Biochar is a stable form of carbon, which can be added to soil to store carbon and reduce net greenhouse gases. Biochar is created when waste organic matter, is burned in an oxygen limiting environment at high temperatures (around 350°C and 600°C). This type of heating process is called pyrolysis.
The quality of biochar is determined by the quality of organic matter that is used, as well as the conditions used in its manufacture.
Production of biochar is an environmentally friendly carbon recycling process. Biochar can be applied to the soil, either alone or combined with nutrients, and it can also be fed to livestock.
Examples of waste organic matter include waste wood chips, crop stubble, green organic waste and primary production waste products.
Studies report a number of benefits and risks associated with biochar. Some of the benefits include:
- generally lowers soil acidity
- can increase soil buffering capacity
- can increase plant productivity
- can increase dissolved and total organic carbon
- can increase cation exchange capacity
- can increase available nutrients
- can increase water retention
- can increase aggregate stability
- can increase microbial activity
- can accelerate nutrient cycling
- can reduce leaching
- can reduce bulk density and N2O and CH4 emissions.
- the contents of the base material and the temperature of the pyrolysis determines the characteristics of biochar
- there is some risk of heavy metal contaminants being present in some base materials
- soil type influences the action of biochar and its carbon sequestration potential
- the production of biochar can be very expensive
- biochar absorbs and concentrates herbicides and pesticides in the root zone.
"Biochar made from material such as manure or broiler litter will have a greater nutrient content than a biochar made from carbon rich materials such as municipal green waste or tree prunings".
Case Study - Holla-Fresh
Case Study - A circular economy. BioChar in the Limestone Coast
A prime example of the circular economy in action in South Australia. Local company Bio Gro provides wood residue to Holla-Fresh Herbs at no cost for use as a heating fuel. Afterwards, Bio Gro takes away the biochar that is produced as a natural part of the pyrolysis process.