Easy bamboo biochar

The other day, my internet friend Patrick popped up on Skype to tell me about a simple method of making biochar. He'd been to a talk in Tokyo, and he knew from my blog that I'd be interested. How did we used to manage without the interweb, and how impoverished would we be if it was taken away?

The trouble with this method is, most metal cans are of standard sizes, and they haven't been designed with charcoal making in mind. However, being one who takes a keen interest in places where rubbish accumulates, I managed to find an eccentrically-sized can that just fits through the hole in the top of my incinerator.

Cutting the bamboo to the right size took much longer than I had bargained for. A frog in the bushes got rather excited by the sawing noise and felt stimulated to compete. Consequently, there was a general cacophony this morning in the garden. Fitting the slivers tightly in the can also took a while and involved some hammering.

It seemed a shame to waste the space between the bamboo, so I pressed some spare rice husks into service as filler. (Is there any purpose to which rice husk is not ideally suited?)

I put part of a thick rice bag over the top of the can to get it into the incinerator without all the bamboo and rice husk falling out.

There seemed to be a lot of scrap wood and bamboo around the garden to use for fuel, but I made two trips to the bamboo grove anyway, to scavenge dead culms. In the end, I used a lot of fuel.

Ignition! Off to a good start...

Oh shit! I hadn't expected quite such intense calorific output...

Fortunately, I'd prepared two buckets of water and a watering can too. The heat was phenomenal, and when embers spilled out from the holes in the bottom, the already dry grass around caught fire very easily. I had to resort to the watering can a number of times, and if I hadn't been paying attention, the fire brigade would have been out.

The instructions say that you can easily tell when the pyrolysis gas catches fire, but perhaps because I had such a jolly old conflagration going, I had no idea. Not that I wasn't paying close attention either -- I was most anxious not to burn everything on our property to charcoal.

The seemingly vast quantity of fuel burned down to very little ash

After more than an hour of cooling, the inner can was still very hot, but not so hot as to reignite.

Since I hadn't observed pyrolysis, I was concerned that I might still have a lot of brown bamboo. But all of it was gratifyingly black, except for the tips of a few bits in the middle. The quality of the charcoal seemed to be very high -- clean, glassy and brittle. I expect it will be very easy to crush and mix into soil.

Judging by the way the bamboo was all bent and twisted, I suppose it must have got rather hot in the little can.

In general, this seems to be a good way of making charcoal, but next time I'll use much less fuel. Bamboo burns very hot and fast, so I believe the same result can probably be achieved without the 4 ft flame.