Thursday, March 20, 2014

Terra Preta - Finished Bio-Char and Applying it to the Garden

At this point, it's been a day or two since I've made bio char in the TLUD,  I usually let the bio char sit in the barrel for at least a day to make double sure it has cooled down.  There is supposedly a remote chance that it can reignite if you take the lid off while it's still warm, although I've found that it's usually cool enough after it's sat overnight.

On this run, when I took the lid off, the bag that I used to start the fire had turned to carbonized paper.  If you look close, you can sort of see that the part that had been burning before putting on the lid has turned to ash and is gone, but the rest of the bag is still there and you can even read what was printed on the bag, but soon after I grabbed it with my meaty fist (my hand doesn't seem to take good pictures)  it crumbled into small pieces of bio char.
A chunk of wood was almost the same way, before I picked it up, it was an intact piece of charred wood, but it easily crumbles and has no ash residue.

This time I ended up with about a third of a barrel of bio char from a loosely filled barrel of maple limbs that were about 12-15" long.  When I've used short (4-6") pieces of cedar, I've been able to pack the material into the barrel a little tighter (I still don't worry excessively about getting it 'just right') and I'll end up with more bio char when I'm done.
After you've made your bio char, it's time to turn it into the makings of terra preta.  I usually do that by cleaning out the stock trailer after hauling some cattle (if you don't happen to have a stock trailer that needs cleaning out, you'll have to figure out something else, like using compost or cleaning out your chicken house).

I usually start by throwing a bucket of stock trailer cleanings into a wheelbarrow, then throw in a bucket of bio char, chop it up and mix it together a little with the shovel, then another bucket of manure and a bucket of bio char, etc. until the wheelbarrow is full.  

Spray a little water once in a while to help "charge" the bio char with the beneficial bacteria and microbes in the manure.    If you are really daring and also of the scientific mind, try leaning down close to the wheelbarrow and taking a good whiff, and you should find out that the bio char has already started  to absorb all the aroma from the manure, compost, etc.  That aroma absorption effect is a simplified explanation for how the bio char works to create your terra preta.  All the little microscopic pores in the bio char absorb and release micro and macro nutrients, microbes, etc. and release them to the plants. 

When I spread my bio char mixture in the garden, I'll cover about 100 square feet with an overflowing wheelbarrow.  When I first spread it , it almost looks like I have turned the the entire area black. But as soon as I run the tiller over it, the "OMG, I've ruined this garden forever" black color is toned down, and I end up with a nice dark looking soil with scattered chunks of bio char on the surface.  Those chunks of bio char will start to crumble and be incorporated with moisture, plant growth, and tilling (I tend to think that those chunks laying on the surface might be absorbing Nitrogen and Phosphorus from the air).      

I tilled this before replacing the worn out tines on the tiller, so if your tiller isn't as worn out as mine, you'll get an even better result.

Next time, I'll try to gather up some of the links I've found that have helped me figure out some of this stuff that I think I know about Terra Preta and TLUDs.


  1. I didn't expect the shiny appearance to it. I would never have guessed that any of the paper bag remained behind either. If you have no source of manure, can you direct apply it to your garden and still get at least some of the benefits?

    1. It does have a little bit of a dull glassy shine to it, but most of the shine you might be seeing in some of those photos is from the water I was spraying on it to help it mix with the manure. It soaks up more water than you would think (thanks to all the micro-pores it has) which might be why it turns so shiny when it gets wet.

      You'll read different opinions about what you need to "charge" the bio char with and even if charging is even necessary.

      I've read that you don't want to use chemical fertilizer with bio char because the salts somehow kill the microbes in the bio char, but I've used Miracle-Gro, a stinky bottle of fish emulsion I found in a shed, ammonium nitrate, compost, chicken manure, and cattle manure. It all seems to work for me.

      I've also just spread it out in the garden in the fall and left it for a while before tilling it in (usually I broadcast something like winter wheat and till that in as a winter cover crop). Since wheat doesn't need a lot of fertility at planting, the bio char might not be affecting it at first, and by the time it comes out of dormancy in the spring the bio char has absorbed enough nutrients over the winter that it has started to work the way it's supposed to.

      From what I've read and sort of observed, just spreading the bio-char by itself has the possibility of negatively impacting some crops planted soon after, but it doesn't bother other crops. After it's been in the ground for a season, the negative impacts are supposed to be much less. The only way to know is to experiment, or wait a year or so before you plant something that you can't accept having a poor crop from.

  2. I especially like the fact that your result was from a loosely-packed barrel. That gives me hope that I can deal with debris in a low-effort manner. Most of the instructions I've seen seem to require an afternoon of cutting and packing things just so in order to get a result.

    Now I've just got to get a container figured out. For some reason, I cut the bottoms and tops off of my barrels... maybe I'll weld one back together.

    1. When I was first trying to figure out how to use my first little TLUD, I carefully stacked the wood in it just like you describe with all the cut ends nicely staring back at me from the bottom of the barrel as I slowly built each layer up to the top of the barrel.

      Then I had all kinds of trouble getting it to start burning (I don't think enough air was being pulled up from the bottom), and when I was finally done it hadn't charred all the wood on about the bottom third.

      So, out of frustration I threw all those unburned pieces willy-nilly back into the barrel , topped them off with whatever I had laying around, crammed some straw on top, and lit a match. That time, it worked like it should have worked all along, flames shooting out of the top of the chimney, less smoke, and most of the wood turned into bio char.

      I think most of the stuff posted on youtube is overly-complicated with blowers and double chimneys, because they can't get the fire to burn decently because they are wasting time and effort carefully arranging the pieces of wood like some sort of charcoal manufacturing version of Martha Stewart.

      Throw the wood in there like a 12 year old boy that has been told he has to do something he doesn't want to be doing, and the whole process will be a lot easier and quicker.

    2. The most important part of your TLUD construction is making sure that the lid you are going to use to smother the fire fits tight enough. As long as the bottom hold the wood and the chimney lid is big enough to cover the top and will support the chimney it should work.

      When I replace my barrel, I'll probably find a crowbar to pry open my wallet, and just buy a used 55 gal barrel with a removeable lid that has one of those nifty breakover clamps to keep the lid on so I don't have to lug concrete blocks around anymore. Locally, I've seen them on Craigslist for $15-20.

  3. "like some sort of charcoal manufacturing version of Martha Stewart"

    "Throw the wood in there like a 12 year old boy that has been told he has to do something he doesn't want to be doing"

    LOL... ahh, yeah, that's dang funny man...

    I kick myself because I was at a scrap metal place and the guys had barrels for $7, and I'm pretty sure they had clamp lids. If I eventually get back over there, and they've still got some, I need to get several. They sure are useful for various things. I'm looking forward to the day I can make a barrel smoker too.

    1. I'd probably be willing to pay $7 for just the lid with the clamp.

    2. Yeah, that would sure beat hoisting the bricks since it is something you intend to do repeatedly. I might be wrong about the clamp lids the more I think about it... I'll bet they were the standard barrels and lids.