Experimental IWI: Charcoal-Lime Render

[aockenden]

Im going to use this thread as a way to keep notes on and share results from a new experimental IWI system that follows the same general “insulated render” formula as other systems such as hemp-lime, cork-lime and perlite-lime, however the primary insulating aggregate added to the lime binder will be Biochar instead of hemp, cork or perlite.

I’ve found one example of a similar thing being done by the Ithaka Institute, only they used clay as the binder instead of lime.

Ithaka Institute - Building material

www.ithaka-institut.org

The attributes of Biochar that indicate that it may have great value as an insulating material are:

1. Its low density / high porosity (google images of Biochar under microscope) which should trap lots of air and make a good insulation.

2. Its stability / longevity (Biochar is said to last for THOUSANDS of years even when buried in moist, life-rich soils). I’m hoping this translates to good mold-resistance on the wall.

3. Its moisture-absorption and desorption abilities (hopefully making it a great internal humidity buffer).

4. Its locality, accessibility and affordability (it can be manufactured at backyard scales from waste-stream woods that can often be freely or very cheaply obtained).

5. It’s non-toxicity (assuming you manufacture it from clean, untreated wood) and sustainability (it locks up carbon into the stable plaster like all bio-aggregates and can go right into the garden at the end of its life).

To give this a try I will be manufacturing my own Biochar, crushing it into a medium-grain aggregate and mixing it into a mostly non-hydraulic lime binder. I will then be thickly applying it (4- 6 cm total thickness in 2 or 3 coats) to the interior surface of cold, uninsulated, single-skin modern cement bricks that make up the walls of a small outbuilding which we are converting into a home office.

I’ll keep this thread updated with my progress. I’m very interested to see where this goes and I hope others will be as well.

 

[aockenden]

I’ve started by building a typical backyard Biochar kiln using an old barrel, a piece of sheet metal from a livestock trailer door, an old bit of stove-pipe, a smaller store-bought metal trash bin and a few pop-rivets.

I’m hoping to get my first char session going tomorrow and will report back with results.

 

[aockenden]

I charred my first batch today: I think my outer barrel needs more oxygen draw-holes as I was getting a very smoky burn for the first hour which then improved after I wedged the lid open slightly with a stick. I think there was also a bit of paint and other residue on the barrel burning off which contributed to the smokeyness.

I’ve just had a glimpse in the dark at the results which look generally promising but hard to tell accurately in the dark. I’ve quenched the char with cold water to “activate” it, which supposedly helps pop open the pores even further.

I’ll post pics of the final biochar in daylight tomorrow.

 

[Toby Newell]

You should search youtube for Cody's Lab, he has experimented with making his own charcoal many times, out of many materials, and many times in barrels.

 

[aockenden]

Thanks will do.

 

[aockenden]

Well the initial char session seems to have been a reasonable success! Maybe 15-20% of the load didn’t get fully pyrolyzed but I got 3 buckets of decent biochar out of the kiln. For a first attempt I’m very satisfied with that.

I think the next burn will go even better with a couple tweaks to my setup. I’m going to hack the legs off my large barrel so it sits directly on the ground, then drill many more oxygen intake holes along the bottom and some along the top rim as well. I’m also going to limit the size of the pieces of wood to be charred, as it was almost exclusively the biggest pieces that failed to fully pyrolyze.

I’m now going to do some water-absorption / desorption tests on my existing buckets of char. I will soak a bucket full of char with water for a full day, and then drain off all the excess non-absorbed liquid, and measure the weight of the soaked char. Then I will let the bucket of soaked char sit in a covered, ventilated space and let it dry back out, measuring its new weight daily until it’s fully dry. Then I’ll have some metrics on its porosity and moisture desorption rate.

 

[aockenden]

Here are some bad close-ups of the porosity of the char:

 

[aockenden]

I ran my second char session today with the modifications to the kiln as discussed above. It was a much cleaner burn (partly because all the paint residues had burned off during the first session).

The char that came out of the kiln was even lighter weight, more porous and crunchier than the first batch. I got 3.5 buckets of quality char which is a half bucket more than the first burn.

Here are some better pics of the cleaner burn and the porosity.

