If we burn all carbon in the Earth's crust, by how much would the atmospheric concentration of CO2 increase?

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    $\begingroup$ There are things you can look up. The first hit on the Google search for "carbon content earth crust" brings you to the Wikipedia article Abundance of elements in Earth's crust. Then you search for the thickness of the crust, the size of the earth, and calculate the crust volume. If somewhere along the way your are stuck or doubt your calculations, then is the time to ask. This is not a can you do my work for me site. $\endgroup$
    – Jan Doggen
    Commented Jun 8, 2015 at 13:18
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    $\begingroup$ @JanDoggen It is a place were you can find answers to frequently asked questions. If no one ask the question first, no one with the same doubt will find it. Nobody forces you to answer the question. $\endgroup$ Commented Jun 8, 2015 at 13:23
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    $\begingroup$ I don't think you could burn all the carbon, just that fraction that is stored in fossil fuels. Carbon-containing minerals like limestone would need energy inputs applied to free the carbon/CO2. $\endgroup$
    – jamesqf
    Commented Jun 8, 2015 at 17:47
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    $\begingroup$ Do you mean the bulk of the extractable carbon fuel (coal, tar, oil, natural gas that can be removed). Or the total burnable carbon fuel, most of which cannot be extracted. Or the total reduced (not oxidized) carbon. Or the total carbon without regard to chemical state (mostly unburnable minerals). Those are 4 different Q's with 4 different answers. $\endgroup$
    – Eubie Drew
    Commented Oct 22, 2015 at 17:42
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    $\begingroup$ @Aabaakawad All carbon, as chemical element. This question is answered. Because there are more carbon than oxygen, we can only burn until oxygen runs out, so the answer is 21%. $\endgroup$ Commented Oct 22, 2015 at 19:53

2 Answers 2


Short answer: $\rm CO_2$ levels would increase by $209,460$ $\rm ppm$ by using all the available oxygen.

Long answer: The mass of carbon in Earth's crust is $9(10)^{22}$ $\rm gC$ (grams of Carbon). The mass of the atmosphere is $5.15(10)^{21}$ $\rm g$. If all the carbon was burned, or otherwise moved to the atmosphere, then the limiting factor would be the $\rm O_2$ (molecular oxygen) available for carbon to bond with to make $\rm CO_2$. Oxygen makes up $209,460$ $\rm ppm$ of the atmosphere. So, assuming the carbon bonded with all available $\rm O_2$ and the remaining carbon did not enter the atmosphere, then there would be an additional $209,460$ $\rm ppm$ of carbon dioxide in the atmosphere.


Biological answer: The amount of $CO_2$ would be in the range $100-600$ $ppm$, like it is today. The carbon from the crust would be completely used to produce biomass; there will be more living creatures on Earth.

The lower range of $100$ $ppm$ is defined by C4-plants; their ability to use $CO_2$ collapses at these levels. The upper range is practically only $400$ $ppm$, and it's defined by C3-plants: their ability to use $CO_2$ doubles if the amount rises from $300$ $ppm$ to $600$ $ppm$. As humans produce less than $10\%$ of the world's $CO_2$ it means that even with 5 times the growth, the total $CO_2$ production in the world would only be $150\%$, which the existing plants can absorb at approx $400$ $ppm$ $CO_2$ levels. It's more probable though, that the $CO_2$ level wouldn't arise at all, the existing plants just grows a bit quicker and vegetation would spread to deserts and plankton in the sea would grow more. These phenomena are already observed.

I can only provide a Wiki link on German language. Look the picture Co2-absorbtion by plants

"CO2-Aufnahme" Pls note that 0.02% = 200 ppm etc

The comment of Gordon Stanger forces me to improve this answer.

The evolution of the plants was totally different 60 Million years ago. The plants have of course now built their systems to current levels. If you study Bryophyte, you will find that even $2000$ $ppm$ is not a problem for them; they will just grow like crazy. I've tested that personally, with pure $CO_2$. Unluckily most of the good material I know, is in Finnish language; Mire cover 5% of earth. 80% untouched Mainly Canada and Siberia. They can easily absorb any amount of $CO_2$ you desire to feed in atmosphere. Nowadays the rate might average $4.8$ $t/ha/a$, with $400$ $million$ $ha$ total amount, this alone makes almost $20$ $000$ $Mt/year$. This is comparable for the World fossil energy consumption, which is $13$ $000$ million tonne of Oil Equivalent in year. To point the scales out, approx $60\%$ of fossil fuels are coal, and the rest is hydrogen, which result is water. So these mires can alone absorb the whole $CO_2$ production of mankind. Even if they would feedback as much by themselves.

