Biochar out of sticks

Normally, I prune my food forest at regular intervals, set aside the wood, and wait several months for the wood to season and become better for burning.  However, I realized that I pulled most of the bigger branches out of one of my piles and there was a large pile that seemed to be almost exclusively small sticks, less than an inch in diameter.  I was really frustrated with this at first.  I know that most of the attempts to make biochar out of sawdust or chips fail, as they don't have enough room for the air to flow through and make an efficient fire.  Also the sticks are so skinny, will I get any carbon out of it,  so I can actually have some biochar product at the end?

Enquiring minds want to know, so I tried the experiment.  I needed the space for all of the new pruning I'm going to be doing in the next few months anyway.  I figured that since they are sticks, they won't really fit into a dense pile, and there probably would be enough air flowing through them.  Instead of chopping the rounds with a maul, I moved my barrel to the area of the sticks and loaded them in.  I had to break many of them because they were longer than the width of the barrel.  I was surprised by how quickly the filled up the barrel.   When I got ready to burn, I kept some branches nearby, because I figured that a fire of only thin sticks wouldn't make enough carbon.

I started the fire, and it burned well.  I had set up some chopped, thicker branches nearby, as I normally would.  When the small sticks burned down a bit, I just kept adding more branches, by quickly leaning the chimney lid up and shoving them quickly in the fire.  I kept doing that for quite a while, but it was one of my most efficient burns ever.  After awhile,  I had to come in for dinner, so I finished and I was glad to see it made excellent char!  I think the main thing I have to worry about is collecting the sticks after many dry days, so it isn't wet wood that I'm burning.  Our days here in the PNWet keep getting wetter and wetter until winter, so I need to get going on this when I get some dry days.  Nice to know that I can use the sticks and that I can free up the space for more pruning as that comes in.  

John S
PDX OR

Yes, small bits of wood have more surface area to have rain, mist and dew stick to, so having some wind and sun to dry the surface will help a lot.

Do to my limited ability to do serious biochar, I'm constantly using very small bits and it may not give me the quantities I'd like, it is *much* easier on me to not have to smash the end product up.

I'm really glad that you got good char out of it and hopefully Mother Nature's weather department will cooperate and give you a few more days of appropriate weather!

I use sticks. I tie them in a nice neat bundle, or put them in a paper bag tightly, either way I'm going for a bundle the size of my burn barrel with all the sticks going upwards (for air flow). I light a fire at the bottom, put the bundle on top, tip my barrel, and watch it closely. When the main bunch are done, I stand the barrel up, and put the fire out with a hose. I leave it there till the water cools, then add compost and an air bubbler to the barrel of water and char for a few hours. My barrels are small enough that I can put it on a dolly, wheel it to where I want it, and dump the whole barrel there.
I get small loads, but I do it easily, and get it to where I want it, all in one process. Unfortunately, the place I want it has yet to be a place that's safe to do the burn there and skip the dolly part of it. Dumping it straight out would be easiest, just have not been adding char to good burn areas.

I love the added details, so more people can make biochar that fits their circumstances,  and in general, make use out of materials that we have lying around. I use a dolly to move the barrel around too. It's just so much easier.  I can't burn in the yard, because I live in a suburban area, so I burn with a chimney lid in the driveway.  Then I crush it there by driving over it,  and afterwards, add nutrition (charging/inoculating) before putting it into the yard.

John S
PDX OR

John Suavecito wrote: so more people can make biochar that fits their circumstances,  and in general, make use out of materials that we have lying around.

That's why I comment, when most of the people who make biochar seem to be big guys with the strength to cope with big stuff and move it. I think there's definitely a place for those of us who read the sites on the net and say "well, if I had a crew, maybe...."  I can do it small and slow, by myself, and get good results too! I think that can only encourage others to try it. There are a lot of ways between the big guys and me, and there's probably a way that works for anyone who wants to try one that fits them.

:D

Pearl Sutton wrote:
That's why I comment, when most of the people who make biochar seem to be big guys with the strength to cope with big stuff and move it. I think there's definitely a place for those of us who read the sites on the net and say "well, if I had a crew, maybe...."  I can do it small and slow, by myself, and get good results too! I think that can only encourage others to try it. There are a lot of ways between the big guys and me, and there's probably a way that works for anyone who wants to try one that fits them.

:D

100%. If you can manage a backyard fire pit fire or have a wood stove, you can make biochar. Logs, sticks, woody plants, nut shells, and lots more can be used. Biochar is for all!

Gusty winds blew down quite a few dead twigs off the trees. Most of them were less than 1" in diameter and had smaller side branches. I piled them up 3 ft wide and tall on top of a broken wheelbarrow. It was quite loose so I had to insert strips of cardboard at center top 1/4 position to start the fire. It burned down quite cleanly and I terminated it with dry shredded oak leaves. No water was used for the char but I did need to pick out a few larger branches that were still smoldering and quenched them with water.

