UK Biochar Research Centre
Charchive Standard Biochars

Biomass Pyrolysis Processes: Review of Scope, Control and Variability

Peter A Brownsort
1st December 2009

This review focuses on biomass pyrolysis processes for use in biochar systems. Objectives are to
describe the scope, range of control and degree of variability of such processes.
Slow, intermediate and fast pyrolysis processes are reviewed. Product yield distributions change
depending on feedstock composition and preparation, control of temperature and material flows.
These allow some control over distribution of main products – char, liquids and gases. Typical mass
yield ranges for slow pyrolysis are char 25-35%, liquid 20-50%, gas 20-50%; for intermediate
pyrolysis, char 30-40%, liquid 35-45%, gas 20-30%; and for fast pyrolysis, char 10-25%, liquid 50-
70%, gas 10-30%. Variability associated with char yield is estimated at ±5% (relative). Char yield
should be considered an underlying, but minor source of variability in pyrolysis biochar systems.

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Brownsort PA 2009. Biomass Pyrolysis Processes:  Review of Scope, Control and Variability. UKBRC Working Paper 5