 

[Toby Newell]

Looks like fun. I love playing with fire. Amusing how they rebranded charcoal to omit the 'coal' part and added 'bio' to increase it's enviro mind power. Yes, it locks some carbon up, say compared to full incineration, or full microbial decay into CH4 (much higher warming potential) unless stored as peat. But not quite the same carbon sequestration as say hemp, as some CO2 and CO (that converts to CO2 in a few weeks in the atmosphere) is released in manufacture. Will be interesting to see how it performs. I guess it's a question of the details. Some suitable material destined for full incineration or landfill could potentially release less carbon if converted. I guess a joined up system could be greater use of coppicing to increase carbon uptake via new growth and reduce the amount of unhealthy trees leading to dead wood and rot. Some of the harvested wood could be used to make charcoal and bank some of the carbon. This would work in conjunction with more agroforestry, or as they used to call it in the old days... farming. I'm fairly certain pigs are much happier snuffling around under the boughs of oak or apple trees rather than in sties. I think governments and business needs to realise we need to put real effort into these types of things rather than making pretend targets. Net zero is a peverse, unrealistic propaganda tool meant to keep us consuming in the mean time, it would be nice if we actually tried some interesting ideas at scale. I mean, you can pretty much charcoal anything organic.

 

[aockenden]

Yes well truthfully i’m struggling myself to understand what (if any) distinction actually exists between charcoal and biochar. I’ve heard that true biochar is supposedly pyrolyzed at a higher temp and / or for a longer time and therefore is less oily or greasy than charcoal and shouldn’t really “reburn”.

I’ve bought some proper bagged lump-wood charcoal from the petrol station to compare to, as there are apparently some simple tests you can do to verify the oil / resin content which I intend to do and will report back. I’m willing to entertain the idea it’s just a silly newspeak renaming if I can really find no difference between the two.

As for the carbon capture I’ve read in multiple sources that if you do it correctly, 50% of the original material’s carbon content is maintained as solid charred carbon, and I’m having to actually combust / incinerate approximately the same amount of wood in the outer chamber of the kiln / retort to drive the process vs. the amount of wood I put into the inner chamber to be charred. So that equates to a total of 25% of the needed material’s carbon content being stashed as long-term carbon. Could be better I suppose but it’s also not terrible as a trade off for that longer term stability vs uncharred biomass.

When combined with some rapid growing tree system (like a coppicing system you mentioned) and proper proper kilns (not my backyard contraption) I think there’s potential.

Absolutely agreed on the pig grazing.

 

[Toby Newell]

Ahhhh, I forgot the extra fuel needed to heat the charcoal. Doh. Ok, maybe not so good then! I guess it depends how complicated you get, if you used the waste heat as part of a DHP to heat municipal water that might help. I think where it could possibly be good is to burn dead but pre rotted organic material as microbes convert the carbon to methane which has a greater atmospheric heating potential. You are effectively releasing less harmful CO2 in preference to methane. Mind you, maybe fermenting it in a biofuel generator and to capture that methane and using the heat in a DHP might be better?

Yes well truthfully i’m struggling myself to understand what (if any) distinction actually exists between charcoal and biochar. I’ve heard that true biochar is supposedly pyrolyzed at a higher temp and / or for a longer time and therefore is less oily or greasy than charcoal and shouldn’t really “reburn”.

Ah. There is no difference, simply a marketing gimmick. It's a trendy renaming of charcoal. Unfortunately there is a lot of BS around preying on people's consciences. It's identical. You cannot pyrolise for longer or hotter, it would simply burn! There is no oil or grease in charcoal (I think you mean wood tar ie 'volotiles') Charcoal, the whole point of charcoal, is that it burns hotter because it's simply carbon reacting with oxygen. No water or volotiles to vapourise so less latent heat of vapourisation losses and CO2 is more stable than CO so more heat is released.

Pure carbon burns great, better than non pyrolised organics, that's kind of the point. Diamond is pure carbon and that burns great.

You are locking up part of the carbon but you would have to find a free source of renewable heat to conduct the pyrolysis and try and recover the waste heat. Could be done, but seems quite complex.

I'm not sure I would necessarily trust figures from people if those were the same ones that tried to tell me charcoal isn't biochar and that charcoal doesn't burn! It's a main ingredient in gunpowder and that seems to burn quite well. The only allotrope of carbon that is difficult to get burning is bulk graphite.

 

[aockenden]

Well here’s what I found during my own investigation into the potential diffs between home-made “biochar” and store bought lump wood “charcoal”.

First I grabbed a bunch of chunks of both homemade biochar and store bought lump wood charcoal and dried them on very low heat in my kitchen convection oven (pic 1).

