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Vermicomposting of herbal pharmaceutical industry solid wastes
Ecological Engineering 39 (2012) 1–6
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Short communication
Vermicomposting of herbal pharmaceutical industry solid wastes Deepika Singh, Surindra Suthar ∗ School of Environment & Natural Resources, Doon University, Dehradun 248001, India
a r t i c l e
i n f o
Article history: Received 14 June 2011 Received in revised form 2 September 2011 Accepted 28 October 2011 Available online 19 December 2011 Keywords: Eisenia fetida Industrial waste Vermicompost Composting Waste recycling
a b s t r a c t The efforts were made in this study to decompose the herbal pharmaceutical industrial waste (HPIW) using earthworm Eisenia fetida (Savigny) under laboratory conditions. To achieve the objectives HPIW was mixed with cow dung (CD) in different ratios to produce five different waste mixtures for vermicomposting: T1 – CD (100%), T2 – HPIW (25%) + CD (75%), T3 – HPIW (50%) + CD (50%), T4 – HPIW (75%) + CD (25%) and T5 – HPIW (100%). Vermicomposting caused significant changes in vermibed characteristics. In all waste mixtures, a decrease in pH, organic C, C:P ratio and C:N ratio, but increase total N, available P and exchangeable K was recorded. C:N ratio of end material (vermicompost) was within the agronomic preferable limit (>15). T3 and T4 vermibeds showed better mineralization and waste decomposition rate during vermicomposting. E. fetida produced cocoons in the ranges of 81.0 ± 9.54 (T1 )–306.33 ± 14.31 (T4 ) in all vermibeds. Results clearly suggested that vermicomposting could be an efficient technology to convert HPIW into some value-added products for ecological restoration practices. © 2011 Elsevier B.V. All rights reserved.
1. Introduction The herbal pharmaceutical and cosmetic industry in India is probably the oldest medical care system in the world. The use of herbs to cure general health disorders and complex diseases has been mentioned in the Vedas, an ancient religious work of the Hindus. The ancient herbal healing methods of Ayurveda and Unani deal with the use of herbs and natural products to tackle health conditions (Anon, 2011). In recent years there is growing concern over adverse impact of synthetic chemicals and therefore, people are now moving towards traditional herbal based medical care system. The demand of herbal products and raw materials has been many folds during last two decades and Indian and China both share more than one-third markets of herbal products in the worlds. The total market of Ayurvedic products in India is about one billion dollar (US). An estimation suggests about 400,000–500,000 MT consumption of key raw material in domestic market for herbal product manufacturing. Solid waste generated from these herbal manufacturing industries is an emerging pollutant for terrestrial environment. However such industries (processing units and product manufacturing) produce a large quantity of spent wastes after pre-processing and/or extracting or distillation of active ingredients from raw materials. Such industrial wastes not only spoil aesthetics sense of local habitats but at the same time also create issues of all types of environmental pollution, if proper disposal is
∗ Corresponding author. Tel.: +91 135 2255103. E-mail address: sutharss [email protected] (S. Suthar). 0925-8574/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ecoleng.2011.10.015
not made. In majority of cases such plant-origin waste is dumped openly either at landfill sites or at open space nearby to industrial areas. The emission of green house gases, nutrient enrichments in surface water bodies, nitrate leaching to groundwater, prolification and breeding of disease vectors are the major disadvantages of open dumping of organic wastes (Suthar, 2011). The stabilization of industrial wastes prior to use of disposal could reduce the environmental problems associated with its management (GomezBrandon et al., 2011). There is emerging concern over using waste as resources for land restoration and energy production. The recycling, reuse and resource recovery has been considered as one of the best options for sustainable solid waste management programme. In nature, a variety of decomposers or detritus feeders (fungi, actinomycetes, protozoa, nematodes, annelids, arthropods, etc.) are available which not only decomposes the complex organic substances of wastes but at the same time also enhances the quality of end products. The earthworms have been