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Bilyana Grigorova Pesheva

Bilyana Grigorova Pesheva

University of Forestry, Bulgaria

Title: Dynamics of microflora in the process of composting organic waste and bioplastics


Biography: Bilyana Grigorova Pesheva


The role and dynamics of microorganisms in the composting process of bioplastic and organic wastes is researched. For the purpose of the study, the influence of Polydegralex material upon its introduction into the composting pile is analyzed. By chemical composition Polydegralex refers to oxo-degradable plastic products. Polydegralex contains an additional additive that is both photo- and thermally degradable. The rate of degradation depends on both the quality and the presence of antioxidants in the main component of this foil.  According to the literature, Polydegralex is a specific material that undergoes physical decay under the influence of temperature and sunlight. It is mainly used in the production of disposable and reusable bags. As starting materials for composting, various organic waste was used to which specific biodegradable plastic products were added. Bioplastics are products based on potato starch, corn and other substrates. The organic waste used is divided into two groups, depending on their characteristics - food waste and green waste. During the composting process, the change in the properties and characteristics of both organic waste as well as the added biodegradable products and Polydegralex is monitored. A model experiment was performed in five variants. Each variant includes a different ratio of organic waste to which samples of different bioplastic products and Polydegralex have been added. The experience is set as a vessel by the method of active aerobic composting by periodic aeration (mixing) and maintaining optimal humidity. For all the variants of the experiment, are analyzed (for 5 months), representative microbiological, chemical and physical parameters of the compostable materials. The microbiological analyzes of each variants were performed in the dynamics by dilution method by plating solid media, in triplicate. Traceable and analyzed are representative microbiological indicators - dynamics and change of the microbial communities during the different phases of the composting process - mesophilic, thermophilic and phase of maturation . The results of the study show a different quantitative and qualitative composition of the microflora in the individual variants.  A larger microbial number was observed in the samples with food waste as compared to the green waste samples. During the composting process, nonspore-forming bacteria dominate. The composting of biodegradable plastic products does not have a negative impact on the microbial populations typical of this process. Moreover, biodegradable plastic products are an additional food base for microorganisms. By increasing the mass of biodegradable plastic waste to the total mass of waste, the microbial number increases. The results obtained show that the microbiological activity is enhanced in the presence of biodegradable plastic products and is weakened in the presence of oxo-degradable plastics products.