The invention provides a system designed for the complete conversion of carbonaceous feedstock into syngas and slag. The system comprises a primary chamber for the volatilization of feedstock generating a primary chamber gas (an offgas); a secondary chamber for the further conversion of processed feedstock to a secondary chamber gas (a syngas) and a residue; a gas- reformulating zone for processing gas generated within one or more of the chambers; and a melting chamber for vitrifying residue. The primary chamber comprises direct or indirect feedstock additive capabilities in order to adjust the carbon content of the feedstock. The system also comprises a control system for use with the gasification system to monitor and regulate the different stages of the process to ensure the efficient and complete conversion of the carbonaceous feedstock into a syngas product.