What biochar actually is

Biochar is charcoal-like material produced by burning organic matter — wood, crop residue, husks — in a low-oxygen environment rather than a normal open fire, which leaves behind a porous, stable form of carbon rather than burning the material completely to ash. Worked into soil, biochar can improve water retention and provide a long-lasting habitat for the beneficial soil organisms covered in our soil health training, in a form that persists in soil for years rather than breaking down within a single season the way fresh compost does.

A simple method for making small batches

Producing biochar at a genuinely small, household scale does not require specialized industrial equipment. A simple method uses a metal drum with a smaller container of dry organic material placed inside it, sealed with a tight-fitting lid with a small vent hole, then heated from outside by a controlled fire around the drum; the limited oxygen inside the inner container carbonizes the material rather than burning it fully to ash. This method takes practice to get right and produces modest quantities at a time, which suits the scale most of our members are working with.

Preparing biochar before use

Raw biochar straight from production should not be added directly to soil, since in that state it can actually draw nutrients out of the surrounding soil rather than contributing them. We teach members to 'charge' biochar first by soaking it in compost tea or a diluted manure slurry for at least a week before working it into a bed, which allows the porous structure to absorb nutrients and beneficial microbes rather than pulling them from the soil once applied.

What biochar can and cannot do

Biochar is not a substitute for compost or regular organic matter addition; it is better understood as a long-lasting structural improvement to soil that works alongside, not instead of, the ongoing organic matter practices covered in our soil health training. Its main practical benefit for our members is improved water retention in Nairobi's sometimes sandy or compacted urban soils, which matters directly for households already managing tight water budgets through mulching and drip irrigation.

We are still building experience with biochar within the organization, and we present it to members as a promising but more advanced technique to try once the fundamentals — composting, mulching, sensible watering — are already well established, rather than as a starting point for someone new to growing.

A genuinely low-cost soil carbon option

For members with access to a reasonable supply of dry crop residue or offcuts that would otherwise be burned or discarded entirely, biochar production turns a genuine waste stream into a soil improvement input at very low cost — the only real expense is the time and care needed to run a safe, controlled small batch. As with any new technique, we encourage members to start with a small test batch and a small test bed before committing significant material or space to biochar production.

Safety considerations when producing biochar

Producing biochar involves a controlled fire, which requires the same basic fire safety precautions as any open burning — a clear, non-flammable area around the production drum, water or sand on hand in case of an unexpected flare-up, and never leaving an active burn unattended. We treat these safety basics as a required part of biochar training rather than an optional add-on, given the real risk of an uncontrolled fire in a densely built area like Babadogo.

Members interested in trying biochar production for the first time are encouraged to do so alongside a more experienced member or trainer for their first attempt, both to learn the technique correctly and to have a second person present for basic fire safety.

We present biochar to members as a promising but more advanced technique, worth trying once the fundamentals of composting and mulching are already well established, rather than as a starting point for someone new to growing. As with any new technique, starting with a small test batch and a small test bed avoids committing significant time or material before a member has confirmed it works well on their own specific plot. We continue to build our own institutional experience with biochar and will update this guidance as we learn more about how it performs specifically within Babadogo's soils over multiple seasons, since our current understanding, while promising, is still based on a relatively small number of member trials rather than extensive local data.

Key takeaways

  • Biochar is stable, porous carbon produced by burning organic matter with limited oxygen.
  • A simple drum-based method can produce small batches at household scale.
  • Raw biochar must be 'charged' by soaking in compost tea before adding to soil.
  • Biochar complements, rather than replaces, ongoing organic matter and compost practices.

Frequently asked questions

Can I add raw biochar straight to my garden soil?
No — it should first be soaked in compost tea or a diluted manure slurry for at least a week, or it can draw nutrients out of the soil.

What's the main benefit of biochar for Babadogo's soils?
Improved water retention, which matters directly for households managing tight water budgets in sandy or compacted urban soil.

Is biochar a substitute for regular composting?
No — it works best alongside ongoing compost and organic matter addition, not instead of it.