Friday, July 12, 2013

Carbon Materials Definition


Biochar is commonly defined as charred organic matter, produced with the intent to deliberately apply to soils to sequester carbon and improve soil properties (Lehmann and Joseph, 2009).

Biochar is generated from organic matter (mainly from waste), is treated at temperatures between 300~600°C via pyrolysis (carbonization), when higher temperatures are applied (800-1100°C) activation occurs. 

Biochar or charcoal?

The only difference between biochar and charcoal is in its utilitarian intention; charcoal is produced for other reasons (e.g. heating, barbecue, etc.) than biochar.

Carbon cycle:
Carbon-based molecules are crucial for life on earth, because it is the main component of biological compounds. Carbon is also a major component of many minerals. Carbon also exists in various forms in the atmosphere. Carbon dioxide (CO2) is partly responsible for the greenhouse effect and is the most important human-contributed greenhouse gas.

This diagram of the fast carbon cycle shows the movement of carbon between land, atmosphere, and oceans in billions of tons of carbon per year. Yellow numbers are natural fluxes, red are human contributions in billions of tons of carbon per year. White numbers indicate stored carbon.

Carbon materials definition

Activated carbon: 
(Material) charcoal for application to soil (noun). Charcoal produced to optimize its reactive surface area (e.g. by using steam during pyrolysis).

(count noun) A soil that has been modified profoundly through human activities, such as addition of organic materials or household wastes, irrigation and cultivation. 

(Concept) “charcoal (biomass that has been pyrolysed in a zero or low oxygen environment) for which, owing to its inherent properties, scientific consensus exists that application to soil at a specific site is expected to sustainably sequester carbon and concurrently improve soil functions (under current and future management), while avoiding short- and long-term detrimental effects to the wider environment as well as human and animal health."

Black carbon:
(noun) All C-rich residues from fire or heat (including from coal, gas or petrol)

Black Earth:
(mass noun) Term synonymous with Chernozem used (e.g. in Australia) to describe self-mulching black clays

(mass noun) 1. Synonym of ‘charcoal’; 2. charred organic matter as a result of wildfire  (verb) synonym of the term ‘pyrolyze’

(mass noun) charred organic matter 

(count noun) A black soil rich in organic matter; from the Russian ‘chernij’ meaning ‘black’ and ‘zemlja’ meaning ‘earth’ or ‘land’. 

(mass noun) Combustible black or dark brown rock consisting chiefly of carbonized plant matter, found mainly in underground seams and used as fuel. 

Organic carbon: 
(noun) biology C that was originally part of an organism; (chemistry) C that is bound to at least one hydrogen (H) atom. 

Terra Preta: 
(noun) Colloquial term for a kind of Anthrosol where charcoal (or biochar) has been applied to soil along with many other materials, including pottery shards, turtle shells, animal and fish bones, etc. Originally found in Brazil. From the Portuguese ‘terra’ meaning ‘earth’ and ‘preta’ meaning ‘black.  (Verheijen, F.G.A et al, 2010).

Sunday, July 7, 2013

Biochar Origins

Soils have the ability to absorb carbon dioxide and influence its concentration in the atmosphere. Biochar can be used to increase the ability of soils to sequester carbon and simultaneously improve soil health. 

What is biochar?
Biochar is just charcoal made from biomass—which is plant material and agricultural waste—hence the name ‘biochar’. It is a fine-grained charcoal produced from pyrolysis: the slow burning of organic matter in a low- or no-oxygen environment. What differentiates biochar from charcoal is its purpose; it is produced as an additive to soils, mainly to improve nutrient retention and carbon storage. [1] Although the history of biochar extends thousands of years, its science is still relatively poorly understood.

Image source: Odette V.

History of biochar
The term ‘biochar’ was coined in recent times, but the origins of the concept are ancient.[2] Throughout the Amazon Basin there are regions—up to two metres in depth—of terra preta.[3] This is a highly fertile dark-coloured soil that has for centuries supported the agricultural needs of the Amazonians.

(Image source: Google Images)

Analyses of the dark soils have revealed high concentrations of charcoal and organic matter, such as plant and animal remains (manure, bones and fish). Terra preta’s productivity is due to good nutrient retention and a neutral pH, in areas where soils are generally acidic.[4] Interestingly, terra preta exists only in inhabited areas, suggesting that humans are responsible for its creation. What has not been confirmed is how terra preta was created so many years ago.

Many theories exist. A frontrunner is the suggestion that ancient techniques of slash-and-char are responsible for the dark earth. Similar to slash-and-burn techniques, slash-and-char involves clearing vegetation within a small plot and igniting it, but only allowing the refuse to smoulder (rather than burn). [5] Combined with other biomass and buried under a layer of dirt, the smouldering char eventually forms terra preta. [6] It is from these hypotheses of early slash-and-char practices that modern scientists have developed methods for producing biochar.

Image source:


1. J Lehmann and S Joseph, eds, Biochar for environmental management, Earthscan publishing, London, 2009.
2. EG Neves, RN Bartone, JB Petersen and MJ Heckenberger, The timing of Terra Preta formation in the central Amazon: new data from three sites in the central Amazon, 2004, Springer: Berlin; London.
3. Terra preta means ‘dark earth’ in Portuguese.
4. pH stands for potential of Hydrogen and measures acidity. A neutral pH is neither acidic nor alkaline; J Lehmann and S Joseph, p. 67.
5. Slash-and-burn techniques are the cutting and burning of vegetation to make way for agricultural activities.
6. E Ring, ‘Amazonion Terra Preta’,, 27 November 2007, viewed 30 June 2009,