Composting of sugar-cane waste by-products through treatment with microorganisms and subsequent vermicomposting

Bioresource Technology 101 (2010) 6707–6711

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Composting of sugar-cane waste by-products through treatment with microorganisms and subsequent vermicomposting Rahul Kumar, Deepshikha Verma, Bhanu L. Singh, Umesh Kumar, Shweta * Vermiculture Research Station, D.S. College (Dr. B.R.A. University), Aligarh 202 001, UP, India

a r t i c l e

i n f o

Article history: Received 31 December 2009 Received in revised form 18 March 2010 Accepted 24 March 2010 Available online 18 April 2010 Keywords: Bioinoculants Drawida willsi Vermicompost Sugar-cane industries Integrated system of composting

a b s t r a c t The waste by-products of the sugar-cane industry, bagasse (b), pressmud (p) and trash (t) have been subjected to bioinoculation followed by vermicomposting to shorten stabilization time and improve product quality. Press-mud alone and in combination with other by-products of sugar processing industries was pre-decomposed for 30 days by inoculation with combination of Pleurotus sajorcaju, Trichoderma viridae, Aspergillus niger and Pseudomonas striatum. This treatment was followed by vermicomposting for 40 days with the native earthworm, Drawida willsi. The combination of both treatments reduced the overall time required for composting to 20 days and accelerated the degradation process of waste by-products of sugar processing industry, thereby producing a nutrient-enriched compost product useful for sustaining high crop yield, minimizing soil depletion and value added disposal of waste materials. Ó 2010 Elsevier Ltd. All rights reserved.

1. Introduction India produces an average of 270 million tons of sugar-cane per year (Zeyer et al., 2004). During the production process considerable amounts of by-products such as pressmud, bagasse and sugar-cane residue are produced. Part of these by-products can be utilized for the production of molasses and alcohol; however, there still remains a considerable amount of waste to be disposed. Therefore, there is considerable economic interest in the technology and development processes for effective utilization of these wastes (Zhang et al., 2000). As a result emphasis is now on aerobic composting, that converts wastes into organic manure rich in plant nutrients and humus (Singh and Sharma, 2002), and biodegradation of lignocellulosic wastes through an integrated system of composting with bioinoculants and vermicomposting have been studied (Hunsa Punnapaya et al., 1999; Maboeta and Rensburg, 2003; Valaskova and Baldrian, 2006; Dale, 2007). By-products of sugar-cane processing are ideal substrates for breeding of earthworms (Pramanik et al., 2007; Manna et al., 2003) and give a product rich in chelating and phytohormonal elements with a high microbial content and stabilized humic substances (Atiyeh et al., 2001). Furthermore, combining vermicomposting with com-

* Corresponding author. Tel.: +91 571 2405680; fax: +91 571 2420343. E-mail address: [email protected] (Shweta). 0960-8524/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2010.03.111

posting also accelerates the composting process thus reducing the time required for composting (Frederickson et al., 1997; Nedgwa and Thompson, 2001). Since some epigeic earthworm species require pre-decomposed waste (Lee, 1985), it would be desirable to decrease the pre-decomposition time period of the waste initially with certain efficient microbes. Lignin is the most recalcitrant material present in by-products of sugar industries and decomposes only at the later stage of decomposition (Manna et al., 2003). The rate of decomposition can be enhanced by treating the wastes initially with certain efficient microflora (Singh and Sharma, 2002). Pleurotus sajorcaju, Trichoderma viridae and Aspergillus niger are known to degrading hemicelluloses and cellulose (Banitez et al., 2000; Buswell and Chang, 1994; Nedgwa and Thompson, 2001; Milala et al., 2009). Inoculation with phosphate-solubilizing Pseudomonas striata may help solubilize phosphorus and increase its availability to plants (Eiland et al., 2001). Therefore, these microbes could be used as inoculants during pre-decomposition to reduce the time of composting. The present study tested the technical viability of an integrated system for composting waste by-products of the sugar-cane processing industry with the goal of shortening the stabilization time and improving compost quality. The specific role of the bioinoculants P. sajorcaju, T. viridae, A. niger and Pseudomonas striatum in predecomposting of sugar-cane wastes was assessed and cellulose, hemicellulose and lignin contents were analyzed to evaluate the effect of the microbes on growth of earthworms, and quality of the compost.

