You are right in both statements, the waste charcoal being added back in is free heat in caloric valve that would normally be lost to the garden. And is does fill in spaces and help move H2O through the system making H2. This is because there is no heat being used to make it into charcoal and the charcoal creates more heat. It is a win win anytime you do this.
All it takes is some screening out the ash and fines. You do not want to put fine charcoal engine grade charcoal into the hopper it will constipate the charcoal bed and that is not good.
I have been doing this for two or more years now, and it works for me. It give me the extra power to go up hills with out having to blend in gasoline fuel. I look at it this way. After passing the nozzles the gasifer is a charcoal gasifer just with extra moisture to deal with, and more soot to filter out of the moist gases.
I still have in operation my grate shaker.
I occasionally use it going down the road. Most of the builds do not use them any more. A push of the buttom shake the grate fill more power to the engine with out moving the gas pedel. Got charcoal use it the second time around. Use it and reuse it up and it is gone.
Bob
The charcoal ads to the active glowing carbon % needed to do all kinda conversions.
In my experience, more carbon = less Tar passing thru
Hence: Charcoal gasifier with highest % carbon = no tar 
But, the converted tar ads an non neglectible quantity of mixed potent gasses.
Somehow i can see and measure more benefit from adding Tar/condensates instead of water.
In a stationary system its easy to manage to get and maintain a steady state level.
A homebrewed versitail system is far more challenging, a kinda art-form to operate them , not for lazy mindsettings…
Not sure what you mean by this; it seems to go against what you are trying to say?
When you are already burning wood you are Making fines already. Some of the smaller engine grade charcoal seems to plug my gasifer up at the grate. Pop corn size and larger is alright. It might work for someone else gasifer.
It just doesn’t work for my setup. I plugged my Char bed up at the grate trying to use the finer charcoal. It would work great in a charcoal only gasifer. I like to run my charcoal bed loose and slip charcoal. This is how I make it so fast. I dump my ash often. 200 to 250 max miles. I save the smaller charcoal for my charcoal gasifer. I have three 30 gallon barrels of it for my emergency generating use.
Nothing going to waste until it is just ready to go into the garden and that is not waste at all.
I just reuse and reuse and reuse that wood I worked preparing by the sweat off my brow.
Bob
Fines in the garden are a good use.
I had a thought that fines could be introduced to the gasifier on sort of a fluidized basis. One option would be to meter out the fines directly into the intake air, very close to the nozzle (for better safety) or as it’s own feed into the combustion zone (though again, near the air nozzle so it fluidizes. Such a “booster” would be especially good in a wood gasifier that’s running a bit cool from say moist fuel.
Fines have very high surface area and so fluidized in fresh air they will burn very quickly and vigorously - maybe too quickly? It’d be careful with amounts and blow back if you investigate. And avoid optimal stoichiometric ratios of air and carbon in the delivery. You want either a very lean mix of fines (air intake) or a very rich mix (directly introduced - separate from air intake).
Think of it like water drip in reverse?
Gas producers are talkers, they have a voice for those who choose to lessen. They will tell us if something is too complicated, too simple, too weak, too heavy and too whatever. So try and then lessen to what is being said from your creation. It is a two way street. A true team effort.
You can also make it from a tulip bulb planter, 4" auger on amazon was $20. I am still stuck in the city and can’t risk testing something this large but this is what I came up with under limited resources. I expect the center won’t get enough air and there will be brands. Will report back when I can try it out…
I was able to test the barrel. I couldn’t get in a good rhythm, I felt like so much of my charcoal was going up in flames. The middle burns slow and the outside ring burns fast since that’s where the air holes are. I loaded it too full one of the refills and put it out, it billowed a long time. Found it difficult to time it - when to draw down the charcoal and how much, and then how much wood could be added.
I’m sure with experience you could get it running smoothly but I only had an afternoon and couldn’t really get it going reliably. Final comment, it seemed to do best with more uniform wood chunks. To me, a huge selling point of charcoal gasifier efficiency is the ability to make engine grade fuel without needing a chunker, so I think I’m going to stick with the TLUD barrel making method or eventually go with a retort. The device obviously was working for the guy in the original video so I am probably doing something wrong, but putting this experiment in the done pile for now.
The tulip bulb auger worked wonderfully though! Pulled and ground up the charcoal nicely
Y’know I bet the auger idea would be great for a TLUD. When the batch is done just auger it all out at once into a sealable drum or metal garbage can. Then it’s at least mostly crushed and you’d only have to sift the fines.
uniform chunks helps a LOT to get an even burn. It is the same problem I had.
Dry wood also helps reduce the smoke considerably. It just doesn’t get hot enough with higher moisture wood the airflow isn’t even enough. Once you get a coal bed going the wet wood burns fine and with secondary air it is almost smokeless, but you aren’t making much char at that point. I am making maple syrup with the semi-punky wood, and spring brush clean up, mixed with some dry hardwood so it isn’t all lost. The brush actually burns a lot hotter. 
