, both are outside the thermally relevant atmospheric IR window (defined by water vapor) which goes from 8 to 14 micrometers wavelength. Compared to the water vapor present in the earth atmosphere, methane has a neglectible contribution to the overall absorption spectrum in the thermally relevant IR range at 300K.

If there are political reasons for phasing out methane from human use, please state them as such, and not in the name of science. If scientists are abused to supply arguments for enforcing political goals, science will ultimately loose its credibility as an objective image of reality, and it is not that we want! It is our first duty as scientists to preserve the objectivity of science, in order to not deprive mankind of its most important vision tool!

Kind Regards

Edgar Mueller
lana (May 12, 2016 4:19 PM)
Mr Mueller,
Methane is a potent greenhouse gas for 3 reasons.
1. Its IR absorbance peaks are in opposite locations of the more abundant CO2 and water absorbance bands meaning it absorbs strongly in key regions of reflected IR spectrum not absorbed by other greenhouse gases.
2. Methane contributes strongly to forming near ground level or tropospheric ozone which is also a dramatic greenhouse gas (reflected IR absorber). Because tropospheric ozone is formed, not emitted, it is proper to account for increased greenhouse effects of ozone produced from other gasses emissions' according to their contributions' in forming tropospheric ozone. Ground-level methane emissions are key drivers of near ground and tropospheric ozone formation.
3. Methane may only have an 8-12 year half life, but it degrades to CO2 and water, the two most significant greenhouse gases with very long half-lifes.

It absorbs in a key region (7-9 um). It creates ozone which absorbs in a key region 8.5-14 um). Then it degrades to CO2 and water, the two most abundant absorbers. By definition, over its lifetime an atmospherically emitted methane molecule will cause more reflected IR photons to be absorbed than a CO2 molecule similarly emitted.

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