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2. Methods

2.5. Compost analysis

2.1. Microbial source

Total Kjeldahl nitrogen (TKN) and total organic carbon (TOC) of the pre-decomposed bioinoculated residue and the vermicompost were measured with the Micro-Kjeldahl method (Shaw and Beadle, 1949) and Walkely and Black’s Rapid titration method (1934), respectively. Total phosphorus (TP) was determined spectrophotometrically (Fiske and Row Subha, 1925) while total potassium (TK) was detected by the flame emission technique by Flame photometer (Pearson, 1952). Cellulose, hemicellulose and lignin were determined by neutral detergent fibre (NDF), acid detergent fibre (ADF), and acid detergent lignin (ADL) using the Fibre bag system following Dutta’s method (1981) (Table 1).

P. sajorcaju, A. niger and T. viridae were procured from IMTECH, Chandigarh and the P. striatum was obtained from Indian Agricultural Research Institute, New Delhi. The fungi were cultured on Potato Dextrose Agar (Stevens, 1981) at 25–28 °C while the bacterium was grown on Pikovaskaya media (Rao Sundaro and Sinha, 1963). 2.2. Experimental set-up Press-mud (p) alone and in combination with bagasse (b) and sugarcane trash (t) were used as substrate for the pre-decomposition studies. Finely chopped substrate was pasteurized by dipping it overnight in 0.1% formalin. Pre-decomposition of the sterilized industrial wastes of sugar mills was done in pits (1 m  1 m  1 m). The experiments were conducted with 60 kg of substrate. Pure cultures of P. sajorcaju, T. viridae and A. niger (500 g mycelium per ton substrate) and P. striatum (50 ml/kg substrate having 106 cells per ml) were inoculated after 6 d of pre-decomposition with the following microbe combinations: P. sajorcaju (P) only, P. sajorcaju + T. viridae (PT), P. sajorcaju + T. viridae + A. niger (PTA), P. sajorcaju + T. viridae + A. niger + P. striata (PTAP). For mesophilic aerobic digestion, turning was done manually every 4 d. The temperature was not allowed to exceed 26 °C. The substrate with different treatments was pre-decomposed, in triplicates, for 30 d and then subjected to vermicomposting for 40 d. Moisture content was determined using an infrared moisture detector and held constant by adding water.

2.6. Statistical analysis Results are the means of three replicates. One way analysis of variance (ANOVA) was done using the INDOSTAT programme. The objective of statistical analysis was to determine any significant differences among the parameters analyzed in different treatments during the composting process.

Table 2 Percentage of total organic carbon (TOC) in sugar-cane waste by-products (press-mud alone and incombination) during microbial pre-decomposition (0–30 days) and subsequent vermicomposting (70 days). Treatment

2.3. Vermiculturing For vermicomposting of the pre-decomposed waste, the earthworms Drawida willsi Michaelsen were cultured in cow dung employing the windrows method (Gratelly et al., 1996). 2.4. Vermicomposting The pre-decomposed substrates were vermicomposted, in the pits used for pre-decomposition, for 40 days. Moisture was maintained at about 60% of the water holding capacity, Fifty earthworms (D. willsi) were added to each pit containing the predecomposed sugar processing industries by-products, press-mud (p), press-mud + sugarcane trash (ps) 1:1, press-mud + bagasse (pb) 1:1, press-mud + sugarcane trash + bagasse (psb) 1:1:1. Sampling was done every 10 days. Composite samples (about 100 g) were collected from three sites in each pit. The earthworms and cocoons were removed manually and vermicompost was chemically analyzed.

