What is Biochar?
The biochar is the pyrolysis product of biomass (high temperature degradation in inert atmosphere).
The term Biochar bring together a lot of different kind of biochar. Each kind of biochar is characterised by one biomass, one type process, a lot of process parameters (temperature, residence time…). Consequently all biochar are single with single physical and chemical properties.
How produce Biochar?
The biochar is product from one or several biomass. The biomass is placed few minutes in a reactor and be heated to a température between 400°C and 900°C. The pyrolysis particularity is the inert atmosphere in the reactor that differentiates it from combustion.
During the process, three products are generated : Syngaz, bio-oïl and biochar.
The Biochar is not a charcoal!
The Biochar differs from charcoal by the process temperature. In fact, the charcoal is produce at temperature lower than 400°C to have maximum solid matter. Due to the low temperature, the charcoal contain a lot of volatil matter. They are usefull for the combustion, but phytotoxic.
Rather, the process temperature of biochar is higher than 400°C to have a « clean » material with agronomic benefits.
And the Biochar in Agronomy?
The pre-columbian civilizations, 3000 years ago, used a similar process like the pyrolysis to produce soil amendment : the Terra Preta. The high part of carbon, organic matter and nutrient confer single agronomic properties.
The rediscovery of Terra Preta, in the 19th century, increase the scientific studies of Biochar, with a lot of agronomic interest.