Biochar is a type of charcoal produced by heating organic material (plant or animal waste) to temperatures greater than 250°C in a low oxygen environment (this process is called pyrolysis). From this process, a carbon-rich, stable-structured and inert carbon product is generated.
Biochar can reduce carbon dioxide (CO2) released to the atmosphere because pyrolysis traps the carbon in the biochar, which otherwise would be released through decomposition or burning of plant material. Biochar is stable in soils and, depending on the type of source material, can remain in soils for hundreds to thousands of years.
Benefits from applying biochar
Productivity improvements are more likely on sandy soils, and the benefits include:
- increased nutrient retention and reduced leaching
- increased cation exchange capacity
- improved soil structure and water-holding capacity
- decreased soil acidity and increased habitat for microbes.
Biochar has the potential to reduce fertiliser requirements while crop productivity is maintained, or increase crop yields at lower rates of fertiliser use due to reduced leaching. The benefits vary depending on the type of biochar and the nature of the soil in the treated paddock and in some combinations, the impact may be detrimental.
Opportunities in using biochar:
The activity of applying biochar is deemed ‘additional’ to normal practices for the Carbon Farming Initiative.
Risks from applying biochar
There are several risks:
- Biochar is expensive and economic returns are unlikely for commodity agriculture.
- Obtaining sufficient quantities of biochar is difficult because there is no large-scale production.
- Not all soil and biochar combinations will provide a positive result.
- The quality of biochar material is variable. Some material produced as by-products of industry may contain impurities and toxins, with an unknown impact on the food web, microbial processes and nitrification.
- Biochar absorbs and concentrates herbicides and pesticides in the root zone.