Making use of garden waste producing biochar - feasible?

We have a lot of garden waste (as well from customers), most are sticks and twigs too small for the fire.
Gardening Australia shows a lady cutting the whole stuff up for the compost bin with a pair of secateurs; my guess is that with a garden a bit bigger than a courtyard the most likely result will be carpel tunnel pain.
If I made biochar out of that "waste' would I have to cut it to small pieces?

small sticks can be turned into charcoal which can then be turned into biochar. Biochar always starts out as charcoal it is the microbiological organisms that turn that charcoal into biochar.

For small sticks you will need a container with a fairly tight fitting lid, this is so not much oxygen can get in and create a too hot fire.

I like to use a cookie tin type container for this and I have two or three 1/8 inch holes drilled in the lid of this container.
I pack the container with twigs then put the lid on and this goes onto a rack above a fire.
You don't need a lot of heat, but you do need enough heat for a long enough period to cook the twigs.
I pull my tin off and back on several times during a one hour burn, usually, if the fire is pretty close to the tin, it only takes about 30-45 minutes to turn the twigs to charcoal.

Once I have created enough charcoal I add it to a compost heap and let it become inoculated with the microorganisms that are living in the compost.
When it has been in the heap for about a month and has gone through one or two turns of the heap, it is ready for a garden bed.

Most of the time you want to add the biochar as a layer that is around 3 inches below the surface of the soil.

Redhawk

With a two can retort, you can cram as many sticks as you can into the thing, so it is very feasible.  No need to cut, except to get it to fit in the inner can.  Anything difficult gets burned in the outer can to create the heat ...  but the drier the better for the process.  Wetter/green wood tends to smoke in the outer fire too.   You want the wood to be dry so that it heats up fast in both the heating wood and the wood being heated.  You do not want steam in your inner can system, or you want to minimize it.  It could cause a steam build up explosion-danger.  hugulkultur works fine with sticks too if you don't want to wait for the stuff to dry, or don't want to go with the char process. With char, it's best to store the wood, enough to dry it so that it snaps easy, and then make char with it.  It would require a bit of a rotational process if you have a lot of wood coming in regularly to your system.

Garden waste works well.  My last batch of charcoal I made from old blue jeans.  I have used cotton towels, ragweed stems, sticks and twigs of all sizes.  I haven't used bones yet but plan to in my next batch.  I think you can use pretty much any organic material.  I only cut stuff up enough to get it in the can.

I saw pictures and they use wood in the outer chamber probably to increase the temperature, isn't that a waste of firewood? I want to use debris only!

Look at the cone-kiln designs. You keep adding more material during the burn process, and they can handle thin twiggy material well, without lots of additional processing like cutting and trimming so they fit in a barrel.

And if you don't want to spend hundreds of dollars on a metal cone kiln you can just dig a pit in the earth the shape of a cone kiln and do the same thing in this fire pit.  I've been doing it for years.  It works great and doesn't waste any of the wood....it all converts to Biochar.  Here's one example.  Not perfect, but you get the idea.     Just start with small diameter wood.  Then move up to any larger diameter wood (not too large or you should split it because it won't have time to fully char unless you do this in a fairly large pit).  Finally finish with small diameter wood, dried grasses, etc.  You layer in more wood as the wood below it converts to charcoal.  When heated, wood generates flammable gases and charcoal.  The flammable gases burn and consume the oxygen so that it can't get below these burning gases to the charcoal below it.  You keep layering new wood over the charcoal as the flammable gases stop being produced to generate more gases (and more charcoal).  Eventually the pit will be filled with your Biochar and you can then quench it with water from a hose.  The resulting steam will help react with tars in the charcoal to clean it's pore structure up so that you'll have better Biochar.  After the hose treatment has been done for a bit you can add buckets of water to speed up the quenching process.  Fill those buckets while you're doing the burn.  After that I turn it a bit with a shovel to make sure it's fully wet out.  If there's still any dry spots I keep going at them with the hose until it's all wet.  Dry spots could cause the pile to reignite (never had that happen, but I'm pretty thorough).  Then you can let it finish cooling and use it in your compost, in sheet mulches, anywhere where organic matter is breaking down.  That will help build the microbial and nutrient levels in the Biochar.  I promise....super easy, very satisfying and no expenses, just a great way to clear up your brush while building fertility that will last hundreds to thousands of years.  