10 days

20 days

30 days

70 days

*

p (control) p+P p + PT p + PTA p + PTAP

46.87 ± 0.12 45.22 ± 0.52* 44.62 ± 0.12* 45.03 ± 0.10* 45.14 ± 0.11*

42.47 ± 0.19 40.54 ± 0.02* 41.22 ± 0.10* 44.11 ± 0.01 41.84 ± 0.10*

47.18 ± 0.18 44.98 ± 0.05* 44.97 ± 0.16* 44.73 ± 0.05* 44.73 ± 0.05*

46.63 ± 0.01* 56.63 ± 0.18 47.13 ± 0.05* 47.79 ± 0.05 47.52 ± 0.05

ps (control) ps + P ps + PT ps + PTA ps + PTAP

44.88 ± 0.10 43.60 ± 0.10* 42.01 ± 0.07* 41.88 ± 0.20 41.88 ± 0.24*

40.27 ± 0.19* 37.79 ± 0.01 37.29 ± 0.19 36.97 ± 0.20* 37.38 ± 0.17*

43.37 ± 0.16 41.88 ± 0.15 41.48 ± 0.10 41.02 ± 0.10* 41.01 ± 0.11*

43.88 ± 0.01* 42.70 ± 0.18 42.29 ± 0.05 42.80 ± 0.06* 42.56 ± 0.05

pb (control) pb + P pb + PT pb + PTA pb + PTAP

48.09 ± 0.20 46.59 ± 0.21* 46.03 ± 0.10 46.01 ± 0.14* 46.07 ± 0.04

44.41 ± 0.17* 41.40 ± 0.16 40.90 ± 0.11 40.35 ± 0.12 45.11 ± 0.11*

47.74 ± 0.17 46.35 ± 0.01* 46.03 ± 0.31* 45.95 ± 0.20 45.41 ± 0.01

47.30 ± 0.01 47.98 ± 0.05 48.20 ± 0.06 48.75 ± 0.15* 48.41 ± 0.02

psb (control) psb + P psb + PT psb + PTA psb + PTAP

47.11 ± 0.02 46.03 ± 0.06* 45.80 ± 0.12* 45.25 ± 0.02* 45.30 ± 0.01*

42.13 ± 0.12* 41.94 ± 0.20* 41.05 ± 0.04* 39.65 ± 0.01* 39.66 ± 0.01

47.88 ± 0.01* 45.54 ± 0.01 45.34 ± 0.07* 44.85 ± 0.02* 44.85 ± 0.02

48.97 ± 0.15* 48.44 ± 0.02* 48.64 ± 0.12 48.99 ± 0.03* 49.34 ± 0.04*

All values are mean and standard deviation of three replicates. p = press-mud; s = sugar-cane trash; b = bagasse; P = Pleurotus sajorcaju; T = Trichoderma viridae; A = Aspergillus niger; P = Pseudomonas striatum. * Significant (P < 0.01).

Table 1 Chemical analysis percentage in relation to sugar-cane waste by-products (press-mud alone and incombination). Parameter

Total organic carbon (TOC) Total Kjeldahl nitrogen (TKN) Total phosphorus (TP) Total potassium (TK) Cellulose Hemicellulose Lignin

Substrate Press-mud (p)

Press-mud + sugarcane trash (ps)

Press-mud + bagasse (pb)

Press-mud + sugarcane trash + bagasse (psb)

55.06 ± 0.10 0.85 ± 0.19 0.53 ± 0.04 1.72 ± 0.01 62.69 ± 0.01 23.07 ± 0.02 10.07 ± 0.02

51.21 ± 0.20 0.80 ± 0.10 0.58 ± 0.04 1.28 ± 0.01 68.72 ± 0.01 24.07 ± 0.01 22.37 ± 0.02

56.05 ± 0.20 0.82 ± 0.20 0.53 ± 0.02 1.60 ± 0.01 65.73 ± 0.02 25.07 ± 0.01 16.70 ± 0.02

56.07 ± 0.01 0.81 ± 0.01 0.55 ± 0.02 1.62 ± 0.01 68.69 ± 0.02 26.71 ± 0.02 18.37 ± 0.01

All values are given in percentage. All values are mean of three replicates.