Then I took them out of the oven, let them cool and then selected pieces from each type of char to sum up to a total weight of 1.9 dry ounces (pics 2 and 3). One thing I noticed already here is the difference in apparent volume between the two piles. The volume of the biochar pile is much larger than the lump wood charcoal which must mean the density of the biochar is lower, aka it’s more porous.

Then I submerged each pile in its own container of water. Both types of char floated so I weighed them down with plates to force them to totally submerge (pics 4 and 5).

I left them submerged for about 8 hours. Then I removed each piece from the water bath, shook it thoroughly to get all the surface water off and then re-weighed each pile. The “biochar” weight increased from 1.9 to 3.7 ounces, meaning it absorbed water equal to about 100% of its dry weight. The “charcoal” weight increased from 1.9 to 2.8 ounces, meaning it absorbed only about 50% of its dry weight (pics 6 and 7). This is further evidence of the higher porosity of the biochar vs the charcoal.

Also it’s worth noting that during the submerged period, 2 lumps of “charcoal” actually sunk while none of the “biochar” did. Given that the amount of water absorbed by the “charcoal” was less than the amount absorbed by the “biochar”, this would also point to a lower porosity / higher density in the “charcoal”.

The one obvious uncontrolled variable here is the wood-species. My biochar was mixed pine / cedar / oak while the store bought charcoal is some kind of African wood I can’t remember the name of. A better test would control for that.

I’ll do a burn test tomorrow to see how differently they react to exposure to a torch.

 

[aockenden]

Also ran another char sesh today. Best yield so far, only about 10% wasn’t completely pyrolyzed. 4 buckets of quality char.

Hoping to crank out another tomorrow. I’ve already got 11 buckets of char but idk how many I’m actually going to need and there’s still plenty of scrap wood to clean up around the smallholding / workshop areas.

 

[Toby Newell]

Charcoal makes a great fuel if you make too much. Biochar is just a name, semantics, it's all charcoal, simply a rebrand, it's all partially burnt organic matter. The bio part comes from how it is produced. If you used a sustainable fuel to pyrolise it, if you used the waste heat to do useful work, heat water etc, or captured the wood gas (synthesis gas /synth gas) produced and used that to do useful work, heat water etc, then your charcoal would be considered bio char, ie environmentally friendly (whatever that means!) charcoal. Seeing as you do not appear to have done any of those things then what you have been making is charcoal, according to the definition, but as I said, just a name, there is no physical difference. The physical qualities of the resultant char are mainly down to the temperature used, time heated and feedstock used. I wouldn't trust the origin of the store bought stuff, they could add coal dust to it etc, they do that in China. You can do comparative tests using similar sized chunks from the same wood batch. If your store bought charcoal is African it is likely to be mopane which is one of the worlds's most dense woods, almost twice as dense as oak, that might help explain the density difference. Charcoal ranges from around 50 to 90% carbon, the longer you cook it the less dense it will get, maybe you bought cheap charcoal, or maybe you just made better charcoal than them! Lighter charcoal is generally considered better. If you cook it for long enough in the presence of any steam you will activate some of it making it even less dense, up to 3x less. Try buying some Japanese Binchotan! Slightly more spendy, now that is amazing stuff.

Small branches of oak would probably make the best charcoal for your purposes. It is dense and has a good structure, Binchotan is made from a Japanese (Quercus) oak, although it is more shrub like. Char for activated carbon is made from sugarcane, rice husk and coconut shell. I am guessing for insulation you would want slightly bigger chunks so that the pores don't get filled with lime. For mass production utilising a waste product like rice husk seems like a good idea, not sure about coconut as coir can also be a useful byproduct of coconut shells. Maybe sugarcane waste is better? I think we produce quite a lot of that. I think it's all about using every last bit of the resources we harvest and not wasting any.

And remember to wear gloves, pyrolysis produces some of natures most powerful carcinogens, mostly PAH's, notably BaP (super powerful class 1 carcinogen) and is thought to be the main culprit for lung cancer in smokers and is the primary reason why creosote is restricted and also, apparently, responsible for testicular cancer in chimney sweeps via skin contact, when they used to climb into the chimney (chimney sweeps' carcinoma) which was the first ever recorded occupational health disease. Possibly you should wear an FFP2 dust mask as well to be on the safe side. But don't get overly worried, PAHs and BaP in particular are mostly responsible for the carcinogenic effect in BBQ'd and roasted meats etc, anything roasted in fact, and of course some of the health problems associated with solid fuel burning in stoves / open fires. So to have any significantly increased risk you would probably need to make charcoal every day for years without protection.

