Sciencemadness Discussion Board - Author asking for basic chemistry ideas for fiction.

Author asking for basic chemistry ideas for fiction.

beethelzar - 17-10-2016 at 05:59

*I have no real chemistry background (just an amateur author) so please excuse my limited description.
Can someone suggest how oxygen (O2) in ambient air, could be removed permanently and with little cost. Such as by either attaching it to another molecule, or by splitting it into two atomic oxygen first, then attaching them to another material for storage.

I first thought of splitting O2 electrically, then storing as O3 ozone. But quickly learned ozone has a half-life of 12 hours, so not useful.

So is there any low cost process you can suggest that can use readily available and preferably free materials from nature, to attach to oxygen O2?

Perhaps combining O2 with an element from salt, saltwater, iron oxide, limestone, or anything else that is available most areas.

The desired process is for mass O2 conversion by many people worldwide to do cheaply over a long period. It is for inclusion in a story which must be plausible fiction (so this process must be possible).

Will come back tomorrow to check. Thanks

Metacelsus - 17-10-2016 at 06:07

Burn things, then store the carbon dioxide in rock formations (similar to some carbon storage schemes).

AngelEyes - 17-10-2016 at 06:20

Combine it with Hydrogen and store as water?
Water contains 88.8% by weight Oxygen whereas Carbon dioxide is only 84.2% (assuming my maths is correct). Also it's easier to store water than carbon dioxide...

Other options include rust (iron oxide), chalk (calcium carbonate) or gypsum (calcium sulphate) - all are common non-toxic materials and easy to form.

zwt - 17-10-2016 at 06:39

Quote: Originally posted by AngelEyes

Combine it with Hydrogen and store as water?

The problem with that is that hydrogen is produced either from hydrocarbons (which could simply be burned to form carbon dioxide and water, rather than first extracting the hydrogen), or from water - the first case is a waste of time and energy, while the second releases as much oxygen as could be captured. Similarly, rusting iron would require having metallic iron first. Metallic iron is produced mainly from iron oxides, again releasing as much oxygen as could be captured. Calcium carbonate and sulfate have similar drawbacks, and are also less straightforward to synthesize from the oxygen in air.

[Edited on 17-10-2016 by zwt]

zwt - 17-10-2016 at 06:42

Quote: Originally posted by beethelzar

Can someone suggest how oxygen (O2) in ambient air, could be removed permanently and with little cost.

Quote: Originally posted by beethelzar

for storage

The most practical way of removing the oxygen is probably an oxygen concentrator. It would have to be stored as a cryogenic liquid or at high pressure.

Any process meeting your description would require tremendous amounts of energy (if "many people worldwide" are doing it), probably more energy than humanity has available for such a pursuit, if the goal is to capture a large fraction of the oxygen available in the atmosphere.

Disclaimer: The people you're asking here are the sort who can easily find the flaws in even the most well-written fictional science. If your goal is simply to suspend the disbelief of those who can't find the flaws in something like Breaking Bad, the advice you're getting here might be too realistic. For a fictional writing, you could always make something up that wouldn't actually work, like 'Scientist discovers new compound while working in his kitchen, denser than lead and made mostly of oxygen, Si<sub>2</sub>AlFeO<sub>36</sub>.'
You could do like Vonnegut and have a fictional polymorph of oxygen which is solid at room temperature, and which causes any gaseous oxygen it contacts to solidify.
Really, you'll need to ask other writers to get good writing advice - paging BromicAcid!

[Edited on 17-10-2016 by zwt]

CuReUS - 17-10-2016 at 07:43

Quote: Originally posted by beethelzar

Can someone suggest how oxygen (O2) in ambient air, could be removed permanently and with little cost. Such as by either attaching it to another molecule

I know just the chemical for you

Quote:

When in alkaline solution, it absorbs oxygen from the air

https://en.wikipedia.org/wiki/Pyrogallol
pyrogallol can be made from gallic acid which is found in nature.

P.S.- a way to remove O₂ from the air,sounds like a Nazi weapon to me

mayko - 17-10-2016 at 07:50

Quote: Originally posted by Metacelsus

Burn things, then store the carbon dioxide in rock formations (similar to some carbon storage schemes).

We're already removing a small but detectable amount of oxygen from the atmosphere this way!

Keeling, R. F., & Shertz, S. (1992). Seasonal and interannual variations on atmospheric oxygen and implications for the global carbon cycle. Nature, 358.

