Pyrolysis and roasting :

Pyrolysis is a thermochemical transformation of biomass that takes place under the action of heat, in the absence of oxygen.

Torrefaction is a slow thermochemical treatment of biomass in the temperature range between 200°C and 300°C, in the absence of oxygen.

Torrefaction is a pyrolysis process that takes place at low temperature.

High-temperature pyrolysis” and “torrefaction” products:

Effect of pyrolysis temperature on biochar quality :

Cation exchange capacity (CEC), pH and specific surface area of biochar increase with increasing pyrolysis temperature, while carbon yield decreases.

Variation in cation exchange capacity (CEC), pH and specific surface area of biochar as a function of pyrolysis temperature (Lehmann 2007).

The following figure shows that the optimum pyrolysis temperature is around 500°C.