Abstract: An upright, cylindrical down draft gasifier has a rotatable grate which supports a quantity of pyrolyzing biomass materials. As the grate is turned, charcoal particles thus formed fall through apertures in the grate and into a collection chamber. Simultaneously a high quality combustible gas is continuously withdrawn. A number of stationary, horizontal rods are disposed above the grate to retard and mix the reactant in the column and force a portion of the charcoal particles through the apertures. Additionally, the rods, in conjunction with the grate, present a shearing action on larger charcoal particles until the latter are crumbled and consequently fall through the grate. As the speed of the rotable grate is increased, the quantity of combustible gas and high quality charcoal is enhanced such that the heating value of the final product is also greatly increased.