Composting of selected organic wastes from peri-urban areas of Harare, Zimbabwe

Abstract

Purpose The study investigated the effects of poultry and goat manures on the kinetics of potassium fixation and release in some sandy loam and loamy soils of Ogun State, Nigeria. Methods The treatments consisted of poultry and goat manures applied at 25 g and 100 g/5 kg soil set in completely randomized design with three replicates. Potassium fixation and release kinetics were computed from the analytical data. Results Experimental soils was sandy, slightly acidic, low in nutrients with 80% fixed potassium. However, manure application resulted in 74% reduction of the amount of K fixed by the soils. Elovich and power functions had the best fit for K released in soils treated with goat manure. The K release pattern in poultry manure-amended soil is best described by the parabolic diffusion, Elovich, and power functions, while the first-order equation described K release in soils treated with cattle manure. The potassium release rate constant correlated positively with K uptake. Conclusion The ability of the studied soils to fixed K was reduced with the application of organic manures. Potassium fixation decreased with increase in organic manure rates, 100 g/5 kg soil tends to be the optimum rate, and poultry manure had greater effect on the fixing and releasing power of K.

Physico-chemical, microbial and phytotoxicity evaluation of composts from sorghum, finger millet and soybean straws

“…This is due to the fact that as composting progresses, organic substances undergo loss of weight due to mineralization into soluble forms and subsequently become concentrated due to drying. The drying process enables accumulation of mineral salts such as phosphate and ammonium ions contributing to higher EC (Mhindu et al 2013). In the present study, EC of all the compost materials increased from the initial 0.2-0.7 to final 0.8-1.2 mS cm −1 which is still within the limits of favorable EC for enabling seed germination.…”

“…On the other hand, temperature in composting reactors of finger millet straw and soybean straw at 75 cm depth was observed to be 42-60 °C during the first 10 days and then declined to less than 40 °C. However, temperatures were comparatively lower in finger millet straw and soybean straw reactors probably due to the drier or recalcitrant nature of these straws as indicated by their high TS/VS contents which offer greater structural complexity resisting microbial degradation (Mhindu et al 2013). In all the composting reactors, high temperatures (> 50 °C) during the first 10 days indicate successful initiation of hydrolytic/fermentation phase of the composting process and reflect a very active decomposition process in the reactors.…”

Co-composting of green waste, food waste and phosphoric rock. Comparison of two-stage composting with traditional composting.

“…Ash content was lower than 60% in both treatments, according to the requirements of the NTC 5167, and lacked signi cant statistical differences comparing TA and TB. However, TB had relatively higher values compared to TA which can be linked to the intense organic matter degradation during the rst 10 days, which are re ected in mass loss in the form of CO 2 [49]. This high degradation can also be associated with the addition of PR in both treatments that provide nutrients and energy for microorganisms, accelerating transformation processes [5].…”

Organic waste composting and sustainability in low-income communities in Palestine: lessons from a pilot project in the village of Al Jalameh, Jenin

“…Heat generated through thermophilic phase is used to disinfect the compost. The first layer is typically constituted by dry plant material, in this case using strong grass straw and long stalks of maize as used by Mhindu et al (2013). The straw and stalks of maize were broken into fragments of short length and sprinkled in the shallow trench.…”