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3. Results and discussion The chemical analyses of press-mud individual and in combination of other by-products of sugar processing industries are presented in Table 1. Data in Table 2 reveals a significant decrease in total organic carbon (TOC) at 20 days in all the treatments during pre-composting decomposition with bioinoculants. The best results were obtained when psb was treated with the combination of three (PTA) since the TOC content decreased from 56.07% to 20.28% during pre-decomposition composting and gradually came down to 12.60% during vermicomposting. Our observations are supported

Table 3 Percentage of total Kjeldahl nitrogen (TKN) in relation to sugar-cane waste byproducts (press-mud alone and incombination) during microbial pre-decomposition (0–30 days) and subsequent vermicomposting (70 days). Treatment

10 days

20 days

30 days

70 days

p (control) p+P p + PT p + PTA p + PTAP

0.80 ± 0.01 0.84 ± 0.05* 0.83 ± 0.10* 0.84 ± 0.20* 0.84 ± 0.10

0.95 ± 0.20 1.45 ± 0.20* 1.48 ± 0.25* 1.58 ± 0.10* 1.58 ± 0.15

0.95 ± 0.20 1.45 ± 0.30* 1.48 ± 0.01 1.50 ± 0.18* 1.52 ± 0.18*

0.90 ± 0.20 1.42 ± 0.18* 1.42 ± 0.15* 1.40 ± 0.10* 1.40 ± 0.18*

ps (control) ps + P ps + PT ps + PTA ps + PTAP

0.80 ± 0.20 0.81 ± 0.10 0.80 ± 0.18* 0.84 ± 0.20* 0.84 ± 0.28

0.98 ± 0.10 1.45 ± 0.15 1.45 ± 0.01 1.59 ± 0.10 1.56 ± 0.15

0.96 ± 0.02 1.45 ± 0.01 1.45 ± 0.02* 1.42 ± 0.01 1.56 ± 0.02*

0.92 ± 0.05 1.40 ± 0.05 1.40 ± 0.10 1.38 ± 0.10 1.38 ± 0.20*

pb (control) pb + P pb + PT pb + PTA pb + PTAP

0.81 ± 0.20 0.81 ± 0.01* 0.80 ± 0.03* 0.84 ± 0.05 0.83 ± 0.01

0.95 ± 0.20 1.45 ± 0.15* 1.44 ± 0.10* 1.59 ± 0.20 1.52 ± 0.25*

0.95 ± 0.01 1.45 ± 0.01 1.44 ± 0.20* 1.51 ± 0.18* 1.50 ± 0.15

0.93 ± 0.20 1.40 ± 0.02 1.38 ± 0.02* 1.36 ± 0.01* 1.38 ± 0.01*

psb (control) psb + P psb + PT psb + PTA psb + PTAP

0.81 ± 0.01 0.82 ± 0.20 0.83 ± 0.20* 0.84 ± 0.05* 0.84 ± 0.50*

0.98 ± 0.10 1.52 ± 0.02* 1.56 ± 0.02* 1.61 ± 0.01 1.60 ± 0.01

0.98 ± 0.01 1.56 ± 0.10 1.57 ± 0.20* 1.62 ± 0.25* 1.60 ± 0.20

0.96 ± 0.02 1.40 ± 0.01 1.42 ± 0.01* 1.40 ± 0.00 1.40 ± 0.02*

All values are mean and standard deviation of three replicates. * Significant (P < 0.01).

