NOVELTY - Plasma-assisted waste gasification system (10) comprises reactor (16); gas quench unit (18) for partially cooling synthesis gas from reactor; heat recovery unit (22) located downstream of gas quench unit to extract thermal energy; scrubber located downstream of heat recovery unit; two sensors connected to an inferential sensing mechanism (78) which is capable of estimating temperature of synthesis gas in the reactor, based on measured first temperature and flow rate, and measured second temperature and flow rate, using a mass-energy balance relationship.    USE - As plasma-assisted waste gasification system for converting a waste stream into a synthesis gas (claimed).    ADVANTAGE - The system performs robust operation of waste gasifiers in the presence of constant variations in waste feedstock, with controllable gasifier temperature conditions, and complete dissociation of all volatile organic compounds in the feedstock. The Optimization and control of the gasifier temperature facilitates a stable and high performance operation of the gasification system. The gasification system includes a control unit that utilizes the estimated gasifier temperature obtained from the inferential sensing mechanism, to stabilize the gasifier temperature to a set-point that enables conversion of almost all of the hydrocarbons and potential toxic compounds into syngas. The gasifier temperature can be controlled by adjusting the power of the plasma torch; or by adjusting the oxygen flow-rate to optimize the oxygen-to-he1 ratio for a given situation; or by varying both the power to the plasma torch and the oxygen flow rate, to adjust the oxygen-to-fuel ratio. By doing so, the overall temperature or energy flux into the reactor, and the composition(s) of the syngas, can be controlled, as compared to conventional reactors in which the plasma torches are focused on the slag at the bottom of the reactor.    DETAILED DESCRIPTION - A plasma-assisted waste gasification system (10) for converting a waste stream into a synthesis gas comprises reactor (16); gas quench unit (18) for partially cooling synthesis gas from the reactor; heat recovery unit (22) located downstream of the gas quench unit to extract thermal energy; a scrubber located downstream of the heat recovery unit; a sensor located between the gas quench unit and the heat recovery unit to measure a first temperature and first flow rate of the synthesis gas exiting the gas quench unit; a second sensor to measure a second temperature and a second flow rate of a low temperature synthesis gas entering the gas quench unit, where the first sensor and the second sensor are connected to an inferential sensing mechanism (78), where the inferential sensing mechanism is capable of estimating the temperature of the synthesis gas in the reactor, based on the measured first temperature and first flow rate, and the measured second temperature and second flow rate, using a mass-energy balance relationship that is based on the measurements of the two sensors. The system further comprises a cyclone located downstream from gas quench unit, air separation unit for providing oxygen to reactor, control unit to control the temperature of reactor, and power generation unit. An INDEPENDENT CLAIM is included for producing synthesis gas from a plasma-assisted waste gasification system involving measuring the first temperature and the first flow rate of the synthesis gas exiting the gas quench unit; measuring the second temperature and the second flow rate of synthesis gas recycled to the gas quench unit; and estimating the temperature of the synthesis gas in the reactor, using the inferential sensing mechanism, based on the measured first temperature and first flow rate, and the measured second temperature and second flow rate, using a mass-energy balance relationship that is based on the measurements of the two sensors.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of plasma-assisted gasification system.    Plasma-assisted waste gasification system (10)    Reactor (16)    Gas quench unit (18)    Heat recovery unit (22)    Inferential sensing mechanism (78)