Biochar particle size - does it matter at all?

It has been years that I gave up on grinding biochar. As long as it is not bigger than 2-3 inches, it is all fine. I did not see any ill effects, any problems or such. Some -or most- prefer to grind it down to, well almost, dust.
Here is what Cody did on youtube: an experiment.

Long story short, he made some mistakes while conducting. So the experiment cannot be reliable. Nonetheless he comes to conclusion that particle size is not a major parameter.

You can come up with many reasons against, such as why grass not tomatoes, but I tkink it is still very useful.

Thanks Cody!

that's great to hear. I've tried a variety of methods and my conclusion is I am only willing to stomp on it, nothing more. I tried blending it and all that's going to do is get me buying more blenders. The other methods just cause me heartache.

This is an interesting video.  I am reluctant to come to many conclusions from it.

I became skeptical at first when he said that inoculating your biochar so that it is full of life takes several months at a minimum.  I have shown data in this forum that shows that that is not true.  I inoculate mine typically for a week or so.  https://permies.com/t/151346/year-biochar-results


His soil appears to be astonishingly dry-like powder.  That would favor large chunk size for him, but not for everyone. That's the conclusion that these guys came to, and it makes sense, when you think that a larger chunk will store water like an underground sponge. https://permies.com/t/151845/Biochar-fruit-trees-podcast-Orchard

I think he's right about the factor of the chlorination. It will damage the ability of the biochar to hold microbes, since it is there to kill microbes.

It's hard to imagine that particle size doesn't matter.  My friend, a Phd in Materials science, explained that smaller particle size means more access to the microbe hotels, and therefore a greater effect.  

I agree with S Ayalp that growing grass is not very hard and not too applicable to permaculture. Tomatoes, fruit trees, berry bushes or almost anything complex would have been a much more applicable test.  

I applaud him for trying to be so careful in making as objective of an experiment as possible.

Even if there are problems with this experiment, I applaud him for doing it.  We need more data, and interpretations of data.

John S
PDX OR

From what I understand the requirements for differing particle size will depend on the main objective of adding Biochar to the soil.  Smaller particles will have dramatically more surface area and, as such, be able to support more surface microbial activity, the volume of such particles will be lesser and therefore be able to absorb and hold less water.  Larger particles, moving more towards lumps, will have much less surface area and a much greater water holding capacity.  

I’m preparing a Biochar compost mix to amend a very sandy soil in a fairly dry climate with sporadic rainfall so have opted for more larger particles as water retention is higher on my list of priorities. I chopped the char with a spade before removing it from the burn pit whilst it was still damp, reducing dust particles to a minimum.  For smaller particles I would just have chopped for longer.
It’s now blended with the compost, absorbing nutrients and growing microbes in preparation for use in the spring.

I agree with you, Sam Rellim.

I have posted this elsewhere in this forum.  In your case, larger clumps makes more sense.  When it tends toward dry, large clumps are better, to retain moisture in the soil.   I wonder if the biochar gets inoculated more slowly this way,  and if it becomes effective and helpful more slowly this way.  I am extrapolating from how when you put uninoculated char into your soil, it is less effective for the first year or so, before eventually becoming biochar and helping the soil.   It seems that the inside of a large clump would become inoculated more slowly.  

I live in a frequent rainfall area and we have clay soil, so my strategy would be different than yours.  

John S
PDX OR

Phew, it seems like a lot of work to grind char in a precise manner. Interesting scientifically, and no doubt it has more relevance in container gardening or commercial applications where people do the cost-vs-benefit-vs-time analysis.

To my mind, char is a long-term proposal. The stuff that I can't get finer than chopping with a sharp shovel will be ground up by freeze/thaw over time. It will do its magic long after I'm gone, and the next gardener will benefit, perhaps without realizing it. My shadow has left the soil deeper and richer. That thought sits very well with me.

I’m sure you all have run across “Dr TLUD”s website, I thought this analysis of biochar was really interesting http://www.drtlud.com/wp-content/uploads/2012/08/All-Biochars-Version2-Oct2009.pdf

I had never heard of or seen Dr. TLUD's site.  Thanks for adding the article. Very technical discussion.  I learned from it, even though I am neither an engineer, nor a professional scientist. My brain hurts.  Now I need a beer.
John S
PDX OR

Dr. TLUD's website:

http://www.drtlud.com/biochar/

John S
PDX OR

Size definitely matters. I prefer mine to be <3mm.
That size has the most impact on improving heavy clay soils. Bigger pieces, anything that manages to gall through a 10mm mesh screen is still great due to its larger water hokding capacity which Sam already mentioned. Bigger than that is a waste of potential in my opinion.