Forgot to mention....you can make the pit any size you'd like.  Rough rule of thumb is half as deep as it is wide.  Save up about twice the pit volume in woody materials and then go for it (the volume of the wood shrinks by about 50% when charred).  Cheers.

Are you able to easily get to Dolph Cooke's place?  Not sure how far away from you he is.
http://biocharproject.org/

Greg Martin wrote:And if you don't want to spend hundreds of dollars on a metal cone kiln you can just dig a pit in the earth the shape of a cone kiln and do the same thing in this fire pit.  I've been doing it for years.  It works great and doesn't waste any of the wood....it all converts to Biochar.  Here's one example.  Not perfect, but you get the idea.  https://www.youtube.com/watch?v=h9J7J4fQHpo  Just start with small diameter wood.  Then move up to any larger diameter wood (not too large or you should split it because it won't have time to fully char unless you do this in a fairly large pit).  Finally finish with small diameter wood, dried grasses, etc.  You layer in more wood as the wood below it converts to charcoal.  When heated, wood generates flammable gases and charcoal.  The flammable gases burn and consume the oxygen so that it can't get below these burning gases to the charcoal below it.  You keep layering new wood over the charcoal as the flammable gases stop being produced to generate more gases (and more charcoal).  Eventually the pit will be filled with your Biochar and you can then quench it with water from a hose.  The resulting steam will help react with tars in the charcoal to clean it's pore structure up so that you'll have better Biochar.  After the hose treatment has been done for a bit you can add buckets of water to speed up the quenching process.  Fill those buckets while you're doing the burn.  After that I turn it a bit with a shovel to make sure it's fully wet out.  If there's still any dry spots I keep going at them with the hose until it's all wet.  Dry spots could cause the pile to reignite (never had that happen, but I'm pretty thorough).  Then you can let it finish cooling and use it in your compost, in sheet mulches, anywhere where organic matter is breaking down.  That will help build the microbial and nutrient levels in the Biochar.  I promise....super easy, very satisfying and no expenses, just a great way to clear up your brush while building fertility that will last hundreds to thousands of years.  

I tried that method and haven't had good luck with it yet.  I'll have to try a few more times and see if I can figure out out I am doing wrong.  I dug the pit to roughly the dimensions of the cone but I don't have the hang out it yet.  I either gets lots of wood that isn't turned to char all the way thru, or I burn it too long and get lots of ash and waste.  I can't seem to get the timing down so that I don't end up with a ton of brands.  I really want to learn the pit method so that I can do larger batches, but so far a retort is the only way I can make good quality charcoal.

Angelika,

If you already have a fire and can use Bryant's method, you will have a very high return on your wood. I use a pitwith care taken to have the initial fire extend all the way to the sides. I have not had Greg's experience with no waste, there must be a conversion of some wood to ash to generate heat, since pyrolysis is endothermic -you MUST add heat or it will not work. Either you need a mixed burn/pyrolysis or retort. I initially used a cone-shaped pit and I found it had two main problems: it had more soil exposure which required much more initial burn to heat the clay soil and generate a reflective surface, and the top burn with the cone shape required a massive amount of small stuff to complete the char. To maintain the required heat I simply couldn't gather little stuff fast enough (I do burns with deadfall mostly) and the top was not as well charred. Simply, it was more work to dig a deep pit and more work to get the char out, but less work during the burn (which is already tiring) and better char return versus the cone pit.

Just my experience.

The cone kiln approach suits me well - despite not actually having one yet. Our burns are usually a lot of large brushy material that gets generated at once (eg hedge trimming), or tidying up trimmings from firewood. I don't like investing time in trimming wood to turn into charcoal - I'd rather burn long messy lengths that pack down as they char.

