Biochar

10 Jan

Biochar dryWe are always in the mood for appropriate technology, especially when it is elegant and inexpensive – perfect for people! So when we heard about the Kon Tiki biochar kiln and how it makes inexpensive, copious biochar efficiently and with minimal smoke our little ears perked up.

Most biochar retorts we have seen are complicated affairs requiring external energy to heat the biomass stock material to the temperatures needed for pyrolysis, with fairly poor efficiency. Not so the Kon Tiki. It’s secret is in the shape (physics, friends). The inverted cone contains the fire in such a way that the biomass stock is not burnt up but the gases are, all without producing excess smoke. It uses no external heat source. And it’s simple to construct if you’re handy.

The link to the Kon Tiki description is here.

Now, by means of full disclosure, we admit that we have not tried the Kon Tiki kiln or other similar kilns. We do have our eye on one suited to backyard charcoal production – the CharCone – here.

If you can’t afford either of these options, it is possible to dig a pit the right shape and make biochar in it. See this presentation.

There is no end to trimming and pruning woody materials here on the Rancho. And given the success of biochar in a few garden beds, we are keen to spread it over larger areas. Several years ago we purchased some biochar for an experiment on new garden beds. This was right before the beginning of the Great California Drought and we were not able to follow through due to lack of irrigation water the last three summers. However, we did have enough left over biochar to dose one of our growing beds in the main garden. That bed has flourished, even more than the rest of our mineralized garden. It was not a controlled experiment, but the biochar seems to have helped. Biochar is supposed to aid:

  • Water retention (in the char pores)
  • Microbial life density (they live in the pores)
  • Mineral retention (trapped in the pores)
  • Source of soil carbon

All of these are useful in our loamy sand. This is in addition to biochar’s role in sequestration of carbon for the long term.

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16 Mar

March 16th, 2014. It’s going to be 90F here today and I just finished spreading 1/2 of the three biochar types, and planting Peaceful Valley’s “Soil Builder” cover crop on them. The test plot is on unimproved soil outside the gardens. I spread each biochar type on a 3’x8′ bed and dug it in. Half of each bed also receive some of last year’s compost. Planted the seed and covered with dirt, then compost mulch to keep moist, then a scattering of straw to also help keep it moist.

Interesting to note the state of the worms in the biochar. I had added worms and bedding to each box last fall. There were no worms at all in the MiracleGro biochar. The control biochar (that had only added compost) had lots of worms while the OrganiCalc mineralized biochar had a few. This has been the worm situation since January. I wonder why? Maybe the nitrogen in the mineralized and MiracleGro biochar caused an early flush of microbes, followed by a collapse?

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29 Oct

If you’ve been following our biochar experiment, you know that we’re trying out several different methods of activation of the char. A couple of weeks ago I introduced some worms from my bin into the biochar bins. My worm bins are simply stacked nursery flat holders, held inside a recycled picnic cooler from Goodwill. I gave each biochar bin a worm flat, loaded up with their favorite food, a mix of dead leaves and kitchen scraps. The worms were free to stay in the worm bin or move into the char.

 

 

 

A couple of weeks later and the worms have multiplied and moved into the char. I’ve fed them a bit of corn gluten meal (about 1 cup each bin) and we’ve gone through a mold episode. The worms are out and about foraging on their own now.
I’ve got them inside in a room off the garage — my old office to be exact (always did seem more conducive to compost than work). I think they could be doing better so I’m going to see if I can’t find a source of their favorite food, bacteria and fungi. Stay tuned…

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15 Oct

Biochar experiment
So we have had this bag of biochar for a little while now and are considering the best thing to do with it. We know that it will need to be charged with microbes and mineral nutrients — the question is what is the best way to do that? Our guide is a recent article in the July 2013 issue of Acres magazine by David Yarrow.  He recommends a 4 step process of charging:

1) Moisten the char.  Get it wet but not soggy.  (This takes more water than you might think it should!  The stuff is very absorbent!)
2) Micronize the char.  A mix of dust and rice size bits is best.  Your char might need crushing but ours was just right already.
3) Mineralize the soil.  The char is like a battery waiting to be charged.  If you don’t add minerals at this step it may rob your soil of needed nutrients and thereby also rob your plants.  We are doing 3 different trials to see which method of mineralization works the best.
4) Microbial innoculation.  We mixed our char with equal parts of semi-composted spent mushroom bedding and a few shakes of mycorrhizal inoculant.  But the compost is really just food for the worms that we added to each bin.  The plan is to let the worms work over the winter, eating the char, minerals and compost.

Wet Biochar
For step 3, we have 3 different mineralization trials going.

1) Mineralized with the OrganiCalc recommendation for our native soil, assuming we’ll spread the mix ½” thick and work it in to the top 6” of soil.
2) Mineralized with MiracleGro plus the OrganiCalc recommendation for gypsum (there is no calcium or sulfur in MiracleGro and our soil is quite low in both).  The amount of MircaleGro was enough to about match the N supplied by the OrganiCalc recommendation, about 5x the single application rate on the label.  Why MiracleGro?  It is a (sort of) balanced source of soluble nutrients and should not have trouble migrating into the char pores.  There is no organic OMRI approved substitute that we know of.
3) No mineralization. We will probably add the minerals later during incorporation of the biochar into the soil.

The plan is to put half on “new” unamended garden and the other half on the existing garden, so 6 trial plots in all.

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10 Sep
Dry Biochar

On a trip to Oregon we stopped in Philomath to speak with John Miedema, one of the founders of the Pacific Northwest Biochar Initiative. John operates an experimental biochar cooker on the site of a log storage yard in Philomath, using the chopped up bits of wood and bark leftovers that would have previously been considered waste to be burned or buried. The result is a light, dry, charcoal type material with a black pigment which I immediately spread onto my nose. We picked up a double bagged 30 gallon bag full to try out as a soil amendment.

It’s not the nutrients in biochar that we are after. We’re hoping instead to use its amazing propensity to hold onto nutrients and create habitat for microbes and beneficial fungi. The process of making biochar, using higher temperatures and a lower oxygen environment than a normal wood fire is capable of, results in a material with amazing properties. Tiny pores are opened in the burnt wood, creating a massive surface area in a very small volume. This surface area will be perfect for holding the cations and anions necessary for plant growth. Also, the char is structured into tiny tubes which catch and hold water and provide the perfect homes for microbes and fungi.
Biochar micrograph courtesy of Ithaka Journal
Our soil is quite sandy and low in nutrient holding capacity, plus being in central California near the coast we experience long dry summers, bright sunlight and breezy afternoons. It is not a natural environment for mycorrhizae; wood left on the ground tends to dry out and be eaten by insects with little to no sign or rot, unlike our western Oregon garden soil which ate anything and everything. If biochar could help us hold and spread out soil moisture, plus create a home for microbes, it may be a profound improvement. Our part of California is prone to late summer wildfires of enormous proportions which litter the ground with the charred remains of chaparral. The result of the fires is nothing short of amazing — the wildflowers go nuts the next few years. Perhaps we can emulate that in our garden.Poppies

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