Your handy guide to charcoal, biochar, and activated charcoal

Hello, fellow fans of burning stuff to make it useful!

This is meant to be a comprehensive guide to to Charcoal, Activated Charcoal, Biochar, what it all means and how to make it.

Charcoal vs Coal vs Charcoal Briquettes vs Lump Charcoal, what’s the difference?

Charcoal is the result of burning carbon-rich vegetable matter in a high temperature and low oxygen environment. Good charcoal is almost entirely pure carbon.

Coal: A combustable black or brown lump material that is mined from the ground. This coal is mostly carbon, along with various other elements like sulfur, nitrogen, and hydrogen. Coal is formed when dead plant matter decays into peat and is converted into coal over millions of years inside the earth’s crust. Coal burns very hot and is often used in metallurgy (though chemical transference from coal into the metal is a risk), but its use and extraction is extremely damaging both to human health and the environment at large.

Charcoal Briquettes: This is made from a combination of several materials. Generally, wood particles, sawdust, and chemical additives like limestone, starch, sodium nitrate, paraffin wax, and petroleum solvents.  These all help with ignition, binding ingredients together, and artificially whitening the ash left behind. Match-Light or Instant-light varieties of Charcoal Briquettes may also have a hydrocarbon sprayed on the surface to encourage quick ignition. If you’re trying to be organic or ‘permaculture’, this is not what you want.

There ARE some options for “natural” briquettes that use hardwood sawdust and cornstarch as a binder. You gotta read the ingredients list & pay attention to what’s inside.

Briquettes are generally square, rectangular, spherical, cylinder or pillow-shaped.

Pure Wood Charcoal, also called Lump Charcoal: This is just chunks of plant material that has been made into charcoal through heating. The wood is unprocessed (not sawdust, no binders). It’s normally more expensive than Briquettes, but you can make your own pretty easily, through the methods described below.

For the rest of this post, I will be using the word “Charcoal’ to specifically mean ‘Plant-based Charcoal’

Burning Wood vs Making Charcoal
While burning wood in a regular well-ventilated campfire, oxygen enters and oxidizes the carbon, turning it into ash. Ash is primarily oxidized carbon.
At high temperatures, violate compounds such as water, methane, and other molecules are also oxidized (broken down), or are evaporated out. In general, an organic molecule will break down & oxidize (burn) at a lower temperature than pure carbon.

Even heavy metals begin to vaporize & become airborne at temperatures where charring occurs, so if you know you’re dealing with material that has been treated with lead, cadmium, mercury, etc, please DO NOT breathe in the smoke of vapors of that fire. Many substances have a vaporization point (becoming airborne in vapors) at a much lower temperature than its true boiling/evaporation point. (Where the material itself turns from a liquid to a gas.)

So, if you want to make CHARCOAL instead of ASH, you just need to take plant matter, limit the amount of oxygen that can touch it while hot, and get strong fire going around it for about a half-hour.

While it's experiencing high temperatures and low airflow, the carbon doesn’t oxidize. It doesn’t turn to ash. You still want to allow a little bit of air to escape, so those expanding gas compounds of non-carbon material wiggling free of their bonds due to the heat can get out as smoke and steam. (And not explode your container)

Charcoal can be made by making a pile of plant matter and covering it with a layer of dirt before igniting.
It can be made in a specialty kiln.
It can be made by placing a metal barrel of wood (with a few holes punched in it) inside a bonfire.
It can be made by putting wood inside a metal lidded pot, and put inside a small campfire.

Charcoal can be made with any carbon-rich plant material. All of these materials can be made into charcoal via the methods described above:

Hardwood or Softwood split logs, dry pine needles, pinecones, seed husks, branches, twigs, shavings, woody vines, reeds, raspberry canes, dried stems, dried leaves, corn husks, dried corn cobs, coconut shells, dried grass clippings, dried moss, peat, dried palm leaves, quite literally any plant that is considered ‘brown’ for the sake of composting can also be made into charcoal.

(Note: please don’t burn or char poison ivy, poison oak, or other obviously-poisonous plants. Just like heavy metal and herbicides can become airborne with heating, so can the rash-causing compounds. You don’t want to breathe in aerosolized Urushiol (the chemical in poison ivy that gives you a horrible rash can also be carried & affect you through the smoke & vapors).