recommended as potential decomposer to recycle a variety of organic wastes generated from different sectors of human society. Utilization of earthworms for waste decomposition is called vermicomposting. Vermicomposting is emerging as a most appropriate alternative to convert aerobic composting (Hait and Tare, 2011). The vermicomposting is stabilization of organic material through the joint action of earthworms and microorganisms. While, microbes are responsible for biochemical degradation of organic matter, earthworms are the important drivers of the process, conditioning the substrate and altering the biological activity (Dominguez and Edwards, 2004). Earthworm’s foregut acts as mechanical blenders and modifies the physical status of ingested organic wastes and
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consequently increases the surface area for digestive enzyme actions. In earthworm, the gut-associated-microbes provide several essential enzymes (exogenous) required for rapid digestions of ingested organic fractions. Further mineralization of nutrients is carried out by microbial communities associated with freshly deposited worm casts (Aira et al., 2007). Vermicomposting has several advantages over conventional thermophilic composting systems in terms of process time, nutrients recovery, microbial richness and phytotoxicity. The traditional composting and vermicomposting methods operate under very different conditions and can produce very different composted products. The potential of vermitechnology in stabilization of a variety of industrial wastes is well documented in published literature. Few earlier author reported the successful utilization of epigeic earthworms for decomposition of food processing industry sludge (Yadav and Garg, 2009), vinasse (Pramanik and Chung, 2011), paper mill sludge (Kaur et al., 2010), distillery sludge (Suthar and Singh, 2009), sugar factory waste (Khwairakpam and Bhargava, 2009), Olive oil mill sludge (Moreno et al., 2000), etc. In majority of previous studies E. fetida was used as candidate species for vermicomposting operation because it can tolerate wide pH range, temperature, moisture and a wide range of putrescible substances and biotoxic compounds (Ganesh et al., 2009). The aim of this study was to investigate the decomposition of herbal pharmaceutical industrial waste spiked with cow dung in different ration using composting earthworm E. fetida under laboratory condition. 2. Methods 2.1. Earthworm, herbal pharmaceutical waste collection and pre-processing The vermicomposting earthworm species: E. fetida used for experimentation was procured from vermiculture unit, Indian Veterinary Research Institute, Izatnagar, India. For stock earthworms were cultured in a circular plastic container containing of 30 L capacity in waste mixtures (cow dung mixed with leaf litter), under laboratory conditions. The stock was further used for laboratory studies on vermicomposting. The herbal pharmaceutical industrial waste (HPIW) was procured from spent material disposing unit of The Himalaya Drug Company, Dehradun which is one of the leading herbal pharmaceutical product manufacturing or processing unit in India. The waste was of mixed type containing spent material after extraction/distillation of herbs and unused part of the plant. The partially composted mixture of HPIW was collected in large-sized cleaned polythene containers and brought to laboratory. In lab the material was shed dried and then stored in dry plastic containers for further vermibed preparation. The cow dung was used as bulky agent for preparation of vermibeds/feed materials for earthworms. Freshly deposited cow dung (CD) was obtained from a local cowshed, Mothrawala, Dehradun. The cow dung was partially dried in shed and stored for further experimentations. The chemical characteristic of fresh HPIW and CD is described in Table 1. 2.2. Treatment design and observations The HPIW was mixed with CD in different ratios (dry weight proportions) to produce five different combinations of waste mixtures: The details of experimental vermibeds are described as: T1 – CD (100%), T2 – HPIW (25%) + CD (75%), T3 – HPIW (50%) + CD (50%), T4 – HPIW (75%) + CD (25%) andT5 – HPIW (100%). Two treatments
Table 1 Chemical characteristics of herbal pharmaceutical industrial waste (HPIW) and cow dung (CD) used for experimentation (mean ± SD, n = 3). Parameters
CD
pH EC Total organic carbon Available P Sulphate Exchangeable K Na+ Total N
9.02 0.877 743.3 580.0 12.96 452.0 18.76 15.20
HPIW ± ± ± ± ± ± ± ±
