Biochar

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 little ears perked up.

Most biochar retorts we have seen are complicated affairs requiring external energy to heat the biomass stock material to the temperatures needed for pyrolysis, with fairly poor efficiency. Not so the Kon Tiki. It’s secret is in the shape (physics, friends). 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.

The link to the Kon Tiki description is here.

Now, by means of full disclosure, we admit that we have not tried the Kon Tiki kiln or other similar kilns. We do have our eye on one suited to backyard charcoal production – the CharCone – here.

If you can’t afford either of these options, it is possible to dig a pit the right shape and make biochar in it. See this presentation.

There is no end to trimming and pruning woody materials here on the Rancho. And given the success of biochar in a few garden beds, we are 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 the last 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. Biochar is supposed to aid:

  • Water retention (in the char pores)
  • Microbial life density (they live in the pores)
  • Mineral retention (trapped in the pores)
  • 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.