Charcoal Kilns - what to buy?

[Woodgirl]

Thanks for your ideas so far. We are making charcoal for barbecues with a pope charcoal kiln, and I'm starting to experiment with biochar with the dusty leftovers. I feel that we should be creating less pollution - hence the interest in the Exeter. A round trip to Richy_B and the village idiot sounds a fun thing to do.

 

I also want something on a smaller scale so that I can clear up all the brush when I'm on my own in the wood. The message from the Coppice Convention in Singleton seemed to be that a clean wood resulting in poor soil is also the most biodiverse wood. (What ever happened to Eco heaps?) None of you so far have experience of the Kon Tiki kiln - google it and see the fun they are having in Switzerland and Australia.

[SteveA]

Do they??

 

Tell me more!

 

Yep, here's as far as I got....

 

"We can also offer a smaller vertical machine that will produce 25-30kg

per day. It is made of stainless steel and the current retail price is

£2500 plus VAT. This retort may be more in keeping with your

requirements.

Demonstrations for this machine can only be carried out at Exeter."

 

That sounds great & should be more suited to the scale of our farm...

I had considered using standard oil drums but from what I understand they only last for about 10 burns.

How many burns might we expect to get from your vertical stainless steel machine? cheers, steve

 

"Ah, yes. Oil drums are meant for carrying oil, so are very thin low

quality steel. Hard to say how many burns because none have yet reached a stage where they are yet showing any serious signs of wear. Hundreds of cycles, certainly."

Edited May 20, 2016 by SteveA

[the village idiot]

Thanks Steve,

 

That's interesting. I'll give Robin a bell.

[SteveA]

Thanks Steve,

 

That's interesting. I'll give Robin a bell.

 

If you gather any further info and photos on that would you mind plopping a thread for it on Arbtalk?

I think Robin mentioned they were putting a brochure together for it, but I've not chased it up.

 

We're hoping to get a bit of funding towards the cost.... via EU money, that's because we're part of the EU. ie, not everything is unfunded by the Tory party, yet....

cheers, steve

[jaymo]

I currently us the Pressvess retorts. larger than the standard model. I have two retorts which produce approximately 500 kg per burn. we upgraded our container retorts 12 month ago and haven't looked back since. 500kg of charcoal p/day p/retort aint to bad

[the village idiot]

I currently us the Pressvess retorts. larger than the standard model. I have two retorts which produce approximately 500 kg per burn. we upgraded our container retorts 12 month ago and haven't looked back since. 500kg of charcoal p/day p/retort aint to bad

 

Are they standing up well to heavy duty use? I have not yet encountered an affordable non-warping kiln.

 

I might have opted for the pressvess, but mobility was high up on my priority list.

 

Where are you based?

[openspaceman]

 

I also want something on a smaller scale so that I can clear up all the brush when I'm on my own in the wood. The message from the Coppice Convention in Singleton seemed to be that a clean wood resulting in poor soil is also the most biodiverse wood. (What ever happened to Eco heaps?) None of you so far have experience of the Kon Tiki kiln - google it and see the fun they are having in Switzerland and Australia.

 

Kon Tiki is just an inverted lid and derives from traditional pit charcoal making, John Evelyn writes of using bavins on an open fire like this and quenching.

 

One can do much the same with an open top 45 gallon drum if the material is dry enough, the offgas flame shielding the newly formed char from oxidation whilst simultaneously radiating heat back to the top layer, once char has formed add more wood.

 

The most productive method I found was to use a traditional two ring kiln in June and grapple load it with lop and top felled in March, with all the cordwood above 3" already removed the raw material was both dryish and small enough to char quickly so the kiln was full off char in a morning. Big problem was then sealing the kiln well enough to prevent it burning away. Quenching would be fine for biochar. I found 50% of the char produced would riddle out and provide lumpwood within the bioregional B&Q spec but it had that ashy grey burned look rather than the shiny black metallic look of good BBQ charcoal.

 

If your material is well dry, below 20% then a simple TLUD burn will yield 20% by weight of small <1" material in a 6" flue or ventilation pipe for small quantities of biochar plus it makes a nice patio heater.

[agg221]

Kon Tiki is just an inverted lid and derives from traditional pit charcoal making, John Evelyn writes of using bavins on an open fire like this and quenching.

 

...the offgas flame shielding the newly formed char from oxidation whilst simultaneously radiating heat back to the top layer, once char has formed add more wood.

 

Quenching would be fine for biochar. I found 50% of the char produced would riddle out and provide lumpwood within the bioregional B&Q spec but it had that ashy grey burned look rather than the shiny black metallic look of good BBQ charcoal.

 

This is basically what I am doing - pit burning, adding layer by layer when the surface just starts to ash and quenching at the end. I am burning dry brash, up to 3" diameter, plus some bigger leylandii. Hard to say on yield as you just keep throwing it in, but it seems OK. I am riddling out at 1" and above as charcoal (mine is looking nice and black and shiny rather than ashy), below 3/8" as biochar. In between gets thrown in a barrel of water to separate out stones and wet it down, then thrown through the shredder. Surprisingly little dust and a good even material as the output.

 

Roughly, 1.5hrs to burn, then quench, stamp down well and take out the unburnt ends. Digging out and riddling takes a long time as my riddles are too small, but if I make them wheelbarrow-sized I reckon I could process a burn in about half an hour, total yield ~250l of char.

 

So far I have found I need a supply of short logs to fill in the ends. Getting the timing right on adding more is fairly easy to judge but I haven't found a good way to finish a burn - the last layer tends to end up ashing on the outside before the middle is charred. The best option I have found so far is to cover the pit over with a metal sheet once the last layer starts to ash, then wait 15mins before quenching.

 

Very low impact, zero investment (beyond a pick and shovel) and whilst I am using a fixed location, it would be very easy to dig pits where you want them and fill them in again afterwards. The only thing you need is some water - I am finding about 20l from a watering can is enough if I take out the unburned ends and stamp it down well, then riddle quickly afterwards (the lumps going in the barrel deals with anything still 'live' and the fines don't seem to keep burning, and get mixed with grass cuttings soon after anyway).

 

Alec

Edited May 20, 2016 by agg221

[jaymo]

Are they standing up well to heavy duty use? I have not yet encountered an affordable non-warping kiln.

 

I might have opted for the pressvess, but mobility was high up on my priority list.

 

Where are you based?

 

Hmm if I'm honest there is slight warping.. I am also yet to find a kiln that doesn't suffer from this.

We did consider the carbon gold design which if memory serves me correctly used direct heat rather than the usual indirect. It had two large cylinders You would load processed wood into the top and unload 'charcoal' from the bottom.

I got the impression it was still in the testing stage and they wanted to use us as Guineapigs. Don't get me wrong they had some fantastic ideas but unfortunately they just went proven with this new design we saw.

 

Pressvess have a large factory based in West Midlands, definitely worth a visit if you get the invite. Nick Harris is the designer ( in my opinion really knows his stuff)he would build to whatever specs you require. after sales is good too.

 

We have two of the large pressvess retorts. The first was purchased 12 months ago which we would burn 3 times over 3 days, then couple of months later we had the second retort. Now we burn both retorts, twice over 4 long days. Producing about 2000 kg per 4 day week. I work for a large estate based in Kent.

[richy_B]

Jaymo, can I ask how much you're kilns were? Presume these are quite pricey.