Pyrolysis Explained

I was a little hesitant to point this out because I thought: that is so obvious, that anyone who does not understand is not going to be able to discuss anyway.

But, what is meant by pyrolysis?

I see that the word is of Greek origin:
Pyro - πῦρ - fire, fever
Lysis - λύσις - separation

Based on the translation it means: fire-split.

According to the Webster dictionary Pyrolysis is chemical change brought about by the action of heat.
As discussed on this form, Pyrolysis is chemical change brought about by the action of heat in absince of oxygen. Which is followed by oxadative combustion in the engine.

I have here a kind of fancy grill called Cobb I used to cook my dinner on:

Am I correct to say that the orange arrow in the photo points to the pyrolysis zone?

Does anyone else call this “smolder” or “smoldering?” which refers to the process of burning slowly with no flame, like on a charcoal grill until you remove the lid and it flare up.

Please let the record show that I ask this question on evening of January 6 2024.



I think your cooker is using oxidative combustion, as you put it, burning the charcoal with oxygen in the air to produce heat and CO2. Pyrolysis with an external heat source probably produced the charcoal that the briquettes are made from. Often the two are combined, with some of the wood or other biomass being burned to produce the heat to pyrolyse the rest of the material. For wood gas for engines, carbon monoxide, hydrogen, and methane are the main end products. Less heating can produce wood alcohol and other liquids, including tars.


I forgot about smoldering. I think it is both oxidation and pyrolysis. The heat comes from oxidation, and the smoke is pyrolysis products.


No. Smoldering wood is partly pyrolising but not charcoal. Charcoal is preety much just pure carbon so nothing to split here. All it does is slowly oxidise.


Welcome to the DOW JoePA.
Your foods cooker shows venting holes in its top cover yes?
How the charcoal combustion heating process is partially controlled, I expect.
Slowing the released food steam moistures to internally foods cook too.

Now to me the only pyrolysis taking place is that heating cooking off of the moistures in the foods.
So yes indeed pyrolysis is fire splitting out with heat the factors that can be readily volitized out of a composite solid.
Good fuel grade wood charcoal and this should have already been done.
Your charcoal shown in the illustration is not pure wood charcoal but a commercially made cooking fuel with binders and often added in fine wood particles to give the food a smoky flavoring.

Now the step past pyrolysis is wood fuel torrification. Done on wood fuel chunks and large chips. Those having been surface heated through pyrolysis driving out. To surface charring. That charring actually the remaining cells carbons still remaining with a cellular mineral framework intact.
Then making these into mini-self containing “reduction” gasifier units.
In your food analogy . . . foods first high heating quickly surface seared sealed. Then slower self-steaming cooking from the insides.

Ha! Ha! See? In real-use the phase steps are flowing and should be continuous. The steps phases expanding and contacting with needs usage demands. And the use up of the available fuel mass. Flowing one into another until all that remains if the true mineral ash.

Conceptualizing in steps is just a convenience.
Useable, workable results needs flows understandings and appreciations.

Solid fuel to energies music.
In my case, and most here; the solid fuel beginning is wood. What I can grow as mine on my property.
IMHO only your own site grown wood-for-fuel is a true Freedom fuel.
All other obtained woods can; and will be compared to other fuel energy sources. Dribbled out for your use. Regulated. Taxed. Controlled by others.
No manner of detailed understanding of wood-to-enrgy will break this vicious cycle of keeping-you-dependent.

Steve Unruh


Thanks, Kristijan. I missed that the question was about smoldering charcoal, not smoldering in general.