Optimization ofMunicipal SolidWaste Vermicomposting Parameters
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Date
2014-11
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Addis Ababa University
Abstract
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
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Keywords
Optimization, Vermicomposting, Municipal solid waste, Esenia fetida, Response surface methodology, Spinach