In my previous post we looked at What is Biochar and why you should be interested.
In this post we will specifically look at how to make it at home for your home growing..
I was a complete novice going into this- I had read a lot and done the research, but no one had shown me any specific methods of how one might make the stuff- so it really was a “learning by doing” experience.
Materials you will need:
- Metal container- needs to be tight-closing and sturdy as it will be acting as your ‘biochar cooker’.
- Organic material for ‘charring’- many people suggest anything from leaves, brambles and wood chips will make effective biochar, but as a first attempt I would suggest cut hard wood pieces and/or twigs
- Fire place/pit/drum – as you will see my experience suggests a drum or pit will work better, as you can contain it better, it uses less fuel and creates greater heat intensity- charring quicker and better.
Step One: Preparing your container.
I got these two containers (pictured) from my local recycling center for a pound. They are old metal biscuit containers and will work perfectly for the job.
They are very tight-fitting, which is essential, but I will need to make “escape holes”- under extreme heat the pressure inside the containers would potentially force them to explode if there wasn’t a small out-let for the gases of the charring wood to escape from. The hole can’t be too large, or it will allow too much oxygen into the container- allowing flames to enter, at which point your wood would burn off to ash completely.
Step Two: The wood to char.
As this was an experiment, I wanted to experiment with different types of wood. In container “A” I filled dried twigs and sticks, that would usually end up as kindling on the fireplace. In container “B” I added larger blocks of cut wood- I wanted to see how a denser material would char in comparison to the twigs. This was mainly Ash wood with a small amount of Hazel. I suggest you just experiment- some people have reported success with charring anything from leaves, to bark, to brambles-as long as it’s dry and organic…give it a go!
Step Three: The fire.
In keeping with my “experimental approach”, I decided to create two different fires. One would be on the ground, where I would rest a container on the burning embers, whereas the other fire would be in a fire barrel/drum- where I could attach the container just above flames and control it’s exposure to the heat easier. Although the fire drum takes longer to create glowing embers (due to less oxygen exposure than an open fire), the heat intensity is eventually far greater (for the same reason) and I also used less fuel for it. Hindsight would suggest the barrel method in future, but I do apprecikate not everyone ahs access to one, so the open fire will char just as effectively.
Step 4: The waiting game..
Once you have placed your filled container onto the heat source, it’s a matter of waiting and watching. Make sure your hole in the container isn’t allowing flames inside and keep your fire stoked.
From the picture in step three, you can see a plume of what looks like smoke coming from the hole in the container- this is actually the gases of the wood. They are actually extremely combustible- if only there was a way of retaining them..
Step 5: The finished Product…
Depending on the container, woods you are using, heat intensity of your fire etc.. the time to char will be variable. The twigs on the open fire took about an hour to fully-char through, whereas the blocks of wood in the drum took only 40 minutes- a clue is shortly after the gases lose their white colour. If you do take it out to check and notice it is too early, you can always put it back in again, just make sure it is closed tightly- an extreme change in temperature can cause the tins to change shape.
Step 6: Storage and Pulverization.
Once cooled, check charring is consistent all the way through. At this point it can be pulverize to a powder, or left until needed. The best mess-free approach to this, is adding the contents into a strong plastic bag and smashing it up in there. If you don’t plan to use the Biochar in your compost or soils for a while, keep them in a tight container and somewhere dry until use.
I will shortly add another post on how to do this step more fully and then how to best apply it to your garden, so keep checking back. Any feedback, questions or your experiences would be greatly received in the comments section below or via my contact page at the top.