0.01 0.02 34.4 2.0 0.07 15.87 0.15 0.26
8.08 0.264 641.26 678.0 14.44 187.67 23.99 46.8
± ± ± ± ± ± ± ±
0.22 0.20 12.2 2.65 0.22 7.37 0.61 1.71
were composed of pure CD and HPIW (without any dilutions). The waste mixture acts as bedding as well as feed for the composting earthworms. For vermicomposting experimentation, 300 g waste mixture (dry weight basis) was filled in plastic circular containers of 2 L capacity (one for each mixture). The waste mixtures moistened with distilled water to maintain appropriate moisture level for initial decomposition of waste mixtures. These bedding were kept for 1 week for initiation of microbial degradation and softening of waste mixture). For vermicomposting experiments, 20 earthworms were collected from the stock culture and released into each different container containing 300 g of substrate material. The experimental beddings were kept in triplicate for each waste mixture. The moisture content was maintained at 55–65%, throughout the study period by periodic sprinkling of adequate quantity of water. The containers were placed in a humid and dark place at room temperature (27–28 ◦ C). In order to measure the changes in chemical characteristics of waste mixture during vermicomposting, the homogenized samples were drawn at 0, 10, 20, 20, 40, 50 and 60 days from each experimental container. The samples were oven dried (48 h at 60 ◦ C), and stored in sterilized plastic airtight containers for further physico-chemical analysis. The chemical characteristics of all waste mixtures used for experimentation were described in Table 2. During first observation (after 10 days) the inoculated earthworms in waste mixtures were counted to assess the overall mortality (%) in vermibed. The changes in earthworm population, growth and live weight were measured during vermicomposting experiment in all vermibeds by following method as described by Suthar (2009). Total earthworm population and total cocoon numbers (fresh and residual) in each experimental container were measured at the end. Earthworms and cocoons were separated from the parental waste mixture by hand sorting method, after which worms were washed in tap water to remove adhering material from their body and subsequently weighed live weight basis without voiding their gut. Separated cocoons were counted at the end and then introduced in separate bedding containing partially decomposed cod dung. On the basis of observed information other data sets: biomass change (%), growth rate, reproduction rate (cocoon worm−1 day−1 ), mortality, etc. were produced for different waste mixtures. 2.3. Chemical analysis The pH was measured using a digital pH meter (Metrohm, Swissmade) in 1:10 (w/v) aqueous solution (deionized water). Electrical conductivity (EC) was measured using a digital conductivity meter. Total organic carbon (TOC) was measured after igniting the sample in a Muffle furnace at 550 ◦ C for 60 min by the method of Nelson and Sommers (1996). Extractable phosphorous was measured using the method described by Olsen et al. (1954). Total exchangeable cations (K+ and Na+ ) were determined after extracting the sample using ammonium acetate (Simard, 1993). Total Kjeldahl nitrogen (TKN) was measured using the method described
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Table 2 Chemical characteristics of initial and vermicomposted waste mixture from different treatments (mean ± SD, n = 3). Treatmenta
pH
Initial waste mixture T1 9.02 ± 0.017 8.79 ± 0.90 T2 8.72 ± 0.03 T3 T4 8.67 ± 0.04 T5 8.08 ± 0.22 Vemicomposted waste mixture 8.75 ± 0.23 T1 7.50 ± 0.05 T2 8.09 ± 0.04 T3 T4 7.41 ± 0.05 T5 8.24 ± 0.06
TOC
0.877 ± 0.02 0.396 ± 0.04 0.550 ± 0.10 0.340 ± 0.02 0.264 ± 0.20
743.3 754.47 730.40 643.46 641.26
± ± ± ± ±
34.35 9.34 6.39 6.07 12.20
15.20 24.10 33.0 37.9 46.8
± ± ± ± ±
0.26 0.33 0.77 1.24 1.71
580.0 610.0 531.76 585.9 678.0
± ± ± ± ±
2.0 2.0 2.54 3.43 2.65
452.0 281.3 315.3 324.3 187.67
15.87 7.09 7.76 4.5 7.37
18.76 20.68 20.90 21.9 23.99
± ± ± ± ±
0.15 0.31 0.44 0.87 0.61
426.10 608.8 542.2 535.6 540.9
± ± ± ± ±
35.9 10.21 27.88 15.6 7.19
22.60 42.45 52.40 49.76 59.94
± ± ± ± ±
0.39 0.33 1.04 1.55 2.11
614.3 635.3 562.0 634.3 712.67
± ± ± ± ±
5.51 4.16 4.36 5.51 15.37
526.1 ± 7.49 414.0 ± 7.81 342.1 ± 9.84 374.67 ± 15.27 213.67 ± 5.67
16.25 14.53 16.22 19.33 19.66
± ± ± ± ±
1.43 0.57 0.69 1.53 0.74
0.99 0.69 0.82 0.80 0.70
± ± ± ± ±
0.03 0.05 0.06 0.06 0.05
Ntot
Pavail
Na+
EC
Kexch ± ± ± ± ±
Units of all the parameters except pH and EC are in g kg−1 . The EC values are in S/cm. a For treatment compositions see text.
