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The biomass gasification is complex and proceeds primarily through a two-step process, pyrolysis followed by gasifi-cation. Pyrolysis is the decomposition of the biomass feedstock by heat. This step, also known as devolatilization, is endothermic and produces 75 to 90% volatile materials in the form of gaseous and liquid hydrocarbon derivatives. The remaining non-volatile material, containing high carbon content is referred to as char. Volatile hydrocarbon and char are subsequently converted to syngas in the second step, gasification.

While pyrolysis begins at temperature in excess of 500°C (930°F), gasification reactions are predominating at temperature nearing and excess of 1,000°C (1,830°F). The following are the details of the reactions during gasification process.

Exothermic Reactions

Combustion: C + O₂ → CO₂

Partial Oxidation: 2C+ O₂ → CO

Methanation: C + 2H₂ → CH₄

Water Gas Shift: CO + H₂O → CO₂ + H₂

Carbon Monoxide Methanation: CO + 3H₂ → CH₄ + H₂O

Endothermic Reactions

Steam Carbon Reaction: C + H₂O → CO + H₂

Boudouard Reaction C + CO₂ → 2CO

See also: Biomass – Gasification.