If you can't be bothered to crush it, which is understandable because crushing it is most of the work unfortunately, then you can opt to use the char in deep litter animal systems and if you sieve the compost at the end of that process you can just toss everything back to the deep litter system after you've sieved your compost through a 10mm mesh screen. Ideally with a large tumble sieve so you are not wasting time with manual sieving.

Alternatively you can use the larger biochar pieces to create water reservoirs in wicking bed systems, use it in grey water systems, banana circles or even fill whole trenches with it to essentially create permanent hugulkulturs that won't sink or break down.

A short clip of my compost sieve
https://youtu.be/iC3_f6NFao8

What do folks think about biochar powder, inoculated in compost tea and applied through a drip system?  

I have fungal dominated compost with loads a humates in three different Johnson Su bioreactors.  I'll be using it in an IBC tote compost tea brewer to make fungal dominated tea (I hope).  I'm planning to apply it through a drip irrigation system.  I've applied lots of compost last summer via shovel (~160 cu yds) and would like to apply another ~200 yards this summer, but the amount needed is starting to become time prohibitive.  I have ~4 acres of elderberries (~10,000 plants), in the Missouri Ozarks where elderberries are native.  My soil structure still isn't very good (sand or clay).   I notice that some products for drip systems contain biochar.  I've been looking into biochar for quite a while and have the start of a TLUD system but never finished it.  I've watched and read the links in this thread on biochar and particle size.    Anyway, that is the background....

I'm wondering if it would work to include biochar in the compost tea brewer and then distribute it through a drip system.   Any thoughts or experience from folks would be welcome.  thank you

Mike

Douglas Alpenstock wrote:will be ground up by freeze/thaw over time.

I used to think that very thing, but it hasn't worked as far as I can tell.  The larger chunks I have used don't seem to have broken down at all through several winters.  I may be mistaken of course, but that seems to be the case.

I personally use everything from powder to larger chunks.  The largest are maybe an inch or so on any given side.  I'm not convinced it matters much, but I'm open to the idea that it does.  So far, I'm just using different sizes because my "run over it" method of crushing in no way makes it uniform sizes.  The charcoal dust is from both crushing, and to a far larger extent, the very small wood shavings I have used in the last couple batches.

I don't know what kind of drip system you have, but mine gets clogged by powders.  I would input the biochar directly into the soil as I do now.  The compost tea helps by adding the microbes, but with biochar, it is the product itself that provides the hotels for microbes.
John S
PDX OR

I got lucky and found a machine that crushes my biochar into a nice crumbly mixture. Particles range from fines up to about 5mm with the occasional bigger bark flake or chunk that got through when a piece of unburnt material deflected the movable roller.

Action shot:

Phil,

What kind of machine is that?

John,

I have drip tubing with built in 0.5 GPH emitters.  I was thinking/wondering if it would essentially stay in solution or whether it would clog things.  

I noticed that Pacific Gro has a fish hydrolysate product that includes biochar that is supposedly suited for drip irrigation, I've been looking at their product for my compost tea so I didn't feel too bad about asking them about how this produce works in a drip system.   If I could sustain a rate of adding it by hand to the soil around each plant and do a plant every 10 seconds (doubtful over extended periods) it would take 28 hrs.  so yeah, if need be I will apply it by hand, but if I can avoid that labor I'd rather do that.  Alternately I guess if I had enough innoculated biochar I could broadcast it with a spreader.  Thank you for the feedback.

Hey Sam, it's a custom rig. Two 300 mm steel drums, powered by a 5HP 3-phase motor. It was built to crush bottles at a recycling facility. Then it did a gig pulverising volcanic scoria. Now it munches my biochar, and I'm just about to load the trailer with another half cube and go feed it. A really lucky find, since I'm gearing up to sell biochar and getting the crushing issue sorted was holding me up for a while.

John - I asked the vendor that supplied the drip tubing.  The description for the drip tube say "Large turbulent flow path allows particles to pass freely".  So I asked how large of particles.  I'll post what I learn...

Phil,

That is awesome.  very nice.  For a while I was looking at vacuum impeller units but they are pretty expensive and I wondered how long the impellers would last.  Your machine seems like a better approach.

Sam-I have used fish hydrolysate a lot when making my compost tea.  After bubbling it, typically for 24 hours, I would have dregs at the bottom, whether I was making a fungal tea or a bacterial dominated tea.  I poured the tea out from the top while making it, and sprayed it through my system.  I would have to manually unclog the sprayer from time to time. I always filter it before going into the sprayer, however,.  At the end of spraying, I pour the dregs as a drench onto plants.  I bet there are other ways than digging it in.  There may be some kind of a wheeled barrel cart with a giant spigot that wouldn't clog.  You may have to build it.  I have read so many innovations on this website that I want to encourage more so that people in every different situation can benefit from these practices.