by Singh and Sharma (2002), who have reported a similar loss of 30.10%–26.48% of TOC content during composting of wheat straw and 12.75% during its subsequent vermicomposting. Our results, however, contradict the earlier observations of Nedgwa and Thompson (2001) and Komilis and Ham (2006), who reported a more rapid degradation of substrate during vermicomposting than composting. This appears to be the effect of adding microbial consortium in our study which increased the initial degradation process during pre-decomposition. We conclude that the decrease in TOC percentage was optimum at 20 days pre-decomposition and that the stabilization time was decreased from 40 days to 20 days. Data on the percentage of TKN during pre-decomposition and subsequent vermicomposting are summarized in Table 3. During initial pre-decomposition at 20 days, the nitrogen increased in all treatments, and no significant changes were observed afterwards. The increase in percentage of TKN was maximum when P. sajorcaju, T. viridae and A. niger were added together in press-mud alone or in combination with other by-products at 20 days of pre-decomposition. Ginterova and Maxianova (1975) and Singh and Sharma (2002) have shown the ability of P. sajorcaju to fix atmospheric nitrogen. In our study, we also observed that wherever the inoculation of substrate was done by P. sajorcaju, the nitrogen percentage invariably increased in all the treatments. Further, it has been demonstrated by Rao Subha (2005) that the process of degradation is accelerated by synthesis of auxins like indole acetic acid and gibberellins, vitamins like thiamine, riboflavin, pyridoxin, cyanocobalmine, nicotinic acid and pantothenic acid, growth substances and antifungal antibiotics by A. niger and T. viridae. This may have influenced the growth of other inoculated microbes in our study. Table 3 reveals that the nitrogen content decreased during vermicomposting which may have been due to ammonification, NH3 volatilization and denitrification as reported by Bernal et al. (2006). These findings are also supported by Benitez et al. (1999) who observed a 36% loss of total nitrogen during vermicomposting of sewage sludge. Pre-decomposition and vermicomposting both resulted in a loss of carbon because of mineralization (Tables 2 and 3). The decomposition of the waste during vermicomposting was slow compared to that of the pre-decomposition process and might have been due

Table 4 Percentage of total phosphorus (TP) and total potassium (TK) in relation to sugar-cane waste by-products (press-mud alone and incombination) during microbial predecomposition (0–30 days) and subsequent vermicomposting (70 days). Treatment