Screen Shot 2016-10-17 at 11.43.00 AM.png - 74kB

aga - 17-10-2016 at 10:03

https://en.wikipedia.org/wiki/Oxygen_scavenger

woelen - 17-10-2016 at 10:48

Removing oxygen from the air on a planetary scale is not possible within reasonable time with the amount of resources available to us now. Of course, we can introduce minor fluctuations in the concentration of oxygen, but no one ever notices that kind of fluctuations, except with sensitive and accurate measuring equipment. If you want a plot with oxygen depletion in the atmosphere, such that people start to suffocate worldwide, then you need to bring in something unknown and well beyond what we are capable of, or you need to allow thousands (millions?) of years for the process.

Texium - 17-10-2016 at 11:02

A large asteroid made entirely of metallic sodium crashes into the Pacific Ocean...

woelen - 17-10-2016 at 12:45

Yeah, these are highly abundant in our solar system.
I see them every day in the sky

Sometimes I catch one. This is how I restock my sodium supply. A pity that there are so few potassium asteroids and I never have seen a cesium asteroid at all

beethelzar - 18-10-2016 at 13:25

Thanks guys. Very helpful.
The story 'is' based on oxygen depletion with anticipation of ocean phytoplanton loss and further global deforestation over the next few hundred years greatly limiting the planets oxygen replenishment. At a future time when widescale irreversable environmental damage forces the populous to stop the systems in place by any means -> oust governments and religions, and then live right, within our longterm means. This story attempts to provide a plausible approach to do this.
At 21% O2 now, only an extra 3% removed will mean our bodies will not function well, another 3% and all life dies in time.
By the time something like this might be necessary, say 200 years, only 2% of remaining oxygen may tip life.
So the fictional story aims to look ahead, and give leverage to stop an unrealistic global lifestyle.
Again, any other ideas... I'll check back later.

CuReUS - 19-10-2016 at 02:32

correct me if I am wrong,but I think this is the gist of your story:
in the distant future,due to rampant deforestation coupled with indiscriminate burning of fossil fuels and destruction of oceanic algae and phytoplankton due to dumping of chemicals in the ocean,the world faces a shortage of O₂.To prevent this calamity,humans start "storing" O₂ which they will release when judgement day comes.
I have just one question.Will humans stay on earth once it becomes uninhabitable? won't they just push off to mars ?
Also I was thinking about it and I think there might be a way to remove all O₂ ,either by making a wormhole to another galaxy and then pumping all the air out or reducing earth's gravity so that all the air escapes to outer space.But like woelen said,it isn't possible to do that now with current technology

[Edited on 19-10-2016 by CuReUS]

ficolas - 19-10-2016 at 05:54

There is an estimation of 3.000.000.000.000 or 3*10^12 trees in the world.
Live trees are arround 50% water, 50% dry wood.
Suposing 100% of the wood is celulose, wich it isnt, we can estimate the amount of O2 used up if we burned all the trees in the world (if we knew the mass of the average tree)
Glucose combustion is:
C6H12O6+6 O2=6 CO2+6 H2O, so for every 180 (glucose molecular weigh) grams of glucose burned, we "trap" 192g of oxigen.

The average mass of the atmosphere, is 5×10^21g, and it is arround 20% oxigen, so 10^21g of oxigen in the atmosphere.
Now lets calculate the needed average tree size, in function of a percentage of oxigen in the atmosphere.
3*10^12*0.5*m/180*192 = percent*10^21

Setting that percent to 1, the average tree size would need to be 6.25*10^8g or 625tons

I dont know what the average tree, but it isnt close to 625tons.

For a closer number, the min amount of oxigen needed in air for a human to not have big problems while breathing, is ~15%,
That number dont get us that closer to a realistic average tree mass, so conclusion: Not gonna happen if all the trees in the planet were burned. Need mo' science fiction.