John S
PDX OR

John,

Any fish hydrolysate products you would recommend?  Do you worry about the sprayer tip not passing the hyphae or damaging it.  

I was thinking for foliar teas I would spray from up top and for soil teas try to go through the drip line.  I'm still waiting for a reply from the drip line vendor so we'll see.  lots to learn...

Elaine Ingham used to teach classes in my area. She mentioned that if your screen is too fine, it won't be good for fungal teas.  They require a large molecule to be effective. If you use a cloth, you will filter out the good microbes you are trying to input into the plants.  I have experimentally confirmed this.  One approach that they recommended was to use a paint strainer from a paint store.  They prevent bigger clogs, but retain the size needed to have the good stuff intact.  It made a huge difference, especially in battling fungal diseases, like scab or rust.

My state has tragically banned the sale of fish hydrolysate to "protect us" from doing something that might harm us!!   I now just buy a piece of fish from the market, cut off a small piece, chop it up in the blender and use that. I cook the rest.  

John S
PDX OR

I'm trying to imagine how someone would do harm with fish hydrolysate are teenagers trying to huff, snort or smoke it?  pure insanity.  

As for mesh size, I believe I heard that 200 micron mesh would be fine for fungal tea, does that sound right to you?

Phil Stevens wrote:I got lucky and found a machine that crushes my biochar into a nice crumbly mixture.

That looks like a grain roller from my farm boy days. It crimps grain kernels, crushing them so cattle/chickens could actually digest them instead of passing them through whole. I remember a big row of removable magnets over top that would catch larger metal shards before they passed through.

The place (Drip Depot) where I got the drip tube got back with technical information.  The drip tube has labyrinth filters at each emitter designed to reject particles >254 microns.  

Looks like I will need to do a small scale test...

Sam Thumper wrote:I'm trying to imagine how someone would do harm with fish hydrolysate are teenagers trying to huff, snort or smoke it?  pure insanity.  

As for mesh size, I believe I heard that 200 micron mesh would be fine for fungal tea, does that sound right to you?

I think when the government does this, it is usually protecting some company that donates money to a powerful congressman to lock up access to their product only.

Yes, 200 microns sounds right.

John S
PDX OR

John,

I've been thinking more about how you make your own fish hydrolysate.  I should have thought about that.  An acquaintance of mine manages a fish hatchery, I've asked him what they do with the dead fish.  That said, now I'm wondering if they dose the tanks with antibiotics.  Any references for making hydrolysate that you would recommend?

I was on the yahoo groups compost tea group, and there was a guy from Alaska who had a lot of details. I think he sold a compost tea brewer. This was in the early days and both Elaine Ingham and Jeff "Teeming with Microbes" would chime in frequently.   Yahoo groups doesn't exist anymore. Some people sell the stuff that is actually boiled first, which isn't fish hydrolysate and isn't nearly as good.  The microbes have been killed.  When they banned fish hydrolosate here in Oregon, a guy just suggested that I buy a small piece of fish , chop it up and put it in a blender, put it in the compost tea, and it worked really well.  I would just proportionalize it for a larger set up.  It doesn't smell as bad, but it really needs to be chopped up in the preferably high speed blender.  Chunks of fish won't do it.  

Sorry, I don't have any ready-made links with recipes.

John S
PDX OR

I think this was the guy from Alaska.  HUGE amount of information here, mostly on compost tea, which as most here know, is one of the most common and recommended inoculants for biochar.

http://microbeorganics.com/

John S
PDX OR

I use the quench method to make my char.  There is rarely a piece over an inch or two.  Once it is charged, I surface broadcast it around my trees.  I figure it will eventually get buried by fallen leaves, manure, dead grass etc.  But before it does my hooved animals will break it up a bit more.

Fast method to make small sized biochar ->

s


I have done this and I can attest that it makes fast work of breaking up the char and make about 1/8th inch biochar,  with the water there is no dust to deal with.

I am testing some biochar in my aquaponics grow beds as I am curious as to if there wil be enough nitrogen.


There is much to be examined with biochar, and I don't believe all experiments are the same.

I love Cody's work as he does the experiment, then honestly looks back at the experiment to see what the results were.       The experiment needs to be done again as Cody said using consistent water source without killing the bacteria.

I was watching a video of a man who runs his truck on wood  "Wayne Keith".    And he noticed that where he dumped out the charcoal from his wood gas reactor the grass was much greener than the grass elsewhere.       This brings to my mind what if we were to just dump the charcoal at the top of the garden bed and see if there would be results......    


There is tons of room for experimentation for biochar.
 

This is a fantastic development Mart!  This is the best innovation in grinding biochar that I've heard since driving over it between panels of plywood, which I use.  I believe that I will investigate pricing of a garbage disposal today.  It will cost money, of course, but it seems that since I have seen the benefits of biochar, it could be a reasonable cost at this point.