Heat required to turn plant matter into charcoal

In Feurdean’s experiments on charcoal production and the effect temperature had on biomass loss during charring; Leaves, sphagnum moss, and tree trunk wood produced the lowest amounts of charcoal per unit biomass during charring, and lost their mass more rapidly with increasing temperatures. Leaves of heathland shrubs, forbs, and ferns, as well as fern stems with leaves produced the most charcoal per unit biomass, and retained the greatest mass at higher temperatures.

Fuels rich in cellulose and hemicellulose, like leaves and ferns, were able to turn to charcoal at lower temperatures on average, BUT had a narrow temperature range before turning to ash. (200-400 degrees Celsius / 400-750 degrees F)
Fuels rich in lignin (like wood), turned to charcoal at a wider range of temperatures. (160-900 degrees C / 320-1,650 degrees F)

So, if you want to turn non-wood plant matter into charcoal, you'll want lower temperatures & careful temperature control - while wood charring is far less fussy.

Source: Experimental production of charcoal morphologies to discriminate fuel source and fire type, by Angelica Feurdean from the Department of Physical Geography, Goethe University, Germany. (Revised January 2021)


Because of the low temperatures required for grass & leaves to turn to charcoal, and the ease of acquiring those things throughout the year, it could be an attractive source of charcoal to create biochar for a home gardener, or otherwise a useful way to put huge piles of dropped leaves to use.
It can also be a reliable source of charcoal for crushing & turning into your own custom briquettes, by adding a binder. (You can mix flour & water with crushed charcoal to make a thick paste, then put into a mold or an egg carton to make DIY briquettes.)

–

What about Biochar?

There are two commonly-used definitions of 'Biochar'.
The first, used by many gardening folks & seen here on Permies, is 'Charcoal that has already been inoculated with nutrients, so that as it breaks down in the soil it acts as an organic slow-release fertilizer.' This can be made by dumping charcoal into compost bins, into compost tea, or mixing it with manure.

Basically, treating charcoal or activated charcoal as a molecular pantry.
You 'Charge' it, or 'Stock' it, and turn it into biochar by soaking charcoal in nutrients that microflora crave. Those molocules adhere to the porous surface of the charcoal, until the charcoal breaks down.

This stockpiles nutrients in a place that won't rinse away as easily as free-floating molecules would.

The Other Definition
The other definition... actually means exactly the same thing, but approaches it from the opposite direction.

Instead of "Charcoal or Activated Charcoal that is inoculated for use in soil amendment" being the definition, professional biosystems engineers, and plant & soil scientists separate Biochar from regular Charcoal by 'Intended use' and 'material origin'- that is, because the charcoal is intended to be used as a soil amendment AND it is purely carbonated plant matter, it is biochar.

Wood Lump Charcoal, Charcoal made from coconut husks or other plant matter, and Biochar are all carbon-rich solids from plants that are put through pyrolysis. Chemically, physically, they are the same.

The main difference is LINGUISTIC.
Most people think of wood-based charcoals when you say 'Charcoal', and 'Biochar' more broadly includes other plant matter.
Additionally, 'Charcoal' colloquially includes items like charcoal briquettes, which may have petroleum additives and are not appropriate for soil remediation.

So, the difference between 'Biochar' and 'Charcoal' is not a chemical one, but rather a language choice for clarification & specification: Biochar is purely carbonized plant matter (charcoal), which is intended to be used in soil remediation.
Biochar is NOT charcoal briquettes, or any other charcoal-based product which includes processed fillers or synthetic additives.

This version of 'Biochar' does not imply that nutrient inoculation has already been performed, only that it is intended to be used for that in the future.

---

What about Activated Charcoal?

Activated charcoal is to Charcoal is like popped popcorn is to corn kernels. It’s more porous, ‘fluffier’, and has a larger surface area.
Activated carbon is a much more powerful molecular binder - while Charcoal is a magnetic pantry to hold onto molecules, Activated Charcoal is more like a supermagnet with an attached garage. It is more aggressive about sucking up other molecules & has more storage space to keep them held.