I could add other burnables to the calculations, but I dont think there would be a big difference. (the calculations are very rough estimates tho)

[Edited on 19-10-2016 by ficolas]

[Edited on 19-10-2016 by ficolas]

Texium - 19-10-2016 at 06:27

Ok, so assuming that all of the trees and vegetation are burnt up, with the lack of photosynthesis, as oxygen is consumed, it would no longer be replenished. A human consumes about 550 liters of oxygen per day (786 grams), so based on the world population being 7.4 billion people, our collected breathing uses up 5.8 million metric tons of oxygen every day. Sounds like a lot, but as ficolas pointed out, there's 10¹⁵ metric tons of oxygen in the atmosphere assuming it's 20% oxygen. Based on the breathing requirements of humans alone, for a 5% reduction in the oxygen content of the Earth's atmosphere without oxygen being replenished, it would take 23,619 years after all of the plants have been burned up or destroyed. There are of course many, many other animals that require oxygen so that time frame might be significantly shorter, but it gives you an idea of how infeasible it is.

Source: http://health.howstuffworks.com/human-body/systems/respirato...

Sulaiman - 19-10-2016 at 07:15

Maybe either Planet X or XI have oceans of liquid oxygen that could be imported?

Oceans of liquid methane and ethane are known to be available https://en.wikipedia.org/wiki/Lakes_of_Titan

woelen - 19-10-2016 at 09:25

Changing the atmosphere of a planet takes a LOT of time. It took almost a billion years for the first photosyntheizing life forms on earth (cyano bacteria) to change the atmosphere from a reducing one (mainly CH4, NH3 and small amounts of H2S) to an oxidizing one (O2). The atmosphere, although compared to the planet it is very thin, contains a LOT of oxygen and it took a LOT of time to produce this and hence it will also take a LOT of time to remove this.

If the OP wants a story like this, then change the setting. E.g. put people on a large generation ship heading towards some exoplanet where life is possible and people deplete the oxygen in the air in the large generation ship. Such a thing might be feasible, although in that story, it is the huge amount of energy needed which may be a game-breaker, or the huge amount of time needed to reach that exoplanet (e.g. with our current fastest technology it would take appr. 50000 years to reach the Proximay Centauri system, which is 'only' 4.3 lightyears away from us).

beethelzar - 19-10-2016 at 12:05

I guess we would add oxygen consumption by animals, fossil fuels, which I assume would be significant when/if replenishment rate is much lower.

====

Quote: Originally posted by ficolas

There is an estimation of 3.000.000.000.000 or 3*10^12 trees in the world.
Live trees are arround 50% water, 50% dry wood.
Suposing 100% of the wood is celulose, wich it isnt, we can estimate the amount of O2 used up if we burned all the trees in the world (if we knew the mass of the average tree)
Glucose combustion is:
C6H12O6+6 O2=6 CO2+6 H2O, so for every 180 (glucose molecular weigh) grams of glucose burned, we "trap" 192g of oxigen.

The average mass of the atmosphere, is 5×10^21g, and it is arround 20% oxigen, so 10^21g of oxigen in the atmosphere.
Now lets calculate the needed average tree size, in function of a percentage of oxigen in the atmosphere.
3*10^12*0.5*m/180*192 = percent*10^21

Setting that percent to 1, the average tree size would need to be 6.25*10^8g or 625tons

I dont know what the average tree, but it isnt close to 625tons.

For a closer number, the min amount of oxigen needed in air for a human to not have big problems while breathing, is ~15%,
That number dont get us that closer to a realistic average tree mass, so conclusion: Not gonna happen if all the trees in the planet were burned. Need mo' science fiction.

I could add other burnables to the calculations, but I dont think there would be a big difference. (the calculations are very rough estimates tho)

[Edited on 19-10-2016 by ficolas]

[Edited on 19-10-2016 by ficolas]

beethelzar - 19-10-2016 at 12:52

Adding all other animals to the equation, there are probably more than 100,000x more animals than humans.

I just tried to find an estimate, but there are an estimated 24 billion livestock, 24 billion domestic chickens etc
And 10^15 fish and those pesky bugs may also use up a lot.

I read elsewhere that all oxygen would be used up in ~1 year given no replenishment. Which seems confirmed by your figures, when all life is added.

I may be way off but it makes for a good story if it is a possible.

Quote: Originally posted by zts16

Ok, so assuming that all of the trees and vegetation are burnt up, with the lack of photosynthesis, as oxygen is consumed, it would no longer be replenished. A human consumes about 550 liters of oxygen per day (786 grams), so based on the world population being 7.4 billion people, our collected breathing uses up 5.8 million metric tons of oxygen every day. Sounds like a lot, but as ficolas pointed out, there's 10¹⁵ metric tons of oxygen in the atmosphere assuming it's 20% oxygen. Based on the breathing requirements of humans alone, for a 5% reduction in the oxygen content of the Earth's atmosphere without oxygen being replenished, it would take 23,619 years after all of the plants have been burned up or destroyed. There are of course many, many other animals that require oxygen so that time frame might be significantly shorter, but it gives you an idea of how infeasible it is.

