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Biochar and Its Many Forms
 Luisa Marin
Luisa Marin
23 December 2025 at 11:36 am

Activated vs Unactivated Biochar

Why the Difference Still Gets Missed, and Why Charging Is Not Optional

Biochar use is expanding fast across agriculture, carbon projects, and environmental cleanup. Yet one basic distinction remains blurred. Activated and unactivated biochar are often treated as variations of the same material. They are not. They serve different functions, behave differently in systems, and deliver value under different conditions.

Unactivated biochar is the direct product of pyrolysis. It has a stable carbon structure and a pore network suited for biological systems. In soils, it supports microbial habitats, improves water retention, and helps nutrients cycle over time. This makes it appropriate for soil improvement and long-term carbon storage, especially at field scale.

However, there is a condition that must be stated clearly.

Unactivated biochar intended for agricultural use must be charged before application. This is not a recommendation. It is a requirement, particularly for biochars produced at temperatures above 550 °C.

Fresh biochar has empty pore space and strong adsorption capacity. If applied directly to soil, it will bind nutrients and temporarily compete with plants. Yield drops, early growth slows, and users conclude the biochar failed. In reality, the process failed.

Charging biochar with compost, manure, digestate, microbial inoculants, or other organic matter fills pore space with nutrients and microorganisms. This accelerates microbial establishment inside the pore structure and aligns biochar function with soil biology from the start. Projects that skip this step undermine results and distort conclusions about biochar performance.

Activated biochar follows a different pathway. It undergoes additional processing with steam, CO₂, or chemicals at high temperatures to create extremely fine pores and high adsorption capacity. This is ideal for filtration, wastewater treatment, and contaminant removal. In soils, those same properties often work against agronomic goals. Nutrients bind too tightly. Availability drops. Costs increase without added soil benefit.

Much of the confusion comes from language. Activation is often framed as an upgrade. More surface area is presented as universally positive. In practice, performance depends on function. Soil systems need stability, biological compatibility, and proper preparation. Remediation systems need adsorption strength. These requirements do not overlap as often as marketing suggests.

Cost reinforces the distinction. Unactivated biochar delivers value in land systems only when charging and application are done correctly. Activated biochar delivers value only when adsorption performance is the objective.

The takeaway is direct.

  • Activated biochar is a precision material for cleanup.
  • Unactivated biochar, properly charged, is a soil-building material.

Treating them as interchangeable, or treating charging as optional, leads to poor results and avoidable skepticism about biochar itself.

Questions for the community

  • Where do you still see uncharged biochar applied in agricultural projects?
  • How often is charging explained as a requirement rather than a suggestion?
  • Should standards, training materials, and procurement language state this more explicitly?

Credit: Biochar Innovators Society, LinkedIn article

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  • Mike flynn

    15 January 2026 at 3:36 pm

    we use both activated and unactivated biomass chars. we primarily use activated wood char, as an ingredient, in a cascade to make different end products. The only time we use unactivated is when we can make time our friend and allow Mother Nature time to weather it. For example, we spread unactivated char, in the fall, knowing it will overwinter and be ready the following May.

    • Luisa Marin

      15 January 2026 at 4:33 pm

      Thanks Mike for sharing how you use your activated biochars and when you partner with Mother Nature to charge it slowly and naturally!! Star Struck

  • Mike flynn

    18 January 2026 at 12:34 pm

    Luisa,

    From a terminology standpoint, we, as soil&plant health product formulators (cooks with lab coats) like to differentiate biomass chars, as modified vs unmodified (raw). Because in addition to activation there are such modifications as encapsulation, microbial colonization/carrier, biostimulant coating, nutrient coating, for example. Biomass chars are an ingredient platform for innovation. Folks leave much value on the table when they view chars, as products, and think they are selling bread when they are really selling flour, in my most humble opinion.

    • Luisa Marin

      19 January 2026 at 10:29 am

      Mike, do you mind elaborating a little bit more on this? Biomass chars are an ingredient platform for innovation. Folks leave much value on the table when they view chars, as products, and think they are selling bread when they are really selling flour, in my most humble opinion.

      How can biochar producers and product formulators and users benefit from this point of view? Or what would be a recommended shift in approaching biochar more holistically?

      • Mike flynn

        19 January 2026 at 1:52 pm

        Luisa,

        If you look at biomass chars or any organic input, as ingredients, than you are open to looking for other ingredient pairings. This shift in perspective allows for recipe development. For example, looking at blends of different chars together rather than just the char you make. All organic inputs wear many hats at the same time. Looking at organic inputs as ingredients allows one to craft more resilient solutions. Mike

        • Mike flynn

          19 January 2026 at 2:00 pm

          Luisa,

          One more thought about biomass chars, as ingredients, we take the perspective that we are cooks, with lab coats. We are doing recipe development to create a resilient solution. We are not spending our time designing yet another trial to provide chars work. We learned that chars work 20+ years ago. Our goal now is the show how best to use the chars, in combination, to make craft an outcome that is effective, economical, and executable, as defined by the grower. It is a ‘village’ approach. Mike

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