What is your end goal with biochar?

John Suavecito wrote:Thom Bri-I would be careful if you have alkaline soils, because ash is so alkaline, that it may move your soil too far away from neutral Ph.

John S
PDX OR

Well then what is the best thing to do with the ash that is separated out from the biochar? Where does that go for optimum recycling? You can't make char without making some ash...in my experience, maybe almost equal amounts.

Denise Cares wrote:

John Suavecito wrote:Thom Bri-I would be careful if you have alkaline soils, because ash is so alkaline, that it may move your soil too far away from neutral Ph.

John S
PDX OR

Well then what is the best thing to do with the ash that is separated out from the biochar? Where does that go for optimum recycling? You can't make char without making some ash...in my experience, maybe almost equal amounts.

I don't worry about it. It gets mixed with so much other stuff. The oak leaves are acidic, for example, as are the tea and coffee grounds. If I suddenly start having trouble getting plants to grow, I'll consider worrying.

If you look at a natural burn, a forest fire, lots of ash left over. Farmers all over the world burn off the weeds and trash every year, not a problem. Ash is only a problem if it is concentrated, or if the natural soil is already tending alkaline.

I'm in the northeast of the US, so our soil is so acidic that I could add all the ash I can find and never end up with soil that is too alkaline. But if you already have alkaline soil and adding wood ash would be counterproductive, it could always be used for landfill cover (mixed with soil and other things).

That totally gets me thinking about biochar in landfill cover...it's better in soil, obviously, but when we're getting to the point where we're making SO much char we don' t know what to do with it, landfill cover wouldn't be a bad way to absorb odor and sequester carbon. </tangent>

Denise Cares wrote: "
Well then what is the best thing to do with the ash that is separated out from the biochar? Where does that go for optimum recycling? You can't make char without making some ash...in my experience, maybe almost equal amounts. "

I would be careful about your process if you are making as much ash as biochar. Maybe you are quenching it too late? I had to adjust the timing of my quenching at the beginning.  Especially if you already have soil that is alkaline.  I make only a tiny fraction of ash compared to my biochar, and my soil is naturally acidic.
John S
PDX OR

Started as just a way to dispose of deadfall/brush and get something out of it without having to buy a chipper.  Now I want 4 acres of terra preta.  Not sure how long I will keep up the current production rate though, it does take up a lot of time.

Gray Henon wrote:Started as just a way to dispose of deadfall and get something out of it without having to buy a chipper.  Now I want 4 acres of terra preta.  Not sure how long I will keep up the current production rate though, it does take up a lot of time.

Just think, thousands of years from now, some future civilization may be trying just what happened on your land to make it so much more productive than land nearby. Keeping future archeologists employed!

And your current rate is clearly quite a bit...there's no shame in slowing down. It's a lot better than stopping outright after getting burned out!  

Thom Bri wrote:

Denise Cares wrote:

John Suavecito wrote:Thom Bri-I would be careful if you have alkaline soils, because ash is so alkaline, that it may move your soil too far away from neutral Ph.

John S
PDX OR

Well then what is the best thing to do with the ash that is separated out from the biochar? Where does that go for optimum recycling? You can't make char without making some ash...in my experience, maybe almost equal amounts.

I don't worry about it. It gets mixed with so much other stuff. The oak leaves are acidic, for example, as are the tea and coffee grounds. If I suddenly start having trouble getting plants to grow, I'll consider worrying.

If you look at a natural burn, a forest fire, lots of ash left over. Farmers all over the world burn off the weeds and trash every year, not a problem. Ash is only a problem if it is concentrated, or if the natural soil is already tending alkaline.

That seems logical Thom.  I was also wondering what John Suavecito would reply since he's the one who gave the cautionary comment about it.    I see his reply now above.

Blasting dooks on charcoal till the day I die!  XD

Or using a 3" layer of homemade charcoal on the bottom of about 6" of woodchip dook matrix (tamped together such that the matrix supports a footstep without any significant movement, should it ever come to a footstep)

Leaving lush biochar soil in the wake.

In 2024 I completed one of my biochar goals.  I have a dug well and there was a large low spot not far from it that would just fill up with anaerobic muck.  When it was dry there this summer, I raked it all out and filled over it with a mix of sand and biochar so that the water could still sink there, but within this new biofilter.  Now when forest biomass drops in that spot it won't be staying wet for half the year and going anaerobic not far from my well.  It went from a bad spot to a beautiful forest garden path.  In 2025 I will be adding a few plants into it, including 2 juneberries.  Kicking myself for not taking before, during and after pictures!