Source: http://health.howstuffworks.com/human-body/systems/respirato...

beethelzar - 19-10-2016 at 13:20

Now my last question for my story, I promise.
I looked at the conversion of air to Nitric Oxide NO, which converts automatically to NO2 I believe.
Could this possibly be done with the following patented design or similar process.

Patent US5396882 - Generation of nitric oxide from air for medical uses - Google Patents http://www.google.com/patents/US5396882

I've considered the low output volume, but building a device with perhaps 100 chambers in a block, with each having a car coil and extended sparkplug gap, it may be possible cheaply to convert my target of 35kgs p/d of oxygen per unit. And operating by solar power of perhaps 1000w panels. So cost is low and chemical components are both from air.

Is this even plausible? At first run it seems ok.

Sulaiman - 19-10-2016 at 14:48

Solar powered platforms in very low orbit,
(or held up by helium or hydrogen balloons ?),
liquefying air sucked up by a very wide, strong, light, long tube,
using the expansion of boiled-off nitrogen as a jet to maintain orbit,
and the coldness to help with liquefaction and storage.

AJKOER - 20-10-2016 at 06:51

Actually, a possible and relatively fast on geological scale (but still a great number of years) to destroy oxygen, as I will detail below, is as a consequence of volcanic activity. But to store oxygen? Perhaps a much better approach is to mitigate oxygen consumption (along with saving ozone) with advanced, now only partially fictional, technologies like nuclear power in place of burning fossil fuels and even subsurface intervention to limit volcanic eruptions.

With respect to the chemistry of how vulcanism could consume oxygen, for example, start with a massive volcanic eruption putting dust which is rich in organic matter (hereafter referenced as X) and transition elements salts (including iron Fe(II)/Fe(III) and Cu(I)/Cu(II) as examples), and associated gases like H2S and SO2 into the upper atmosphere. Next, a possible reaction, absence solar light, with oxygen (O2), and say Fe(II), resulting in the formation of Fe(III) and the superoxide radical in a process referred to as metal autoxidation:

Fe(2+)/Cu+ + O2 ↔ Fe(3+)/Cu(2+) + •O2-

Reference see: https://www.researchgate.net/publication/11374766_Generation...

Then, continuing with a possible path in the presence of acid::

•O2- + H+ = •HO2

•HO2 + •HO2 → H2O2 + O2

Fe(2+)/Cu+ + H2O2 → Fe(3+)/Cu(2+) + •OH + OH- (with iron, this is the Fenton reaction and with copper a Fenton-type reaction, see "Fenton chemistry at aqueous interfaces" at https://www.google.com/url?sa=t&source=web&rct=j&... )

Fe2+ + Cu2+ ↔ Fe3+ + Cu+

where the above coupled redox reaction between iron and copper salts (and or other transition metals including, for example, manganese and even trace amounts of cobalt) could foster the Fenton (or Fenton-type) reaction (see discussion and references at https://www.sciencemadness.org/whisper/viewthread.php?tid=53... ) along with the presence of solar light which would enhance the formation of the hydroxyl radicals by resupplying Fe(2+), for example, via a photo-Fenton mechanism given by:

Fe(3+) + H2O + hv → Fe(2+) + •OH + H+ (See, for example, https://www.google.com/url?sa=t&source=web&rct=j&... )

Also, directly with powerful UV exposure that occurs in the upper atmosphere from ozone via the reaction:

O3 + hv (from UV light) → O2 + O (see https://www.niwa.co.nz/publications/wa/vol16-no1-march-2008/... )

where the monoatomic oxygen (O) further reacts with water vapour to produce hydroxyl radicals:

O + H2O → •OH + •OH

And, also the action of solar light on any formed hydrogen peroxide:

H2O2 + hv → •OH + •OH

Next, having created the so called reactive oxygen species, including the very powerful hydroxyl radical, expected reactions with SO2 and H2S gases with possibly water:

SO2 + H2O = H2SO3 = H+ + HSO3- (aq)

And, a subsequent reaction with hydroxyl radical:

•OH + HSO3- (aq) → H2O + •SO3-
•SO3- + O2 → •SO5-
S05- + X → SO5(2-) + •X+
•X+ + SO3(2-) → X + •SO3-

Illustrating that once the sulfite radical anion ( •SO3-) is created from the action of a single hydroxyl radical with dissolved SO2 in, say, a water droplet, given the presence of an accomodating organic substrate, a cyclic reaction can ensue consuming a large number of oxygen molecules! Reference: see equations (24), (25) and (26) in article "Free-Radical Chemistry of Sulfite" by P. Neta and Robert E. Huie, available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1568601/ .

