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Originally Posted by Turtle
No need for oven. From what I have gathered from these articles you don't want 'activated charcoal' for making these terra preta soils & you do want (need?) to crush it up. Some sources say you need 20% to 40% charcoal by volume to get the microbes churning & happy.
The solar oven is low temp (about 450deg F they said) & you shove in your garden waste instead of composting it.   |
BBQ charcoal seems cheaper than horticultural charcoal. The BBQ charcoal I purchased looked like it had been some sort of worked or turned timber. It had a hole in the middle and was hexagonal. It was certainly a lot cheaper that horticultural charcoal BUT how do I know if it is the right stuff? Charcoal doesn't say on the packet what temperature it has been produced at. From what I've read some of the plant resins need to be left in the charcoal for the bacteria to latch on to it
It was easy to pound the BBQ charcoal into a powder with a brick. I got into a rhythm a bit like native pounding of grains into flower.
One of the traditional ways of making charcoal is by coppicing
see
http://www.rbgkew.org.uk/gowild/wild.../charcoal.html
"How is charcoal used today?
In Britain today, charcoal is used as fuel for domestic barbecues, in fireworks and in medicinal biscuits. As it can absorb gases and impurities, it is employed in chemical, water and vodka filtration. Approximately two thirds of the estimated 60,000 tonnes of charcoal sold in Britain every year are used in barbecues. Of this vast quantity only 3 per cent (1,800 tonnes) is produced in England. A large proportion of the remainder is derived from unsustainable harvesting in the tropical forests and mangrove swamps with the cheapest imports coming from South-east Asia. This is particularly disturbing when one estimate suggests that there is 800,000 tonnes of low value wood including over-mature coppice in the south-east of England alone. This wood is currently of little economic value but could be used for the production of high quality British hardwood charcoal.
How is charcoal produced?
Charcoal production is dependent on heating wood without enough air for complete combustion. Under these conditions, water is expelled from the wood and volatile substances such as tars and oils are released, leaving charcoal containing up to 90 per cent carbon. In most charcoal production processes, some of the wood in the kiln is burnt to produce the necessary heat. If thoroughly air-dried wood is used, ideally with a moisture content below 20 per cent, then 4 tonnes will yield 1 tonne of charcoal. This yield is halved if unseasoned timber is used since a higher proportion of the wood in the kiln has to be burnt to provide the required heat.
Many different kilns are used throughout the world. Some, known as earth kilns, utilise only materials from the woodland to seal them. At Wakehurst Place, a less labour-intensive portable steel kiln is moved around the woodlands to each new coppice block. Other initiatives in Britain could lead to huge static kilns to which timber growers take their coppiced wood.
Charcoal from Wakehurst Place
At Wakehurst Place up to 3 tonnes of BAR-B-KEW charcoal is made each year. Like other British hardwood charcoal, it has a high carbon content which makes it easy to light and quick to reach a high cooking temperature. These qualities make it a superior product to most imports and it provides an alternative to charcoal produced from endangered sources such as tropical rainforest and mangrove swamps"
This is a good site on UK copicing
http://www.englishcharcoal.co.uk/
"AD 43-410
By Roman times iron was being produced in large-scale processes. To fuel the considerable production, many thousands of acres of coppice were brought under management and invariably the iron works were situated close by. Such was the scale of production that slag was commonly used as a sub-base for new roads.
However, charcoal was not limited to use as a fuel. The wood tars produced were used for caulking ships and the lighter pyroligneous acid (which the Egyptians had used for embalming) may have had a use in the production of dyes. Charcoal posts were used for construction support in wet areas where ordinary timber would have quickly rotted whilst crushed charcoal had uses in the filtration and purification of liquids."
There is even a Yahoo coppicing group!
http://finance.groups.yahoo.com/grou...1?viscount=100
Both these websites mention plant resins in the charcoal.
Is it important for these to be left in the charcoal?
Some of the Cornell Uni papers seem to think so
Am I fussing over nothing?
Perhaps I need to suck it and see.
The TV show I saw on coppicing years ago involved building a special bonfire. The bonfire was specially constructed so that it burnt slowly over a number of days. I haven't found how to construct this yet.I guess i won' be able to do it in suburbia anyhow. It does seem to be the way to go for farmers however.
I don't think my wife or the smoke alarm would appreciate me producing carbon in the oven
(Not energy efficient anyway).
Let me know how you go with the home made solar furnace. I have lots of long hard "poles" off palm fronds. They are sort of bent so don't make good tomato stakes -but might make good charchol!
"Manufacturing Charcoal
Charcoal is made when wood is heated under conditions where there is insufficient air for complete combustion. In this process the water contained in the wood is first driven off before the wood begins to break down. A series of chemical reactions then follow which result in the release of volatile products. Charcoal – a solid black residue is left.
Manufacture of charcoal in the UK is now largely carried out in portable kilns. These kilns are circular steel drums of about eight feet diameter and a least four feet in height. There is a removable lid and a number of chimneys, which vent from the bottom of the kiln. The timber is carefully placed in the kiln leaving a central void which forms the starting point for the fire. When the kiln is full a fire is lit in the central void and allowed to establish before the lid is loosely placed on the top of the kiln.
Over the next couple of hours the amount of air to the kiln is carefully controlled before the lid is sealed using earth from nearby. The kiln then vents from ground level and burns for around 24 hours providing perfect conditions for the production of charcoal. All vents are then sealed and the combustion process dies down. The kiln is then allowed to cool before it is safe to remove the charcoal. The cooling process can take several days. The image below illustrates the early stages of the combustion process before the lid is properly sealed.
The ring kiln is a relatively modern replacement for "the traditional earth burn."
The traditional earth burn is what I want to know about!
O well another day, another hunt for cheap charcoal.
I do have a lovely bacterial tea brewing made of yeast, sugar, milk, plant materials, an old bottle of Spiralina (seaweed), kitchen scraps and a spoonful of liquid fertiliser. It is bubbling away nicely. (I do hope my wife doesn't find it.
(I have to smuggle in chook poo as she says it "stinks"
Re: Terra Preta
semantics is not always just pedantic quibbling. ~ douglas r. hofstadter
Re: Terra Preta Soils. How do you make them?
I understand; however, the burning of material releases CO2, wheras a solar oven burns nothing for its heat. The energy required to make charcoal is a potnetial polluting problem in itself. More to come on my experiment.
