I spent the month of September 2011 back on the farm, getting it into shape and making batches of biochar. At the end of the month i took a truckload of the char down to Josiah’s biochar operation in Puna, where it was inoculated and ground up. Back at the farm, the living char was spread all over, especially in the tea field.
Deb asked me one day to write something about how biochar fits into our farm. I scribbled a flowchart onto paper, and today put it into the computer; it looks like this:
Ideally, it’s a continuously flowing cycle; there is no “waste” and no need for unsustainable inputs; that’s the goal. The chickens provide meat and eggs to the humans, and poop to the compost cycle; the biochar stabilizes the nutrients in the urine and compost, making them plant-available longer. You can see how the compost pile is the engine in the middle of everything.
Those of you following the biochar-hawaii list know that i’ve stopped using my kiln, and am now focused on making biochar in a pit. This is both for reasons of scalability and wear; my 55-gal steel drum kiln/retort could only make ~23-gal of char, and the surrounding kiln blocks cracked from repeated heating.
Hence, a pit. Mine is lined with blocks for clean char and easy unloading. Continuously fed wood, pyrolysis occurs at the air-starved bottom of the pile, gradually the pit fills up, then i cover and let it cool for a day, before opening and scooping out the finished char:
That first small pit worked well, so i made it bigger and sure enough, it scales well:
Width
Length
Depth
Gallons
Cubic feet
# of blocks
Gallons of Char
24
32
16
53.2
7.11
33
16.5
32
48
16
106.4
14.22
48
34
32
48
24
159.6
21.33
60
68
32
48
24
On second burn:
82
That 82-gallon operation took 2.5 hours to do the burn, then 2.25 hours the next day to unload, crush, sort, sift, and load into buckets. That’s 82/4.75 = 17.25 gallons of char per hour of work. That’s not bad, given that i’m working with some cheap concrete blocks, a piece of old corrugated roofing, and a shovel. With more money and technology, like a continuous pyrolysis machine, you could certainly get vastly more char per hour of labor, but those machines start at $100,000. I’m feeling quite happy about my pit. The Biochar2010 album has all the pictures.
I gave a biochar talk to the Kona Coffee Grower’s Association on June 2. 10 minutes of that talk got uploaded to YouTube. I then addressed the Hawaii Tropical Fruit Growers on July 19, that time with a fancy presentation with charts and pictures. Next will probably be an evening talk in Waimea on August 8, and then a 1-day workshop on making and using biochar here at our farm, date TBA.
I recently did a second and third burn in my biochar kiln, tweaking each time. The story is best told in pictures:
Upon detailed inspection, the April test burn actually gave good results. Four white buckets are completely charred material, two orange buckets incomplete, one mixed and one of material from the surrounding fire.
Completely charred wood from retort, and the incompletely charred – only a small amount, and generally from the bottom of the barrel, perhaps due to a lower temperature there.
Preparing for burn #2, using smaller wood and some changes to the kiln.
Added a layer of firebrick at the base. Ideally, it should enclose the whole chamber, but that would take a lot of actual masonry.
More air inlets, allowing air into all four corners.
The ‘chimney’ is formed by the blocks themselves.
Smaller wood scraps for burn #2.
Opening the kiln after burn #2.
As before, the material at the bottom of the barrel (top, when inverted like this) is less charred, but everything above (below) it is completely charred
Much of the sticks that look brownish on the outside are actually completely charred black on the inside
Burn #3
Got the fire real hot this time, you can clearly hear the “whoosh” of the pyrolysis gasses from the barrel joining the fire
Sifting/crushing/sorting the result. Some 1/2″-minus has direct uses. The rest will soak in nutrients to charge it, then goes through the chipper-shredder to make “charged fines” – biochar fertilizer.
As a followup to my last biochar post, i was sent the following document from Karl Frogner of UBI. Karl asked me to make it available, so i’ve put it here: Biochar Ovens, until UBI has a place for it on their own site.
It describes experiments conducted in Mongolia on making biochar in a steel drum where the combustion occurs in a metal center tube. Innovative and fascinating! I want to try it here on my farm, but i’ll have to somehow locate some heavy large-diameter metal pipe, and be able to make holes in it.
My friends Josiah and Jay down in Puna are producing biochar using a classic pit method, which seems to work well. I may end up making char that way as well, but there is some criticism on the biochar list of open burns, saying that emissions aren’t fully combusted and carbon yield is low, recommending a kiln or even better, a retort (closed “cooking vessel”). So, i looked at plans online and found two approaches, the two-drum and the Twin Oaks, particularly as built by Kelpie in Oregon. The first approach is too small a batch and requires multiple drum sizes, the second requires expensive metalwork including pipes and welding. I came up with a hybrid of the two approaches which should be cheap, simple and high yield.
I did my first trial fire-up yesterday. The trial results are from this picture onwards.
Results were promising, but need tuning. I learned a lot from this trial run. Some indications:
The kiln fire needs to be strong and hot and heat up fast. My kiln burned moderately, for a long time, so it didn’t fully cook the retort.
