Half a croissant, on a plate, with a sign in front of it saying '50c'
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Removing atmospheric CO2

Method for extracting and storing excess atmospheric carbon
  [vote for,

[1] Feedstock: self-assembling solar panels - plants. Biomass from either waste, extraction from the environment, or farmed. Eg. farm waste, forest floor detritus / algae filtered from seawater in area where displacement of such will provide space for more algae to naturally grow / algae or other plant farms, such as elephant grass.

[2] Pyrolysis: (a) Heat from end of cycle [5(a)] is used to assist in drying feedstock before it enters pyrolysis (perhaps providing fresh water?). (b) Feedstock is fed into pyrolysis chamber where it is heated substantially using energy from [3]. (c) Volatiles extracted, leaving behind carbon char.

[3] Electrical generators and heat return: Pyrolysis gas/waste produced by [2(c)] combusted to provide heat and electricity for both [2(b)] and [4(b)].

[4] Carbon conversion: (a) Carbon char from [2(c)] is granulated, moved and compacted into small spherical moulds. (b) electrical energy produced during [3] is used to heat carbon spheres to a very high temperature, such that the carbon is totally or partially converted to graphite (to get density to at least 1.5g/cm3).

[5] Energy return: (a) Hot graphite from [4(b)] has most of its heat returned into the cycle at either the pyrolysis stage [2(b)] and/or preheating the feedstock [2(a)].

[6] Disposal of graphite: (a) graphite is loaded onto a ship, or otherwise conveyed to a deep and still portion of the ocean. (b) it is send down a long tube to both minimize dispersal on ocean floor and to extract gravitational potential energy produced by the induced water flow through the tube due to the higher density of the graphite compared to surrounding water. This energy could be used to assist in charging the transport vehicle/system.

[7] Storage of carbon: carbon in the form of graphite/char will be stored deep in the ocean. It is non-reactive and will be eventually subducted or, more likely, mined for feedstock for future building projects (such as computing substrate or large structures).

Hopefully I’ve not messed up too badly with all the cycles involved above (will edit as needed), and of course this is just one way of achieving the process I’d like to see. There are many skipped details, but it’s a good rough outline.

Simply said:

Plant matter has a large amount of energy stored within it -- stored solar power essentially. This energy can be used to convert as much of the carbon within the plant as possible (some may need to be burned) into a stable form of carbon that can be indefinitely stored in a safe location, in a passive manner. The idea is to create a system that does not require external energy input, such as fuels and electricity, but still has a net positive output of carbon in a form that may be safely sequestered.

TIB, Sep 08 2016

Charcoal enriched fields Charcoal_20enriched_20fields
[bungston, Sep 12 2016]

Biochar long-term sequestration in soils https://onlinelibra.../10.1111/gcbb.12266
Meta-study of Biochar carbon sequestration “residence time” in soils [Frankx, Sep 14 2019]

A mole of moles https://what-if.xkcd.com/4/
What happens if you get lots and lots of moles together? [Frankx, Sep 14 2019]

Cumulative carbon emissions https://www.co2.ear...lobal-co2-emissions
Global cumulative carbon emissions (half-way down the page) 545GtC [Frankx, Sep 16 2019]


       The concept of using charcoal generated from biomass as carbon sequestration is not new, and it could work.   

       However until we quit digging carbon out of the ground (coal) and burning it, there is absolutely no reason to partially burn biomass and bury it. We should skip the burying of carbon and mining of coal and just burn the biomass completely.   

       If we ever stop digging up coal then we can ask the question again relative to hydrocarbon fossil fuels (oil and natural gas). Hydrocarbon fuels (especially natural gas) produce less CO2 per unit energy than pure carbon because the hydrogen burning also releases energy. So theoretically if you're burning natural gas there could be some small advantage to simultaneously creating charcoal and burying it. However I suspect that due to inefficiency in any complicated process, you'd still get more energy per unit of CO2 if you just burned the biomass completely and left more of the natural gas in the ground.   

       If we could switch to fully renewable energy, this could work, but in that case it seems like it might be easier to just bury the biomass without pyrolysis. Any idea how to quantify that?
scad mientist, Sep 08 2016

       That's the second serious idea I've read here in 20 minutes. What's happening to this place?
RayfordSteele, Sep 08 2016

       [scad]: this idea is irrelevant to the reasons why we have anthropogenic greenhouse gases in the atmosphere. Of course the status quo re energy production is highly illogical from the stance of environmental damage, though it does make perfect sense to those blind to science and obsessed with money.   

