Is CaCl2 needed for activated charcoal?

I want to make charcoal for fuel but am interested in what it takes to make “activated charcoal”. In looking at a few sites, instructions include soaking in a CaCl2 (calcium chloride) solution. CaCl2 is a desiccant. I’m wondering about the purpose of the CaCl2. One site said to use either bleach or lemon juice if CaCl2 isn’t available.

A chemist buddy used to make biochar through pyrolysis. He said char was hydrophobic to the point of being pretty much rot resistant. If the pyrolysis drives off all moisture, it seems it wouldn’t need a desiccant. What I’ve handled “chinked” almost like a metal sound.

Also, what is the difference between charcoal, activated charcoal and biochar?


I have heard about the lemon juice before. The important thing is activated charcoal is charcoal with all the tars baked or cooked out of it. It is carbon now. The tiny voids in it is amazing, a very small piece of charcoal with so many micro wall spaces of voids inside itself. And all it takes is heat to do this. This is the secret place where hydrogen emerges by oxygen being use up to keep the super white hot carbon burning.


Thank you! That’s what I was thinking regarding the heat driving off the moisture.

I’ve also been fascinated by the microchannels of biochar. From what I understand, the biochar is inert but it’s like a huge condo for bacteria. It provides lots and lots of surface area for bacteria to thrive. All we need to do is get the good bacteria growing.

I’d like to make biochar for fuel and food. The big chunks go into the gasifier and the fines go into the soil.


Over the years, I have gone “round and round” trying to figure out the difference between “charcoal” and “activated charcoal”.
Never did seem to get a clear answer.
Assuming (and I know what THAT means) that, in either case, the charcoal has had all the tars, etc., cooked out, I don’t see any difference.
Okay, so let’s say you are using charcoal for a filter of some sort. After a while, stuff sticks to the charcoal as the medium (air, water, etc.) is passed through it. At some point, enough of the “micro wall spaces” get covered by the stuff that a fair amount of the medium passes through without getting trapped. At that point, I’d consider the charcoal to be NOT “activated” any more.
To my simple mind, all you have to do is to heat the charcoal enough (in free air) to drive off the bad guys, and you again have “activated charcoal”…
Comments? Clarifications?

Pete Stanaitis


Yes you are correct Pete. Charcoal filters you buy, they only last so long and then you throw them away. Why they are all plug up with impurities.
So activated charcoal is fresh clean charcoal.


Hi Pete, just as you say, activated charcoal can be re-activated, or “cleaned” much depending on what it’s used to filter.
In Swedish “traditional” moonshining, (highly illegal) activated charcoal are used to filter “brännvin”(swedish vodka) in this case the charcoal can be heated in an ordinary kitchen owen, 300°c, around an hour, (smells terrible, and fire hazard) this charcoal are after cooling of, as new, only the dust has to be replaced with new activated charcoal.


It is too easy to make. Just put it in the garden and start with a new batch.

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Im sorry, i was a little wrong in translation, i meant activated carbon, this is harder to make if i remember correctly? Could be made from ordinary charcoal, im no expert in this but i believe it was a process when the charcoal should be heated to glowing in a closed container, then “super-heated” steam lead through it, to open up the porosity?
This is the activated carbon i know, that is used to filter liquids, gasses and stuff.
I belive the language barrier makes me mix up things? :blush:


Goran is right. Activating is coking the char and then pumping the steam through it. There may be other methods I’m not aware of. Bio-char is any thing but hydrophobic. I innoculate it in batches made in five gallon buckets. Each bucket is filled with the particles left after I sift my fuel sized char and that is anything smaller than quarter inch. I add a gallon of urine to that and a quart of water with other amendments mixed in it. In a few days it will be all absorbed and then I spread it out for a day to dry completely.


Here’s an interesting article on activating charcoal for filtering water. His tests are simple enough to understand, and the results are encouraging, especially if you like simple.



The difference between the methods is the size of the pores you create. So the more water capacity it has, the larger the pores are. It would be interesting to find a chart with the 1394a capacity and equivalent pore sizes.

I was just looking at this for water treatment. A chart like this

gives you a rough idea of what you are shooting for. It differs a bit from other stuff I have read about the actual numbers but in the relative ballpark. If you get to fine, it clogs too fast, and if you get too big it doesn’t catch everything you want.

And I have wondered for a while how hard it would be to make and be consistent about it because you have to get very consistent sizes. A screen with a hole bigger then the bug you are trying to keep out, doesn’t keep the bugs out. Granted, if you do get a few holes bigger then the target, because it is essentially many many layers of tightly packed carbon, it isn’t going to let any through.

But right now I’m using a spin down filter and an electronic water conditioner to see if that locks up the calcium or whether it is a bunk claim.


Oh and just because I thought I had seen it all and I think this is funny. There is a company called Flat-D that makes char based flatulence odor control products.


This is TLDR (to long didn’t read fully) but this goes through several procedures to test activated carbon for specific types of substances. It is a pretty nice reference. I swiped it off (I haven’t poked through their site, I just found it with google.)

Test_method_for_Activated_Carbon_86.pdf (1.3 MB)


Thanks Sean.

What a great idea for Christmas and birthday presents :grinning: :grinning:


I wonder if they make them for dogs? Sometimes I can hardly see the TV from my eyes watering.


charcoal or activated carbon…

There are clear definitions of what activated carbon means, what it should be…

Many different types can bee made…

High quality charcoal does not mean it is “activated”

There is a so called iodine adsorption requirement for most kind and or a methyl blue adsorption number.

Fresh charcoal , high temp, might repel water from its surfaces , but when washed with methanol and dried, it really adsorbs water at a high rate…

Different purposes = different ways to make it activated…

Been doing research and test over the past years up to usp grade…


I did not know this. Good information. :slight_smile:

If you treat it with methanol, it absorbs water, but is it similar to steam treating or do you also have to do that to fracture it first? For the steam treatment can you get away with soaking it in water, then just heating it to 900C? My latest thought was either to microwave it or put it in an insta-pot. :slight_smile:

I am going to assume that more porous materials to start with are better(?), since most water filters are coconut shells, which the US equivalent would be like willow and grapevine. Ironically, most of the video’s for willow and grapevine charcoal are for making black powder. :laughing:


Frangula alnus - Wikipedia , this plant used to be bought for the production of charcoal for gunpowder, it was necessary to remove the bark and dry the wood,…


Im late to the party and l see Koen, the expert on the topic alredy chimed in.

The difference. Any charcoal, as l understand, will work adsorbing stuff. The catch with acticated charcoal is just that its pores are more opened, providing more surface area for the adsorbtion. This is done by passing superheated steam trugh glowing charcoal. The steam eats away a part of the charcoal on the surface (the whole surface, in the pores) enlarging tge surface area.

Guess whats happening in a gasifier… exactly that. So the sliped char from a gasifier is activated carbon. Koen, do l remember that right?


Apart from chemical infusion to charcoal to activate it , i was always told that you quench the glowing charcoal into cold water helps to open the cell structure massively and if you need even higher porous then re heat and quench again ,.
10 years ago we were offered $500 a cubic meter for Bio char , but the quality would have to be pretty well spot on time after time , we gave that a miss but we did supply a soap maker with very finely ground charcoal that was mixed into there soap , that worked really well for a year or 2 , before we got a complaint that 1 customer had scratched her face using the soap due to there being a slightly larger piece that passed through the grinding prosses , we decided after that it was not worth the hassle due to how the world was going towards suing everyone that makes anything that ever goes wrong , back street manufacturers don’t stand a chance these days