One thing that I realized on my last biochar burn of the year: it's important that the sticks are dry.  I tried to put the sticks into my barrel. They were mostly dry.  It smoked a little bit more than it usually does.  I am still going to make biochar out of little sticks, but I'm going to do it in the summer, when everything is really dry.  With branches that are a little bit thicker, they seem to dry off better, and you're not putting in the sheer number of pieces. It's a little easier to control the dryness with larger pieces.  

I don't burn biochar in the winter here, because it's so wet, cold, and dark. When I start up again in the spring, I"ll only make biochar with moderate or larger pieces, because they dry off better. These are more like 3/4" or bigger,  but once the summer comes again, I'll finish up the piles of sticks in making my biochar.

John S
PDX OR

I suppose how dry the sticks need to be depends very much on what specific method you use. We only use the trench method, and almost exclusively with sticks and thin branches. Our last few burns, a large part of the feedstock was green spruce branches, from very recently cut trees. Not only that, we did at least two of the burns under the rain (well, drizzle at least) to minimize the risk of losing control of the fire.

We started it up with a bunch of birch bark and dry spruce branches, and once it was burning nicely we started adding green spruce a little at a time. The fire told us very clearly when we'd been adding too much green spruce too quickly, by producing lots of smoke. When this happened we either added some dry(ish) branches, or just waited a bit before feeding it more green branches. I think we did roughly two-thirds green, one-third older (but not exactly dry) feedstock, though it's hard to compare amounts.

As far as I can tell, these burns made good-quality char, and must have been decently efficient. Quite a lot of the resulting char was made up of whole, charred spruce needles! So yeah, it depends.

Excellent point, Eino.  

I think that TLUDs are much more efficient with dry stock, whereas the trench method might be ok with stock that is a little more moist.   I can't use the trench method because I live in the suburbs.

John S
PDX OR

If I am going to burn a pile of small sticks but at a low temperature say under 500 C, what is the best way to do it? It is so loose and bulky so tend to have too much oxygen.  It is hard to fit inside a container or small space without a chipper.

I am asking because I want to burn some small bamboo sticks in low heat for silicon-rich biochaŕ. According to literature, high temperature will transform the phytoliths into more the crystaline forms and thus less bioavailable. I usually burn sticks as a open fire and the temperature should be well over 500C.

One thing I had to do to help the fire, was to break some of the sticks.  Like you said, it was too airy. Not enough wood in one space.  Some were less than 2 cm or 1/2 inch wide, but 2 feet long.  I broke them enough that the density was just right for a good burn.  They didn't burn as long as heftier branches, but they burned well.  I just had to put more in later to get the same amount of char output.

JohN S
PDX OR

May Lotito wrote:If I am going to burn a pile of small sticks but at a low temperature say under 500 C, what is the best way to do it? It is so loose and bulky so tend to have too much oxygen.  It is hard to fit inside a container or small space without a chipper.

Is it loose because of a lot of side branches? If so, I'd use loppers to give you a larger percentage of at least semi-straight bits.

If it's culms with side branches still attached, something like a piece of rebar whacking parallel to the stem, knocks the side branches off amazingly easily (much easier than either a saw or loppers), but it's difficult to describe the action in words.

If you've got a bunch of pieces that are simply too long, I'd try using an electric saw to cut to length.

FYI, I'm not sure that Bamboo chips all that well - it's stringy and yet flexible. Hubby said he was going to try some, so I'll ask how it went as I'm not home right now.

Hi Jay, my bamboo are probably much smaller than you would imagine. They are a few ft (1-2m) tall and branch right at ground level. They are very wiry and won't snap.

I am looking at traditional rice husk char making. People burn large pieces of wood in the top center of a  conical pile of husks. Put a chimney type structure on top and use the heat from the smothering center to char the husks. I am thinking about putting a few big hot chunks of wood in a pit first and put the whole pile of small bamboo sticks and leaves on top. Somewhat like the trench method but the bamboo will be charred from the heat underneath without any ignition.

May, one design that works well for bamboo is a long trough, Warm Heart style. I had one made that's 2.4 m long and it's useful for coppice rods and long pallet boards as well as bamboo. I'm all about reducing the number of steps in the process.

I am finding that when I make a biochar burn out of sticks, I have to do it in the summer or early fall, when it is really dry as a bone. I've been digging them up with my hands. They get mixed in with old leaves and are almost turning into soil.  The sticks are not as dense as they were a couple of years ago, but it's still useful as a way to make biochar.  I've got my piles on rotation now.  After about 9 months, they are fair game, but I'm usually finishing off a different pile at that point. I most often get to them in between a year and 2 years.
John S
PDX OR