As part of that project I also dispersed biochar in the forest widely around my well to further protect the water quality.  Besides helping the overall life systems in that space to thrive, biochar also adsorbs PFAS and heavy metals.  I live on a slope and sadly don't really trust the water quality coming off the neighbor's property.  

Earlier, I had a goal to biochar all of the trees that I thought  would readily benefit from it, like pie cherries and American persimmons.  Then I wanted to do all of the yard within a few feet. I waited on the trees that were already doing well.  The medlar was one that was doing really well, so I waited. After biocharring it, the flavor has improved, the length of the season has improved on it, and the size of the tree has grown.  Now I am considering that all of the trees that were already doing well, might also have a clear improvement anyway. So I'm biocharring them too.

John S
PDX OR

What is the goal is my question too?  My answer reading so far seems to suggest the answer is 25% of my soil should be char.  If the goal is super soil 4 feet deep that means I need roughly 27 acres by 1 foot (for a 4 component mix).  Do the math and convert back to cubic yards and that gives wanting to make 43560 cubic yards of char.  I would argue the goal is to slowly build for that watching when law of diminishing returns really slows down or goes negative.  If I can get to 50% or more then the goal is even tougher and if diminishing returns start at 10% then it is way less.  

The initial goal is 4 to 6 inches of each of the 4 components (soil, char, wood chips, high nitrogen bio-matter), in the garden space.  Even that is years off.

If you can get to 1% of your topsoil volume in the places that matter most, that would be a reasonable goal. I don't think anyone could realistically get much more than a couple of percent on a large scale given how much material that would require.

Phil Stevens wrote:If you can get to 1% of your topsoil volume in the places that matter most, that would be a reasonable goal. I don't think anyone could realistically get much more than a couple of percent on a large scale given how much material that would require.

I fully agree it is very unrealistic.  But it may still be a desirable goal as terra preta can increase the total soil of its type on its own.

My goals with biochar are 1) soil improvement, and 2) convenience.  My property produces volumes of woody debris, as any good permaculture property should.  I cut some for mushroom logs.  I use some to create brush piles for habitat around the edges of my food forest.  But what to do with the rest?

I refuse on principle to let the city haul it off.  I used to run what I could through a wood chipper, but that was too slow.  I have determined with some moderate degree of confidence that burning excess debris for biochar, although time consuming, requires less time and expense than chipping it.  This is the "convenience" goal fulfilled.  Plus, I value biochar as an end product more highly than just plain mulch, which I can import in bulk for nearly free in any case.

Biochar is more valuable in terms of $$$ as well.  My local Walmart sells a 20% biochar compost blend for something like $7/gallon, if I recall.  I don't recall who produces it.

I plan to divide the char I am producing into two streams.  One I will add to my own humanure composting system, ultimately feeding worm bins, and thus returning to my soil as biochar-enriched worm castings.

But the other I will add to a more conventional composting system in order to produce biochar-enriched compost that I can (hopefully) sell as a soil amendment on a local online farmers' market at an equivalent price to the commercial product I have observed.  With luck, I can earn enough selling this amendment to pay for the whole biochar production process.  If so, then I can consider whatever biochar ends up back in my own soil a pure bonus.

I will update in time as to how these plans worked out.  First, I need to build myself a machine to chip my charcoal into flakes ready to be inoculated via either of my two compost streams.

BTW, I am surprised to read several posters in this thread contemplating the possibility of "too much" biochar.  I seriously doubt that there can be such a thing as too much, either globally or in the context of any one person's backyard endeavors.  Granted, my suburban-scale homestead is a lot larger than many other suburban lots, at one full acre.  Perhaps there could be too much biochar in any one particular potted plant, but that's about all I am willing to concede.

I am not even attempting to calculate the total volume of biochar I might produce or what soil concentrations of biochar I might end up with.  I am currently burning whatever excess biomass I accumulate until it is all gone, and I'll do the same in the coming years so long as I figure that it remains a good use of my time.  And whatever amount of biochar ends up back in my soil, I'm sure I could use more!

My end goal has changed a little bit with biochar.  At first I thought I'd give extra biochar to the plants that were struggling.  I also want to give biochar to plants that only occasionally struggle. My pineapple guava shrubs did fine for 20 years, then struggled when it was really hot and dry one year.  I biocharred and mulched them, and I added ollas for the hot part of the summer. They did better and resumed fruiting.  However, that was the bare minimum amount of biochar.  It was just a circle around the dripline that was about 2 inches wide.  Since they clearly suffered in that drought and almost died, I want to avoid that situation.  I am adding more biochar around them so that they don't just barely survive.  I want them to be resilient and thrive.  Hopefully, this will help them even more.

John S
PDX OR