Whats the fuss about Biochar?

What is Biochar?

Biochar is a type of charcoal formed from the heating of natural organic materials (such as crop waste, wood chip, municipal waste, or manure) in, critically, an oxygen limited environment. This process of producing this type of charcoal is called pyrolysis.

Due to the particular structure of biochar it is chemically and biologically more stable than the carbon from which it was made, thus making biochar difficult to break down. So potentially it can remain stable in soil for hundreds to thousands of years.

The creation of biochar via pyrolysis also produces bioenergy in the form of synthesis gas (often called 'syn-gas'). Such syn-gas contains a variety of gases which could be used to produce heat and power.

Biochar history

Creating biochar is nothing new, by the way. Ancient Amazonian cultures used it to make soil, called 'terra preta', that is still fertile and being used hundreds of years later. In fact after harvested for use in potting mix, it is so fertile it is able to regenerate!

Part of terra preta's 'secret' is that big quantities of essentially biochar was dug into the soils by these ancient people. Such biochar contained useful nutrients to help plants growth, but its main benefit is in its complex structure to provide a home to bug quantities of nutrients, microbes and moisture in such a way that plants can use it easily.

Greenhouse gases

Interestingly when biochar and bioenergy are produced via pyrolysis it is a carbon-negative process (i.e. more carbon is consumed or captured than produced). This is because the organic materials being burnt are a normal part of the photosynthesis cycle, so when such carbon is taken out of the cycle by the biochar process there is an overall reduction in carbon in the atmosphere.

Also, due to biochar's high degree of stability, the carbon can remain 'captured' in soil for potentially many centuries. This means biochar is a simple way of 'sinking' carbon out of the atmosphere.

Agricultural Benefits

As hinted at with the way Amazonian's have used biochar it can be used as an excellent soil conditioner. Various studies have shown that adding biochar to agricultural soils can boost water and nutrient retention and crop yields, whilst lowering nitrous oxide emissions from fertilizers, by 50 to 80 percent!

Other biochar benefits

Biochar can be used as a dietary supplement for animals, providing additional minerals, maintaining a healthy digestive system, reducing flatulence (which is a source of methane).

Biochar can also be used to reduce the smell of slurry and the ammonia emissions from slurry (ie. sweeten the dung). Plus the nutrients in the dung become closely mixed with the biochar, reducing the effort needed to mix the biochar with the soil

How to Make Biochar yourself

You can make a basic form of biochar yourself; admittedly you will not be able to capture the syn-gas and probably release an amount of carbon dioxide back into the atmosphere; but given the benefits to your garden its worth having a go at making biochar yourself..

Step 1 - dig a trench

to make biochar right in your garden, start by digging a trench in a bed. Use a fork to loosen the soil in the bottom of the trench and you’ll get the added benefits of this “double-digging” technique.

Step 2 - fill it up with wood

Now pile brush and wood into the trench. Make sure its reasonably dry or it won't all burn as intended.

Step 3 - light and watch.

Now light the fire and watch. You want to have a fire that starts out hot, but is quickly slowed down by reducing the oxygen supply. You can tell what is going on by watching the smoke. The white smoke, produced early on, is mostly water vapor. Then as the smoke turns yellow, the resins and sugars in the material are being burned. But when the smoke thins and turns grayish blue, dampen down the fire by covering it with about an inch of soil to reduce the air supply, and leave it to smolder.

Step 4 - Put out the fire.

Once the organic matter has smoldered into charcoal chunks, use water to put out the fire.Well done, now you have biochar to use in your garden!

Once you get experienced with this technique, you can apply it to general pile burning by quickly adding additional material before the center 'burns out' and progressively starving the center of the fire of oxygen - then when you get to the gray smoke stage put the fire out with water.

> Whats the fuss about Biochar?