Low-temperature gasification produces a number of heavier hydrocarbons
along with carbon monoxide and hydrogen. These heavier hydrocarbons are
further cracked, separated, and used for other applications. High-temperature
gasification is carried out at temperatures above 1200 °C, where biomass is
converted mainly into hydrogen and carbon monoxide. Primary gasification is
often followed by the shift reaction, as described in the next section, to adjust
the hydrogen-to-carbon monoxide ratio to suit the downstream application.
In any case, the product gas must be cleaned before it is used for synthesis
reactions. Special attention must be paid to clean the syngas of tar and other