First, a bit of irony from something I wrote a year and a half ago.
"There are many good ideas for homesteaders out there, but they often require
significant time and energy to maintain. Brewing compost tea or making biochar
are two things I considered. They are excellent ideas, but would I be able to
balance the time they required with everything else? Would I be able to
provide all the components myself or must I continually buy something to
maintain them? The answers to projects like this are subjective because there
are many individualized factors to consider. We chose other soil building
methods because they worked better for our homestead goals and routine."
The advice remains sound, but now I have to move biochar as an example into
the never-say-never category! It was Dan, actually, who decided to undertake
the project. We have a lot of waste wood, and the question is always what to
do with it. How do we put it to good use?" The answer is to make biochar.
What is biochar and why would we want to learn to make it? Good questions!
What it is. Biochar (biocarbon) looks like natural charcoal (as opposed
to commercially made briquettes), but it isn't. Charcoal contains wood resins, which make it combustible and give
smoked food its flavor. Biochar is a step beyond charcoal. The resins have
been baked out, leaving a stable, porous, carbon char. Its most
common use is for soil building, where the pores become habitats for
beneficial soil microorganisms and store water and nutrients.
What it's used for. It has lots of uses.
- In the garden (needs to be inoculated first - see below)
- sequesters carbon
- provides a habitat for beneficial soil microbes
- retains soil moisture and nutrients (reducing runoff and erosion)
- decreases soil acidity
- removes soil contaminants such as hydrocarbons and heavy metals
- increases microbial life
- binds soil nutrients
- improves physical structure of soil
- provides long-term soil productivity
- Water purification
- rainwater tanks
- greywater systems
- aquaculture
- In barns, kennels, cat litter, and composting toilets
- odor control (absorbs ammonia)
- absorbs moisture
- reduces pH
- Feed additive
- absorbs toxins in the digestive tract
- improves digestion
- improves feed efficiency
- reduces nutrient losses
- reduces methane production
- improves animals' overall health
- Poultice additive to draw toxins out of a wound
How is it made? Biochar is made by heating biomass without oxygen. This is called pyrolysis and can be achieved in a number of ways. Some people make it by simply putting
corncobs or woodchips in a lidded dutch oven on the stove and baking it. Others burn it in pits or in retort kilns. To make ours, Dan built a top-lit updraft kiln, also called a
TLUD (tee-lud).
The TLUD is a type of gasifier and works just as the name says; it's lit at the top and draws air up
from air holes in the bottom. It's not as complicated as it sounds! It's
actually very simple. There are numerous variations on this, but this is how
Dan made ours with two barrels with lids and some old ductwork.
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Outer 55-gallon steel drum (burn barrel) with air holes
(primary air
intake is at the bottom and secondary at the top.)
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Inner 30-gallon steel drum holds the biomass. Fire burns in the outer
ring.
(Note: This was our first try, and we've learned that smaller pieces work better.) |
The wood inside the inner barrel will become our biochar. It is filled with "feedstock" (the biomass to be baked into biochar) and the lid put on the small barrel. Fuel wood is packed
under and around the inner barrel, with kindling on top. The kindling is
lit, and the chimney is placed on the top.
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A hole cut in the barrel lid accommodates the chimney.
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The process goes through
several stages.
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Initially, smoke is emitted as the fire
burns out residual
moisture in the wood.
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The red glow indicates that the temp is
hot enough to begin
burning wood gases.
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Once the gases are burning well, there is no smoke.
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The kiln is allowed to burn itself out, and once cool, the chimney is
removed.
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This is the biochar which is basically char with the wood resins
burned away.
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How do we know we've made biochar? - Crushes easily
- Has a fragile, almost tinkling sound
- Has no smell or taste (it's sterile, so it's safe to eat)
- When crushed with bare hands, the black residue washes off easily. With charcoal, residue is difficult
to wash off because of the wood resins.
What other materials can be used to make biochar?
- corncobs
- corn stalks
- woodchips
- twigs
- bamboo
- basically, any dried biomass; small pieces work best
How long does the process take? Once the TLUD is going, it needs no tending and will burn itself out in several hours. So the only time involved is in loading the barrels, starting the fire, and later unloading the biochar.
How do I inoculate it for the garden? Making biochar burns away all life and nutrients. So when first removed from the
kiln, biochar is sterile and void. If added to garden soil at this stage,
it will begin to absorb soil nutrients. Unfortunately, during this time it
is competing with plants for those nutrients. Once charged with
absorbed nutrients, it will begin feeding the soil, but the process takes at least 3 to 6 months.
The best and quickest results are seen when biochar is inoculated
(charged) first. There are a number of ways to do this:
- Soak in liquid fertilizer. Fastest way, takes about a day.
- compost tea
- comfrey tea
- nettle tea
- manure tea
- compost worm casting tea
- Urine - place it in a bucket with drain holes and cover with pee. Takes 2-3 weeks
- Mix 4 parts biochar, 1 part rock powder, 1 part worm castings, and ½ part flour or molasses. Cover. Takes at least 2 weeks.
- Mix it into the compost pile (10-50%). Takes 2-3 weeks.
- Deep litter. Mix it into the chicken litter in the coop, where it helps deodorize. It will be inoculated by the next time the coop is ready to be cleaned out.
- Mix with equal parts fresh grass clippings. Cover and let sit until clippings are decomposed. Takes about 2 months.
- Worm castings - equal parts with biochar. Sprinkle with flour, corn meal, or molasses. Cover. Takes about 2 weeks.
When I first looked at biochar years ago, I found only the complicated ways to inoculate it. As with all new endeavors on our homestead, it must be asked whether the benefit outweighs the time and expense. (See my post on "The Time to Benefit Ratio.") There are only so many hours in a day! Finding simpler ways to inoculate biochar changed that ratio. For us, simply adding it to the compost pile and deep litter significantly increased the benefit factor.
How do I apply it in the garden? Since ours is mixed in with the compost, I'll apply it as I do compost. I'll use it to cover seeds and top dressing. For new beds or transplants, I'll mix it into the soil. Some no-till people prefer to make slits in the soil with a shovel and sprinkle it in. It can also be tilled in or worked in by hand. Mixed with compost, it makes good potting soil.
Caveat. Various biochars are not equal, so results may vary. From what I've read, some benefit can be seen the first year of application, with continued improvement over the years.
Okay. That's all my notes about biochar! It isn't all there is to know, of course, and it's another fascinating subject to study. But it's a start and a good homestead solution for our woods and garden "waste."
