Making Biochar

As we’ve been building our compost piles, I’ve also been looking for other organic ways to build our soils. According to Biochar International adding biochar to the compost or soil can enhance the soil by improving water retention and providing a better micro climate for soil microbes. OK I’ll give it a try – anything to improve our soil.

First thing I need to understand is biochar is not the same thing as charcoal from a fire pit. It’s produced through a process called pyrolysis which involves heating biomass with little or no oxygen to drive off volatile gasses. The product produced is a fine-grained, highly porous charcoal that helps soils retain nutrients and water. What’s great about producing your own biochar is that you can use whatever waste biomass you have available. You don’t have to cut down trees to produce biochar.

So how do we make biochar? There are loads of examples of biochar kilns or retorts on the internet. We decided on a simple to make TLUD (top lit up draft) kiln using a 44 gallon drum with a smaller inner drum. Marc, Rayape and I spent a day converting the drum into a kiln and making a chimney with a piece of flat iron. Again thanks to the internet we learnt how use a riveting tool and how to change the cutting blade on the grinding wheel.

We used coconut shells left over from cooking for our first firing and old bamboo posts for our second firing. We collected firewood left from clearing the area where Siana and Marc set their tent up so no additional trees were cut. It was really amazing how quickly the temperatures built up once we put the chimney on. It just roared!

Now we have plenty of biochar for adding to our current compost piles. In future I think we’ll need a larger can for the inner drum.