With respect to H2S, its reaction wih the hydroxyl radical forms the reactive sulfanyl radical, which further can react in the presence of oxygen and water as follows (reference, see https://en.m.wikipedia.org/wiki/Sulfanyl ):

•OH + H2S → H2O + •HS
•HS + O2 ⎯H2O→ •SO2- + H+
•HS + O2 → •OH + SO
•SO2- + O2 → SO2 + •O2-
•O2- + H+ = •HO2
•HO2 → 1/2 H2O2 + 1/2 O2
1/2 H2O2 + hv → •OH
SO + O2 → SO2 + O (see http://www2.nau.edu/~doetqp-p/courses/env440/env440_2/lectur... )

Which in total implies a net consumption of oxygen again and introduces SO2, which can form an O2 consumption cycle as detailed above.

Bottom line, a rise in vulcanism may present significant adverse consequences to our atmospheric composition in the long term without considering the adverse effects of acid rain on plants and the blockage of sunlight on photosynthesis (which produces oxygen). However, it is apparently likely that the latter effects of a so called 'volcanic winter' is more immediately threatenting than the depletion of oxygen (and similarly ozone) to human survival if history repeats (see, for example, "Extinction Events That Almost Wiped Out Humans", by Ed Grabianowski at http://io9.gizmodo.com/5501565/extinction-events-that-almost... ).

[Edited on 20-10-2016 by AJKOER]

beethelzar - 20-10-2016 at 09:35

This is a tad above my head, being trained as a computer programmer I know little about chem.

As you do, could you comment on the possibility of converting ambient air for the purpose of generation of nitric oxide.
Above I mentioned a patent which uses a large spark gap to convert to NO.
I just want to know, is this perhaps rubbish? IE just a patent?
Or if I design a unit with an air flow tube with say 100 spark gaps, that NO or NO2 would actually be a significant part of outflow.
The story is about people the world over building these devices levering governments, corporations and religions to halt and live better than environmentally balanced.

[Edited on 20-10-2016 by beethelzar]

aga - 20-10-2016 at 10:55

The Birkland-Eyde process just has a spark in normal air which gets the N₂ to react with the O₂ to make NO, NO₂, NO_x.

Simple as that really.

Quote:

as a computer programmer I know little about chem.

I'm a programmer that knows a little about chem ! (very little really).

Texium - 20-10-2016 at 12:38

Quote: Originally posted by beethelzar

This is a tad above my head, being trained as a computer programmer I know little about chem.

As you do, could you comment on the possibility of converting ambient air for the purpose of generation of nitric oxide.
Above I mentioned a patent which uses a large spark gap to convert to NO.
I just want to know, is this perhaps rubbish? IE just a patent?
Or if I design a unit with an air flow tube with say 100 spark gaps, that NO or NO2 would actually be a significant part of outflow.
The story is about people the world over building these devices levering governments, corporations and religions to halt and live better than environmentally balanced.

Yeah what you describe is the Birkland-Eyde process, as aga noted. It used to be one of the main processes used for making nitric acid. The reason that it is no longer used is that it consumes a huge amount of energy, so if you wanted to conduct this on some gargantuan atmosphere-consuming scale, I don't know where you'd get the energy required for that.

AJKOER - 20-10-2016 at 12:43

Quote: Originally posted by beethelzar

Yes. To quote from one of my prior threads:

"One interesting paper is "Treatment of N2O impulsed microwave torch discharge " by M.Jasinski, et. al., April 2004 . To quote: "Results of using a moderate–power (several hundred Watts) pulsed microwave torch plasma (MTP) to the conversion of atmospheric-pressure nitrous oxide (N2O) into nitrogen oxides( NO, NO2 and N2O4) are presented." with a claimed efficiency between 70% to 90% depending on the power of the microwave. Link: https://www.google.com/url?sa=t&source=web&rct=j&... "

Link: https://www.sciencemadness.org/whisper/viewthread.php?tid=34...

