In-vessel composting, a contribution to sustainable solid waste management, was conducted on source-separated waste materials generated in Abeokuta city, south-west Nigeria. Feedstock (household, agricultural and municipal waste) and the resultant composts were chemically characterized using standard procedures. Identification and changes in the microbial population during composting, the effects of composting on waste volume reduction (WVR) and elemental composition of composts were evaluated. Product performance on plant growth and metal uptake were then assessed using African spinach (Amaranthus hybridus) in a screen house for 8 weeks. Metals were determined in acid digest using atomic absorption spectrometry. Compost yields and WVR ranged from 35.28 to 48.68% and 51.66 to 64.72%, respectively. Compost heavy metal (Cu, Cr, Zn, Ni, Cd and Pb) concentrations (mg kg( -1)), ranging from 0.67-0.82; 0.13-7.5; 0.001-0.22; 1.67-18.33; 6.50-17.67; and 0.83-6.00 for Cu, Pb, Cd, Ni, Cr and Zn, respectively, were within limits for class A+ composts. The effect of composting varied with element type and significantly (p < 0.05) reduced microbial population by 44.44 to 88.46%. Plant height, leaf number and biomass yield gave positive correlations (r = 0.950 to 0.977; 0.978 to 0.989 and 0.99, respectively; p < 0.05) with applied compost rate. Low-metal composts were produced but the presence of Cd and Pb in plant tissues calls for further research on the long-term effect of products on plant metal uptake in amended soils. The study is a contribution to the data bank of composting as a low technology waste management option in the developing countries.
Ceramic wastes are found to be suitable for usage as substitution for fine and coarse aggregates in concrete production. This study is an investigation into the utilization of waste tiles as partial replacement for fine and coarse aggregates in concrete. The control mix and other mixes containing cement, water, granite and partial replacement for sand with crushed tiles (in 5%, 10%, 15% and 20% proportions) were cast, cubed, cured and crushed. Also, another mix containing cement, water, sand and partial replacement of granite with crushed tiles (in 25%, 50% and 75% proportions) were cast, cubed, cured and crushed. The specimens were tested for their respective compressive strengths using the Universal Testing Machine (UTM) on the 7th, 14th, 21st and 28th days of curing. At 28 days, the compressive strength value of 5% of fine-waste tiles replacement was 20.12 N/mm2 while that of 10%, 15% and 20% were 14.24 N/mm2, 11.04 N/mm2 and 10.12 N/mm2 respectively. Moreover, at 28 days, the compressive strength of 25% of coarse-waste tiles replacement shows an increase to 22.45 N/mm2 while that of 50% and 75% were 18.4 N/mm2 and 12.2 N/mm2 respectively. Thus it can be concluded that fine aggregates can be substituted at 5% waste tiles while coarse aggregates can be substituted at 25% waste tiles.>/p>
This study investigated the production of silicon from bamboo leaves to solve the challenge of silicon in solar market using Optimization approach. The effect of three independent variables of: temperature, time and amount of bamboo leaves were studied using Box Behnken design. The best process level observed from the Box Benhken Design and optimal predicted process were used to produce silica. It was then subjected to X-Ray Diffractometer to determine the most reactive silica. The most reactive silica observed was used to produce silicon. Silicon obtained was subjected to X-Ray Diffraction and Scanning Electron microscope. It was concluded that nanosilicon was produced which can be used as a solar cell component to solve the challenge presently in the solar market.
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