Thoughts on Crushing Biochar

This was a response to a thread located here https://permies.com/t/242903/Breaking-char-smaller-pieces#2834559  but I felt it would be a good stand alone post too.  

First I want to say I love the responses by Michael Cox (in the original thread), and I agree we need not stress over crushing.  That said there is some real value so here is what I do.  Also like Micheal since I do almost open top burns (cone kilns) my pieces most start pretty small anyway.  The quench alone fractures things a lot.  So I recommend start with heavy quenching alone will save a lot of work.

When my burn is done I quench, I leave it over night in the kiln and move it to buckets the next day.  

I have two screens, one is half inch and one is quarter inch.  I chop a bit at the char in the buckets with a sharp shooter shovel (if you don't know this is what I mean, https://amzn.to/4eSWAbQ ).  I put it though the 1/2 inch screen and push a bit with a hoe when I do this breaks up more.  

I then put what went though the 1/2 inch screen though a 1/4 inch screen and separate into three grades.  

1/2
1/4
Large

I get about 2/3drs of a batch into one of the smaller grades.  Now if you are going to crush further you only deal with what needs crushing based on your goals.

You can toss the big stuff into a bag and do the drive over it with a vehicle thing now MUCH more effectively as you are dealing with less and well trust me it crushes better.  Put that back though the screens.  You could also do that with the half inch but I don't.  All up to you but again you are only processing the part needing it.  

What I do with each "grade"

1/4 and finer - Goes in my feed for Ducks/Geese/Chickens, twice a week a tbs goes in the dogs food.  Also what goes in my worm bins and the big thing is it is what goes in my potting soil/starter mix.  Any I don't use for that goes into animal bedding in the coop.

1/2 if I need more 1/4 it goes in a bag and gets a crush, otherwise into the animal bedding.  That is a 1-2 year process before it gets to a garden.  Because once a year the deep litter goes into bioreactors.  By then a lot of it is smaller anyway.  If not who cares, it works wonderfully.  

Large - most of this is about the size we used to call "nut coal" in the coal industry (about a nickel to a quarter in size).  None is ever very big.  So if I need more it gets the bag and drive over trick and a couple screenings.  And sorted again, into the three classes.  But what if i don't want to crush more.  First it is also fine in bedding but I think we are missing a reality here, biochar is CHARCOAL and damn good charcoal.  

So gasp I end up with may be 20% of a run as large, I keep it separate and when I want to cook with charcoal I use it for that purpose.  It is fantastic for it.  I use the "side baskets" (like this in a weber kettle https://amzn.to/3B1BIBn ) and it works way better than briquettes and you get a lot more in due to more space efficiency.  

I can hear it now (OMG it is for muh soils and my CO2 sequestrations).  Hold on, you cook all the time the heat comes from somewhere.  I am using huge amounts of waste that would otherwise all go back to the atmosphere in break down if I didn't make the char.  I get bad ass soil amendments, but I also get fuel from scraps.  

My reasoning is despite it sounding like a ton of work, it isn't, super easy and fast.  So I spend more time making char then crushing it.  So I make a LOT more.  So more goes into the soil in the end.  

I will also say I have used a wood chipper and it works wonderfully.  WHEN you get the moisture just right which can be tricky.  But doing the big stuff after screening usually can do that.  But this all seems VERY hard on the chipper and when it is too wet it is a real tar looking mess.  One hack is after you do it put a few buckets of wood chips in to help clean it out and toss those in the compost or bedding but I have honestly quit this for a simpler model.  

Last it is really cool to make char in a grill then cook in that grill with some of the char you made.  Do you own a Weber Kettle Grill or one of the hundreds of clones of it, then you have a kiln.  Don't have one, check Craigslist or FB Marketplace you can likely get one in good shape for 50ish bucks.  Hell get two at that price.  A kettle is a PERFECT cone kiln, dare I say it works better then some you can buy marketed as kilns.  

Here is a video of me using one to make biochar, I just added a rotisserie ring, so I can up my yields by about 25%.  Any questions ask, I don't post here often but I always answer questions when I do so.

Happy to hear you say we need not worry about crushing because it's a hunch I've had from the beginning and I've only crushed for specific needs a time or two.

I've got two vessels of top down burned biochar mixed with an entire hunting lodges worth of teal carcasses, what should I expect to see when I dig into them? I don't have plans for it other than to leave it for a couple years and see what it turns into. And then consider it's application.

Also wanted to say thanks for being enthusiastic about biochar. Between you and Skillcult I've learned a lot and it's only encouraged me to use it more and do more experiments. If you're ever in East Texas give me a shout, I can send you home with some fruit trees. I've been wantin to meet ya for a while and I intend to get out to one of your workshops one day.

And using old grills for a kiln is actually genius, they're a southern staple, every other yard has one.

Thanks I just played with an idea to make crushing it a bit more effective with the drive over a bag of it method it worked really well.  Video will be out in about an hour as soon as it renders.  

Basically by screening before crushing it crushes a LOT better which makes a hell of a lot of sense when you think about crush vs. compact and empty spaces.  

It effectively with very little work reduced a full bucket of "large" to a third of large, a third of 1/2 and a third of fine.

I did it with a bucket of 1/2 and got about 1/3rd fine and about half of still 1/2.  

Really simple method and I don't think I will be putting it into my chipper ever again.  

Here is a video that shows my sorted sizes and what happens when you sort BEFORE you crush with the drive over it in a feedbag method.  The improvement is amazing

I drop a piece of old metal plate about a quarter inch thick and eighteen inches square into the wheelbarrow, tip a feedbag of charcoal on top and plonk the top of a sledghammer on it a few times. Layer it through the compost, preferable with a layer of carp over it and if possible several months before I need it.
I recently planted out a heap of my bug damaged feed corn- got thirty three plants from about five hundred seeds. I planted the rows on my absolute best compost- with the added fish and charcoal- and with big gaps of no corn. Some of the plants were nearly a foot high but I dug them up last week and moved them into a block for better pollination. Since then we've had several warm to hot days with lots of rain- the plants showed no sign of stress from being moved which was a relief. Now I just need to figure out what to plant on the compost where the corn was supposed to be.

Not crushing and not inoculating will still work. It just depends on your scale and your time frame. If you've got lots of acres and you're making your biochar in a 100 foot long trench, crushing and inoculating are probably logistically difficult.  If you are living on your farm for the rest of your life and you're young,  you've got a lot of time to recoup your investment.  

If you've got a barrel or less of biochar on a small urban or suburban lot, crushing and inoculating is relatively easy.  In a small space, you probably don't want to give up 2 years of fertility on every bit of land you biochar every week.  You just don't have that much space, and to render it unproductive for 2 years is a waste of time. A lot of people also are planting in containers or small beds.  Most Americans move at least every 5 years, so you're amping up the productivity for someone else, who will probably not appreciate it.  I sold my permaculture suburban lot, because I needed a different place.  The guy flipped it, made a lot of money, and now it has nothing to do with permaculture.  A lot of that work has gone for naught.

John S
PDX OR