by Jackson (Jackson, 1975). Biodegradability coefficient indicated the organic matter (OM) contents: OM % = (100 − Ash content %). Biodegradability coefficient (Kb ) was calculated using the following equation (Diaz et al., 1996): Kb =
(OMi − OMf ) × 100 OMi (100 − OMf )
where OMf is the organic matter content at the end of process and OMi is the organic matter content at the beginning of the process. 2.4. Statistical analysis One-way ANOVA was used to analyze the differences between treatments. A Tukey’s t-test was also performed to identify the homogeneous type of the data sets. SPSS® statistical package (Window Version 13.0) was used for data analysis. All statements reported in this study are at the p < 0.05 levels. 3. Results and discussion 3.1. Physico-chemical changes in waste mixture during vermicomposting The earthworm caused significant changes in the chemical characteristics of waste mixtures during vermicomposting process. The worm-worked material was more stabilized, odor-free, and dark brown substance with high range of plant available forms of soil nutrients. There was significant reduction in pH value of all waste mixtures after vermicomposting process (Table 2). The range of pH in vermicomposted material was 7.41–8.75 (Table 2). pH of relatively higher in initial substrate materials, especially in CD vermibed. In worm-worked waste mixtures pH shifted towards to downward scale and this could be due to the production of CO2 , ammonia, NO3 − and other intermediate organic acids during waste decomposition processes. Pramanik et al. (2007) suggested that decomposition of organic material leads to the formation of ammonium (NH4 + ) and humic acids. The combined effect of these two oppositely charged groups actually regulates the pH of vermicomposting substrates. The difference in pH for different experimental containers may be attributed to degree of mineralization and microbial activities which directly affects the production of intermediate compounds during waste stabilization process. pH of substrate also importance because it directly affects the colonization of major decomposer (bacteria and fungi) in decomposing waste feed stocks. Electrical conductivity (EC) showed significant changes after vermicomposting process in all waste mixtures. The EC in wormworked waste mixture ranged from 0.70 ± 0.20 S/cm (T5 ) to
0.99 ± 0.03 S/cm (T1 ). EC was relatively higher in vermicomposted material than initial materials in all vermibeds. Overall, the increase in EC was in the ranges of 12.9 (T1 )–165.2 (T5 )% for different waste mixtures. The EC increase was in the order: T5 > T4 > T2 > T3 > T1 (Table 2). EC increased in CD vermibed but to a lesser extent. The increase in EC could be to reduction of organic matter and release of different mineral salts: phosphate, ammonium, potassium, etc. The results indicate that mineralization rate was higher in T5 and T4 waste mixtures than other waste mixtures. Hait and Tare (2011) reported average increase in EC of about 35.4–56.4% in vermistabilized sewage sludge. Ash contents indicate the organic matter mineralization and waste stabilization. In this study there was significant increase in the content of ash in all vermibeds. In vermicomposted material the maximum ash content was in T1 (573.9 g kg−1 ) followed by T4 (464.4 g kg−1 ), T5 (459.1 g kg−1 ), T3 (457.8 g kg−1 ) and T2 (391.2 g kg−1 ). As compared to initial contents ash content increased in the ranges of 28–123.5% in all vermibeds. Total organic carbon (TOC) showed decrease than initial contents in all vermibeds after decomposing wastes through earthworms. The maximum decrease was 42.6% in T1 followed by 25.74% (T3 ), 19.31% (T2 ), 16.77 (T4 ) and 15.62% (T5 ). The loss of carbon as CO2 due to microbial respiration and assimilation of simple carbohydrates leads to TOC reductions from waste mixtures. Moreover, carbohydrates and other polysaccharides which are considered major source of carbon are digested rapidly by earthworms and some fraction of digested substances is then assimilated into worm biomass. The greater TOC reduction in CD (T1 ) may be due to microbial richness of substrate materials. In such beddings the microbial respiration may leads to rapid C loss through CO2 production. Also, earthworm fragments the waste feedstock into fine