After looking at some of the models, I decided to use a 55 gallon barrel (200 liters?).  A lot of the people seemed to think that a pit would create too much pollution.  I made a chimney for the top of the barrell and put it a lot of holes.  It gets doused right before it goes to ash.  It makes really high quality charcoal. I found this video to be the most helpful.  My main changes were I would measure the lid chimney and draw around it.  THen cut.  Also there is a learning curve on when to douse it.



This is the system that I am currently using.
John S
PDX OR

John, I suppose you can make a lot of pollution when making Biochar in a pit or in any kiln for that matter if not run properly.  My pit produces virtually no pollution and the Kon Tiki, which functions like a pit, has been measured to produce very, very little pollution.  Early dousing, before everything is converted to char, is one way to produce pollution in any system.  Open pits, kilns, whichever method folks choose, I'm very excited to see people making piles of Biochar!

I saw pictures and they use wood in the outer chamber probably to increase the temperature, isn't that a waste of firewood? I want to use debris only!

 Well it takes some kind of energy one way or the other to cook rice and veggies.  I make char, and make supper.  To me there is no waste...   ...but maybe I'm just a pyro at heart!   I've never tried to get into the cone thing.  It might work to cook on that, without wasting wood.  

I think we decide for the drums, we can put it on the terrace and have a hose there and it is completely safe. I don't want to start a filre.

we can put it on the terrace

Wherever you do the burn should be clear of dry material, just to be safe.  One thing to consider is to make sure that your drums are completely cold when you open and dump them out.  I've had some that were still warm but the internal chars were still hot---they burst into flames, causing quite a fright.  I wasn't dousing with water at that point in my process; now I do.

I use the same technique as Greg and thank him for the detailed explanation. I don't use anything larger than what I can cut with loppers, a pit about 1 1/2 foot deep, 4 feet wide amd 6 feet long, and at the end of the burn the raspberry canes I started the burn with are still clearly recognizable. Not much ash if you keep going with the feed. I find I do not have time to do much besides drag and feed, it goes really fast and if the material is dry anf fed without adding too much at once, very little smoke. It took years of hemming and hawing and not being able to afford a steel retort type system before I decided that some compromise on carbon release was an ok compromise from not making any char at all. Perfect being the enemy of the good reasoning. I just burned the summer's worth of prunings from the orchard and garden and got 55 gallons of char from a burn that lasted maybe an hour.

I had a similar experience JW.  I was planning on it for years.  Finally, I noticed someone giving away 55 gallon drums for free. Then I had to wait because everything was so wet here.  My wife was worried that someone would call the fire department.     Then I watched the video I referenced above and drilled the holes with the metal bits. We cooked some vegies on top so it was a barbecue. I am really glad I got the ball rolling. I've been crushing the char and inoculating it. I should be able to put it in the yard fairly soon.  Like you, I hope to be on a regular schedule. I just cut a whole bunch of mulberry wood, but it will need to dry for several months before I can char it.  That will probably happen next summer when it is dry.
John S
PDX OR

Well, I got as far as scoring a 55 gallon drum....

I've built a TLUD from a stainless steel stock pot.
It runs great on pellets, I've not had such luck with other things.
I've just scavenged a steel dryer drum.
Open on both ends, I can see it working as a big tlud, with the addition of a lid and chimney/afterburner,jolly roger style.

Less babysitting, plus I might be able to vent into an oven, or distill water ,or even heat a retort, something like this:

Fire is a bit of a male thing. Despite having no time he got immediately hooked onto that, read a lot and ended up burning in a metal drum we already had. There was a lot of smoke and the neighbour came over (what an excuse for drinking a beer). Today we will tip it over but the upper layer looks perfect. Simply metal drum no holes no nothing.
One big question is that in order to get a stuffed drum you will have to chop the material in pieces, how is that done without heaps of work?