More air inputs. I was hoping to limit openings to focus the heat inside. I put vents on the left and right and front, but the fire seemed to want more air.
A round barrel in a square box isn’t great geometry for a fire, which tends to burn separately in the four corner “zones”. I could try stacking the blocks in a more circular arrangement, like a hexagon/octagon. If i stay with this arrangement, i’ll need air vents specifically pointing into each corner.
Chimney. I figured a simple rectangular hole at the back should suffice, since it worked for Kelpie. But mine didn’t seem to draw well. Charcoal kilns for a thousand years have had proper chimneys. I’ll probably need one too.
Insulation. I used regular CMUs because they’re cheap and available. No doubt better insulation would result from using firebrick, thereby focusing more heat inside. I could also fill/bury the hollow tile walls, even if they’re dry-stacked.
The half-charred results of this trial aren’t useless; they could still be used for a less-smoky cook fire, or dropped through my shredder to make mulch with a more stable carbon content. However, the goal remains easy, cheap, reliable full pyrolysis. If it doesn’t pan out with this design, i could always switch to a pit, or hybrid brick-lined pit, or other ideas.
Tea: We did our third tea harvest on November 30, processed as a green tea. We have actual packaging now with a logo and label. Several people bought it to give as a holiday gift. As our first green, it was delicate and floral and nice, and it sold out quickly.
Biochar: the first solid results are in. Test 1 (green beans) didn’t work well as plants varied widely within each plot. Test 2 (popcorn) showed promise with the char plots growing better, but heavy rains this fall prevented any of the plots from maturing to compare yield. Test 4 (taro) is still in progress as taro grows slowly at our elevation. Test 3 (sweet potatoes) was harvested yesterday:
8 plants, control: 13.8 lbs
8 plants, with char and IMO: 21.2 lbs
That’s around 50% more tuber, and here’s the picture, control on the left:
To deal with the pig attacks, we added a strand of barbed wire at ground level running all the way around the garden fences. We also got a trap from neighbors, and the first night we caught a big mama pig:
She managed to escape, but since then we’ve caught three smaller pigs. They go to a neighbor who, i believe, fattens them up for eating.
Two more biochar tests area in the ground, this time using IMOs as well as char. Crops: popcorn and sweet potatoes. Posted to the hawaii-biochar group.
The HFU Potluck-Seed Exchange in Honoka’a last Friday was excellent, great turnout, tons of food, interesting seeds.
If you missed it, the next one is August 14.
I had a horrible fever that raged for 2 days, nausea, delirium, then a strange red patch on my leg. At the ER on Sunday, they said it’s a staph infection, put me on antibiotics and bed rest. Sad to say, this mean little to no farm work for a week or more.
The barrel tax was defeated today. It’s a little depressing, a sign that the top-down powers that be can’t make even a little step in the right direction. As it says, “A bill to fund food and renewable energy projects is left to die.”
While i was in California, our first batch of biochar arrived, from Biochar Engineering thanks to the nice folks at EcoTechnologies Group. Yesterday i launched my very first field test, using peanuts. I have enough char to do many more tests, in the newly expanded upper field area, with other crops like sorghum, corn and potatoes. There are so many different combinations to test – varying amounts of char, different crops, use of microbial inoculants such as Natural Farming IMOs and Bobby Grime’s Aerobically Activated Compost Tea (AACT).
I have launched a mailing list, biochar-hawaii for the growing community of biochar-interested people here in Hawai’i. If you are interested in making Hawaii agriculture sustainable and reducing climate change, come join us!
I’ve been studying biochar for a year now (see my biochar notes), and just this week the first major book on the subject arrived, Biochar for Environmental Management. It’s academic, and dense with science, but totally fascinating. Imagine my surprise in chapter 5 when i encountered a reference to this paper:
Hoshi, T. (2001) ‘Growth Promotion of Tea Trees by Putting Bamboo Charcoal in Soil’, in Proceedings of 2001 International Conference on O-cha (Tea) Culture and Science, Tokyo, Japan, pp 147-150
It even turns out to be online! See the paper in English as pdf, and the English website which has a more detailed version (in Japanese) with pictures, which shows all the stages from harvesting the bamboo and making the chacoal, to spreading the char in the field and measuring the bushes.
A quick summary: A 10-year test begun 1998, which in year 3 the tea was already showing 20%/40% greater height/volume, using only a rather small amount of char (100g/m2 a year, or 500g/m2 once). The composition of the harvested tea was the same, so the main benefit is reduced need for fertilizer.
For those of us trying to grow tea organically/sustainably, in poor soils like our Hawaiian clay, this is huge. They didn’t test with large amounts of char (1-3 kg/m2 is typical of tests on other crops) so more might be even better, and it should be fully complementary to all the other organic approaches (EM, IMO, compost tea, etc.) so there is a lot of exciting things to try!
As a followup to my last biochar post, i was sent the following document from Karl Frogner of 
