On Biochar

23 05 2017

Last weekend, as the threat of looming downpours for much of Tasmania was forecast, I went to a biochar workshop organised by the Huon Producers’ Network, and I reckon it was the best thirty five bucks I ever spent……. I’ve read quite a bit on the matter, and have always been fascinated by Terra Preta. Having cut down some fifty trees to make way and building material for our new house, I’m not exactly short of biomass to get rid of…. I had four huge piles of the stuff, and unfortunately, sometimes even the best laid plans have to yield to reality and two of them have been burned to make way for ‘development’ on the Fanny Farm. Each time I burned the piles, I got the guilts knowing all that resource was going to waste and contributing to climate change, but having inadvertently put several tonnes of wood in the wrong place (designing my patch is an evolutionary process) and having no quick means of moving them, I just put a match to it. At least, the ash went on the current market garden patch……Image result for biochar kiln

I had some expectations of what I was going to be shown, but they were all thrown out the window…. I had been expecting to see kilns such as the one at right which are all enclosed for the purpose of starving the fire of Oxygen so as to pyrolise the wood and make charcoal. My friend Bruce in Queensland has been making charcoal this way for thirty years to satisfy his blacksmithing habit (and those of many others I might add), and he has this down to a fine art. But it appears there’s a revolution underway…..

The presenter on the day was Frank Strie, who thirty years ago emigrated from Germany with his whole family to Tasmania. “We started to plant lots of different fruit trees” Frank says on his website, “such as Cherries, Apricots, Peaches, Plums, Prunes and various apple and pear trees. And of course, we wanted to grow our own vegetables. Also, about 20 years ago we established a Hazelnut Orchard, which covers nearly one third of the property.” It’s all organic of course, and he sounds like he’s pretty good mates with Peter Cundall, Tassie’s gardening guru…… See his Terra Preta website.

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“The baby”

The fact that he brought three kilns on a trailer and the back of a ute all the way from Launceston just shows how versatile and portable his gear is.

The new kilns are open topped, and most interestingly, funnel shaped. They make the process faster – like maybe half the time or better – and allow for activation of the charcoal (which is what turns it into biochar) all in one go. Being able to just tip the finished product onto the ground instead of laboriously shoveling it out of the kiln looks good to this old man with a bad back as well.

Andrew, a local also known as Stretch – and so tall he can’t fit in photos – was also there to ably assist Frank; he’d organised20170520_121304 lots of firewood and stacked it in piles of graded sizes along with cardboard and kindling. We actually got three kilns started; from a smallish one designed for hobby gardeners, to something that will make a cubic metre at a time (and double up as a BBQ!) to the farm sized device I could probably use but can’t afford….. though there is now talk of buying one as a community resource which is a darn good idea!

The idea of the funnel shape is that as the air outside is heated, it rises up the sides, and when it reaches the lip, a vortex effect is created causing the air to be sucked into the kiln speeding up the burn. The ‘big one’ even comes with a skirt that acts as a venturi, speeding up the air as it is squeezed between the kiln and skirt at the lip of the kiln. The effect was clearly visible, though nigh impossible to catch in a still photo.

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The ‘smothering’ effect is created by simply adding more and more firewood to the pile. Before combustion is complete, the fire is quenched (with water on this particular day, but normally a liquid fertiliser would be used) from the bottom up. The bottom of the kiln is plumbed to a pipe which can be used for both removing excess liquid, or adding it under pressure from an IBC on, say, the back of a ute. On the day, Frank used a garden hose, because we could not do what he normally does because of where we were….

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On the day, the kiln was not filled to capacity due to location and time constraints, but you can clearly see the results. The big kiln even comes with a winch to tip the biochar out for easy work, and if it wasn’t for the fact I’m far too busy house building and counting my remaining pennies, I would buy one tomorrow,

To learn more about biochar, here is an interesting link supplied by Frank that anyone keen on this process would find enlightening. I think this is definitely the way of the future, a bright light among all the rubbish we see every day about renewable energy and electric cars. This has the potential to sequester huge amounts of Carbon, and even more importantly, prepare farm soil for the post oil era looming on the horizon.

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