You don't need to chop everything small if you are happy to keep adding stuff to the top. As the material burns the charred wood falls down to the bottom of the drum. With no air supply at the bottom it is protected from burning by the combustion zone above.

Watch the videos on cone kiln operation. You keep adding more and more material and the char layer gets thicker and thicker.

Cool idea, William.  It looks like you could run a regular TLUD biochar system for 55 gallon barrell but put a retort in there too, on top of it, using the heat again.  I just may have to try this at some point.
John S
PDX OR

I have a lot of branches from my dead pine processing that I could use for this, but they are presently all damp from rain and sleet.  They are awkward twisty branches and some quite large and would not suit working with my little retort.

you can make the pit any size you'd like.  Rough rule of thumb is half as deep as it is wide.  Save up about twice the pit volume in woody materials and then go for it (the volume of the wood shrinks by about 50% when charred).

 I may try this method in the spring.

Are people able to use greener (fresh cut, not dried and cured) material in these cone burns?  It seem like it would be alright, though not ideal, as damper material would create a less hot fire, but at least in an open pit there is not much chance of a steam build up in the cone.   If not green wood, can a person use damp wood (from standing dead material, like my pine) that has been left outdoors?

Roberto pokachinni wrote:
Are people able to use greener (fresh cut, not dried and cured) material in these cone burns?  It seem like it would be alright, though not ideal, as damper material would create a less hot fire, but at least in an open pit there is not much chance of a steam build up in the cone.   If not green wood, can a person use damp wood (from standing dead material, like my pine) that has been left outdoors?

I have tried it and the results were never good.

Yeah, you REALLY want to use dry.  The more moisture the more steam and smoke.  It makes it very unpleasant and polluting.  If you really want to use wet stuff check out "hydrochar".  That process can use fresh cut, wet stuff.  Seems much less easy to do, however, as it's done at elevated pressures.  If you try it keep a strong eye out for safety in every part of that process.

you REALLY want to use dry

I have tried it and the results were never good.

 Thanks guys.  That's what I suspected.

I have also heard this from other sources. I have only tried very dry for that reason, and it has been really excellent so far (knock on chopped pieces of wood).
John S
PDX OR

I have also heard this from other sources.

 Yes.  I only do dry wood in my retort. I always thought that this was best and have had good results.  I was just curious if the open pit might be different. Thanks for your input John.  

Greg Martin wrote:.  If you really want to use wet stuff check out "hydrochar".  That process can use fresh cut, wet stuff.

Wow. One word "hydrochar" sent me on a serious deep dive. If anyone else is interested, Google DIY, hydrothermal carbonization.

I think biochar would have a great future. We have a green bin here which is not green at all, without going into details here- it would be far better producing biochar. Garden 'waste' is garden waste because it comes in bulky pieces. No one really wants to cut up tree prunings which can be readily composted. But even for biochar you have to cut up the pieces that they fit in the ton, which is a bit bigger. The second problem is that the material has to be very dry, which in some areas would pose problems either of neighbours complaining about unsightly heaps or firehazards or it simply is too moist.

Angelika Maier wrote:The second problem is that the material has to be very dry, which in some areas would pose problems either of neighbours complaining about unsightly heaps or firehazards or it simply is too moist.

It's easy to put your barrel up on 3 or 4 bricks.  Fill it with the wood you want to turn to charcoal and put a piece of tarp over it when it is going to rain, leave the top open in good weather, and you can dry the wood right in the barrel you are going to burn it in.

Another option is to build a simple box to put it in.  I built mine in about 15 minutes.  I used pallets and lined them with cardboard so the box would breath well but the wood won't fall out.

I am currently using one of the same ideas as Todd.  I chopped a large part of my mulberry tree, but I didn't want it to become a haven for rats, squirrels, voles, etc.  I chopped it into pieces to dry faster and put it into the barrel.  It will take a few months to dry, but then it will be ready and take up less space.  I like the idea of putting it on bricks to dry even faster.
John S
PDX OR