Gasification, a slight variation on the combustion process, is a thermo-chemical process that converts solid materials into combustible gases (carbon monoxide, methane and hydrogen) and other by-products. By exposing biomass to extremely high temperatures (~800 °C) in an oxygen-reduced container, and with the presence of steam, the molecules break down into their separate components. The solids and liquids left behind are called charcoal and tar. Gas produced by this method is called syngas.
Most biomass materials can be used in this process, but not all in the same gasifier. Gasifiers are sensitive to input feedstock and are designed to receive a certain feed material that has a specific moisture content range. Staged combustion is used to ensure complete combustion of the biomass. The complete gasification process takes place in a controlled environment, and the resulting syngas can be piped out and used for various purposes.
Syngas, mixed with oxygen, can be fed into a combustion chamber where it is burnt, much in the same way that natural gas or propane is combusted. The gas can be used to power turbines, create electricity, or used in modified combustion engines.
Syngas can also be converted to bio-alcohols, which are then separated and purified to produce ethanol, methanol, and other valuable products.
The typical steps for gasification include:
• Preparation of waste material by removing non-calorific components.
• Heating the biomass in a low oxygen environment.
• Cleaning (scrubbing) to remove certain particulates and soluble components.
• Combustion or further refining to create preferred products.
Gasification BIC Factsheet
Pyrolysis and Gasification Factsheet
Gasification Technologies Council