Comparative assessment of plant resources as substrates for bioshlam production

Z. Shindarska, V. Kirov, G. Kostadinova, B. Baykov
It was made a comparative assessment of the main technological parameters of the silages of different types as a source for the production of biogas as well as it was given an assessment to the bioshlam derived from them. For this purpose the following silages were studied: corn silage, sweet corn silage, forest silage and silages of straw and three types of beet (sugar beet, red beet and fodder) in a ratio of 10 : 90%. It was found that the investigated energy resources in terms of the technologically permissible parameters (dry matter, organic matter, macro and micro-elements) can be used as raw materials in the mix for biogas production. The forest silage as a general term which is specific for each forest ecosystem, due to substantial differences in the structure of the biocoenoses as well as in the soil composition, can be an alternative raw material to the energy crops for the production of biogas with dry matter content of 26.68%, organic carbon content – 39.50% and nitrogen content – 1.30%, as the ratio between them is 30,38:1 (C:N). After methane fermentation, a high rate of mineralization of organic matter is observed in all tested materials, expressed by high values in the bioshlam of the main macro-elements (N, K, P, Ca and Mg). Established concentrations of the 8 toxic elements (Cu, Zn, As, Cd, Cr, Hg, Ni and Pb) in the bioshlam, derived from the studied plant materials, are below the critical limit for the soil and plants.