What happens to all the burnt carbon compounds?

[noquacks]

People,

I often wondered, about what happens to all the carbon compounds, primarily cellulose, from the "wood" of plants/trees after a fire destroys the plant. Isnt the product a combination of charcoal, or outright burnt wood/carbon? If so, isnt it true that such a state of carbon will not react in nature, since carbon is so difficult to react with any compound.  Imagine- how can charcoal react to form new plant growth if it has been destroyed by natural fires/volcanic heat/etc over billions of years. The plants growth comes from CO2 in the air, then converted to cellulose, then burns up in a fire, and cannot react anymore(?). 

Doesnt that mean that eventually the carbon amount subjected to intense heat events will be "used up" on Earth?

 

Thanks, people. 

 

[Ken Fabian]

Incomplete combustion leaves an abundance of charcoal and partially burned materials. Fires will reduce the amount of leaf and other organic material but increase the amount of charcoal in soils - so the premise that it is lost due to fires is actually the reverse of what happens in practice. Intense fires can eliminate most charcoal and burn with little carbon residue but that is localised. Charcoal has beneficial effects in soil, providing a framework that microorganisms take advantage of.

[noquacks]

So, in a routine fire, burned matter , mostly charcoal is actually not fully "carbonized"? And charcoal compounds can react to give new building blocks for new life forms? 

Edited June 30, 2021 by noquacks

[MerieuxMarylandPfeifield]

Apparently carbon is 100% unmeltable, but only when in Earth's atmosphere. 

[MigL]

Carbon compounds readily with a large number of elements.
It is, in fact, one of the most 'compoundable' elements, and is the basis for its own branch of chemistry, Organic Chemistry.

[chenbeier]

Generally to answer the headline. The carbon is burnt to carbondioxide and this can be used again to produced new plants.

[exchemist]

3 hours ago, chenbeier said:

Generally to answer the headline. The carbon is burnt to carbondioxide and this can be used again to produced new plants.

Yes, but I think what the questioner is getting at is what happens to the charcoal that is produced, for instance in forest fires.

The suggestion is that this, being elemental carbon, is biochemically fairly inert and thus should remain in the soil indefinitely. It seems a fair enough question. Though the amount of carbon that can get locked up in this way is pretty minor, I should think. I don't know of any soil processes that would convert charcoal to more reactive carbon compounds, anyway. 

[chenbeier]

Not to forget all the minerals left in the ash. The name  pottash is coming from that. Mainly potassium carbonate.

Carbon itself as charcoal is more less like aktive coal. This probably will remain long time.

[Ken Fabian]

21 hours ago, MigL said:

Carbon compounds readily with a large number of elements.
It is, in fact, one of the most 'compoundable' elements, and is the basis for its own branch of chemistry, Organic Chemistry.

True, yet in the form of charcoal in soil it is quite stable and resistant to microbial breakdown. In boreal forest soils that can be hundreds to thousands of years. I doubt it lasts so long in tropical conditions but I only did a brief lookaround for relevant info.

From "Charcoal ecology: Its function as a hub for plant succession and soil nutrient cycling in boreal forests"

Quote

Charcoal is highly resistant to microbial decomposition and thus remains in soil for thousands of years, providing recalcitrant carbon to boreal forest soils. The abundant pores in and on charcoal surfaces have powerful adsorption abilities that can influence biogeochemical cycles and plant succession after fire. Our review details the influence of charcoal on plant and soil systems and explains the complex direct and indirect pathways of these influences that occur during succession after fires in boreal ecosystems. Among these pathways, the most important pathway through which charcoal influences plant and soil systems relates to the element composition and nutrient availability in soils and to the abundance of phenolics released from Ericaceae plants in the understory of boreal forests.

Sounds like it is more like a catalyst than a chemical "feedstock" in soil; it promotes biogeochemical processes without being used up. Porous, high surface area and adsorptive ie attracts and holds surface coatings of other materials and microorganisms. It's role appears very significant and complex, including promoting nutrient mineralisation .

[noquacks]

19 hours ago, chenbeier said:

Generally to answer the headline. The carbon is burnt to carbondioxide and this can be used again to produced new plants.

But the carbon that remains did not convert to CO2 gas. It remained a black residue/by product. (right?)

