Barefoot Biochar :  Making Agricultural Charcoal at Home.
The information here is from Geoff Moxham's research over 4 years and RIC's Project 540 small kiln research.
Making Charcoal for Agriculture - 101
Rule 1: Use Dry Feedstock. Drying wet wood uses much more energy during pyrolysis, and makes dioxins.
Rule 2: Don’t Make Smoke. Smoke also contains methane, which is very greenhouse positive, and pyrolysis gases are toxic. A tarry smell indicates poor agricultural charcoal, due to incomplete pyrolysis, called torrefaction. Smoke also annoys neighbours and the EPA, and that smoke is fuel value you’re not getting. 
Rule 3; Control The Air. To stop smoke add air, or feed fuel slowly. This applies to your space heaters and fuel stoves. To stop smoke intelligently, smoke is directed at the high temperature zone of the reactor fire. 
Efficient burning with lots of air destroys all the toxic VOCs (volatile organic compounds) in the gases from woodsmoke.  In a good reactor, these gases will provide 20% more useable heat (for power, or drying), on top of the heat needed to pyrolise the load and produce charcoal.
To stop air destroying your hard-won charcoal (devastating, I can tell you) you must have reasonable seals, for the load to cool without air.
That’s all there is to it… almost…you might like to set up systems to solar dry the feedstock for a year, to bring it to a dry storage area, a cutting area, a batch loading area, a state of the art pyrolising area, a process-heat drying-area, a char pulverizing area, an inoculating area, and finally  dispatch to the spreader. Not much. The thing is… it’s going to be worth it.
Biochar still has the best prospects for sustainable bottom line reasons alone. 
*In a recent agricultural trial at Wolllongbar DPI research station, corn, grown with agrichar amendments, outperformed all conventional agricultural amendments
* biochar gives resilience to drought and wet 
* biochar establishes a set-and-forget reserve of soil carbon, that ensures the family farm is passed on in better condition, & with guaranteed longevity (mean residence time is 1,300 years)
* co-generation of remote, power is possible with woodgas gensets,
* Process heat can be used to dry crops, heat water, dry wood/ feedstock.
If you just want to fool around and make some char, if badly, here are my ratings out of ten for the old methods, arranged, worst first:
1/10 – open burned trees in windrows, wet, usually fired many times. (yield = 0 - 5%) carbon positive, dioxins.
2/10 –  “the cigar method”, timber pushed into trenches, covered with soil and lit one end and smouldered for weeks. (5-10%yield), nasty, archaic, torrefaction, dioxin. Makes GHGs.
5/10 – piles of light weedy waste (lantana?), dried to a crisp, and fired on the ground with little smoke, and quenching with water. (<20 %) simple, but lye fills char, some torrefaction. Carbon neutral.
6/10 – open topped drum with airtight lid, with dry, slow feed, no smoke and snuffing when red coals are reached, using bottom vent plugs. (>20%) almost passes, but still lossy, easily re-ignites, often torrefaction. C- neutral.
The importance of air.
The air supply to a pyroliser is usually divided into primary and secondary air. The primary air supplies the initial fire that heats the charge of wood. Secondary air is extra air supplied to burn all the off-gases completely to CO2.”Dry” wood at equilibrium moisture content (EMC) is about 15% water 40% char, and 45% volatiles, depending on species. 
 Folke Guenther on the terrapreta list at bioenergylists, found a simple vast improvement to the drum firing technique. This is done by simply inverting the drum full of wood over a stable, flat, base-plate. The weight of the drum holds the rim with a good enough seal to let the gases out, in a neat ring of fire that washes over the reactor. The seal is good enough to not let air enter in the cooling stage. A shroud to insulate the primary fire is best.
Please consider donating to the project at RIC, which has non-profit status at http://www.rainforestinfo.org.au/aboutthe.htm#Australia.
Links that are useful in approx order of brilliance:
David Yarrow’s files page:  http://tech.groups.yahoo.com/group/carbon-negative/files/Public%20Press/
Going carbon negative, many links. Rick Davies: http://www.shimbir.demon.co.uk/biocharrefs.htm
Rise portal on biomass. This site is the full quid:  http://www.rise.org.au/info/Tech/biomass/index.html
Peter Harris University of Reading: http://www.personal.rdg.ac.uk/~scsharip/Charcoal.htm
Big Gav's big biochar rave:   http://www.energybulletin.net/node/46569  
MIT:  the case for burying charcoal: http://www.technologyreview.com/Energy/18589/
Eprida corn trials pics: http://www.eprida.com/home/index.php4
Lukas Van Swieten’s Wollongbar trial; Ag Today Feb. 07
http://www.dpi.nsw.gov.au/archive/agriculture-today-stories/february-2007/agrichar-trialled-wollongbar
Kelpie Wilson: Best lay person's introduction to terra preta.
