NOVELTY - A process extracts a combustible gas from wood in a reactor into which steam and air are injected in the presence of a mixed inorganic catalyst. The wood biomass is heated, dried, further heated by a combination of hot steam and air, thus producing gas. The raw gas is then partially cooled and extracted from the raw gas and purified for use as motor fuel. The biomass is successively dosed with the multi-functional mixed catalyst.    USE - To convert biomass, e.g. wood, into a gaseous motor fuel.    ADVANTAGE - The gas has improved anti-knock characteristics than prior art wood gas. Further, it has a higher proportion of simple hydrocarbons and an increased calorific value.    DETAILED DESCRIPTION - After the biomass has been discharged into the upper part of the reactor (zone a) it is heated by hot steam to 100-200 degreesC, and air is bled off. The wood mass in zone 'a' is then further heated to 300-400 degreesC by the admission of hot steam by jets in the upper part of the next zone (zone 'b'). The coked mass in the reactor mid-section (zone 'c') is exposed to twin supplies of hot air. The air admitted does not exceed 0.7 kg/kg dry biomass, raising the temperature stepwise from 500 to at least 750 degreesC. The glowing coke is released rapidly through the reactor waist zone, but falls slowly through the lower section (zone 'd'). the temperature above the waisted zone does not exceed 900 degreesC, but falls rapidly below the waisted zone to 700-300 degreesC. The product raw gas is drawn from the reactor at 300-400 degreesC and cleaned. The spent biomass is released at the base of the reactor as ash.    An INDEPENDENT CLAIM is included for an assembly for use in the above process.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional side-view through the reactor used in the above method (includes non-English language text).    reactor (1)    charge insert (2)    steam release jet ring (3, 4)    hot steam jet ring (5)    air jet ring (6)    hot air jet ring (7)    waisted zone (8)    raw gas outlet ring (9)    structure within zone d (10)    raw gas shaft (11)    steam/air heating system (12)    ash discharge (13)    insulation system (14)