Five energy plants from different regions of the world were pyrolyzed by non-isothermal thermogravimetry and effluent gases were detected through a mass spectrometer. Thermal decomposition characteristics, quantification of emissions, reactivity, and process kinetics were determined. Among the fuels tested, miscanthus was the most reactive, while jatropha was more heterogeneous. A first-order parallel reactions model fitted the experimental results with great accuracy. Miscanthus and willow can be characterized as high-quality fuels and produced higher amounts of carbon oxides and lighter hydrocarbons at lower temperatures. For jatropha, cardoon, and sunflower co-gasification or co-firing is suggested, in order to avoid nitrogenous emissions.