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Monday, September 6, 2010

Forest biochar

Biochar 101 

Biochar or Agrichar is doing the rounds in the news as a solution to a range of problems, including declining soil health and Carbon dioxide emissions from Industry and Agriculture.

Biochar is created by burning organic materials in low oxygen conditions so that a proportion of the carbon does not escape as Waste gases but stays behind as a solid and relative inert form of carbon we commonly know as Charcoal. The lack of sufficient oxygen prevents combustion to the end point where only mineral salts remain, known as Ash. Ash contains plant nutrients but it is caustic and water soluble so what canot be used quickly leaches away.

Most Charcoal is produced for industrial and fuel uses and ends up being burned anyway.The better industrial charcoal is made from Trees either in plantation or from felling natural forests. In this setting Charcoal is a great waster of a natural resource, as only 15-35% of the Carbon in Wood is retained in the marketable product.

However, Change the intent and feed stock origin and the whole game changes. Better Biochar is made from Low value organic wastes such as husks, shells, sawdust, short fibres, cleared brush and palm wastes to name a few, interfere greatly with cropping and tillage or general operations in Farming, Industry and forestry. They are generally low in plant nutrients and so naturally slow to break down, they do add some soil organic matter but often with great nuisance. They may contain inhibitory compounds that retard the growth of the next crop, or may harbour disease for the next season. Left to compost naturally the loss of carbon is almost complete with very little joining long lasting slow soil carbon pools. Any organic gardener will lament the sheer quantities of mulches and manures they have carted onsite, only to see it swallowed up by the soil. There is benefit, but it is easily undone by a few years of neglect, and it is a constant struggle to build and mantain on farm soil organic matter. Because of this, carbon that can be fixed by conversion to stable black carbon is a highly efficient gain and not a waste.

One of the benefits of Biochar is that it joins a store of carbon that is extremely resilient and long lasting. Charcoal is used by archaeologists to date prehistoric human settlements, and seams of charcoal exist from when land plants had only recently evolved. Even today many ferns like charcoal in their potting mixes, or will not germinate in the wild unless there is charcoal in the seedbed.

Biochar complements other Active and passive pools of Carbon in the soil by improving soil structure and decreasing bulk density so that roots, fungi and soil fauna can move around more easily. Chemically it helps form aggregates that stabilize other soil organic matter against loss by oxidation.Biochar does not replace living soil and Humus, it protects and complements it!

In this way a yield from an annual harvest of waste Peanut hulls, converted to 20% of its volume in Char and re-incorporated represents a boom to stable soil carbon levels that is unheard of by any other means within that time frame. It is also produced onsite or nearby and so is not robbing peter to pay paul.

Because Biochar is bulky but light and full of pores, it decreases the heaviness to the soil, helps it hold more water and more air, and helps prevent tight compaction. In amongst these spaces are sticky chemical sites that hold onto plant nutrients and slow the leaching process.

The Video

The clips show a man in Hawaii using Biochar to turn a carbon rich but infertile site into a rich Garden.
Rank vegetation in degraded areas`after logging and regrowth offers a ready onsite source of carbon.
Using a simple method the materialis converted to a Biochar that enhances the local soil.

Our own method we developed several years ago is very much like this method. Its is Low tech, used onsite materials and apart from simple labour, which you supply yourself, is free.

Our own methods used more grasses, like lawn clippings, Vetiver, Bana grass, bamboos, as well as wood prunings and woody fruits pits and capsules from Fruit and ornamnetal trees. By Turning the Hard,noxious, diseased elemenst of the garden to char they are defused.

Now in the tropics the use of Palm wastes including fronds, seeds, sheathes and trunks is most appropriate.


Biochar 2

Biochar 3

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