Biochar - 2 drum method

There's a lot on the internet about biochar being really beneficial for soil fertility and as a way of removing Carbon from the atmosphere. The basic science seems to be that the charcoal provides " habitat" for the soil organisms and also helps prevent the leaching of nutrients by heavy rain.

One of the waste products here is palm fronds- they hang around seemingly forever without rotting and, as they are so bulky, they make the yard look untidy (not that we try and have a "show garden" ). My solution is to use them to make biochar that I then dig into the vegetable garden.

I use the 2 drum method as it is simple and effective. The outer drum is an old 44gal drum and the inner is an old galvanised rubbish tin. I cut up the fronds and pack as much into the rubbish tin as I can - stomping it down to fit more in. It is then stood upside down inside the 44gal drum and more palm frond pieces , bits of wood are packed around this and then it is lit. After it is obviously burning, the lid goes on. The idea of the chimney ( a piece of 90mm galvanised stormwater pipe) is to create draft and thus more heat. When the contents of the rubbish tin heat up, they release wood gas which ignites as it escapes from underneath, thus increasing the heat even more. I have used other methods to make biochar but this is the easiest and most effective albeit in small quantities.












I have put several batches onto the vegetable garden and did a small trial of lettuce and beetroot with and without biochar ( a row with some in the bottom of a shallow trench and another row without) The lettuce was definitely better with the biochar underneath. The beetroot was much the same but I suspect the pH was wrong for this plant in this part of my vegetable garden.
Comment on the Internet is that it takes a couple of years to really work well, and it seems to need to be "activated" by soaking in a fertiliser solution.






It is a good way to recycle palm fronds into something more useful even if it does not have a dramatic effect. My double drum system is really cheap to make although it will probably rust out fairly quickly.

Tom