Make charcoal in your own backyard

Erin Rasmussen

Vuthisa, November, 2009

They have kindly put together a great How to Make charcoal in your own backyard

I recently did some trials with 2 x 55 gal drums inside my fabricated Portable Metal Kiln. I recently increased the kiln width from 1.1 to 1.4 metre diam to accept 3 x 55 gal drums and although more testing is required I am satisfied with the MO. I have created a Google Group to discuss issues around its construction and usage. http://vuthisa.com/biochar/
Cost: Under $800
Availability: DIY

Regards
Kobus

Updated September, 2012:

I have gone away a bit from the TLUD principle as I started from a very polluting open top burn approach and using feedstock that is not uniform in particle size. Very wasteful, and as in Dan's case I ended up with a lot of fines (http://vuthisa.files.wordpress.com/2012/09/img00177.jpg). The only cost effective way that I could improve emissions of the Transportable Metal Kiln was to convert it into a retort, by using the heat from the conventional burn to heat the inner retorts. The flow rate of the air through the outer burn will be high, probably around 1.5 m3/sec and the quantity of feedstock necessary to provide the heat to the inner retorts before the reaction becomes exothermic will probably match the closely packed feedstock volumetrically inside the 3 x 55 gal drums, which will ultimately yield the biochar. The burn is seen as successful only if ash remains in the outer vessel and all the biomass inside the 55 gal drums is pyrolysed. I don't need a TLUD type flow rate to ensure complete carbonisation, but the consumed wood in the outer drum has to be included in the overall yield percentage calculation. The addition of a conical lid and chimney (much akin to the New Hampshire metal kiln design) has increased the draft needed to vent emissions. In the conventional open drum burn I would place ±550 kg feedstock and end up with 120 kg charcoal, but 50% will be fines. In the 3-drum retort I would probably also use 550 kg but end up with ???? I would not like to venture an answer at this early stage, but hopefully end up with more than just 60 kg of biochar. The principal advantages of my three drum retort should be the 25% yield of char from the retort contents, coupled with the ability to use lower quality fuel as the starter fuel (outside the drum) and the self-stopping of the retort design (better safety, no need fro water), and the self-running aspect (light it and step back).

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