Most of the energy is produced at stage 4 when
the combustible gases, which are mainly a
mixture of carbon monoxide (CO) and hydrogen
(H2), are burned some distance away from the
grate at a high temperature, while maintaining
the temperature range on the grate required at
stages 1 and 2 to convert the solid material to
energy. These features are essential to prevent
the formation of slag on the grate.