Note: Charcoal and Activated Charcoal/Activated Carbon ADsorbs things. It doesn’t ABsorb things.
When something is ADsorbed, particles stick to the surface due to molecular forces like positive/negative charges. A magnet ADsorbs iron particles.
When something is ABsorbed, the particles are soaked into the matrix of the material. A sponge ABsorbs water.

How to Activate Charcoal
Activated Charcoal (also called Activated Carbon) is made by EITHER heating charcoal in temperatures exceeding 600 degrees C (1,100 degrees F) while in a no-oxygen environment (This requires using a special chamber where you can heat up your charcoal in the presence of something like Argon instead of a regular mix of air to prevent any oxidation), OR crushing normal charcoal to a powder, adding an strong acid, strong base, or salt, then heating it again to temps between 250-600 C (400 - 1,100 F) <-- much more accessible!

Recipe for activating charcoal:
> Pickle Crisp - Calcium Chloride - a type of salt. You can buy it in big tubs at most places that sell pickling materials.
> Water
> Charcoal


Step 1: Make charcoal. Then powder charcoal by smashing with a hammer or using mortar and pestle.

Step 2: Be careful, this step generates heat. In a STAINLESS STEEL (not aluminum) bowl;  Make a 25% solution of calcium chloride with water, at a 1:3 ratio.
If you have 600 ml of water you want 200 grams of calcium chloride. You want to make enough of the solution to completely cover the powdered charcoal.
Using tapwater is fine, because the amount of trace minerals in tapwater is basically nothing compared to how much the carbon can adsorb.

Step 3: Add your solution to your powdered carbon, a little bit at a time. You may not use all of your solution - once it reaches a thick paste consistency (like peanut butter), stop adding more solution and just mix the paste until smooth. Get out all the lumps.

Step 4: Cover the bowl with a towel and let it sit untouched for 24 hours to allow the chemical reaction to continue.

Step 5: Drain off the liquid using a coffee filter or very fine muslin cloth. Put the sludge back into your metal pot.

Step 6: Take your pot of nearly-activated-carbon, put the lid back on, and put it into a fire that exceeds 200 degrees C (400 degrees F) - a normal campfire should do the trick. Keep it on the fire with the lid on until it stops steaming, and then take it off to let it cool - don't open the lid until it's completely cool.

Congrats, you’ve activated your charcoal!

WARNING:
When ingested, Charcoal and Activated Charcoal will ALSO bind to medicines in your gut, along with helpful vitamins, minerals, and antioxidants from our food instead of letting the body absorb it. Our bowels pass the charcoal much faster than the charcoal takes to release those nutrients and medicines back to us.

DO NOT ingest activated charcoal within 48 hours of taking, or expecting to take, any type of necessary medicine. Especially antidepressants and anti-inflammatory medications. The charcoal will likely deactivate & adsorb it - or at the very least make it less effective than that dose should be.

Charcoal and Activated Charcoal is not absorbed by the bloodstream. It stays in the digestive tract until excreted via bowel movement. This means it has no ability to remove alcohol from the bloodstream.

Well, under what circumstances CAN I use charcoal on people or animals?

Medicinally, orally, to treat acute poisoning or food poisoning (they ate something poisonous or spoiled: NOT envenomation. Charcoal won’t stop a spider or snakebite)

Medicinally, orally, to treat some types of parasitic worms.

Medicinally, orally, to relieve symptoms of bacterial infection in the gut, by absorbing bacterial-secreted toxins. (Does not kill the bacteria itself, but can help the body fight those bacteria by adsorbing their main weapon. Activated carbon has no significant influence on the microflora content of the gut biome - it does not kill bacteria when ingested)

Decoratively, as a powder or paint application to the skin.

