NOVELTY - A biomass gasifier comprises a gasification chamber (20) having a biomass inlet at an upper end and a char outlet at a lower end; a U-shaped char tube (30) having a base and vertical limbs (54); and a blower (62) having a suction side connected to second limb of char tube for inducing a flow of gas through the gasification chamber and also has a pressure side for connection to a consuming device. The first limb of char tube is positioned to receive char from char outlet of gasification chamber and second limb terminates upwardly at a level above char outlet of gasification chamber.    USE - For gasifying biomass and agricultural crop waste.    ADVANTAGE - The air flow induced by the blower provides oxygen to support combustion of the biomass. The temperature distribution in the gasification chamber depends on the distribution of the supply of air to the gasification chamber. If the temperature at a given location in the gasification chamber is sufficient for the biomass to smolder, supply of air to that location will accelerate the exothermic oxidation reaction, thus increasing the temperature, whereas if the supply of air is discontinued the reaction is starved of oxygen and the smolder may be extinguished. By providing several air inlet tubes at different levels in the gasification chamber, it is possible to control the temperature distribution in the gasification chamber. The vibrators keep the biomass and char in an agitated state, preventing formation of bridges and gas channels.    DETAILED DESCRIPTION - A biomass gasifier comprises a wall structure defining a gasification chamber (20) having a biomass inlet at an upper end and a char outlet at a lower end; a U-shaped char tube (30) having a base and first and second vertical limbs (54); and a blower (62) having a suction side connected to the second limb of the char tube for inducing a flow of gas through the gasification chamber and also has a pressure side for connection to a consuming device. The first limb of the char tube is positioned to receive char from the char outlet of the gasification chamber and the second limb terminating upwardly at a level above the char outlet of the gasification chamber. The biomass gasifier further comprises at least one vibrator for agitating the contents of the gasification chamber; and a hopper for feeding biomass to the inlet of the gasification chamber. The base of the char tube is inclined downward from the first limb to the second limb and is provided with a drain valve for removing ash slurry from the char tube. The wall structure defines a gas exit chimney that is open downward into an ash box and the second limb of the char tube extends upward into, and terminates in, the gas exit chimney. The second limb of the char tube flares upwardly, to allow progressive expansion of gas flowing through the second limb to the gas exit chimney. The ash box is provided with a drain valve for removing ash slurry from the ash box.    DESCRIPTION OF DRAWING(S) - The figure shows a vertical sectional view of the gasifier.    gasification chamber (20)    hoper (26)    char tube (30)    drain valve (34)    vertical limb (54)    blower. (62)