Energy generation is predominantly based on fossil fuels. This is related to their high energy density and abundance of resources, as well as market availability and maturity of conversion technologies. Increasing awareness of environmental concerns reflected in relevant regulations regarding the allowable levels of emission of contaminants in energy sector on the one hand, and increasing energy demand on the other impose, however; the need for development of more environment friendly energy technologies and wider utilization of renewable energy resources. Since the latter still faces technological and efficiency problems reflected in unsatisfactory economic characteristics, the efforts could be made to combine the advantages of stable supplies of coal, availability of marketready, highly efficient and environment friendly gasification technology and utilization of renewable energy resources, biomass. Production of hydrogen as a prospective, environmental friendly energy carrier in the process of cogasification make this option even more attractive, especially if some synergy effects could be observed. In the paper the experimental results proving the influence of a fuel blend composition, in terms of biomass type and content, and process temperature on the total gas volume, gas composition, carbon conversion rate and process efficiency are presented. Synergy effects were reported in cogasification of coal and biomass of selected energy crops under operating conditions adopted, including increase in the total gas and hydrogen yields when compared to the values observed in coal and biomass gasification. A correlation between ash composition and the synergy effects was also stated. The energy crops types and steam cogasification operating parameters optimal in terms of hydrogenrich gas production were also determined. (C) 2014 Elsevier Ltd. All rights reserved.