• CadeJohnsonM
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    8 months ago

    This is a nice informative video. I wish the creator would tell us his qualifications - though at the end he does refer to a source for his ideas - Living Web Farm (which I have not checked out).

    He states several times in the video that crushing biochar is detrimental, and maybe he is right. But the high porosity of biochar is a microscopic feature which may or may not be affected by breaking up the char. In the related material, activated carbon, particle size is chosen on the basis of optimizing flow of air or water through the media, not because it has any effect on the capacity of the carbon to adsorb. So put a pin in that point - it may be inaccurate. Big pieces may take longer to adsorb AND release nutrients. The interior of big pieces may not be accessible to plants or fungi (though in the fullness of time the carbon pieces will break smaller and smaller).

    Biochar is becoming one of the most common and discussed ways of CDR - it is so accessible to the average person in many variants. I suspect that in the long run, the means of making char will become much more sophisticated and the gas produced by pyrolysis will become a valued product itself - not something that we’d want to burn. But that is for another decade or two . . .

    • Treevan 🇦🇺@aussie.zone
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      8 months ago

      Just finished as well. For anyone reading, 1.75x or 2x speed is still understandable.

      It’s a good starter video. It probably oversells the benefits a tad, the ‘potential’ is there for improvement over time and I guess he indicates as such. I’m always wary about “miracle” product labeling.

      There are quite a few studies about biochar particle size which he didn’t reference, and as Cade mentions, the structure is visible only under an electron microscope, crushing the char into a particle size that matches horticultural sizing isn’t a bad thing. Dust has its issues, no one recommends biochar crushed to dust, not that I’ve seen anyway.

      I did a quick LLM search on particles and it references a couple of the particle studies:

      The ideal size of biochar particles depends on the specific application and soil type. Here are some key points to consider:

      • Water retention and availability: Smaller biochar particles have higher water retention and availability, making them suitable for light-textured soils[4]. Most biochar intrapores have diameters less than 0.01 mm, which provide a water potential of less than -16.5 kPa[2].

      • Improvement of heavy clay soils: Biochar particles smaller than 3 mm have the most significant impact on improving heavy clay soils[1].

      • Plant growth and biomass production: Plant biomass production is generally maximized at intermediate biochar particle sizes, with particle sizes of 0.5-2.0 mm showing the best response[3].

      • Soil hydraulic properties: Biochar particle sizes of >2 mm, 2-0.5 mm, and 0.5-0.25 mm are hydrophilic, whereas 0.25-0.063 mm and <0.063 mm are hydrophobic[6]. This can affect the soil’s ability to absorb and retain water.

      • Amazonian terra preta: Most biochar particles found in Amazonian terra preta are between 10 and 20 μm (micrometers)[5].

      In summary, smaller biochar particles are more suitable for improving water retention and availability in light-textured soils, while larger particles are better for enhancing plant growth in a variety of soil types. The specific application and soil conditions should be considered when determining the ideal size of biochar particles.

      Citations: [1] https://permies.com/mobile/t/152616/Biochar-particle-size-matter [2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5466324/ [3] https://www.mdpi.com/2073-4395/13/5/1394 [4] https://www.sciencedirect.com/science/article/pii/S1319610320301502 [5] https://sfbiochar.com/?p=en.biochar_preparation [6] https://bsssjournals.onlinelibrary.wiley.com/doi/10.1111/ejss.13138