Basically, make a fisk hook out of Aluminum foil and connect it inside an expandable container (which is further compressed to avoid containment bursting) resembling a light bulb filament. In a microwave controlled to produce only short burst , the Al produces large sparks which are technically an impulsed microwave torch discharge. In an atmosphere of laughing gas, N2O (sold in stores like ingestable CO2 cartridges) and oxygen enriched air, the science and my experiment clearly produced nitric oxide NO, NO2,.... The latter gases reacts with aqueous acidified bleach (forming hypochlorous acid, HOCl) producing nitric acid HNO3, at least on a small scale (limit of vessel size in the microwave).

[Edited on 20-10-2016 by AJKOER]

beethelzar - 20-10-2016 at 15:06

Didn't write "knows a little", I wrote "knows little", as in almost nothing. But I'm loving reading about it for the first time. Almost as good as physics :-)

Quote: Originally posted by aga

The Birkland-Eyde process just has a spark in normal air which gets the N₂ to react with the O₂ to make NO, NO₂, NO_x.

Simple as that really.

Quote:

as a computer programmer I know little about chem.

I'm a programmer that knows a little about chem ! (very little really).

[Edited on 20-10-2016 by beethelzar]

ficolas - 20-10-2016 at 15:42

Quote:

Almost as good as physics :-)

</3

< / 3

[Edited on 20-10-2016 by ficolas]

CuReUS - 20-10-2016 at 18:43

Quote: Originally posted by zts16

I don't know where you'd get the energy required for that.

antimatter ?

beethelzar - 21-10-2016 at 11:54

[
This was just totally friendly cheeky.

rquote=464484&tid=70055&author=ficolas]

Quote:

Almost as good as physics :-)

</3

< / 3

[Edited on 20-10-2016 by ficolas][/rquote]

aga - 21-10-2016 at 12:29

Quote: Originally posted by beethelzar

Didn't write "knows a little", I wrote "knows little"

Erm, yeah.

My response was merely a slay on plurds.

beethelzar - 22-10-2016 at 11:27

Hi guys. To finish this up. You were right, the energy for reducing 1% oxygen by a method like in the patent I linked to above, is ludicrous. Air->NO Industrial machines efficiency is much better but not even close.
The waste product of this process is NO or NO^2.
As the level of NO^2 in our atmospere is 0.000002% as compared to O^2 which is 20.95%, the ratio may allow a new attack (plausible) on our global environment for my writing purposes.
I haven't done necessary research yet, but it does look promising. As this was about leverage to oust global powers if necessary in future. NO^2 poisoning wasn't considered, just oxygen depletion.
Still I thought I'd mention to you great guys, as free and open exchange of ideas.
Cheers.

aga - 22-10-2016 at 11:46

You're welcome.

Do we get a free copy of the book, each ?

Signed of course, just in case we can one day sell 'em for loadsamoney and buy some chemicals to mess with.

beethelzar - 23-10-2016 at 16:37

More chemicals, more chemicals. Ha

PHILOU Zrealone - 27-11-2016 at 08:29

Into a closed recipient, Cu dissolved into NH4OH takes O2 from the air to make Cu(NH3)4(2+) and leave only N2 and rare gases.

Fiction...

A gigantic directional solar eruption drives hot H2 from the sun into the earth atmosphere where it explodes into a whooosshh fireball forming only water vapour and leaving N2, CO2 and rare gases....

[Edited on 27-11-2016 by PHILOU Zrealone]

zed - 2-12-2016 at 16:42

Yet, there have been times in our geological history, when there was very little free oxygen in the atmosphere.

We live on what is largely a big ball of Iron. If a significant amount of that Iron were burned in the Atmosphere.....Zippo to life.

Also to be considered: there is a lot of Carbon lurking about, both as coal, and as Methane Hydrate. This has led to mass extinctions before.

Seems to me Siberia caught on fire once. There were long lasting consequences.

CuReUS - 3-12-2016 at 00:53

a few days back,I was watching a show called-"doomsday:10 ways the world will end" and the episode was "rogue planet".If the earth got too near to a huge planet,the gravitational force of that planet would suck out earth's atmosphere.The same thing could happen with a black hole-https://youtu.be/i0Q3yk7KzYA?t=133