engleski

Composting of olive mill waste and tobacco waste in a closed reactor

In Croatia a large amount of agro-industrial wastes, like olive and tobacco waste, are generated during production of olive oil and cigarettes, respectively. These wastes are characterized by high values of chemical oxygen demand (COD), biochemical oxygen demand (BOD), phenols, suspended soils, low pH value, high electrical conductivity and cannot be disposed on the landfill. These wastes can be treated by composting process. Composting is an environmentally friendly and effective technology to treat or manage organic wastes. It is a biological treatment in which aerobic mesophilic and thermophilic microorganisms transform the biodegradable organic matter into CO2, H2O and a stable organic matter-compost. Many factors like moisture, C/N ratio, airflow and pH value have influence on composting process and thereby they have to be in optimal range. The objective of this work was to conduct composting process of mixture of olive (OW) and tobacco (TW) waste in column reactors with effective volumes of 1 dm3 and 10 dm3, respectively, during 28 days. The airflow in reactors of 1 dm3 and 10 dm3 was set at a 0.08 dm3 min-1 and at a 0.84 dm3min-1, respectively. Three different experiments were conducted in smaller reactor (1 dm3) with different initial C/N ratio from 25/1 to 35/1 and from the obtained results the best was set up in a larger reactor of effective volume 10 dm3. The initial moisture in both processes was 60 % and pH value about 6. During composting process samples were collected periodically and the most relevant physical-chemical (pH - value, moisture content, dry matter (DM), volatile solids content (VS), N content) and microbiological characteristics were determined. Carbon dioxide (CO2) and ammonia (NH3) was absorbed in 1 mol dm-3 sodium hydroxide (NaOH) and in 4 % H3BO3, respectively. CO2 and NH3 was analysed daily by titration 1 mol dm-3 and 0.1 mol dm-3 HCl. From obtained results of composting of olive and tobacco waste in a smaller reactor, the C/N ratio between 30/1 and 35/1 gave the best results, higher conversion in less time. It was found that emission of carbon dioxide depended on temperature while emission of ammonia mainly depended on pH value in composting mass. The most of carbon dioxide was evolved in the thermophilic stage of composting process due to the highest activity of microorganisms.

Composting, tobacco waste, olive mill waste, closed reactor

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