Healthy soil and sustainable growing

[Zachary Domike <zdomike@yahoo.com>]

This list covers desert temperate climates like the south of Portugal to 
temperate rainforests like mine here in New Zealand.  

Where wood rots fastest is in warm humid climes, but Dieter's comments are 
true, rotting wood is not always quick soil. Depends on local conditions.  My 
experience is that charcoal is an excellent soil conditioner for clay soils.

The wood that the goats would not eat and was too small for firewood is very 
slow to compost in the cold rainy winters and also slow to compost in the dry 
cold summers.  Whole twigs remain intact after two years while the 
surrounding organic matter was a sticky humus that had all been through a 
worm or two.  I did tie up bundles of these twigs for firing up the beehive 
oven and also the retort.  

A slower method for modest quantities of twigs is Harvey Ussery's chicken 
run.  But the highest use, at least for my heavy clay soil, would be an 
example of charcoal wood-in-the-ground named Terra Preta or Biochar.  Not to 
buy it, but make it, as I did in a 55-gal drum retort.

The actual technique is very important, as it is easy to burn it all into 
ashes, releasing the carbon.  To convert wood into  charcoal requires heat 
and a sealed container, restricting oxygen that would combine with the carbon 
as CO2. I made a fire under the sealed steel drum full of agricultural waste. 
 It bursts into flame very briefly as the oxygen disappears, then scorches 
for a while as the impurities evaporate.  The retort function was difficult 
to make and ineffective, so I eliminated that tubing.

Producing charcoal is not easy, but the value to the soil was notable.  The 
charcoal made the structure much lighter, especially when compared to adding 
sand to the same soil.  The quality of the worms indicated that the soil was 
much better, too.

Somebody will find a cheap way to save carbon from escaping from agricultural 
wastes that are currently burned in too many parts of the world, and thus 
save tons of carbon per season.  My next project is a wood pile buried under 
a layer of cardboard and clay, fired to make an oven, and charcoal for 
spreading on the planting beds . . . just need to fine tune the 
low-technology.

Anybody else tried some version of that charcoal production?

Zack