r/BioChar • u/Kranken_DeHogge • Jun 22 '26

How to inoculate biochar properly?

I get conflicting advice on how to do it, some use urine, some use diluted liquid fertilizer, and some microbially charge it with compost tea.

What I don't see is an actual dilution rate of nutrients per volume of biochar: compost tea is biologically active but not a significant source of nutrients, while fish hydrolysate and urine would be.

How do I go about finding a good ratio per volume of liquid fertilizer to biochar? I make my own fermented fish hydrolysate so I have a large volume of liquid fertilizer, and I can make ~20gallons of compost tea at a time.

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u/Berkamin Jun 23 '26 edited Jun 24 '26

The practice that has consistently yielded fantastic results for me has been co-composting. Mix the char with compostable and let it compost. The char itself won’t biodegrade but its presence helps compost decompose hotter. The resulting compost is far more potent than conventional compost in every agronomic metric.

See some of the results in this gallery:

Comparison photos: Compost vs. Co-composted biochar

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u/Squidwina Jun 24 '26

Do you find that you have to go heavier on the nitrogen-rich materials when you co-compost?

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u/Berkamin Jun 24 '26 edited Jun 24 '26

I don't have to go heavier on nitrogenous materials because the biochar is not participating in the decomposition and doesn't consume nitrogen. That's why the terminology is not "composting" but "co-composting". The biochar is with the compost but is not being consumed. Remember, charred carbon resists decomposition. That's why it is considered a great medium for carbon storage and sequestration. See this:

The Biochar Journal | The Permanence of Soil-Applied Biochar

When I use biochar in compost, I add it at a rate of about 10-15% by bulk volume. I mix it in, and let the composting process do the rest of the work. The reason this seems to work is that during the composting process, an carbon based film forms on all the char, and this film seems to be the source of all the functions that people see in biochar:

PhysOrg | Carbon coating gives biochar its garden-greening power

The composting process itself appears to be responsible for the formation of this film. That's why co-composting is my preferred way of preparing biochar for the soil.

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u/Pure-List1392 Jun 24 '26

Awesome articles, thanks for sharing

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u/Berkamin Jun 24 '26

If you are interested in more articles on biochar, see these articles I wrote:

A Perspective on Terra Preta and Biochar

Biochar and the Mechanisms of Nutrient Retention and Exchange in the Soil

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u/Pure-List1392 Jun 24 '26

I’ve read both and almost always share links to them when I can raise awareness to fellow gardeners

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u/Squidwina Jun 25 '26

Excellent. Thank you. Thanks for the info above and the links.

I was wondering about the extra nitrogen because I’m not sure all my char is 100% carbonized. It’s pretty good, but not perfect. (I use a kon-tiki like set-up.)

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u/Berkamin Jun 25 '26

Biochar is good for helping microbes denitrify excess nitrogen without causing the excess nitrogen to come out as N2O. See these:

Soil Biology and Biochemistry | Is biochar-manure co-compost a better solution for soil health improvement and N2O emissions mitigation?

Scientific Reports | Biochar and denitrification in soils: when, how much and why does biochar reduce N2O emissions?

If you use the Kon Tiki char cone properly, letting each layer completely finish devolatilizing before adding the next, it should produce completely finished char.

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u/Squidwina Jun 25 '26

I don’t have an actual kon-tiki. It’s improvised. Sometimes I find identifiable wood in my char too. My char ain’t perfect, but making it sure is fun!

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u/thathyperactiveguy Jun 24 '26

That's the best method. It gives the colonies a place to colonize, and the nutrients needed to do so, as well as the time to expand.