Biochar is a wonderful soil amendment.  It is made from organic material burned in the absence of oxygen via pyrolysis.  Once burned, the char is processed in a method called activation, which hydrates the char and gets the mineral retention and microbial life a kick start.  Biochar may be combined with clays to form a super-charged soil amendment.  We like to add up to 10% activated biochar to garden soil.  It is an excellent addition to raised beds and to grow mixes.

Here are a few of the benefits:

  • Water retention (in the char pores)
  • Microbial life density (they live in the pores)
  • Mineral retention (trapped in the pores)
  • Nitrogen trapping
  • A long term source of soil carbon

All of these are useful in our loamy sand. This is in addition to biochar’s role in sequestration of carbon for the long term.

There is no end to trimming and pruning woody materials on our one acre ranch. Given the success of biochar in a few garden beds, we were keen to spread it over larger areas. Several years ago we purchased some biochar for an experiment on new garden beds. This was right before the beginning of the Great California Drought and we were not able to follow through due to lack of irrigation water for three summers. However, we did have enough left over biochar to dose one of our growing beds in the main garden. That bed has flourished, even more than the rest of our mineralized garden. It was not a controlled experiment, but the biochar seems to have helped.

We are always in the mood for appropriate technology, especially when it is elegant and inexpensive.  So when we heard about the Kon Tiki biochar kiln and how it makes inexpensive, copious biochar efficiently and with minimal smoke our ears perked up.

Many biochar retorts we have seen are complicated affairs requiring external energy to heat the biomass stock material to the temperatures needed for pyrolysis. Not so the Kon Tiki. It’s secret is in the shape. The inverted cone contains the fire in such a way that the biomass stock is not burnt up but the gases are, all without producing excess smoke. It uses no external heat source. And it’s simple to construct if you’re handy.

We have a smaller version that is designed for backyard biochar production – the CharCone.

But there is no need to buy anything in order to make biochar.  It is possible to dig a pit the right shape and make biochar in it. See this presentation.