Naked Science Forum
Life Sciences => The Environment => Topic started by: Nadeem Gabbani on 02/12/2019 17:10:37
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Robert asks:
What amount of atmospheric heating is there by burning a volume of methane compared to the average lifetime greenhouse effect of the same amount of un-burnt gas?.
Who can help?
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Long story short: it is better to burn it.
Burning 1000 kg of methane releases about 5×1010 J. But methane that is released into the atmosphere ends up "burning" anyway (converting methane and oxygen to carbon dioxide and water), in the upper atmosphere, releasing the same amount of energy, just over a longer timescale, and higher up in the atmosphere. The different location and timescale of the conversion of methane and oxygen to carbon dioxide and water may introduce a small difference in how much of that energy goes into heating the air near the surface, but this also ends up being minuscule compared to the amount of energy that can be trapped by adding 1000 kg of methane to the atmosphere.
Before degrading into carbon dioxide, methane is much more potent as a greenhouse gas. Over the course of 100 years, 1000 kg of methane "traps" about 30 times as much energy as 1000 kg of carbon dioxide.
Calculating precisely how much energy gets trapped in not straightforward, and depends on many assumptions (for example adding 1000 kg of methane to an atmosphere with 400 ppm carbon dioxide will not necessarily have the same effect as adding to an atmosphere with 600 ppm carbon dioxide). But as a rough approximation, having increased atmospheric carbon dioxide concentrations from 300 ppm to 400 ppm required about 5×1014 kg of carbon dioxide being released into the atmosphere. This is predicted to change the temperature by about 1.5 °C over the next century, which would require on the order of 1025 J (based on the heat capacity of the atmosphere and oceans--as worked out in the 3rd reference below). This works out to about 2×1010 J/kg or 2×1013 J for 1000 kg of carbon dioxide, so this would be on the order of 6×1014 . (10000x as much as burning--and probably 1000000x as much as the difference between burning on purpose and slow oxidation in the upper atmosphere)
https://en.wikipedia.org/wiki/Global_warming_potential
https://www.epa.gov/ghgemissions/understanding-global-warming-potentials
https://scholarsandrogues.com/2013/05/09/csfe-heat-capacity-air-ocean/
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Over the course of 100 years, 1000 kg of methane "traps" about 30 times as much energy as 1000 kg of carbon dioxide.
Methane is a reducing chemical. The atmosphere is oxidising. No way is the atmospheric lifetime of methane 100, years, or even 10.
Reading these descriptions of climate doom, I can't help noticing how much of it is just made up. Like fairy stories.
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Iron and cellulose are reducing too... I guess trees and bridges can't last more than a year either... Wake up sheeple! Thermodynamics is everything and kinetics is meaningless!
*checks facts* (https://www.sealevel.info/methane.html) oh wait, methane has a half life of about 8 years in the atmosphere... which means that if you release 1000 kg into the atmosphere today, in 100 years it would be down to about 200 grams. Obviously, most of it is gone within the first 25 years (down to 125 kg after 24 years), but (as mentioned in the references provided in my first post), it is standard to calculate relative warming over a period of 100 years.
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Over the course of 100 years, 1000 kg of methane "traps" about 30 times as much energy as 1000 kg of carbon dioxide.
Methane is a reducing chemical. The atmosphere is oxidising. No way is the atmospheric lifetime of methane 100, years, or even 10.
Reading these descriptions of climate doom, I can't help noticing how much of it is just made up. Like fairy stories.
Thank you for confirming that you prefer to believe your hunches rather than facts.
We can now take that into account when considering any other posts you make.
I may even remind you of it.
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Methane releases will degrade over time so a constant supply of so much a year will increace global greenhouse gasses to a level that is sustained.
Burning methane constantly will give 4 water and 1 co2 particle and a considerable increace in air temperature aiding water evapoutation at the planet surface of liquid water further adding to increaced temperature and the trapping of infra red near the surface, again increacing surface temperatures. Any water that is helped to evapourate will contribute to the warming effect, but providing you do not continually burn methane this will be a momentary increace.
Burning beats releasing as heat can be emmitted to space quite easily over a short time. If all hydrocarbons where released atmospherically rather than burned we would have a very serious problem. Methane will persist long after the heat and water vapour has dissipated and fallen.
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this will be a momentary increace.
Unless the Sun shinesBurning beats releasing as heat can be emmitted to space quite easily over a short time.
How?
The Earth is big.