Fluidised bed steam gasification has proven to be a possible way of converting biomass and plastic undesirable wastes into fuel gases. The addition of plastics to pine wastes decreased CO content, but increased H-2 released, up to values of 50% (v/v). The highest gas yield obtained was 1.96 Nl/g daf for 98% of energy conversion, when 60% (w/w) of plastic was in the feedstock. The steam/waste mixture ratio seems to have a small effect on gas composition. Temperature is the parameter that most influenced gases composition. The: rise of temperature favoured the formation of H-2 and decreased the formation of hydrocarbons, tars and char. At 885degreesC and in presence of 40% (w/w) of plastic, conversion to char was around 2%, whilst feedstock conversion to gas was around 90%. In this paper, the effect of experimental conditions on gasification process, with the aim of enhancing the gas production and improving its composition and energetic content was analysed.