Browsing by Author "Gebrekrstos, Teklebrahan"

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    Optimization ofMunicipal SolidWaste Vermicomposting Parameters
    (Addis Ababa University, 2014-11) Gebrekrstos, Teklebrahan; Worku, Teshome (Ass. professor)
    Today, increasing population and rapid development are resulting for generation of large amount of solid wastes in developing countries. Most of these wastes are usually disposed in open dumping site, open spaces, rivers or burned in the streets without any treatment due to lack of proper management techniques, awareness and commitment of the society and the government, which creates severe environmental pollution and health hazards, hence it was thought to attempt use of municipal solid waste for cheap and ecofriendly treatment methods like vermicomposting. It is the process of compost formation by earthworms. Optimization of process parameters for the vermicomposting of municipal solid waste using Esenia fetida was investigated using response surface methodology (RSM). The three parameters and their ranges namely moisture content (60-90%), C/N ratio (20-30), and worm stocking density (0.8-2.0 kg/m2) were chosen from the previous study of vermicomposting. The experimental data on the quantity of N, P and K were fitted into a quadratic polynomial model using multiple regression analysis. The experimental results and software predicted N, P and K values were comparable. The individual parameters effect as well as effect of interactions between the vermicomposting parameters on N, P and K was analysed using various graphical representations. A three-level three factorial Box-Behnken design technique under RSM using numerical optimization method was used to optimize their interactions, which showed that a moisture content of 74.62%, C/N ratio of 23.21, and worm stocking density of 2 kg/m2 were the best conditions. Under these conditions, the maximum predicted yield of N, P and K was 2.82%, 1.58% and 1.28%, respectively. The produced vermicompost was found to be better in desired level of composition of macro-nutrients i.e., N, P and K and the efficacy of the prepared vermicompost has been studied on the spinach vegetable plant. A plastic pot set-up with soil was used to determine the effects and efficiency level of vermicompost on the yields of spinach. The study was conducted through effect of increasing concentration of Vermicompost (0% (control), 50% and 100% w/w) in target plant growth. Total leaves wet weight and number of leaves has been studied. Results showed that the number of leaves produced using 100% VC was 2.67 times greater than the number of leaves produced using 0% VC and 1.6 times greater than produced using 50% VC and leaf wet weight of the spinach plant produced using 100% VC was 2.2 times greater than produced using the control (soil) and 1.2 times greater than produced using 50% VC. Thus, vermicomposting of municipal solid waste is an excellent and ecofriendly method of municipal solid waste management. Key words: Optimization; vermicomposting; municipal solid waste; Esenia fetida; response surface methodology; spinach