As of July 2022, there are no scientific studies that support the use of charcoal or activated charcoal in facial care, beyond its exfoliant (rough texture) properties.
Its ability to ‘remove toxins’ has been studied several times, and there is currently no evidence to support that property when used in topical skin creams.
There are also no published studies that support the use of charcoal in whitening teeth. (But there is evidence to show that the black powder can settle into tiny cracks and pores in the enamel and darken the tooth)

Charcoal is not a cure-all. It can't cure or clear the effects of acid, iron overdose, lithium, alkali, alcohol, or chemicals from gasoline.
For some people who are more sensitive to it, or if you take a very large dose in a very short time, charcoal can cause vomiting & constipation. While there is no 'toxicity', you can have adverse effects from administering it.  (In the same way a glass marble is not poisonous, but if you eat several marbles your gut may feel uncomfortable until they pass out the other end)
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Other Uses for charcoal

Activated Charcoal filtering chlorine, heavy metals, and other substances from tap water.
Whole charcoal sticks can be used as a writing utensil.
Powder-ground charcoal + Drying Oil (like linseed) = Black oil paint.
Powder-ground charcoal + water + Vinegar = Black Ink (For use in calligraphy or watercolor. Shape before using)
Powder-ground charcoal + sulfur + saltpeter = Black Powder
Charcoal + compost/nutrients/compost tea/urine = Biochar. ← if you want your biochar to be able to hold way more nutrients, then use activated charcoal instead of normal charcoal.

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Note on Calcium Chloride regarding its use in organic farming  & activating charcoal:
You can extract Calcium Chloride by applying hydrochloric Acid to Limestone.
Stomach acid (found in mammalian stomachs) is hydrochloric acid. Hydrochloric acid is also naturally occurring around volcanoes and hot springs, as a result of hydrogen chlorine gas dissolving into water. So, it's also possible to find naturally-occurring Calcium Chloride where volcanic-produced hydrochloric acid meets limestone.

Calcium Chloride is commonly used in canning foods to keep them crunchy, as an electrolyte in sports drinks and bottled water, and in cheesemaking to restore the balance between calcium and casein protein. It is used in marine aquariums as a bioavailable calcium supplement for carbonite-shelled animals like mollusks.  

However, major manufacturers of Calcium Chloride use several different synthetic chemicals manufacture it en-masse. Because of this, NOSB voted to allow Calcium Chloride ONLY if natural food-grade sources are used, OR it is used specifically as a foliar spray at minimum levels to treat calcium deficiencies.
Since I am recommending using food-grade sources, and only small amounts are used, this should be in accordance with NOSB guidelines.
(Source: National Organic Standards Board Technical Advisory Panel Review from 2001, page 2)

Thanks! Bookmarked for future reference.

Great post, Toko.  Full of information.  Sounds like I will be needing to activate my charcoal before nutrifying it.

John S
PDX OR

A follow up question about the activation.  I only seem to be able to get my char down to the size of pea gravel or regular gravel.  Can you still activate it with calcium chloride if you can't get it down to powder?
Thanks,
John S
PDX OR

I can't think activating the charcoal is too crucial a step (edit - in making biochar that is, you would want to for medicinal or chemical purposes). Presumably the more active it is (which I think is just a matter of increased surface area?) the better the charcoal becomes as a nutrient 'battery'. I found this site which goes into a bit of detail on making activated charcoal. They suggest lemon juice can be used as an alternative to Calcium chloride, which may be easier to get hold of and dispose of. It's a cooking site, but the principals will still be the same I think.
As regards size, if you can't powder your charcoal the exposed surface will be less, but that exposed surface will still be enhanced by the activation so you will still get some effect. (I'll make up some numbers here). Suppose you have particles of charcoal of 5mm and crush them to 1mm, you get an 6 fold increase in surface area. If you then activate them you might get an increase of 1000 fold from emptying the pores (this from Activated_carbon). Maybe if you haven't crushed it the effect would be only 100 fold, since only the surface accessable pores will be cleared. The difference is in the accessable area of the carbon - the internal pores of normal charcoal tend to be filled already with unburnt hydrocarbons so will take longer to accumulate the nutrients and fungi that we want to encourage.
In my opinion it's just a matter of time though. The pores are still there, and in time the charcoal will get crushed and mixed into the soil with cultivation and harvesting, so increasing the surface area a bit. The pores will slowly get filled by diffusion, as long as the soil is damp enough for water to be present. Having different size pores to suit different biological organisms would also be useful, but that is a function of your charcoal feedstock. I don't suppose the original makers of terra preta activated their charcoal, it was time that created the substance as a happy accident.

