The main goal of this research is to promote a more efficient use of wheat straw for cleaner energy production by co-firing straw pellets with solid and gaseous fuels (wood pellets, propane) and to assess the impact of the mixture composition on the gasification/combustion characteristics and heat energy production. The effect of straw co-firing on the gasification/combustion characteristics was studied using a pilot device combining a biomass gasifier and a combustor, with swirl-enhanced stabilization and electric control of the swirling flow dynamics. The effect of straw co-combustion with wood and its co-firing with propane on the development of gasification/combustion characteristics was estimated from complex measurements of biomass thermal decomposition, swirling flow velocity, flame temperature, composition profiles and heat output from the device. The results prove that different elemental composition and calorific values of the mixture components and the variations of the heat input by the propane flame allow to control the thermal decomposition of straw pellets at their co-combustion with wood and co-firing with propane, whereas the formation of flow dynamics is responsible for the ignition and combustion of volatiles (CO, H2) and for the composition of the products. The obtained results show that electric field effects on the flow dynamics can be used to control the thermal decomposition of straw pellets and thermochemical conversion of volatiles, depending on the bias voltage of the axially inserted electrode.