 

[aockenden]

And remember to wear gloves, pyrolysis produces some of natures most powerful carcinogens, mostly PAH's, notably BaP (super powerful class 1 carcinogen) and is thought to be the main culprit for lung cancer in smokers and is the primary reason why creosote is restricted and also, apparently, responsible for testicular cancer in chimney sweeps via skin contact, when they used to climb into the chimney (chimney sweeps' carcinoma) which was the first ever recorded occupational health disease. Possibly you should wear an FFP2 dust mask as well to be on the safe side. But don't get overly worried, PAHs and BaP in particular are mostly responsible for the carcinogenic effect in BBQ'd and roasted meats etc, anything roasted in fact, and of course some of the health problems associated with solid fuel burning in stoves / open fires. So to have any significantly increased risk you would probably need to make charcoal every day for years without protection.

Thanks for bringing this to my attention, I honestly wasn’t aware there were any carcinogens being potentially produced by pyrolysis. Since you mentioned it I’ve looked more into the issue and I’m considering paying to have mine tested if I can find an affordable PAH testing provider.

If there ARE carcinogenic substances being produced in any potentially harmful quantities then I would stop making it immediately and would call it an interesting and fun experiment but not something I’d be comfortable using inside my house as insulation (or in my garden for that matter!).

 

[Toby Newell]

Thanks for bringing this to my attention, I honestly wasn’t aware there were any carcinogens being potentially produced by pyrolysis. Since you mentioned it I’ve looked more into the issue and I’m considering paying to have mine tested if I can find an affordable PAH testing provider.

If there ARE carcinogenic substances being produced in any potentially harmful quantities then I would stop making it immediately and would call it an interesting and fun experiment but not something I’d be comfortable using inside my house as insulation (or in my garden for that matter!).

Np dude. Tbh I wouldn't be too worried, nor would I waste time and money getting the PAHs tested. 100% PAHs are produced, even when frying bacon.

As far as I know the char itself isn't that bad and once encapsulated into your lime the danger would be pretty much zero, so feel free to go ahead with that. I think it's the residue and the smoke. All incomplete burning creates them, they get kind of concentrated in the tar, so I guess you certainly would want to dispose of the tar residue carefully and wear gloves, it's why creosote is partially banned and maybe wear a mask if you are hanging around the smoke (I mean gas, there shouldn't be a lot of smoke) when creating the char.

Coal tar is worse because there are sulphur compounds and a lot of napthelene but wood tar still creates the PAHs. They are naughty because BaP for example is 5 benzene rings stuck together. Any organic ring compound (aromatic) has a bunch of delocalised electrons in the middle that love to react with stuff, especially other organic compounds, like DNA. Benzene is bad (1 ring) but Toluene ( benzene with a methyl group on one edge) is better as one of the electron sites is stolen by the methyl group. Xylene (dimethyl benzene ie has two methyl groups attached to a benzene ring) is even safer as the ring electrons are even less localised due to the two extra groups. BaP has 5 pure benzene rings together so is a super powerful mutagen.

Context is important, you would probably need significant long term exposure to elevate your risk appreciably, cigarette smoke contains PAHs and some people inhale that several times a day for decades without severe effects. Just wear gloves when cleaning any tar and try not and breathe what probably is lovely smelling smoke!

 

[Herefordhouse]

when are you expecting to test the insulating properties of your homemade charcoal? It seems like a very interesting and financially viable prospect for my reno project

 

[aockenden]

when are you expecting to test the insulating properties of your homemade charcoal? It seems like a very interesting and financially viable prospect for my reno project

I’m still manufacturing char at the moment. I don’t have a good feel for the volume I’ve actually created so far because it’ll change once I crush it into smaller aggregate sizes to mix into the lime render / plaster.

Here’s how much I’ve got so far.

My non-hydraulic lime is all slaked and ready to go.

I also need to finish bricking-up half an old doorway to turn it into a window reveal and need to pay for the existing corrugated asbestos roof to be removed. And then need to rebuild the roof and only THEN can we actually apply the plaster. Honestly, probably won’t be ready to apply it until end of summer or this fall.

 

[aockenden]

Ahhhh, I forgot the extra fuel needed to heat the charcoal. Doh. Ok, maybe not so good then! I guess it depends how complicated you get, if you used the waste heat as part of a DHP to heat municipal water that might help. I think where it could possibly be good is to burn dead but pre rotted organic material as microbes convert the carbon to methane which has a greater atmospheric heating potential. You are effectively releasing less harmful CO2 in preference to methane. Mind you, maybe fermenting it in a biofuel generator and to capture that methane and using the heat in a DHP might be better?