In my area, I find that the natural freeze/thaw cycle gradually breaks my char into powder. After two years in the soil, it's invisible to the naked eye.

On other sites, I have read where drenching the burning hot coals with cold water activates the char by puffing it out.  Both of these may be promising practices that aren't quite up to the level of crushing it or inoculating it in terms of evidence.   Of course, not everyone drenches their burning hot coals with cold water, so the calcium chloride activation may be less crucial for those who drench.

John S
PDX OR

I wouldn't worry too much about activating your charcoal for something like Biochar - especially en-masse!
Normal charcoal will work just fine without spending extra money and time prepping it. You can use that time creating more charcoal instead of activating it.

For making your own water filtration media, or keeping it on hand for emergency poisoning situations (Especially useful for people who keep grazing livestock and might have poisonous plants that they haven't been able to clear entirely out of the pastures) - I think having Activated Charcoal is preferable. It's more thorough, and in the case of poisoning will buy you more time in an emergency situation to get to proper medical care.

Toko Aakster wrote:Hello, fellow fans of burning stuff to make it useful!

Perhaps this isn't the place to ask this question, but since this is all about 'burning stuff to make it useful', I'll go ahead and ask.

Last fall, we had a very large fire mitigation effort at our place, and they removed tons of 'junk' ladder fuel, piling it up into burn piles.  We later had someone come and burn all the burn piles.

Some of the burn piles continued to smolder and ended up catching all kinds of duff and roots on fire in the middle of the night, which we had to put out with water, since there isn't enough dirt in those areas - just basalt rocks and duff.

In both instances, there is quite a bit of 'burned stuff' that didn't burn completely to ash.

Can any of that be used for soil improvement?

The easiest way I've found to make bio char is by using a cut-down 300 gallon fuel barrel along with a 55 gallon oil drum. I cut the 300 gallon barrel down so it's about 12 inches taller than the 55 gallon barrel. This end piece is made into a lid. Add a 6-inch stovepipe to the lid to help the air draft up through the fire, thus getting the fire super-hot. Some draft holes are placed around the bottom of the 300 gallon barrel to provide air for the fire.  

The 55 gallon barrel goes inside the 300 gallon barrel. Place some small holes at the first ring up from the bottom, about a third-of-the-way up from the bottom of the 55 gallon barrel. These holes will assist in directing the heated combustible gases from the char material into the fire to get the super-heating action (positive feedback reaction). Cut the top out of the 55 gallon barrel, leave a lip so a piece of stove gasket can be placed between the barrel and the lid to make a seal. The plant material you want to make into bio char goes into the smaller, 55 gallon barrel.

I use Eastern Red Cedar pieces to make bio char. Let the cedar dry for a year, cut them up into ~3 inch chunks. Place the chunked material into the 55 gallon barrel. After a year of drying most of the water moisture is gone from the wood (in our environment), but still has residual cedar oil that enhances the burn. Put the stove gasket in place and put on the lid. With the 55 gallon barrel inside the 300 gallon barrel start adding fire material around the 55 gallon barrel.

In the first layer of burn material I place a few feed bags to assist with getting the burn started. Pack the burn material around and over the 55 gallon barrel, put on the lid and start the fire. I prefer to place most of the burn material vertically in the burn barrel. The fire drafts from the holes along the bottom of the 300 gallon barrel, up the vertically aligned seams in the burn material, then out the central smoke stack. As the fire gets hot, the inner char material will start to emit wood alcohols and oil vapor. The wood alcohols and oil vapor are combustible and will pass out the small, knee-high holes in the 55 gallon barrel. The knee-high level is at the level of the fire so the oil feeds the fire and gets the burn even hotter. After about 12 hours the burn is complete. I usually start a burn in the evening, it's done by morning. After the burn, the char material only occupies two-thirds of the space (a 1/3 reduction).