       My idea takes carbon char to the next level by encapsulating it and increasing density enough to sink in seawater where it will remain until mined or subducted. Burying biomass directly as you suggest will not solve much and may make things worse due to methane emissions.   

       There are too many variables to quantify anything here.
TIB, Sep 08 2016

       [+] pyrolysis.   

       Another stream, apart from right-off-the-tree organic waste is garbage. Anything not recycleable that contains carbon, and won't be poisonous, is tossed into the pyrolyzer.   

       Tradeoff is bacteria don't get their lunch. I don't imagine that will bother most.   

       I don't think carbon is reactive enough that simply burying it isn't enough. But, there are plenty of abandoned mines and wells, or, as you propose, it could just be tossed into the Marianas.   

       It might be an idea to stick a pyrolizer between the gas tank and the engine of a car. That way CO2 emissions would be much, much reduced and, while you're driving, your car could knit you a new car.
FlyingToaster, Sep 08 2016

       ^ ummm.... shouldn't that actually be prepended by "If you're going to burn the tree anyways..." ?
FlyingToaster, Sep 09 2016

       I think some sort of credit should be given to long- lived fat people in recognition of their carbon sequestration.
MaxwellBuchanan, Sep 10 2016

       Why hide that charcoal? Keep it up in the fields where it can do some good (link).
bungston, Sep 12 2016

       //I think some sort of credit should be given to long- lived fat people in recognition of their carbon sequestration//   

       And labs. Realistically a -80 is cleared out less than once per lifetime, and they sequester many plastic bags, tubes, boxes and maybe other carbon-based polymers of transient import. Then there's the 464 folders of data, 2 shelf miles of old journals and a couple of hundred lab books. A lab is essentially a carbon sequestration machine.
bs0u0155, Sep 12 2016

       Liquid CO2 will stay liquid at the bottom of the ocean, and tests were made of sequestering CO2 in pools deep down. It proved to diffuse out, and the method is now discouraged as contributing to the acidification of the oceans. (Giant pool covers may still work.)   

       Anyhow, that makes me wonder about long-term effects of this method. The vaguely-similar methods were just dumping hay bales off river deltas so as to get covered by sediment.   

       What happens to graphite in seawater? I'm suspecting something will utilize it, and at the very least it will pull oxygen out of the water and become CO2 again. Large spheres will have less surface area, but will take longer to cover up.
baconbrain, Sep 13 2016

       ^ I was under the impression that elemental C wasn't particularly reactive.
FlyingToaster, Sep 14 2016

       I do not think anything can use C by itself. Graphite and charcoal are stable long term. That C needs to be with O or H for critters to get an edge up.
bungston, Sep 14 2016

       // and they sequester many plastic bags, tubes, boxes and maybe other carbon-based polymers of transient import //   

       They also throw a lot of that stuff away where it is sequestered indefinitely in a land fill.
scad mientist, Sep 14 2016

       I looked up "graphite seawater" and found that the carbon acts like an old-style battery/cell, and will rip the electrons off any metal around. So don't use metal pipes for pouring the pellets in the ocean.   

       I'd not bother putting it in the ocean, anyhow. You'd have to transport it to the ocean, then transmit the electricity back, and you'd lose a lot of the potential energy to water friction.   

       Make building blocks of the stuff, maybe, or buckyballs or carbon fiber. Or save it up for the space elevator.
baconbrain, Sep 15 2016

       Isn't C02 the problem not C? Pity C-O bond, in CO2 doesn't have a very specific resonant frequency, we could HAARP our problems away. Just don't stand near the beam.
wjt, Sep 15 2016

       // Or save it up for the space elevator //   

       That sounds like a good idea. Seriously though, I assume a space elevator made primarily of carbon fiber would not tax our ability to collect carbon. I'm guessing the limitation would be in manufacturing he carbon fiber or in the other materials used to bind the fiber together. I'd love to find out if that impression is wrong if someone wanted to do the math(s). A space elevator would be pretty massive.
scad mientist, Sep 15 2016

       Biochar, like what Bungston said. Improves soil, retains water, returns nutrients, but the C is essentially inert - remove carbon from the atmosphere and return it to geology.
Frankx, Sep 12 2019

       //but the C is essentially inert //   

       Hmm, deep enough C is used by anaerobes to reduce nitrates (NO3-) etc.
bs0u0155, Sep 12 2019

       Hmmm, a butterfly net, with teeny holes could capture the co2.
not_morrison_rm, Sep 12 2019

       //deep enough C is used by anaerobes to reduce nitrates (NO3-) etc.// Strikingly, the average politician contains about 12kg of carbon.
MaxwellBuchanan, Sep 12 2019

       //average politician//   

       ...also curiously, 12kg, that’s a Megamole of carbon.   

