Biochar (again?)

@Tim Harrigan 22009 wrote:

Any connection with the ‘slash and burn’ techniques used in tropical areas over the ages? 😮

Definitely. Slash and burn didn’t just clear forests, it was a fertilization technique. Trees pull up nutrients from deep in the soil, and sequester carbon from the air. Burning them is the shortcut to get all that back out into surface growing crops.

If you were clearing a forest to put in farmland, it might be worth charcoaling the junk trees for the soil, but most of that timber is much more valuable as wood.

@near horse 22015 wrote:

Sorry but from what I’ve read biochar and slash and burn are not the same thing at all. When burning organic matter in the presence of unlimited oxygen, most of the carbon is going up as smoke and CO2 and leaves no (or very little) substrate for colonization by fungi etc – biochar or “terra preta” results in charcoal remaining in the soil to provide places for organisms to inhabit (and build soil fertility and also tie up more CO2).

Funny, I just saw something about this on National Geo tonight – try googling terra preta (I think it is Portuguese for dark or black land). Researchers believe that this technique of maintaining fertility in the Amazon basin may have allowed large numbers of people to inhabit that area without having to move when the soil played out. Pre-European contact estimates are in the million(s) of inhabitants for the area – while the current number is only about 300,000.

There’s a lot of people looking at this as a method for increasing fertility of some played out soils – not something you wold associate with slash & burn.

Yes, exactly. Alan Nation wrote an article about this in The Stockman – Grass Farmer within the past year. I’ll see if I can find it. He termed this swiden or swidden (or something like that) agriculture. He said it was practiced by native peoples all over the Americas, but especially in the humid, tropical areas of South America. He said the furnaces that they used to create this stuff essentially burned year round, with the smoke being a form of mosquito and fly control around their villages.

@OldKat 22017 wrote:

… He said the furnaces that they used to create this stuff essentially burned year round, with the smoke being a form of mosquito and fly control around their villages.

Whoa. Hold the horses folks. Step back and look at the big picture for a second. Wood is carbon and volatile compounds. When you heat the wood (whether in an open fire, woodstove, furnace, charcoal kiln, etc) those components are separated from one another. The carbon and the volatile compounds are both very combustible.

Those amazon furnaces that you describe are charcoal kilns. Start a fire in a mud beehive, seal up most of the air inlets so it will smolder. The idea is to let in just enough air to burn just enough of the carbon and/or volatiles to drive the process (separating the volatiles from the carbon). If we did this in a fancy modern appliance we’d call it “pyrolysis”. The volatiles spew into the atmosphere as unburned fuel with horrible environmental consequences.

Waste 100% of the fuel value in the wood,
dump 50% of that fuel into the atmoshere unburned
… and yet here we are touting the ecological benefits of this practice. Hmmm?

The only way to make this work is to plumb the flue gas to an appliance, and burn it for some USEFUL purpose (powering a sawmill, generating electricity, domestic heating, boiling maple sap, heating water for a dairy, desalinating water, etc). I guarantee you that the amazonian charcoal kilns did none of these … though I don’t doubt their efficacy for mosquito control

Imagine if all the standed offshore oil wells (serviced by tanker rather than pipeline) dumped all the associated natural gas rather than flaring (burning) it off. Flaring is wasteful, but dumping is just plain negligent.

You’ve all heard the hubub about cow farts (a.k.a. methane .a.k.a natural gas). The situation is directly analogous. Methane (unburned fuel) is an incredibly effective greenhouse gas. Far worse than burning to release it’s energy content and its carbon content. Of course it would be even better if we did something useful with the heat of combustion. The bottom line is ‘Don’t dump unburned hydrocarbons’ into the atmosphere (or the water, but that’s a different discussion altogether).

I have a hard time accepting that charcoal production by “traditional” means is ecologically beneficial.

We can bias the process to either consume or produce charcoal but it is critically important to combust the gaseous fuel product as completely as possible.

Regards,

Matt

Geoff, can you describe a sustainable system that included biochar production and use? I am not being critical of the concept, I am all for management alternatives that build soil quality. I am having trouble balancing the scale of production and use. For instance, what does it take to produce a ton of biochar and how much acreage would that cover and have a measurable benefit?

here’s what i know: biochar was used to improve the sandy soils of the amazon basin, and the wood “wasted” that way isn’t wasted at all, it’s investment worth gold in certain soils and climates.
this means mostly sandy soils, who are not very fertile and who don’t retain water.
now, carbon retains water, so the soil will retain water more. second, then one fertilizes the soil, it may help that biochar will bind with manure or organic fetrilizer and enable it to stay in the soil longe. an idea anyway.
third, biochar may provide home for microfauna and flora.

i would try to use it on sandy soils, that’s as far as i know.