This absorption rate varies already from $1$ $to$ $10$ $t/ha$, even though we have not even seen $400$ $ppm$ $CO_2$ values. Well, for a short period during spring such a levels occur. Pls go to Lappland, at that time an experience the crazy growth of nature. They even change their color, to use wider spectrum of sunlight to their usage.

Maybe 60 million years ago all the plants were yellow.

The Comments of Dikran Marsupial answered here:

Tell me, how long did it take those peat bogs to form? Here is told how in 1957 a peat bog was dug clean; in 2010 they measured over 0.5 m thickness; Approx 1 cm/ year. This means that a average thick Finnish peat bog, 1.41 m, could crow in 141 Years.

Next calculate the rate of deposition required to soak up anthropogenic fossil fuel emissions at their current rate. (source, your answer) Current rate is $9200$ $Mt$, i.e. with just $1$ $t/ha$, The worlds mire's 400 Million ha; Absorb $400$ $Mt$, at $5$ $t/ha$, $2000$ $Mt$, and at $10$ $t/ha$ $4000$ $Mt$, i.e. 40%. This is from $3\%-5\%$ of the Earth's land surface.

I think your answer has some mistake on you calculations. Your forest grows only $1.5$ $t/ha$. The average forest growth in Finland is $8m^3$/ha /year. This is -again- approx $4.8$ $t/ha/year$.

Claim: We would need to turn 42% of the Earths land surface into peat bogs (or forests?) I make this simple; according to this link; Peat lands are storing on average 10 times more carbon per hectare than other ecosystems. Peat lands occur in 180 countries and cover 400 million hectares or 3% of the world's surface. So if we have 3%, which counts for 30% of average forest, we only need 3% peat lands and 12% forest. But we have 30% forest!.

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    $\begingroup$ Jokela Turbine's answer is totally wrong, and reminiscent of climate-science skepticism's spurious arguments. A ceiling of only 600 ppm CO2 is demonstrably preposterous, given that the known Palaeogene CO2 averaged about 2000ppm and peaked at well in excess of 3000 ppm. A global transition to C3 photosynthesis is also preposterous, not to mention the resulting global famine (most of our crops are C4). The '600 ppm CO2 ceiling' fails to take into account about 20 feedback mechanisms, the oceanic chemistry effects, and is massively unrealistic about humanity's addiction to fossil fuels. $\endgroup$ Commented Nov 7, 2015 at 9:18
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    $\begingroup$ A "back of the envelope" calculation shows that biological growth is not able to prevent CO2 levels from rising, even from current levels of fossil fuel use it would require reforesting 42% of the Earths land surface, which is clearly impossible earthscience.stackexchange.com/questions/2639/… . Note also that forests are only carbon sinks while they are actively growing, once they mature, they are not going to substantially hold back atmospheric increase any longer. $\endgroup$ Commented Nov 17, 2015 at 10:47
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    $\begingroup$ I take it you mean peat bogs? Tell me, how long did it take those peat bogs to form? Next calculate the rate of deposition required to soak up anthropogenic fossil fuel emissions at their current rate. I suspect you will find that it is not nearly fast enough. $\endgroup$ Commented Nov 17, 2015 at 14:59
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    $\begingroup$ In that case, if the rate is the same as forests, we would need to turn 42% of the Earths land surface into peat bogs, which is impossible. Note the volume of the reservoirs is irrelevant, it is the rate at which the can sequester CO2. You do need to argue about these issues for your answer to be convincing. $\endgroup$ Commented Nov 17, 2015 at 17:12
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    $\begingroup$ Incidentally, this paper (onlinelibrary.wiley.com/doi/10.1111/j.1529-8817.2003.00783.x/…) suggests 72gm^-2 as a maximum sequestration rate, which is 0.72 tons per hectare per annum, which is rather less than your figure, and it is rather doubtful that the whole of the earth wetlands are operating at that sort of rate all the time. $\endgroup$ Commented Nov 17, 2015 at 17:22

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