The highest hydrogen yield (10.98 mmol H2 g1 sample) and concentration (36.1 vol.%) in the non-catalytic gasification of the mixture was obtained for a biomass/plastic ratio of 80/20. According to the literature [13,18], the main reactions controlling hydrogen concentration in the biomass gasification process are decomposition of hydrocarbons and water gas shift reactions. When polypropylene was introduced with the wood sawdust, high hydrogen concentrations were obtained due to PP cracking. However, Pinto et al. [18] predicted that an increase in the plastic beyond 20 wt.% will not result in an increase in H2 concentration in the gas. Fig. 1, shows that the presence of polyolefinic plastics in the uncatalyzed biomass pyrolysis/gasification process increases hydrogen production in the gaseous stream. However, the concentration of H2 in the gas is hardly affected by the plastic content in the noncatalytic process, since it only increases slightly from 30.3 to 36.1 vol.%.