http://www.biochar-international.org/images/Joyful_Liiving_Terra_Preta_Sept-Oct_0207.pdf
The ABC 11 minute video about terra preta called "Agrichar". http://www.abc.net.au/catalyst/stories/s2012892.htm
The BBC documentary, "The Secret of El Dorado". History of Terra Preta
http://www.bbc.co.uk/science/horizon/2002/eldorado.shtml
Greening the Desert: http://www.youtube.com/watch?v=sohI6vnWZmkopact.com/2007/10/towards-carbon-negative-bioenergy-us.html3. PlantSoil 249, 343-357, 2003 Lehmann.pdf
Nature, 2006:  Putting the Carbon back: Black is the new green
<http://www.nature.com/nature/journal/v442/n7103/full/442624a.html>
Science: Smouldered earth: http://www.biochar-international.org/images/Science_20News.pdf
Research confirms that char added to soil boosts crop productivity.
http://biopact.com/2007/06/research-confirms-biochar-in-soils.html
Cornell – Lehmann:  http://www.css.cornell.edu/faculty/lehmann/biochar/Biochar_home.htm 
Anila stoves:  http://www.bioenergylists.org/stovesdoc/ravikumar/Biochar_Anila.pdf
Some Biochar practitioners’ comments : Nardi, a scientist at the University of Illinois, writes in his newly published book, "Life in the Soil," that a square meter of healthy garden soil  is home to 10 trillion bacteria, 10 billion protozoa, 5 million nematodes, 100,000 mites, 50,000 springtails, 10,000 creatures called rotifers and tardigrades, 5,000 insects and arachnids, 3,000 worms and 100 snails and slugs.  Throw in the occasional mammal and a lizard or two, and you get the idea that you don't have to travel to the Brazilian rain forest to luxuriate in the biodiversity at our feet.
In a field day workshop with Doctor Franklin in Oregon as he was speaking about structure and function in Old Growth and Managed Forests. He was expounding at length about structure from Old Growth offering a life
raft effect to numerous other biota as well as serving as a source of long term organic matter. The same is occurring with the terra preta; it serves as a liferaft-offering structure, which in turn supports other functions. We may
find that the chemical properties or terra preta or biochar in soil aren't as important as the physical properties of offering a life raft for soil biota to carry out their functions

Our fields were put to the plow relentlessly until 25 years ago. A little tilling now, for the prospect of these benefits, to get TP into the first 8 inches seems worth disruption of the soil horizons. I think of it as urban renewal, but with really good public housing.

Processing and Inoculating Charcoal for Agriculture 
Whether you’ve found your charcoal in your fireplace each morning, or by intentionally making batches of it, you will get your best first-application results by crushing it finely and inoculating it. Crushing smaller than 10mm is recommended, these fines being easily transported in all directions by worms and other biota.
 So far I have seen 4 practical methods suggested for grinding useful quantities, all preferring wet charcoal to minimize inhalation of dust. Corn grinders efficiently make a very fine “gunpowder grade” char dust, and only work with dry charcoal. I made just 3 kg that way, and required a hot shower.
 1). For small test quantities, first try wet char in a coarse meat grinder. Adding bicycle power, or a 12V motor could vastly improve production rates. This may be the best, quietest, carbon-neutral solution for small gardens.
2). A bigger batch grinding process is to throw wet charcoal into a dedicated grinding “pit” or “bay”, and run the mower over it. It takes just a few seconds, in my experience. Don’t do this with dry charcoal!  This is a very fast way, and I s’pose if you can get an electric mower running on your panels it could even be sustainable, post oil, for a while. Scaled up: It’s using a tractor-slasher in a large bay of sleepers or logs. This is a small-scale commercial method that could produce tonnes per day, if the feedstock existed. Both mower and tractor versions can be finessed with wooden shutters, guides and grates, and a second operator feeding the fossil monster with a front bucket.
3). For higher processing rates you can use an insinkerator/garbage disposal system. This is a cheap accessible way that also allows good inoculation with liquids like biological “teas”, and missing trace elements, using ocean minerals. These can be added drip-wise, as the mix is processed directly into aerated holding or brewing tanks, for 10 -14 days, or applied within the hour
4).  Using a large slab and heavy roller, like a cricket pitch roller, or homemade roller from a drum filled with concrete.
So what exactly is the inoculant? THE billion-dollar question. 
All I can say is: your site decides. Left to itself, the char dust will take up the local biota signature, which would be ideal for native plants and regeneration. In your best garden patch it will take up the biota population that is currently doing the work. But everyone wants it speeded up.  At the moment the discussion is either about adding char to NPK fertiliser applications in mainstream “agro”culture, or making various creative teas from urine, worm juice, compost percolation, and brewed, crop-specific teas. Home inoculation in a plastic barrel for 2 weeks seems to be a common convivial suggestion…so be part of this rather rapidly rising meme and try your own experiments…feed your results to the world through the web…while we still have it.
