CO2 releases per kWh?

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Ptilu
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by Ptilu » 22/03/10, 21:03

Re
Okay, it's just that as you said, I felt like the limit was physical;)
But I do not share your analysis ... nuclear is with coal, the energy that our dear elected officials of the world to fuel our cottages :(
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by bernardd » 23/03/10, 10:11

Christophe wrote:C) This chart summarizes I find:

Image


Surprisingly, it lacks the contributions of direct thermal solar (collectors) and indirect (wood / pellet heating), and photovoltaic solar.

In addition, for wood / pellet heating, it must be taken into account that unused wood, as well as green waste, is left to rot / compost, which produces methane and ammonia.

So burning wood is not only neutral because it has already repelled and recaptured the co2 when it is burned, but in addition it avoids releasing methane and ammonia which are much more annoying than CO2 for the greenhouse effect.
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by Christophe » 23/03/10, 14:36

bernardd wrote:Surprisingly, it lacks the contributions of direct thermal solar (collectors) and indirect (wood / pellet heating), and photovoltaic solar.


Surely because the study was only devoted to thermal and nuclear power plants and not to devices in the home ... but it is true that wood could have appeared alongside biogas ... because there is still some wood cogeneration units in France ...
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by bernardd » 23/03/10, 17:03

However, the choice of centralization / distribution is one of the essential parameters of the architecture, with enormous consequences, but not necessarily direct.

And since it's related to the power structure ...
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by Ptilu » 23/03/10, 17:29

I would add that in the light of some study (which I unfortunately forgot which :( ) the carbon balance of the wood is even negative (storage) if the wood is not rotted ...
Indeed during its growth, a tree stores a large amount of carbon in the soil by losing its antlers. This means that its mass at the time of cutting contains less carbon than it absorbed during its growth. On the other hand, I do not know what is the share of the carbon released during the decomposition of leaves (or needle). But hey, the forest was one of the lungs of our planet long before we burned the wood, thus avoiding putrefaction ...

PS: we weren't supposed to talk about nuclear? ... Oops : Mrgreen:
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by Christophe » 23/03/10, 17:37

Ptilu wrote:I would add that in the light of some study (which I unfortunately forgot which :( ) the carbon balance of the wood is even negative (storage) if the wood is not rotted ...


:?: What "wood" are you talking about? This is not if we make it rot by chance (CH4)?

I do not know what exactly you mean and what study you are talking about but if to say that a forest emits carbon in the long term, it is clearly absurd ...
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Ptilu
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by Ptilu » 23/03/10, 17:52

No, no, obviously I expressed myself as a broomstick, because I wanted to say exactly the opposite of what you understood.

When I say negative carbon emissions, it means that we reject less CO2 than we absorb.

As for the wood in question, obviously the essence or the shape greatly varies this observation. A softwood tree stores less because it takes less time than a hardwood tree to reach maturity. The pellets create emissions during packaging compare to a ster which has been dried without fuel (but the combustion efficiency will be worse ...)

I would love to clarify my reasoning if it is still unclear :)
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by bernardd » 23/03/10, 18:58

Ptilu wrote:No, no, obviously I expressed myself as a broomstick,


Also in wood, I hope ;-) And how much CO2 do you store: -?

Ptilu wrote:A softwood tree stores less because it takes less time than a hardwood tree to reach maturity.


Sorry, not understood the reasoning. It could just absorb faster, right? The important thing is the accumulated dry mass ...

Ptilu wrote: The pellets create emissions during packaging compare to a ster which has been dried without fuel (but the combustion efficiency will be worse ...)


The pellets that I know dry with wood, not with fuel: it's much cheaper :-)

But I come back to the original question:

if wood waste is left to rot in the forest, this wood will produce methane or even ammonia.

if we burn this same wood, it will directly produce co2, for the same number of carbon atoms.

However, methane has a more intense greenhouse effect than co2, that is to say that its quantity of co2 equivalent is greater than the co2 it would have produced by combustion.

So actually, burning wood that would otherwise have rotted, at a very favorable CO2 balance, numerically negative, ie positive for the planet :-)

It remains to estimate it numerically to integrate it into the comparison table ...

We should also integrate direct solar thermal: O CO2?
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by Christophe » 23/03/10, 19:14

Ptilu wrote:The pellets create emissions during packaging compare to a ster which has been dried without fuel (but the combustion efficiency will be worse ...)


Yes, pellets emit more than wood for their production BUT the performance of pellet plants was more important, not sure that it would be worse in the end ...

But wood, in all its forms, rejects NOTHING AT ALL in comparison to fossils ... Ademe even takes 0.0, that is to say!
Example of calculation method for the building: https://www.econologie.com/forums/normes-et- ... t9153.html

Wood is also often criticized for being "imported" from afar and therefore "polluting"? Yes, it is better to use as much local wood as possible, but not because the oil we consume in France is anything but local ...

The annual national production of French oil = 5-6 hours of consumption I believe ...
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by Did67 » 27/03/10, 17:38

Ptilu wrote:I would add that in the light of some study (which I unfortunately forgot which ones :() the carbon balance of wood is even negative (storage) if we do not rot the wood ...
Indeed during its growth, a tree stores a large amount of carbon in the soil by losing its antlers. This means that its mass at the time of cutting contains less carbon than it absorbed during its growth. On the other hand, I do not know what is the share of the carbon released during the decomposition of leaves (or needle). But hey, the forest was one of the lungs of our planet long before we burned the wood, thus avoiding putrefaction ...

PS: we weren't supposed to talk about nuclear? ... Oops: mrgreen:


1) No need for studies. Just think coldly without tangling the brushes.

2) The Carbon contained in the wood is storage if it is wood of work that we don't burn and we don't let it rot. The CO² absorbed by the tree (apart from the leaves, leaves, roots) is well captured. It is a carbon well. But here, we are talking about lumber (and on a human scale - go a few centuries, houses, furniture, we destroy them, we burn or pile up the wood that rots somewhere ... By the way, what recycling of timber frame houses?).

3) The combustion of wood is only CO² neutral. It is the fairly common becoming of large falls (houpier), converted into firewood.

4) The finer falls, left behind, rot. CO² is released. The operation is roughly CO² neutral.

I am skeptical about the importance of ammonia (it is a rather "animal" waste), even if it must be produced a little from vegetable sproteins (ultra-rare in wood!).

On the other hand, the release of CH4 methane by anaerobic digestion is a problem as soon as the decomposition becomes anaerobic ...

5) The leaves, falling down throughout the growth, are partly oxidized and release the CO² previously absorbed. But another part will transform into humus, a stable organic matter, which structures the soil (and colors it in brown / black). So the CO² of this organic matter is also sequestered there.

4) On the other hand, the CO² contained in the roots is not a "well of C". This C is mostly released when the roots rot (although a small part is also converted into humus, which is stored in the soil).

5) In the course of this reflection, this raises awareness of the fact that intensive agriculture, which has reduced the humus stocks of cultivated soils, has been a source of C emissions. Conversely, pass massively organic, with a re-introduction of organic matter (manure, compost) in the cyles, and a re-storage of humus in the soil would be a powerful well of C !!!
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