Ah. There is no difference, simply a marketing gimmick. It's a trendy renaming of charcoal. Unfortunately there is a lot of BS around preying on people's consciences. It's identical. You cannot pyrolise for longer or hotter, it would simply burn! There is no oil or grease in charcoal (I think you mean wood tar ie 'volotiles') Charcoal, the whole point of charcoal, is that it burns hotter because it's simply carbon reacting with oxygen. No water or volotiles to vapourise so less latent heat of vapourisation losses and CO2 is more stable than CO so more heat is released.

Pure carbon burns great, better than non pyrolised organics, that's kind of the point. Diamond is pure carbon and that burns great.

You are locking up part of the carbon but you would have to find a free source of renewable heat to conduct the pyrolysis and try and recover the waste heat. Could be done, but seems quite complex.

I'm not sure I would necessarily trust figures from people if those were the same ones that tried to tell me charcoal isn't biochar and that charcoal doesn't burn! It's a main ingredient in gunpowder and that seems to burn quite well. The only allotrope of carbon that is difficult to get burning is bulk graphite.

OK Toby, after a lot more reading I'm coming around to your belief on this hypothetical distinction between biochar and charcoal (aka, that it's purely "eco-rebranding" to make it sound new and trendy and cool and avoid the dirty word of "coal"). I think you're right. One telling thing for me is that there appears to be no consensus within the group that claims there IS some difference, regarding WHAT the actual distinctions are between the two. If you ask 3 different believers in a difference what the difference is, you will often get 3 different answers. That's usually a bad gut-check for me.

The other thing I found is that even on the "International Biochar Initiative" website under FAQ's, they say...

"Biochar is a solid material obtained from the carbonization thermochemical conversion of biomass in an oxygen-limited environments. In more technical terms, biochar is produced by thermal decomposition of organic material (biomass such as wood, manure or leaves) under limited supply of oxygen (O2), and at relatively low temperatures (<700°C). This process mirrors the production of charcoal, which is perhaps the most ancient industrial technology developed by humankind. Biochar can be distinguished from charcoal—used mainly as a fuel—in that a primary application is use as a soil amendment with the intention to improve soil functions and to reduce emissions from biomass that would otherwise naturally degrade to greenhouse gases."

In other words, "it's biochar not charcoal because our intention is to add it to soil instead of burn it", which to me is a BS reason to rebrand something. I'll submit a request to change the thread-title to include "Charcoal" accordingly.

 

[Toby Newell]

OK Toby, after a lot more reading I'm coming around to your belief on this hypothetical distinction between biochar and charcoal (aka, that it's purely "eco-rebranding" to make it sound new and trendy and cool and avoid the dirty word of "coal"). I think you're right. One telling thing for me is that there appears to be no consensus within the group that claims there IS some difference, regarding WHAT the actual distinctions are between the two. If you ask 3 different believers in a difference what the difference is, you will often get 3 different answers. That's usually a bad gut-check for me.

The other thing I found is that even on the "International Biochar Initiative" website under FAQ's, they say...

"Biochar is a solid material obtained from the carbonization thermochemical conversion of biomass in an oxygen-limited environments. In more technical terms, biochar is produced by thermal decomposition of organic material (biomass such as wood, manure or leaves) under limited supply of oxygen (O2), and at relatively low temperatures (<700°C). This process mirrors the production of charcoal, which is perhaps the most ancient industrial technology developed by humankind. Biochar can be distinguished from charcoal—used mainly as a fuel—in that a primary application is use as a soil amendment with the intention to improve soil functions and to reduce emissions from biomass that would otherwise naturally degrade to greenhouse gases."

In other words, "it's biochar not charcoal because our intention is to add it to soil instead of burn it", which to me is a BS reason to rebrand something. I'll submit a request to change the thread-title to include "Charcoal" accordingly.

I think you need to realise that Net Zero is an incredibly ridiculous and jaw droppingly obvious bunch of lies and a large percentage of the controlling powers of humanity are locked into and grifting off the lie. Once you realise that you can take things with large amounts of salt.

Lol. You have to give it to humans. Faced with an existential crisis of their own making they are furiously making money out of it whilst simultaneously stroking the conscience of the sheep. Whilst largely doing nothing.

Regardless of piffling nomeclature I hope your experiments are going well!