NOVELTY - The plasma-based apparatus (1) comprises a chamber, a feeder (13) in communication with the chamber so that the feeder provides the bio-waste into the chamber, a plasma torch in communication with the chamber so that the plasma torch provides plasma into the chamber for gasifying the bio-waste into the synthetic gas, a system for circulating water to cool the chamber and the plasma torch, a system for providing steam into the plasma torch for the generation of the steam plasma, and a synthetic gas cleaner in communication with the chamber.    USE - The plasma-based apparatus is useful for producing fuel-class synthetic gas from bio-waste including agricultural waste, forest waste, industrial waste and urban garbage.    ADVANTAGE - The plasma-based apparatus is capable of effectively, simply and economically producing the clean and tar-free fuel-class synthetic gas from bio-waste with high energy density.    DETAILED DESCRIPTION - The plasma-based apparatus (1) comprises a chamber, a feeder (13) in communication with the chamber so that the feeder provides the bio-waste into the chamber, a plasma torch in communication with the chamber so that the plasma torch provides plasma into the chamber for gasifying the bio-waste into the synthetic gas, a system for circulating water to cool the chamber and the plasma torch, a system for providing steam into the plasma torch for the generation of the steam plasma, a synthetic gas cleaner in communication with the chamber so that the cleaner receives the synthetic gas from the chamber and cleans the chamber, a heat-isolating lining disposed in the chamber, a water jacket (112) provided between the heat-isolating lining and the chamber so that water travels into the water jacket through the water inlet (113) of the chamber and leaves the water jacket through the water outlet (114) of the chamber, and a crucible disposed in the chamber for receiving ash. The chamber comprises a water inlet, a water outlet, a gas inlet and a gas outlet. A plasma raises the temperature in the chamber to 800-1600 degrees C. The steam-providing and water-circulating system comprises: a steam reservoir in communication with the plasma torch; a water reservoir in communication with the plasma torch and the chamber; a central control unit for controlling the operation of the steam-providing and water-circulating system; a steam re-heater for heating the steam from the steam reservoir again so that the steam reaches a predetermined temperature and is super-heated; and a steam flow controller provided between the steam reheater and the steam plasma torch (12) so that the steam re-heater sends the steam into the steam plasma torch at a predetermined flow rate under the control of the steam flow controller. The plasma torch comprises: a rear electrode; a front electrode in communication with the rear electrode; an isolator provided around the rear and front electrodes; a swirl generator provided around the isolator and formed with a steam inlet element and a steam outlet; a plasma outlet element provided near the front electrode; and a power supply between the rear and front electrodes. The temperature at the center of the plasma torch is as high as 10000 degrees C. The feeder executes a two-phased feeding process, and comprises a tube in communication with the chamber, a case in communication with the tube, a chute for sending the bio-waste into the case, a gate provided between the case and the chute, a horizontal pusher for pushing the bio-waste into the tube from the case, and a vertical pusher for pushing the bio-waste down the tube into the chamber. The water reservoir is: configured for detecting the level of water contained in it and taking in more water if necessary to keep the level in a predetermined range; in communication with the steam reservoir so that the former provides water into the latter that turns the water into steam; in communication with the steam plasma torch so that the former sends water into the latter; and in communication with the chamber so that the water reservoir provides water into the water jacket of the chamber. The steam reservoir is: configured for detecting the level of water contained in it and taking in more water if necessary to keep the level in a predetermined range; and in communication with the steam re-heater so that the former sends steam into the latter.    DESCRIPTION OF DRAWING(S) - The diagram shows a cross-sectional view of a plasma-based apparatus.    Plasma-based apparatus (1)    Steam plasma torch (12)    Feeder (13)    Water jacket (112)    Water inlet (113)    Water outlet (114)    Thermometer. (115)