A method and system for fueling of a burner in a direct-fired device using syngas. A gasifier produces syngas from a carbonaceous feedstock such as biomass. The syngas is fed to a syngas burner. A booster burner disposed between the gasifier and the syngas burner increases the temperature of the syngas. The booster burner may be provided with an approximately stoichiometric or sub-stoichiometric amount of oxidant. Operation of the booster burner may be regulated based on the temperature of the syngas. The syngas burner may be used to direct-fire a device requiring a relatively high flame temperature, such as, for example, a lime kiln.