Hi David , sorry just got to add this , as i dont want you to walk away saying "I done that so move on " before doing that try tilting the bin over around 45degs you will find that aids the burn a good deal better , my one is a square stainless bin around 2 foot square by only around 2 ft high with a auger in the bottom , i just keep throwing in garden branches that i cant bother to use in the home fire and just keep adding to it once the flames start to die down once the fire gets up closer towards the top i start auguring out a a bucket full at a time or just enough to allow the level to go down enough to let me carry on loading more wood in , smaller the better .
Dave
Howdy. I feel I have 2 cents to throw in on the topic. Wood of different sizes has to charcoal at different rates. The more uniform the material (and probably the smaller the diameter, think something like hazel or willow brush), the higher the yield and the faster the throughput. Small diameter material lends itself to mowing and mechanized harvesting and chopping too, long established in the basket making industry and now woody biomass for industrial power. Torrefaction will also work best with such even size small material.
I tend to think charcoal is the better material for syngas, it’s technically simpler and less likely to cause problems, but that depends on how much space you have for production. Charcoal can be made in large quantities if you don’t have to worry about disturbing neighbours. I have approached charcoal making 3 different ways. I made a seachar style TLUD and use it for cooking or boiling maple sap, snuff the char in an airtight container. Makes perfect char, but in small quantities, around 2 1/2 gallons per fire. Very efficient if you are using the heat for cooking etc. I made a type of cone kiln out of 2 split barrels, welded together, essentially a trough, it works great for cleaning up brush in the winter, not too disagreeable to feed in Canada in the mid winter when it might be minus 20C, enjoyable outdoor work actually… 
. The trough once fairly full of glowing char will fill 2 barrels, put the lids and rings on, invert, and in very short time they are snuffed bone dry char.
The other method I’ve come up with is to simply burn a large pile of branches, in short time it will be nothing but coals. The trick is to push / rake it into a pile so it doesn’t quickly reduce to ash, and so you can work beside it without catching on fire. Then it goes into barrels. Snow is handy to avoid taking the temper out of a shovel, otherwise water will do. The brush pile technique is the least efficient by a wide margin, but it is also fast and does the job of cleaning up if you happen to be in a battle against trees. Here the trees are winning the battle. I also have lots of space and no worries with neighbours. The trough system is quite efficient and clean burning once it gets going. The longer material you can throw in the better. Biochar is also selling for good money, and the higher volume methods produce volumes of char, probably a good garden amendment or addition to a compost pile. Cattle like eating charcoal, and it apparently makes their feed conversion more efficient by reducing methane production.
TLUD also stands for “truely loves uniform dimensions”.
Yes, I hope I didn’t come off as too jaded 
I’m curious, do you have any secondary air holes in your bin? If it is just an open topped bin with an auger at the bottom I think that’s great too, it sounds like a flame cap kiln + auger combo. I’ve started using flame cap kiln on a larger scale for clearing the brush.
My worry was that it would fill up with charcoal too quickly. But it never came close and we worked all day. The flame cap yield isn’t close to a TLUD but it consumed the wet brush as fast as I could cut and haul it. Below was for biochar reasons but same principle with the closed bottom kon tiki style if goal was charcoal fuel. I think it’s basically what Gary Tait is describing above with a brush pile, but just with some walls and a sealed bottom to make it go easier.
Hi David , my small 2x 2 has no air holes , the thing i have found is that if you are burning small branches/twig type materiel’s that burn away fast you then need to make sure the second u see flames dyeing down is to get another layer on top , if you do not use up the oxygen with new burnable material then the char will continue to burn away to ash , another reason why a smaller dia bin works better is its easier to keep it covered over with fresh wood .
I do not do a lot of outdoor burning really i just mainly burn small stuff these days outside and all the larger stuff i use in my home fire and thats where the bulk of my charcoal comes from , unless i have real nasty stuff i then may use my “Hookway” style retort and that works great .
Dave
I usually try to layer it. alternating between thin and thick. The twigs burn hotter.
hello david, i can divide the observation of aussie dave, a too big surface can easy make too quick burning away the twigs, especially when you not have the pile ready nearby…
i tried with two metal bath tubs, one narrow to the other, but i think with a single tub the coal yield is more, because the flame cap covers it more easy…
in my climate i would have doubt to get the coal dry again after watering…
We are in the same camp, Giorgio. If I get a little rain on some charcoal when I forget to bring it inside, I just take it to my compost. Very high humidity year round in Appalachia. Only heat could remove the water and I do not have a setup for this yet.
I will be getting a damaged plastic IBC tote from work soon. It won’t be totally hermetic but it will at least protect the charcoal from rain. I know you also use the totes to store charcoal. How do you extract it when needed?
I was wondering the same thing
. I think i read once where they was using a shop vacuum to get in tote. I’ve been using barrels to store mine but as its time to spri g clean i need a better bigger storage unit.
In my experiances engine grade charcoal flows trugh a 6" or larger hole. So maybee you lift it and make a gate?