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Composting of common organic wastes using microbial inoculants

View Article: PubMed Central

ABSTRACT

It is important to use renewable resources to maximize crop yields and minimize the environmental hazards associated with chemical residues. Composting is an age old practice for the biological conversion of organic waste to a humus-like substance which can enhance physical, chemical and biological soil properties. To explore the effect of microorganisms in the composting process, three potent bacterial isolates were selected. Their morphological, cultural and biochemical characteristics were identified, and 16S rDNA studies identified isolates B1U/1 and D3L/1 as Bacillus subtilis and isolate RAT/5 as Pseudomonas sp. Common organic wastes were composted using the selected isolates individually and as a consortium. The C/N ratio of each substrate reduced gradually to 25–30:1 within 120 days and remained constant thereafter. The reduction in NH4+ and NO3− ion concentrations also indicated compost maturity after 120 days. The pH of the mature compost was typically 7.0 ± 0.2, and the PO4−3 ion concentration was high throughout the decomposition process. This study describes the optimization of the composting process using a consortium of isolates from composted soil.

No MeSH data available.


Changes in the phosphate ion concentration during composting. Data are the mean value of three independent experiments
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Fig4: Changes in the phosphate ion concentration during composting. Data are the mean value of three independent experiments

Mentions: Throughout the composting process, the phosphate ion concentration varied between 6.8 and 47.46 mg/kg, depending on the substrate and inoculum (Fig. 4). The lowest phosphate ion concentrations were measured for substrate C7 (rice husks; inoculated with isolate D3L/1, Fig. 4a), while the maximum concentration was measured for substrate C5 (newspaper waste; inoculated with Psudomonas sp RAT/5, Fig. 4c). The phosphate ion concentration remained constant for substrates C1 (fruit waste; with B. subtilis D3L/1, Fig. 4a) and C4 (hay; with B. subtilis B1U/1, Fig. 4b). Dinel et al. (2004) reported that nitrogen deficiency of the substrate could be improved by the addition of phosphoric acid, which could also prevent the excessive volatilization of ammonia. Phosphorus is sometimes applied during composting to maintain a C:P ratio between 75:1 and 150:1 (Taiwo and Oso 2004; Gautam et al. 2010). A high percentage of the phosphate present in compost is available during the plant growing season, but nutrient availability depends on the quality of soil, particularly its moisture content and temperature (Hue et al. 1994; Wen et al. 1997), and the ready availability of phosphate enhances soil carbon and nutrient uptakes (Yadav et al. 1999).Fig. 4


Composting of common organic wastes using microbial inoculants
Changes in the phosphate ion concentration during composting. Data are the mean value of three independent experiments
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3376866&req=5

Fig4: Changes in the phosphate ion concentration during composting. Data are the mean value of three independent experiments
Mentions: Throughout the composting process, the phosphate ion concentration varied between 6.8 and 47.46 mg/kg, depending on the substrate and inoculum (Fig. 4). The lowest phosphate ion concentrations were measured for substrate C7 (rice husks; inoculated with isolate D3L/1, Fig. 4a), while the maximum concentration was measured for substrate C5 (newspaper waste; inoculated with Psudomonas sp RAT/5, Fig. 4c). The phosphate ion concentration remained constant for substrates C1 (fruit waste; with B. subtilis D3L/1, Fig. 4a) and C4 (hay; with B. subtilis B1U/1, Fig. 4b). Dinel et al. (2004) reported that nitrogen deficiency of the substrate could be improved by the addition of phosphoric acid, which could also prevent the excessive volatilization of ammonia. Phosphorus is sometimes applied during composting to maintain a C:P ratio between 75:1 and 150:1 (Taiwo and Oso 2004; Gautam et al. 2010). A high percentage of the phosphate present in compost is available during the plant growing season, but nutrient availability depends on the quality of soil, particularly its moisture content and temperature (Hue et al. 1994; Wen et al. 1997), and the ready availability of phosphate enhances soil carbon and nutrient uptakes (Yadav et al. 1999).Fig. 4

View Article: PubMed Central

ABSTRACT

It is important to use renewable resources to maximize crop yields and minimize the environmental hazards associated with chemical residues. Composting is an age old practice for the biological conversion of organic waste to a humus-like substance which can enhance physical, chemical and biological soil properties. To explore the effect of microorganisms in the composting process, three potent bacterial isolates were selected. Their morphological, cultural and biochemical characteristics were identified, and 16S rDNA studies identified isolates B1U/1 and D3L/1 as Bacillus subtilis and isolate RAT/5 as Pseudomonas sp. Common organic wastes were composted using the selected isolates individually and as a consortium. The C/N ratio of each substrate reduced gradually to 25–30:1 within 120 days and remained constant thereafter. The reduction in NH4+ and NO3− ion concentrations also indicated compost maturity after 120 days. The pH of the mature compost was typically 7.0 ± 0.2, and the PO4−3 ion concentration was high throughout the decomposition process. This study describes the optimization of the composting process using a consortium of isolates from composted soil.

No MeSH data available.