10 days TP

20 days TK

TK

*

*

*

70 days

TP

TK

TP

TK

p (control) p+P p + PT p + PTA p + PTAP

0.53 ± 0.01 0.53 ± 0.02* 0.52 ± 0.01* 0.50 ± 0.02* 0.52 ± 0.01*

1.68 ± 0.20 1.70 ± 0.20* 1.74 ± 0.15* 1.74 ± 0.10* 1.74 ± 0.10*

0.56 ± 0.10 0.70 ± 0.15* 0.70 ± 0.10* 0.74 ± 0.15 0.98 ± 0.10*

1.80 ± 0.10 1.93 ± 0.10* 1.92 ± 0.01* 1.91 ± 0.02 1.90 ± 0.02

0.60 ± 0.01 0.74 ± 0.01* 0.72 ± 0.02* 0.76 ± 0.02 0.98 ± 0.02*

1.88 ± 0.20 1.96 ± 0.20 1.96 ± 0.15 1.98 ± 0.15* 1.96 ± 0.20

0.70 ± 0.20 1.20 ± 0.20* 1.20 ± 0.15 1.28 ± 0.10* 1.78 ± 0.15

1.62 ± 0.20 1.80 ± 0.20* 1.88 ± 0.18* 1.84 ± 0.10* 1.84 ± 0.15*

ps (control) ps + P ps + PT ps + PTA ps + PTAP

0.58 ± 0.01* 0.56 ± 0.02* 0.58 ± 0.15* 0.56 ± 0.10* 0.56 ± 0.01*

1.68 ± 0.20* 1.70 ± 0.21 1.70 ± 0.20 1.74 ± 0.20 1.76 ± 0.15*

0.60 ± 0.15* 0.78 ± 0.10* 0.80 ± 0.12 0.81 ± 0.12 0.98 ± 0.10*

1.80 ± 0.10 1.93 ± 0.15* 1.92 ± 0.10* 1.91 ± 0.10* 1.90 ± 0.12*

0.68 ± 0.01* 0.80 ± 0.02* 0.82 ± 0.15* 0.84 ± 0.10* 0.98 ± 0.01

1.82 ± 0.25 1.96 ± 0.10 1.96 ± 0.25 1.92 ± 0.25 1.96 ± 0.20*

0.84 ± 0.10* 1.28 ± 0.20 1.32 ± 0.20* 1.32 ± 0.15* 1.88 ± 0.10

1.60 ± 0.10 1.80 ± 0.15 1.80 ± 0.15 1.78 ± 0.20* 1.81 ± 0.20*

pb (control) pb + P pb + PT pb + PTA pb + PTAP

0.58 ± 0.02 0.56 ± 0.02* 0.54 ± 0.01* 0.54 ± 0.02* 0.55 ± 0.01*

1.65 ± 0.10* 1.78 ± 0.10* 1.78 ± 0.15* 1.78 ± 0.10* 1.81 ± 0.10*

0.60 ± 0.10* 0.70 ± 0.15 0.78 ± 0.10* 0.78 ± 0.10* 0.98 ± 0.15

1.80 ± 0.15* 1.92 ± 0.10 1.91 ± 0.15* 1.93 ± 0.10* 1.93 ± 0.10

0.62 ± 0.02 0.78 ± 0.02* 0.82 ± 0.01* 0.82 ± 0.01* 0.98 ± 0.02*

1.82 ± 0.25 1.96 ± 0.20* 1.98 ± 0.15 1.98 ± 0.10* 1.97 ± 0.10*

0.80 ± 0.15 1.20 ± 0.10 1.20 ± 0.15 1.34 ± 0.10 1.98 ± 0.15

1.62 ± 0.15* 1.80 ± 0.10 1.80 ± 0.15 1.81 ± 0.15* 1.82 ± 0.15

psb (control) psb + P psb + PT psb + PTA psb + PTAP

0.58 ± 0.01 0.59 ± 0.01 0.58 ± 0.02* 0.58 ± 0.01* 0.59 ± 0.01*

1.68 ± 0.10* 1.72 ± 0.10 1.74 ± 0.15* 1.74 ± 0.10* 1.80 ± 0.10*

0.62 ± 0.15 0.74 ± 0.10* 0.80 ± 0.10* 0.88 ± 0.10* 0.98 ± 0.15*

1.74 ± 0.12 * 1.93 ± 0.10* 1.93 ± 0.10* 1.92 ± 0.15* 1.91 ± 0.10

0.63 ± 0.01* 0.84 ± 0.01* 0.92 ± 0.02 0.92 ± 0.01 0.99 ± 0.01

1.81 ± 0.10 1.92 ± 0.15* 1.93 ± 0.20 1.94 ± 0.21 1.96 ± 0.20

0.88 ± 0.10 1.24 ± 0.15 1.25 ± 0.20 1.24 ± 0.25 1.88 ± 0.20

0.60 ± 0.10* 1.82 ± 0.10* 1.80 ± 0.10* 1.78 ± 0.15 1.78 ± 0.10

All values are mean and standard deviation of three replicates. Significant (P < 0.01).

