Biochar

What is biochar?

"Simply put, biochar is the carbon-rich production obtained when biomass, such as wood, manure or leaves, is heated in a closed container with little or no available air.

In more technical terms, biochar is produced by so-called thermal decomposition of organic material under limited supply of oxygen, and at relatively low temperatures."
(source: S. Joseph and J. Lehmann, Biochar for Environmental Management, 2009)

Application of biochar

Utilisation of biochar in agriculture systems commenced more than 1000 years ago. Ash and charcoal from fires were mixed with soil. In some societies ash and charcoal were mixed with degraded biomass, food and animal waste and soil. These mixtures were often heated at low temperatures in smoky fires and the resultant product (biochar, baked biomass mineral complexes) used for growing vegetables, herbs and medicinal plants.

Thus carbon, nitrogen, phosphorous, potassium and other minerals were recycled to the land ensuring continued high productivity for many centuries. Biochar can be produced from a range of agricultural and urban residues including green waste, manures, paper sludge, bagasse and straw.

The agronomic value of biochar lies in its reactive porous carbon and mineral surfaces. Once biochar is placed in the soil it can interact with soil organic matter, minerals, water and oxygen to increase microbial growth, reduce nutrient run off, react with minerals, absorb water and reduce the effects of toxic compounds. Some biochar can also assist in either increasing or decreasing the pH of soils. These properties can result in enhanced plant growth.

Detailed examination of black carbon (probably derived from biochar) produced in areas where ancient civilisations flourished, and biochar in recent field and laboratory studies, confirms that this carbon can degrade very slowly and continue to provide benefits to crops for decades.