       Reminded me of “a mole of moles” [link]   

       Also [other link] carbon residence times for Biochar vary widely based on soil type and fertility, amongst other factors. Meta-study linked suggests 97% of carbon is sequestered long term
Frankx, Sep 14 2019

       I think 12kg would be a kilomole. A mole of carbon is 12g.
MaxwellBuchanan, Sep 14 2019

       Doh! Yes, a kilomole.
Frankx, Sep 15 2019

       /kilomole/ Moles are pretty stocky.
wjt, Sep 15 2019

       //However until we quit digging carbon out of the ground (coal) and burning it, there is absolutely no reason to partially burn biomass and bury it//   

       I suggest that would only be true if there were a unitary global "we". Absent that, it might not be crazy for one "we" to do this, even while a different "we" (possibly "they") did the opposite.
pertinax, Sep 16 2019

       We (humankind) have released something like 545 billion tonnes of carbon from geological stores to the atmosphere/biosphere since 1870, the year Standard Oil was incorporated. And we (the West, and the UK in particular) are responsible for the overwhelming majority of that.   

       That’s 545,000,000,000 tonnes.   

       To visualise that, it’s something like 250 cubic kilometres of solid carbon. And that’s mostly still in the atmosphere because of our use of oil and coal.   

       Three things.   

       If we make this an “us and them” problem, then humankind will not take fast enough action to repair the damage, because we can always blame someone else - previous generations, billionaires or Other nations or governments.   

       We are here, now, (communicating) using the technology (and having the freedoms) afforded to us as a result of exploiting those energy resources.   

       The top 10% wealthiest humans globally (that’s you and me) are responsible for 50% annual emissions.   

       So we have to: stop burning fossil fuels (by reducing demand, moving to renewables, electric transport, nuclear power)... And Deliver new carbon capture/sequestration technologies and agricultural systems   

       And, possibly, prepare for catastrophic change in our climate, food supplies, and sociopolitical stability.   

       All really really urgently!
Frankx, Sep 16 2019

       // We (humankind) have released something like 545 billion tonnes of carbon from geological stores to the atmosphere/biosphere since 1870, the year Standard Oil was incorporated. And we (the West, and the UK in particular) are responsible for the overwhelming majority of that.//   

       Yeah... no. This fails my sanity checker. It's not a big country in terms of surface area or population, and doesn't have an unusually high emission per capita. And while Britain did kick off the industrial revolution and hence has been burning fossil fuels for longer, the usage really only ramped up in the last century or so.   

       I dredged up a few factoids to back this up:   

       The UK is apparently currently responsible for something like 1% of global emissions per year, and over half of all human-mediated fossil carbon release since the industrial revolution has occurred in the last 30 years.   

       Changing my search terms, I found a paper with a table of cumulative emissions, a few entries from which I include below.   

       Cumulative CO2 Emissions, 1850–2002
Country, % of World
United States, 29.3
EU-25, 26.5
Russia, 8.1
China, 7.6
Germany, 7.3
United Kingdom, 6.3
Japan, 4.1
France, 2.9
India, 2.2
Ukraine, 2.2

       (This does not include emissions from land-use change)
Obviously these are estimated, and you may be able to find slightly different values using different methodologies, but you're not going to find anything legitimate claiming the UK produced more than 50% of the total.
Loris, Sep 17 2019

       [Loris], you're right. The UK isn't responsible for 50% of cumulative carbon emissions.   

       I think it's fair to say "the West" is responsible for the vast majority, and the UK has a special place in the history of emissions. It's great that we've cut our emissions lately.   

       But I shouldn't have suggested that the UK had emitted the vast majority.
Frankx, Sep 17 2019

       //Cumulative CO2 Emissions, 1850–2002//   

       I suspect the situation has changed dramatically from 2002- present.
bs0u0155, Sep 17 2019

       It's grossly unfair to count emissions but not sequestration.
Voice, Sep 17 2019


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