*

30 days

TP

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Table 5 Percentage of cellulose, hemicellulose and lignin content in relation to pre-decomposed and subsequent vermicomposted wastes of sugar-cane waste by-products. Treatment

Cellulose (%)

Hemicellulose (%)

Lignin (%)

30 days

70 days

30 days

70 days

30 days

70 days

p (control) p+P p + PT p + PTA p + PTAP

60.69 ± 1.17 45.63 ± 1.10* 41.12 ± 1.00* 40.02 ± 1.17* 40.02 ± 1.09*

42.63 ± 0.49 30.46 ± 0.10* 24.12 ± 0.18* 20.18 ± 0.25* 22.32 ± 0.20*

33.07 ± 0.32 22.35 ± 0.18* 21.60 ± 0.20* 18.62 ± 0.25* 20.62 ± 0.20*

24.56 ± 0.32 19.15 ± 0.28* 18.97 ± 0.49* 15.54 ± 0.58* 15.50 ± 0.50

14.16 ± 0.38 11.56 ± 0.40* 10.91 ± 0.45* 10.53 ± 0.48* 10.50 ± 0.45

8.76 ± 0.20 5.13 ± 0.25* 3.60 ± 0.38* 3.20 ± 0.40* 3.00 ± 0.45

ps (control) ps + P ps + PT ps + PTA ps + PTAP

68.72 ± 1.17 56.72 ± 1.02* 44.60 ± 1.02* 41.12 ± 0.41* 41.02 ± 0.40*

44.12 ± 0.41* 28.16 ± 0.41* 23.39 ± 0.20 18.73 ± 0.20* 17.64 ± 0.25*

35.67 ± 0.41 20.35 ± 0.41* 20.60 ± 0.40* 17.60 ± 0.45* 17.22 ± 0.40*

28.60 ± 0.58* 18.16 ± 0.48* 17.27 ± 0.40 15.25 ± 0.48* 15.10 ± 0.40*

15.36 ± 0.40 12.16 ± 0.42* 10.91 ± 0.40* 10.51 ± 0.48* 10.00 ± 0.40*

9.26 ± 0.48 5.42 ± 0.58* 3.67 ± 0.49* 3.18 ± 0.45* 3.20 ± 0.48

pb (control) pb + P pb + PT pb + PTA pb + PTAP

65.73 ± 1.02* 57.34 ± 1.17* 45.70 ± 1.10* 43.22 ± 1.02* 42.12 ± 1.12*

40.26 ± 0.25* 22.62 ± 0.20* 20.62 ± 0.40* 16.18 ± 0.48* 17.60 ± 0.20

34.62 ± 0.40 22.32 ± 0.45* 21.65 ± 0.40* 21.22 ± 0.45* 21.22 ± 0.40*

25.32 ± 0.07 18.16 ± 0.41 16.24 ± 0.40* 14.37 ± 0.41* 14.30 ± 0.48*

14.12 ± 0.19 11.62 ± 0.15* 10.60 ± 0.15* 10.58 ± 0.20* 10.32 ± 0.28*

8.80 ± 0.50* 5.18 ± 0.58* 3.52 ± 0.20* 3.23 ± 0.20 2.81 ± 0.25

psb (control) psb + P psb + PT psb + PTA psb + PTAP

68.69 ± 1.10 54.18 ± 1.12* 45.70 ± 1.02* 38.22 ± 1.12* 38.30 ± 1.02*

48.64 ± 0.48* 24.67 ± 0.40 20.60 ± 0.40* 16.73 ± 0.45* 16.20 ± 0.40*

38.67 ± 0.40* 24.25 ± 0.45* 21.20 ± 0.20* 20.13 ± 0.20* 20.10 ± 0.25*

29.61 ± 0.49 20.26 ± 0.48* 18.28 ± 0.49* 16.24 ± 0.40* 16.20 ± 0.40

15.16 ± 0.38* 13.12 ± 0.49* 12.10 ± 0.40* 11.18 ± 0.40* 10.01 ± 0.48

9.26 ± 0.29* 5.10 ± 1.15* 3.52 ± 0.25* 3.42 ± 0.25 3.20 ± 0.28

All values are mean and standard deviation of three replicates. * Significant (P < 0.01).

