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Biodegradation of lignocellulosic waste by composting process

Agro-industrial wastes such as tobacco waste and olive pomace contain considerable amount of organic matter, high concentration of nicotine and phenols, respectively, and can`t be disposed on the landfills. Furthermore, these wastes also contain high concentration of lignin, cellulose and hemicelluloses [1]. These macromolecules can be degraded by composting process and with inoculation of different aerobic microorganisms which posse’s ligninolytic enzymes such as Phanerochaete chrysosporium and Trichoderma reesei [1-2]. Composting is an environmentally friendly and effective biodegradation process of organic waste. It is a biological treatment in which aerobic mesophilic and thermophilic microorganisms transform organic matter into CO2, H2O and compost. Many factors influences on composting process such as moisture, C/N ratio, pH value, particle size and supply of air. Tobacco waste and olive pomace have low and high C/N ratio, respectively, and pH value of olive pomace is very low and moisture is above 60 %. The aim of this research was biodegradation of lignocellulosic material by composting process conducted in a closed thermally insulated column reactor with an effective volume of 10 dm3 with airflow 0.6 dm3 min-1 kg-1VS, initial C/N ratio 30/1 during 28 days. Two different composting experiments were conducted without and with inoculation of different microorganisms which were isolated from tobacco waste and olive pomace such as Pseudomonas aeruginosa, Candida rugosa, Aspergillus fumigatus and Cellulomonas. Also, Phanerochaete chrysosporium and Trichoderma reesei were inoculated because according to the literature have high capability for degradation of lignocellulosic materials [2-3]. During the process, temperature changes in reactor, pH value, C/N ratio, moisture content, volatile matter content, FTIR analyses of substrate, COD of condensate, concentration of phenols, evolved CO2 and NH3 and the number of mesophilic and thermophilic microorganisms were determined. It was found that the biodegradation of lignocellulosic materials with inoculation of mixed cultures was faster and obtained conversion was about 10 % higher. An FTIR analysis shows that some peaks where groups of lignin appear after 28 days disappeared which didn`t happened in the experiment where mixed culture was not inoculated. The highest biodegradation and emission of CO2 was during thermophilic phase. No significant emission of ammonia was detected until day twenty.

Composting, lignocellulosic waste, FTIR analysis

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