biochar insulation?

While looking for something else on the WWW, I came across this brief article:
https://recipes.howstuffworks.com/carbon-foam-burnt-bread-could-lots-dough.htm

Essentially they are turning bread into "carbon foam" and using it as a light weight insulator. I think I've read elsewhere that forms of biochar can be used to insulate and that if it's properly made, only the carbon is left so it's not a fire risk.

So what do all you experienced biochar people think - 1. Would bacteria or mold move in making it unhealthy?
2. Do you feel it's just far better used in the soil than for insulation?
3. What might happen if instead of starting with bread, we started with something like sheep's wool?

Insulator for what? For a home walls would be a really bad idea since this is verry combustible.

It withstands high temps but it gets oxidised and cant be used lets say to insulate a riser of the rocket stove.

Carbon burns quite well, and quite hot (COKE is what is left of coal after the volatiles have been burned off) Char and Coke are almost the same material, pure carbon.
Carbon furnaces (Blast furnaces) burn at over 3000 f, I sure wouldn't want my house or anything else insulated with something used to heat and melt steel.

Do this test, make your best char and let it cool so you can hold it in a  bare hand, set it down, oriented so you can hold a pipe match under the edge of a piece and time how long before it glows red (usually before the match gets close to your fingers).

Yes it could be called insulation because of the dead air pockets but, how good is such insulation compared to any other insulation product for heat resistance (char=0), how much does it settle and compact over a year?, then we can talk about it burning hotter than most house fires without any extra fuel.

It's much less flammable than the wood that people build houses with all the time.  Because all the volatiles have already been derived from the wood to make the charcoal it reduces the flammability.  Having said that, biochar has very thin walls between channels so it's not too hard to light.  There are folks using biochar set in a binder of clay that gets sprayed in.  I would think that that would be really hard to light if not impossible.  Biochar is about as thermally insulative as foam board insulation but will absorb polluting gases rather than give them off.  Another benefit is that biochar is cheaper to produce.  I'm looking forward to a project to do this with.  I like the idea of using a green material like this that will function for centuries and be harmless at the end of it's use.

Check out this online article on the subject:  biochar as insulation

I love how many experienced and knowledgeable people can chime in on a subject like this.  My general tendency when I look at a new application like this is to see what the challenges are with the concept, see how people are adjusting to the challenges, and see how people are doing with them.  I am interested to see how this works out over time.  For my point of view, I am going to say that the jury is still out on how and when it would be efficiently applied as insulation, but I am eager to see what are the better applications and which clearly won't work.
JohN S
PDX OR

I agree with you Greg, if you were to coat the char, that would lessen my own concerns about using char as an insulation material, it would also up the insulating factor of the char since the coating would make it more like a closed cell type of insulation.

biochar might be best in the garden, in fact from what I understand about it once you amend soil with biochar it will increase productivity for generations and beyond, if you need cheap insulation you might look into shredding paper and cardboard treating it with boric acid, makes it flame and bug resistant, and stuff the voids in walls, floors and ceilings with it. there is a commercial insulation made on mass scale the same way that most anyone could do with a leaf shredder

I’m trying to use milled Charcoal from my wood stove as a filler in the basement cinderblock walls. I think it’s a good candidate for the job because it’s free, won’t rot, tolerates the occasional water logging, and after I cap the block with some concrete, it shouldn’t be any fire risk.

[quote=Nelson Burwick.]I’m trying to use milled Charcoal from my wood stove as a filler in the basement cinderblock walls. I think it’s a good candidate for the job because it’s free, won’t rot, tolerates the occasional water logging, and after I cap the block with some concrete, it shouldn’t be any fire risk. [/quote]

While water logging will not result in decay, the biochar is excellent at absorbing water and holding onto it.  A while back,  I placed a sample of water logged biochar first in the sun for a day, then for several hours in the oven to drive off all the moisture.  I was amazed at how long it took to dry it out.  For that reason, I don’t think it would make a good foundation filler.  Take a look at perlite, it drains quite readily.