If you expose the hot char to the air it will continue to burn and you will be left with nearly nothing for your effort. Once you take the lid off, wet the char down to stop the burn. I like to place the char into a 6-foot stock tank. I add water to stop the combustion. When I keep the char wet, a few winters of thawing and freezing pulverizes the char into small shards. I've also placed char on a tarp and hammered it into smaller pieces. We use the char directly as a soil amendment, though I think it works best when mixed into a compost pile. The organisms in the compost pile fill the pores in the bio char with nitrogenous material which enhances soil life.

Loretta Liefveld wrote:

In both instances, there is quite a bit of 'burned stuff' that didn't burn completely to ash.

Can any of that be used for soil improvement?

Loretta, Sorry I didn't see your post earlier: Wood ash is rich in potassium which is good for developing flowers and fruit and for ripening growth to toughen it, Charcoal becomes biochar in contact with soil which acts as a nutrient 'battery' harbouring water and bio-organisms in the soil. It is probably good for your soil especially around perennial plants, but also where you grow fruit like tomatoes. Depending on how good/dry your soil tends to be you may or may not see a real result, but unless they burnt any nasty man made stuff along with the branches, I think it will be good for soil improvement

Nancy Reading wrote:

Loretta Liefveld wrote:

In both instances, there is quite a bit of 'burned stuff' that didn't burn completely to ash.

Can any of that be used for soil improvement?

Loretta, Sorry I didn't see your post earlier: Wood ash is rich in potassium which is good for developing flowers and fruit and for ripening growth to toughen it, Charcoal becomes biochar in contact with soil which acts as a nutrient 'battery' harbouring water and bio-organisms in the soil. It is probably good for your soil especially around perennial plants, but also where you grow fruit like tomatoes. Depending on how good/dry your soil tends to be you may or may not see a real result, but unless they burnt any nasty man made stuff along with the branches, I think it will be good for soil improvement

Thanks, Nancy.  Since this was fire mitigation, they were cutting down dead trees and small trees and bushes that become ladder fuel.  I think there are a couple of places where old fence posts might have been burned, but most of the burn piles in the 7 acres they did consisted of just the ladder fuel.

My soil is clay, clay, clay - mixed with silt, silt, silt (which is almost as difficult as clay, just not as sticky) - mixed with basalt rocks ranging in size from fist-size to basketball-size (and upwards).    The people that built the house just cut off the top of a hill, so there's very little topsoil in most places.   I've been working on amending it, one small area at a time, adding compost, worm castings and gypsum.

I think I would have to inoculate the charcoal pieces.... thinking of putting some of them in my compost pile and some in the worm bin to inoculate.   Because the burn piles were in the forest, on the ground, it's all somewhat in contact with the soil, but I'm thinking it probably needs a little more inoculation.  Maybe I could mix it up with some goose, duck or chicken poop.

Yes, Loretta,
If you look in this forum you will see many, many types of inoculation. It depends on what you've got a lot of .  That poop should work, and you could mix it with other stuff too. A little bit of unburned wood isn't going to be a disaster. It's sort of a min-hugel, but it won't do the same things that biochar will do.

John S
PDX OR

About activating charcoal to be used as biochar, i.e. in the soil. As I understand, actuvating is actually "filling" the charcoal with nutrients sothat it doesn't draw them from the soil. If I understood it correctly, is it possible ti actuvate the charcoal with artificial fertilizer? Like, disolve the fertilizer 20-20-20 in rainwater and use it as activator. Any opinions?

Vase Angjeleski wrote:About activating charcoal to be used as biochar, i.e. in the soil. As I understand, actuvating is actually "filling" the charcoal with nutrients sothat it doesn't draw them from the soil. If I understood it correctly, is it possible ti actuvate the charcoal with artificial fertilizer? Like, disolve the fertilizer 20-20-20 in rainwater and use it as activator. Any opinions?

Activating it is more about feeding and creating a home for microscopic creatures that help plants grow.  Fertilizer generally kills soil life.

I agree with Trace.  Synthetics are harsh and not a way to build soil or microbes.  Most frequently,  people will put nutritious stuff in there, like compost, compost tea, urine, seaweed, etc.  Those things have microbes in them and they also have food for the microbes.  If one were to just spray compost tea on it and leave it in a bucket, the microbes would die.  You want microbes plus natural nutrition.  Putting it into the soil or compost are ways of doing that.