I don't think it would be such a good investment in many parts of Australia, between Socal and Western Kansas in the US, between Spain and Western India, or in North Africa or South Africa.   The nearly complete grinding will damage the water retention benefits in favor of the bioavailability of the microbe housing.  However, I live in an area with plenty of rainfall and moderate evaporation, so it would work well for me.  

It makes me want to check out his book to see if there are other great innovations inside.

John S
PDX OR

Even powdered biochar will still have about the same water retention as granular or lump material. You would need a really fine grind to start breaking it down to the point where you lose the porosity. I don't think a garbage disposal will get it that small....we're talking about nanometer scales here. Try it and see...weighing up samples is easy.

The bigger discussion is the actual water holding capacity of pure biochar compared to mixing it with soil. My average sample holds three times its weight at saturation, but in consulting my Big Book I see a caveat in chapter 19: Much of this is in the spaces between the particles, and when you get soil into the picture things change. The other thing that happens is that clay and soil microbes will clog pore entrances over time, which reduces the ability of water to get in and out quickly.

One change I would make is to get a pitcher of well water, rain water, or in my case, filtered water to put in there. I don't want to kill the microbes with city system water with flouride, chlorine, chloramine, etc.   I think another is that I would grind some biochar, wait while I put in one of my inoculants into the ground biochar in the bucket below, grind some more, wait again while I add another inoculant, etc.  That gives the machine a rest so it doesn't get too hot.  It seems that you can get a small disposal at a big box store for about $50.  I think I'm going to give it a shot.  Great idea.

John S
PDX OR

Yeah, definitely go with untreated water. Or go straight to your inoculating solution. This has some real potential for small scale and as long as you don't have rocks in your original product the unit ought to last quite a while if you're giving it plenty of rest between cycles. Heat building up in the windings is what tends to kill these things.

Phil,
I  think you've got a good point about how YOUR soil interacting with the biochar is a big differential.  We have really thick clay here and lots of rainfall, so I'll grind it as fine as I can.  I don't think that the biochar will remain separated from the soil for very long. Even fine biochar mixed with clay won't drain super fast, I don't think.  It should retain "housing" for microbes though quite well I should think.

If someone had gravelly or sandy soil in a hot dry place, bigger chunks of biochar would be preferred.  I don't live in such a place, but I have read about this from experienced biochar users in such places from more than one source.

JohN S
PDX OR

I get what you're saying, John, but I would do the exact opposite. Bigger chunks for clay in order to get more aggregate structure, and a fine grind for sand. I like having a blend of particle sizes because of the different functions they perform and the fact that our soil, although it's classed as silt loam, has tendencies similar to clay in terms of waterlogging when wet and turning to brick when it's dry.

Our climate is pretty similar to PNW, mild with wet winters and dry summers, and we have a volcanic ash component that gives us a clay fraction, but nothing like Cascades Cement. What I'm seeing in the beds with significant amounts of biochar is that the topsoil is far more friable than it used to be and doesn't go rock hard when it dries out.

It might be worth trying a couple of test plots side by side to see if fine vs coarse makes any difference in your situation.

I am thinking like the other sources that I have read on the topic.  Clay retains moisture really well.  Biochar when ground fine has an unbelievable number of connection/attachment points.  Then the clay doesn't bunch up. It's like loam.  Microbes can get in there, because there are these tiny spaces for microbes, air, and gas exchange.

Sand dries out really quickly.  Biochar powder in dry sand is dusty and ineffective.  It can blow away.  A chunk of biochar, even if it's only the size of a marble, will retain moisture within itself.  The tiny root hairs will find the little chunk of moisture and the plant will be able to withstand the long dry hot summer.

That's how I think about it.

John S
PDX OR

Phil Stevens wrote:Even powdered biochar will still have about the same water retention as granular or lump material. You would need a really fine grind to start breaking it down to the point where you lose the porosity. I don't think a garbage disposal will get it that small....we're talking about nanometer scales here. Try it and see...weighing up samples is easy.

The bigger discussion is the actual water holding capacity of pure biochar compared to mixing it with soil. My average sample holds three times its weight at saturation, but in consulting my Big Book I see a caveat in chapter 19: Much of this is in the spaces between the particles, and when you get soil into the picture things change. The other thing that happens is that clay and soil microbes will clog pore entrances over time, which reduces the ability of water to get in and out quickly.

Yes water will be held in the pore space between biochar and soil particles but the biochar itself will certainly hold less water the smaller it gets.

An easy way to demonstrate this is taking well drained biochar chunks, maybe even drying them in the sun for a day so they are certainly not dripping or anything. Then run them through a hammer mill and witness what a gooey mess it will become as it releases a large amount of water.