fractions which results in increased sites for microbial hydrolytic enzyme actions. The biological mutuality between earthworms and associated microbes is primarily responsible for C loss from the organic wastes. Kaviraj and Sharma (2003) reported 20–45% reduction in TOC contents of vermicomposted municipal solid waste mixed with CD. Similar observations have been reported by Prakash and Karmegam (2010) during vermicomposting of press-mud from sugar industry. There was increase in total N contents in all vermibeds as compared to initial levels after completion of vermicomposting process (Table 2). The total N content in vermicomposted waste mixture was in the range of 22.60 g kg−1 (T2 )–59.94 g kg−1 (T4 ). The maximum increase in total N content was in T2 (76.5% higher than initial) followed by T3 (58.8%), T1 (48.7%), T4 (31.3%) and T5 (28.1%). The N enrichment process during vermicomposting depends upon the microbial populations and proportion of industrial wastes which contains microbial growth retarding
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Table 3 C:N and C:P ratios of initial and vermicomposted waste mixtures from different treatment vermibeds (mean ± SD, n = 3). Treatmenta
Initial
Final
C:N ratio T1 T2 T3 T4 T5 a b c d
48.8 26.6 22.1 17.0 16.1
± ± ± ± ±
1.47b 0.83 0.35 0.56 0.76
C:P ratio 57.37 64.32 56.82 50.3 44.41
± ± ± ± ±
Acceptable (C:N ratios < 20)
C:N ratio 2.67 1.26 0.96 1.05 1.32
18.9 12.7 10.4 10.8 10.2
± ± ± ± ±
1.73 0.07 0.62 0.30 0.53
Preferable (C:N ratios < 15)c
Preferable (C:P ratio <15)d
– √ √ √ √
× √ √ √
C:P ratio 21.85 13.97 13.06 13.56 21.79
± ± ± ± ±
1.22 0.49 0.62 1.89 0.10
√ – – – –
×
For treatment compositions see text. Mean value followed by different letters is statistically different (ANOVA; Tukey’s t-test, P < 0.05). Morais and Queda (2003). Edwards and Bohlen (1996).
substances (Suthar, 2010). Earthworm enhances the N level of vermibed by adding excreta and other secretions. Also, mucus a polysaccharide is secreted by earthworm to moisten the body surface also important to enrich vermibeds with nitrogen fixers. Earthworm also alters the microclimatic conditions of vermibeds which consequently promotes microbial populations responsible for N enrichment. Better microbial population in vermicomposting system (Aira et al., 2007) may an advantage over traditional composting system. Moreover, earthworm adds N-rich substances (excretory products, mucus, body fluid, enzymes, etc.) in substrates during vermicomposting process. Earlier studies have also reported the N enrichment in vermicomposted waste mixtures (Khwairakpam and Bhargava, 2009; Prakash and Karmegam, 2010; Hait and Tare, 2011). There was significant increase in the contents of available P (phosphate) in all vermibeds than initial levels (Table 2). The level of phosphate in end material was in the ranges of 562.0 ± 4.36 g kg−1 (T3 )–712.67 ± 15.37 g kg−1 (T5 ) for different waste mixtures. The maximum PO4 3− enhancement was in T4 (8.25%) followed by T1 (5.92%), T3 (5.68%), T5 (5.12%) and T2 (4.15%) than initial level. The high available P (plant available form of phosphorus) in vermicompost suggests the agronomic potential of vermicompost as potential plant growth media. The phosphorous mineralization is performed partly by earthworm gut phosphatases, and further release of P might be attributed to the microbial activities in deposited casts (Vinotha et al., 2000). Few author suggested the role of P-solubilizing bacteria in phosphorous enhancements in deposited casts of earthworms (Pramanik et al., 2007; Prakash and Karmegam, 2010). PO4 3− enhancement showed drastic variations among different experimental waste mixtures. The highest P mineralization in T4 suggests the suitability of waste substrate for earthworm feed and microbial propagation. The vermicomposted waste mixtures were rich in exchangeable K contents (Table 2). The end material showed higher level of exchangeable and total available potassium contents than initial levels. Exchangeable K was the ranges of 213.67 ± 5.67 g kg−1 (T5 )–526.1 ± 7.49 g kg−1 (T1 ) in end product of vermicomposting process. The maximum increase in exchangeable K was in T2 44.17 (% more than initial) followed by T1 (16.44%), T4 (15.49%), T5 (14.0%), and T3 (8.46%) vermibeds. The waste mineralization mainly depends upon the earthworm activity and microbial population in waste mixture. In general, when organic waste passes through the gut of worm some fraction of organic minerals is then converted into more available species of nutrients (i.e. exchangeable forms) due to the action of endogenic and/or exogenic enzymes (Suthar, 2010). The high range of potassium in vermicomposted material further indicates the agronomic importance of end products. Sodium contents showed slight decrease after processing waste through earthworms. Total sodium in vermicomposted material