 

But so far, thanks , people, for so many helpful replies. I am still unclear though. What am I not understanding..........

[MigL]

13 minutes ago, Ken Fabian said:

True, yet in the form of charcoal in soil it is quite stable and resistant to microbial breakdown.

That doesn't mean it resists compounding.
Every respirator with organic filtering cartridges has activated carbon pellets in it.
They filter the organics by bonding them to the carbon and letting only 'air' through.

Sodium BiCarbonate has similar odour trapping properties.

[noquacks]

15 hours ago, exchemist said:

Yes, but I think what the questioner is getting at is what happens to the charcoal that is produced, for instance in forest fires.

The suggestion is that this, being elemental carbon, is biochemically fairly inert and thus should remain in the soil indefinitely. It seems a fair enough question. Though the amount of carbon that can get locked up in this way is pretty minor, I should think. I don't know of any soil processes that would convert charcoal to more reactive carbon compounds, anyway. 

Right- matter of fact, archaeiologists, etc, have made finds of ancient cultures, based on the charcoal deposits/residues/evidence for their fires for cooking, warmth, etc. Many examples of Native American finds, dated back some thousands of years ago in N America........

[Ken Fabian]

3 hours ago, MigL said:

That doesn't mean it resists compounding.
Every respirator with organic filtering cartridges has activated carbon pellets in it.
They filter the organics by bonding them to the carbon and letting only 'air' through.

Sodium BiCarbonate has similar odour trapping properties.

If it is lasting centuries to millennia in soil it has to be resisting chemical compounding that consumes carbon.

Activated carbon filters chemically combine with organic compounds by adsorption (making a film over the surface). My understanding is any reactivity is confined to the surface and becomes self limiting, which leaves the carbon beneath unchanged. Charcoal is activated by grinding it finely to make more surface area, for adsorption, which creates a protective barrier for the internal material - fine ground because it resists compounding once an adsorptive film is formed.

Edited July 1, 2021 by Ken Fabian
A bit of (re)thinking before I post.

[exchemist]

20 hours ago, noquacks said:

Right- matter of fact, archaeiologists, etc, have made finds of ancient cultures, based on the charcoal deposits/residues/evidence for their fires for cooking, warmth, etc. Many examples of Native American finds, dated back some thousands of years ago in N America........

Indeed. So, also taking into account the other responses, it seems you are right in thinking that charcoal is fairly inert, biologically, though as some posters have pointed out it does tend to adsorb substances and can be a good substrate for the growth of micro-organisms. But, to return to the question you originally asked, only a small proportion of the carbon in  cellulose is converted to charcoal in a fire. Most is burnt to CO2, or CO, which itself can burn to CO2. So only a very small amount of carbon is sequestered in the form of charcoal.  (In fact a lot more carbon is sequestered by conversion into carbonates, in the sea.)  Meanwhile, a great deal more CO2 is being liberated, both by the burning of fossil fuels and by natural processes, e.g. volcanism.

If you are interested in the various natural processes involved, you can look up the "carbon cycle" and find descriptions of the carbon sources and sinks and how they inter-relate:https://www.earthobservatory.nasa.gov/features/CarbonCycle 

 

Edited July 1, 2021 by exchemist

[noquacks]

54 minutes ago, exchemist said:

Indeed. So, also taking into account the other responses, it seems you are right in thinking that charcoal is fairly inert, biologically, though as some posters have pointed out it does tend to adsorb substances and can be a good substrate for the growth of micro-organisms. But, to return to the question you originally asked, only a small proportion of the carbon in  cellulose is converted to charcoal in a fire. Most is burnt to CO2, or CO, which itself can burn to CO2. So only a very small amount of carbon is sequestered in the form of charcoal.  (In fact a lot more carbon is sequestered by conversion into carbonates, in the sea.)  Meanwhile, a great deal more CO2 is being liberated, both by the burning of fossil fuels and by natural processes, e.g. volcanism.

If you are interested in the various natural processes involved, you can look up the "carbon cycle" and find descriptions of the carbon sources and sinks and how they inter-relate:https://www.earthobservatory.nasa.gov/features/CarbonCycle 

 

It has finally sunk in, exchemist. Thanks for taking the time to explain further, although, many members did the same. i now understand much better the whole process of combustion and "burning". Thanks to all here.