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A trough is mobile. (Well, you can drag it around.) Here in Thailand, we keep five of them in circulation among a group of burners. (Big, 2,000 l. jobs.) They use them for orchard tree prunings. The troughs get shared day to day, but seldom, if ever, team to team.
As far as I know, no one in Africa is using a trough. Too costly, requires skills and electrical power not found in villages.
Farmers are using trenches. They each dig as many as they can use. In many cases, farmers collect stalks to burn just before the rains (having left them out for livestock). They then dig their trenches immediately adjacent to the pile.
Where a village is sharing roofing sheets or a farmer has only so many, the number may limit the number of trenches. Since kicking dirt into the trench works fine, too, farmers who want to get on with it may dig and dig and dig.
No idea how much individual farmers make and use. Too early to tell. May end up depending on feedstock. The farms are very small. Apparently, it is not uncommon to have only enough cob for two months of fuel. If farmers char stalk and cob, they might have 1.5 tonnes of biomass. At 20% (generously) they might end up with 250-300 kg of char. If their farm is just 4-5 acres (2 ha or 20,000 m2), then if they plant by hand (9 holes per m 2) then their biochar yield should allow them to use about 100 g of char per hole. Mixed with a healthy dose of organic matter, this ought to give their crops a nice kick. (Remember: the worse the soil, the bigger the boost.)
We would actually recommend using half this amount of char, doubling the organic matter and doubling the number of holes (18 not 9). Under normal (African) circumstances, this should literally double crop size and then some.
On Mon, Nov 18, 2019, 1:52 AM Tom Miles <tmiles@...
In Malawi how many farmers can one pit serve? Or does each farmer dig his own pit?
How much biochar does an individual farmer make and use in a year?
The same question for troughs. Is one trough used by more than one farmer?
From: Biochar@groups.io <Biochar@groups.io> On Behalf Of d.michael.shafer@...
Sent: Saturday, November 16, 2019 10:25 PM
Subject: Re: [Biochar] Trough burning
Amen to long handles! In season, I have no eye lashes, half a beard, no hair on my arms.
We, too, have found that chippers/grinders do not like wet char. We sun dry ours for a couple of days before even trying.
If you have sandy soil, water retention is big and will get bigger. If you are already feeding your soil a healthy diet of organic matter, that's great. Most African soils are terribly deficient and in the heat it will decompose in a couple of months.
Handling a trough is an art. Too small a fire and it will smoke. Too big a fire and you will burn up a lot of C. If you are running smokeless, that's great.
One thought. If you are using roofing sheet, you may burn through pretty quickly. (You can slow this by washing the inside with just clean water when you're done and then inverting the trough.) We are rapidly converting to the trench as cheaper and easier. Dig a trench slightly smaller than the size of the biggest piece of roofing sheet you can find. Make it about 70 cm deep. Run it like a trough. If you have water, you can quench it (and can make a bigger trench). If you don't, slide the roofing sheet over the trench. Cover the edges with the loose dirt you dug out the hole. If you see smoke escaping, cover the spot with more dirt and tamp it down.
Hi : I've been hanging around here for a few years. I was using Jolley Roger tluds and African style kitchen burners.
I added crushed , charged in hot compost and urine, biochar to my gardens. Sandy soil. I have been using compost and manure so I don't see a big difference. I guess less water is needed and maybe greener than neighbors. it's only been a few years.
Recently I started using a small wood chipper to make a fine slurry from my wet doused char. So easy. Till it jams.
I switched to a trough design, tall and narrow, from 2 sheets of old metal roofing.
Way easier than tluds and nearly smokeless. The trick I found is to make it about twice taller than width and damp down big flames with more wood, of course spreading flaming wood around with long handles tool. Too much fun !
Thanks for all the research and work you are all doing.
Bless you for remembering me.
It has been several years and life changes since I followed tera preta issues.
I'm now in an East Tennessee clay environment where Bio Char soils amendments seem most beneficial.
I am most interested in cost effective methods of increasing soil/forest health.