Carbon monoxide in biochar

I'm concerned about producing carbon monoxide while making biochar in the wood stove in my house. Has anyone researched this?

amina re wrote:I'm concerned about producing carbon monoxide while making biochar in the wood stove in my house. Has anyone researched this?

I'm not a scientist, so take the below with a grain of salt (or char), but my understanding is that carbon monoxide is formed when there is a small amount of oxygen involved. If you're keeping most of the oxygen out, you'll at most produce only a tiny amount of carbon monoxide. A regular fire in your wood stove probably produces small quantities of carbon monoxide as well.

Two things make this less risky, I believe. 1st is the the fact that carbon monoxide is flammable, so any produced should burn in the fire chamber of your wood stove. The second is the chimney, where most gasses should escape. It's never a good idea to have the door to your fire box open for extended periods of time on a wood stove, but I don't believe producing biochar should increase risk with CO.

If others have additional info or thoughts, please share....if I'm wrong, I want to know!

I think something that could be done is if you wanted to proceed on testing it, have a carbon monoxide alarm available in the room. Any gasses produced, I would assume, would vent from the chimney?

amina re wrote:I'm concerned about producing carbon monoxide while making biochar in the wood stove in my house. Has anyone researched this?

Hi amina, and welcome to permies! I make lots of biochar in the wood stove and I'm confident that it's safe. The fire is a low emissions design that always has lots of intake air, and when I put the pans in we always get a lot of flame for about 10-15 minutes when the gases are coming out. This tells me that the process has enough oxygen for full combustion and there won't be any unburnt carbon monoxide left over. High temps + plenty of air = no problems.

I would not recommend trying to make biochar in an "airtight" stove that is damped all the way down. This could be a recipe for smoke and CO production and if draft is low it might puff back into the living space. You want to see active flaming for a little while, and this is your indicator that the process is safe.

I don't think it's a good idea to breathe in the smoke while you're burning biochar.  There will probably be some small portion of the smoke that you breathe, if you can smell it, but I don't encourage it.  

If the carbon monoxide is burned, it would create a chemical reaction. My guess is that it would be converted into some other chemical.  I don't have any degrees in science, so feel free to correct my interpretation if it is off base.

John S
PDX OR

Well I am going to be the guy to say, you outta have a monoxide detector near your stove regardless.

I am pretty sure burning wood creates carbon monoxide, at least I know I had to put the dual smoke/monoxide detector in after I got a new wood stove (code compliance...). I know biochar does, almost by definition since it is an incomplete burn.

Either way, don't let the smoke into your house and you will be fine. If the smoke is drafting out, so is the monoxide I am sure. Shoot, or just open a window.

We have a carbon monoxide detector inside the house, and it has never gone off while I'm burning biochar.  My biochar stove is only about 20 feet from the house while it is burning.  I have left the garage door open and had it smell like wood smoke for awhile. I usually close it now.

John S
PDX OR

when biochar is being produced, carbon monoxide does form. But CO is very flammable and if your biochar production is associated with open flame then the CO will be further oxidized to carbon dioxide (CO2) as long as there is excess air to the fire. This is the basis of the top-lit updraft biochar making process and most retort designs - to produce vigorous flames and fully consume the pyrolysis gas that is smoky, smelly, and full of carbon monoxide and hydrogen: converting it to carbon dioxide and water vapor and using the heat from that combustion to make more pyrolysis (heat-decomposition of biomass) happen.

I agree with the excellent comments above.

Carbon monoxide (CO) is a flammable fuel gas that will be burned in an active wood fire. The only danger is if it backdrafts into an enclosed space, which is more likely when the fire is down to coals.

Every living space, regardless of the heat source, needs a CO detector. I personally know two people who had very close calls with "the big sleep."

If you are producing biochar in a stove your wood will release some carbon monoxide. That is not a problem as carbon monoxide is a flammable gas and burns up. I suppose you could generate some if the fire goes out and the wood has not finished off gassing yet but it will still be very hot and want to rise up the chimney naturally. keep the door closed to the stove, have a functioning Carbon monoxide detector to make sure.
Cheers,  David Baillie