John S
PDX OR

Ok, no artificial fertilizer. How about worm castings, how long should it be mixed with the castings to be activated, how long should I wait before mixing it in the soil? And, is pine charcoal ok or should it be hardwood?

Worm castings are superb. Mix everything together and let it sit for at least a few days. Weeks if you're patient. And pine makes great biochar, with a higher carbon to mineral ratio than most hardwoods, and slightly less alkaline.

Worm castings are great! I use them. People have different protocols. There are many threads about them in this forum.  I use ag lime, whole wheat flour, seaweed, compost, worm castings, rotten fruit, rotten wood mycelium and urine to drench them once a day for two weeks, after I've crushed the biochar.  Then I dig it in.

Pine is fine for biochar.

John S
PDX OR

I can see the appeal of biochar in sandy soils to retain nutrients, but I have a very clay soil which naturally has a high CEC. Biochar is supposed to help with aeration of clay soils, which is a benefit, but biochar takes a lot of time to produce (unless you can combine it with another activity, like heating your house) so from my perspective, it is easier to throw down some cover crop seeds to help with aeration than to go the biochar route.

But feel free to convince me otherwise.

M

Maarten Smet wrote:I can see the appeal of biochar in sandy soils to retain nutrients, but I have a very clay soil which naturally has a high CEC. Biochar is supposed to help with aeration of clay soils, which is a benefit, but biochar takes a lot of time to produce (unless you can combine it with another activity, like heating your house) so from my perspective, it is easier to throw down some cover crop seeds to help with aeration than to go the biochar route.

But feel free to convince me otherwise.

M

i don't think anyone has any interest in convincing anyone to use biochar.  Most people that post to this forum I believe are already making biochar, or want to use it and are trying to learn how to make it.  I can give you my reasoning for using it in my heavy clay soil though.

I think biochar has a number of benefits besides aeration.  I think a person with heavy clay soil can broad fork biochar, compost, and other organic materials into their heavy clay soil and make improvements to that soil far, far faster than cover crops alone will do.  I also believe the biochar, especially when mixed with compost will allow any cover crops planted to grow much faster.  I don't see biochar and cover crops as an either/or proposition,  I see them as beneficial things that can be used together.  I have areas that have been cover cropped for years and the soil is still heavy clay, so cover cropping alone doesn't seem to be the answer for me.

I am growing rye as cover crop for 5 years now and the clay is preaty much same, honestly, I haven't seen ANY change. There is a change though on parcel that I throw compost and forest humus. About the charcoal, I have made it in an eart pit preaty easy and almost no time consuming at all, fire it, wait a bit, cover it and let it cool down but, I am affraid to use it, since I have read that if it is not activated, it will suck the nutrients out of the soil, hence my question, ways of activating.

Vase-inoculating/activating is really easy. It just takes a few weeks and some easy to get ingredients.  There are many threads on this topic in this forum.

Maarten-I have heavy clay soil and lots of rainfall, probably like you do, if you're in Kentucky.  Biochar does take some work to get going. Once you get going with it, it's not hard to keep going with it.  The main thing is that biochar is a semi-permanent improvement.  The terra preta soils in Brazil are outstanding quality-way better than any of the soils around there- and the people who made it died off 500 years ago.  They haven't been improving it since then.  One outstanding feature of biochar is that you get better nutrition, better aeration, but also better drainage in a permanent way!  You can add gravel to heavy clay, and it will improve drainage on a semi-permanent basis, but it doesn't add much nutrition or aeration.  Roots in heavy clay drown and go anaerobic in a lot of rain. Then the plants get sick and drown.  

I agree with Trace once again on cover crops.  Do both.  They aren't mutually exclusive.  Likewise with compost or other mulches, etc.

John S
PDX OR

So, I made this today. This is the plan, fil it with worm tea and mix worm castings in it. Since it has little holes on the bottom for drainage, I wanted to leave it in the field so that when it drains, the liquid will drain in the field. Will the charcoal be activated like this? If yes, how long should I wait before mixing it in the ground?

Addendum: I read that when activating charcoal, it takes lots of nitrogen from the "surroundings". So, I have chickens and I know that chicken manure has lots of nitrogen. Would it help more if I add some chicken manure?