 There is a very promising synergy here with existing bio-tea brewers, and fertiliser processors, and I’m guessing, by the deafening silence, that there are quite a few non-disclosure clauses out there, creating enormous cognitive dissonance in people of very good heart, as we barrel over the resource lemming-cliff. 
Health alert-not-alarm: Some charcoal dusts, like rice husk and bamboo, can contain silica, so minimise by wet grinding. All inoculating makes splashes and aerosols somewhere, so take reasonable precautions.   
Charcoal in Animal husbandry.
For All these Animals, Cow, Chicken, Donkey, Duck, Horse, Pig, Sheep and many more
Diarrhea : Prepare charcoal water to have the animal drink. If the animal refuses to drink it use a syringe to put it into the mouth. It will experience immediate results.
Eye Infection : Make charcoal poultice to fit the eye. (** Direction to make a charcoal poultice/compress is in the "Insect and Snake Bite" section.) Fasten it with tape or nylon.
Foot and Mouth Virus : Charcoal doesn't destroy the virus but it adsorbs the virus immobilizing its function.
Snake Bite : Place charcoal directly on the bite or use poultice/compress and have the animal drink charcoal water. Make sure to apply charcoal until the swelling is down.
Wounds : Use charcoal poultice/compress on the wound. Change the poultice until the wound is healed.
Cow: "If you feed charcoal to milking cows, the quality of the fat in the milk improves and the taste is much better than cow that was not fed charcoal. If you place granular  charcoal on the floor for the cows, infection of the hoofs will be prevented and the cow odor will be gone."
Cat: Mix granular charcoal in the litter box as deodorizer.  Your cat will enjoy the freshness of the litter box and you won't have to plug your nose to clean the litter box.
Dog house: Place charcoal in the dog house to deodorize and prevent mite growth.
Fish: Add Charcoal into the fish tank.  There will be more oxygen for the fish to enjoy a fully oxygenated fish tank. Water will stay fresh longer, odor won't be present, and fish will be healthier and live longer.
Plus, you don't have to clean the fish tank as often. 
Application rates:
Positive effects start at 10tonnes/ha = 1kg/sq metre, results improve to 5kg/sq.m., after that C sequestration is a the aim, with continued only slight increases in yield. 
The tests in the Oil Mallee charcoal project in Australia used a rate of 6t/ha (2.68 t/a) in a  100 mm (3.94 in)  wide band, equal to a broadcast rate of 1 t/ha (.45 t/a) for a row spacing of 600 mm (23.6 in ). See
http://terrapreta.bioenergylists.org/oilmalleeiai07
The carbon sequestration potential of Biochar
Erich Knight: Man has been controlling the carbon cycle, and there for the weather, since the invention of agriculture, albeit unintentional. 
If pre-Columbian Kayopo Indians could produce these soils up to 6 feet deep over 15% of the Amazon basin using "Slash & CHAR" verses "Slash & Burn", it seems that our energy and agricultural industries could also product them at scale.
It is my understanding that atmospheric CO2 stands at 379 PPM, to stabilize the climate we need to reduce it to 350 PPM by the removal of 230 Billion tons of carbon. The best estimates I've found are that the total loss of forest and soil carbon (combined pre-industrial and industrial) has been about 200-240 billion tons. Of that, the soils are estimated to account for about 1/3, and the vegetation the other 2/3. Since man controls 24 billion tons in his agriculture then it seems we have plenty to work with in sequestering our fossil fuel CO2 emissions as stable charcoal in the soil.
The reason TP has elicited such interest on the Agricultural/horticultural side of its benefits is this one statistic: One gram of charcoal cooked to 650 C Has a surface area of 400 m2 (for soil microbes & fungus to live on), now for conversion fun: One ton of charcoal has a surface area of 400,000 Acres. Now at a middle of the road application rate of  43 tons/acre yields 26,000 Sq miles of surface area per
Acre. Virginia is 39,594 Sq miles.
Harnessing the work of this vast number of microbes and fungi changes the whole equation of energy return over energy input (EROEI) for food and Biofuels. I see this as the only sustainable agricultural strategy if we no
longer have cheap fossil fuels for fertilizer. We need this super community of wee beasties to work in concert with us by populating them into their proper Soil horizon Carbon Condos.
Terra Preta creates a terrestrial carbon reef at a microscopic level. These nanoscale structures provide safe haven to the microbes and fungus that facilitate fertile soil creation, while sequestering carbon for many hundred if not thousands of years. The combination of these two forms of sequestration would also increase the growth rate and natural sequestration effort of growing plants.
Biochar: A Grand Convergence: In academia: Engineering, agronomy, soil geology, anthropology, bio-chemistry, mycology, zoology. In the Public sector; waste managers, Extension agents, Environmental engineers, Energy Policy makers. In the private Sector; corporate farms, fossil fuel generators, small farmers, and the few charcoal makers left.
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