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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.


Change in C:N ratio for different waste substrates during composting. Results are the mean value from three independent experiments
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Fig2: Change in C:N ratio for different waste substrates during composting. Results are the mean value from three independent experiments

Mentions: The initial organic carbon content was relatively high for each substrate, at between 20 and 80%. The initial C:N ratios were 35:1 (C1; fruit waste), 15:1 (C2; vegetable waste), 60:1 (C3; leaves), 50:1 (C4; hay), 125:1 (C5; newspaper waste), 128:1 (C6; wheat straw), and 76:1 (C7; rice husks), which is consistent with the observations of Hadas and Portnoy (1994). The C:N ratio gradually decreased for all substrates except C2, for which the C:N ratio increased for the first 60 days and then remained steady (Fig. 2). The overall nitrogen loss during later stages of the composting process caused the increase in this C:N ratio. Atkinson et al. (1996) reported that a reduction of 29% of the organic carbon content occurs during composting of organic waste; while a reduction of only 10% in the carbon content was estimated by Erickson et al. (2009) and Umsakul et al. (2010). In this study, the C:N ratio increased in some cases during the first 30 days of decomposition followed by a sharp decrease and was stable after 120 days, although this pattern varied depending on the test organism. When the consortium of three isolates (1:1:1) was used, the rate of decomposition was faster and the C:N ratio reduced to around 25–30:1 at 75–90 days, depending on the substrate. The only exception was for C5 (newspaper waste) which required more than 180 days for the decomposition (Fig. 2d). Of the seven substrates tested, C6 (wheat straw) had a greatest increase in the rate of decomposition while using the bacterial consortium (Fig. 2d).Fig. 2


Composting of common organic wastes using microbial inoculants
Change in C:N ratio for different waste substrates during composting. Results are the mean value from three independent experiments
© Copyright Policy
Related In: Results  -  Collection

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

Fig2: Change in C:N ratio for different waste substrates during composting. Results are the mean value from three independent experiments
Mentions: The initial organic carbon content was relatively high for each substrate, at between 20 and 80%. The initial C:N ratios were 35:1 (C1; fruit waste), 15:1 (C2; vegetable waste), 60:1 (C3; leaves), 50:1 (C4; hay), 125:1 (C5; newspaper waste), 128:1 (C6; wheat straw), and 76:1 (C7; rice husks), which is consistent with the observations of Hadas and Portnoy (1994). The C:N ratio gradually decreased for all substrates except C2, for which the C:N ratio increased for the first 60 days and then remained steady (Fig. 2). The overall nitrogen loss during later stages of the composting process caused the increase in this C:N ratio. Atkinson et al. (1996) reported that a reduction of 29% of the organic carbon content occurs during composting of organic waste; while a reduction of only 10% in the carbon content was estimated by Erickson et al. (2009) and Umsakul et al. (2010). In this study, the C:N ratio increased in some cases during the first 30 days of decomposition followed by a sharp decrease and was stable after 120 days, although this pattern varied depending on the test organism. When the consortium of three isolates (1:1:1) was used, the rate of decomposition was faster and the C:N ratio reduced to around 25–30:1 at 75–90 days, depending on the substrate. The only exception was for C5 (newspaper waste) which required more than 180 days for the decomposition (Fig. 2d). Of the seven substrates tested, C6 (wheat straw) had a greatest increase in the rate of decomposition while using the bacterial consortium (Fig. 2d).Fig. 2

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.