Impact of the Type of Fertilization and the Addition of Glycerol on the Quality of Spring Rape Straw Pellets

This paper presents an analysis of selected qualitative characteristics of pellets produced from rape straw obtained from cultivations subjected to different fertilization treatments and from mixtures of straw selected for testing with crude glycerol obtained as a by-product from biodiesel production. The assessment focused on the following qualities of the obtained pellets: Moisture content, mechanical durability, heating value and main elements, that is, carbon, hydrogen, nitrogen, sulphur, chlorine and oxygen. The obtained results indicated that the different treatment regimens applied in spring rape cultivations had a significant impact on the physicochemical qualities of the straw. In terms of the heating value, traditional fertilization with multi-component fertilizer (NPK) yielded slightly lower chemical parameters (lower carbon content and heat of combustion) than in the case of straw obtained from the control sample and from the plot fertilized with digestate. Furthermore, in all of the analysed mixtures, the 10% addition of raw glycerol improved the mechanical characteristics of the produced straw pellets. After the 10% glycerol addition, in terms of the energetic use of these biofuels, the parameters of the fuel, such as heating value and net heating value, were slightly decreased.