I don't inoculate in containers with holes in them.  I drench them with my mixture, once a day for two weeks, as it lets the microbes and nutrition soak in, but in an aerobic manner.  That way you favor the helpful microbes in the garden. "The cavalry", as Elaine Ingham calls them.
John S
PDX OR

I would like to emphasize that there is a chemical difference between biochar and *most* charcoal, because most charcoal is prepared in a way that preserves a lot of the volatile components in order to keep the energy content high (i.e., if you're making charcoal to burn, you typically want it to have a high energy content, and you do that by minimizing the loss of volatile components).  Biochar, on the other hand, is produced with the goal of burning off all of those volatile components.

Why is this important?  It's important because a lot of those volatile components are soil contaminants that you don't want around your food.  It's almost like having soil contaminated with diesel fuel.  That's why most folks in the biochar field recommend against buying sacks of lump charcoal from the store and grinding it up to put in your garden -- you'd be amending your soil with some pretty ugly (and persistent) chemicals.  Some of those compounds can be broken down by soil bacteria, but it's a.very.slow.process.  So, they can do a good job on the trace amounts commonly found in biochar, but have a more difficult time handling the amount present in charcoal intended for burning.

(Note that the one exception re: charcoal is charcoal meant for things like smithing, which (like biochar) is made with the goal of burning off all the volatile components, to yield a high purity carbon source.)

I have been making charcoal for the last few weeks using a double barrel system. 30gal in a 55gal. It produces better each time. I'm still learning. My last batch was 15-20 gallons crushed. A biproduct of the combustion is ash. Can I just use the hardwood ash for activating it? It's potassium based so plants will love it still Mix ash with water add a little pickling lime to get the proper ph and then put it back in the reactor a few batches later when I can refill the barrel? It would seem its way more valuable for nutrient absorption. Even though I'm really just doing it for soil water retention I want this stuff as potent as possible. What would the proper ph be to make the char active?

jeramiah morgan wrote: A biproduct of the combustion is ash. Can I just use the hardwood ash for activating it?

I'm not sure that will be enough. My understanding is that the best results come from inoculating with a broad spectrum soup of nutients including nitrogen, microbes and fungi from living soil, and perhaps "Vitamin P."

Personally, I've been soaking char with the leachate from my composters. It's the lazy method. Early results look promising.

My understanding is that the best results come from "Vitamin P."

Thanks Douglas.
I have a system figured out on how to innoculate it. I'm wondering more about what alkalinity is required to make activated charcoal. And if ash is ok to use for that reaction rather than pickling salt.

I also have access to lemons and citrus. enough to make an acid version . But I only can find recipes for relatively loose quantities and not a PH that creates the reaction. I would like to be scientific about this I have litmus paper so it's easy to test a solution. I'll reverse engineer the recipes if I can't get a more scientific answer.

Ah! I misunderstood. Good luck with your project!

I agree with Douglas.  Use a wide variety of convenient inexpensive nutrients. I have an orchard, so I use rotten fruit. I live by the sea, so I use seaweed.  I have composting worms, so I use worm compost.  I cultivate mushrooms, so I use old rotten wood.  Urine is great. So is compost tea.  I also use ag lime, which is super cheap, and some very cheap compost, which I can get a lot of, and one cup of whole wheat flour.  Only using ash isn't recommended.
John S
PDX OR

I have heard of the approach that jeramiah morgan is talking about -- I just didn't clue in at first. It has something to do with chemically charging simple char in a specific way, putting it back in a closed retort, and creating "activated charcoal" as a result.

Neat idea. Except activated charcoal (as opposed to simple char) is typically produced in a pressure cooker type environment. This is industrial scale stuff. Totally worth doing~! But absent of a pressure cooker, I am skeptical. Then again, if there is an alternate method, that would be pretty cool.

The version of activation that I am able to do is different.  I have read that pouring cold water on it while it is really hot can puff it up and make more pores.  That's what I do to douse it when I have cooked out all of the oils and tannins.  It's a home version that I don't need a lab and a lot of fancy chemicals for.  

John S
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