to higher initial N concentration, which might have increased the microbial activity in the beginning, thus decreasing the C/N ratio (Eiland et al., 2001). These results, however, contradict observations from the earlier work of Vinceslas-Apka and Loquet (1997) who reported more rapid degradation of substrate during vermicomposting than composting. Better mineralization of organic waste material might have followed higher neosynthesis or polycondensation during the pre-decomposition process because of addition of specific microbial consortium in our study. Chemical analyses of the sugar-cane waste bio-products with different treatments showed an increase in detectable phosphorus and potassium during initial microbial composting, possibly because of mineralization of organic matter (Table 4). However, we observed a marginal decrease in phosphorous and potassium during vermicomposting. Cellulose, hemicellulose and lignin decreased significantly during pre-decomposition and subsequent vermicomposting with maximum degradation with all four by bioinoculants (PTAP) (Table 5). Singh and Sharma (2002) also reported rapid decomposition of wheat straw with a mixture of celluloytic fungi, P. sajorcaju, Trichoderma reesei, A. niger along with nitrogen fixing bacteria Azotobacter chroococcum. The simultaneous activity of microbes present in the gut of earthworms and in the waste substrate might have intensified cellulolysis and lignolysis as suggested by Loquet et al. (1984). The microbial cleavage of the aromatic rings of lignin leads to new polysaccharide and humus in the organic matter (Beyer et al., 2005). A noticeable increase in the number of earthworms as well as the cocoons was observed during vermicomposting (Table 6). This increase in the growth of earthworms with phosphorus solubilizing P. striatum suggests the dual role of bacteria as food material and in enriching the substrate with phosphorus through phosphorus solubilization. This phenomenon has also been reported by Kumar and Narula (1999). Various studies have shown that earthworm utilize micro-organisms in their substrates as a food source and can digest them selectively (Curry and Schmidt, 2006; Subler and Kirsch, 1998). The increase in earthworms’ growth may also be attributed to a low C:N ratio of the pre-decomposed substrate and positive role of bioinoculants used in the present study (Nedgwa and Thompson, 2000).

Table 6 Changes in growth and cocoon production of earthworms (Drawida willsi) during vermicomposting of sugar-cane waste by-products (press-mud alone and incombination). Treatment

Total earthworm

Cocoon

p (control) p+P p + PT p + PTA p + PTAP

89.0 ± 2.00 118 ± 4.00 121 ± 4.00 128 ± 8.00* 128 ± 8.85*

20 ± 2.01* 35 ± 3.58* 39 ± 3.58* 42 ± 3.62* 47 ± 2.55

ps (control) ps + P ps + PT ps + PTA ps + PTAP

92.6 ± 2.16 119 ± 4.16* 124 ± 4.80* 128 ± 6.56* 130 ± 7.56*

22 ± 4.88 35 ± 2.00* 38 ± 3.00* 41 ± 4.05* 42 ± 4.05*

pb (control) pb + P pb + PT pb + PTA pb + PTAP

87.6 ± 2.12 118 ± 4.81 121 ± 6.80* 128 ± 6.00* 128 ± 4.02

20 ± 6.05* 38 ± 4.08* 39 ± 3.05* 42 ± 4.05* 42 ± 2.05*

psb (control) psb + P psb + PT psb + PTA psb + PTAP

93.2 ± 4.06 128 ± 4.58* 128 ± 3.01* 131 ± 3.80 133 ± 3.01*

24 ± 3.08 39 ± 4.80* 40 ± 5.08* 44 ± 4.08* 44 ± 3.80*

All values are mean and standard deviation of three replicates. * Significant (P < 0.01).

4. Conclusion The chemical analyses of the compost produced by pre-decomposing of pressmud with other by-products of sugar processing industries, with efficient microbes followed by vermicomposting point towards the feasibility of an integrated system of vermicomposting. The results suggest that this system would be best for lignocellulosic waste treatment of sugar-cane processing industry. Reduction in the pre-decomposition time from 40 to 20 days would enable potentially conversion of these sugar-cane by-product wastes into value added products in a short time.

R. Kumar et al. / Bioresource Technology 101 (2010) 6707–6711

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