was in the ranges of 14.53 ± 0.57 g kg−1 –19.66 ± 0.74 g kg−1 in different vermibeds. The maximum decrease in sodium was in T5 (29.7%) while T4 showed the minimum decrease (11.8%) in total sodium content at the end of process (Table 2). Overall changes (decrement) in sodium were in the order: T2 > T3 > T5 > T1 > T4 . The results of sodium mineralization of this study are corroborated by the findings of other workers who have reported similar results (Kaur et al., 2010) of sodium loss in vermibeds. They attributed the results of sodium loss to chemical binding. However use of available fractions of salts by earthworm itself could be another important reason for sodium loss from substrates. Biodegradability is considered an important parameter for assessment of rate of waste decomposition in composting processes (Hung, 1993). Yadav and Garg (2009) applied this parameter in vermicomposting trials to measure the organic matter conversion during vermicomposting. The biodegradability coefficient (Kb ) was calculated for different waste mixtures in this study. Kb was in the ranges of 0.34–0.74 for different waste mixtures. The Kb for different experimental container was in the order: 0.74 (T1 ) > T3 (0.56), T5 (0.49), T4 (0.36) > 0.34 (T2 ). Data clearly suggested that the proportion of herbal pharmaceutical industrial waste directly affects the rate of biodegradability. There was significant reduction in C:N rations of vermibeds after completion of vermicomposting. It was due to increase in N content and simultaneously decrease in TOC contents of waste mixtures. The C:N ratio of vermicomposted material was in the ranges of 10.2 ± 0.53 to 18.90 ± 1.73 in different vermibeds. The C:N ratio of final product was in the order: T1 > T2 > T4 > T3 > T5 (Table 3). The maximum reduction in C:N ratio was in T1 (61.3%) followed by T3 (52.9%), T2 (52.3%), T5 (36.6%) and T4 (36.5%). In general, C:N ratio of vermicompost reflects the waste mineralization rate and N enrichment process of ready material (Suthar and Singh, 2008). It is suggested that in vermicomposting sub system, the loss of carbon as carbon dioxide due to respiratory activities of earthworms and associated microflora, and simultaneously adding of nitrogen in substrate material by inoculated earthworms (through production of mucus, enzymes and nitrogenous excrements) lowers the C:N ratio of waste mixtures. The parameter traditionally considered determining the degree of maturity of compost and to define its agronomic quality is the C:N ratio. The C:N ratio below 20 is indicative of acceptable maturity, while a ratio of 15 or lower being preferable for agronomic use of composts. In this study the C:N ratio of all vermicomposted waste mixtures were within the preferable range (<15) for agriculture use. C:P ratio of vermicomposted material was in the ranges of 13.06 ± 0.62 (T3 )–21.79 ± 0.10 (T5 ). Data clearly suggested that C:P ratio of vermicomposted material was within the acceptable limit as suggested by Edwards and Bohlen (1996), i.e. <15:1, except in T1 and T5 (Table 3). The C:P ratio of 15:1 of vermicompost is considered ideal for better assimilation by plants.
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Table 4 Earthworm productions during vermicomposting process (mean ± SD, n = 3). Vermibeds
Mean initial total earthworm weight (g)
T1 T2 T3 T4 T5
11.04 10.88 10.54 9.80 9.51
± ± ± ± ±
0.14 0.58 1.08 0.90 1.97
Net earthworm total biomass at the end (g) 18.40 26.40 59.39 59.60 35.76
± ± ± ± ±
4.11a 6.06ab 3.92b 27.62b 2.82ab
% change in total earthworm biomass during vermicomposting 66.98 144.0 470.4 495.2 284.04
± ± ± ± ±
39.6a 64.2a 100.0b 220.9ab 58.1b
Total cocoon production
81.0 142.67 238.67 306.33 234.0
± ± ± ± ±
9.54a 8.83a 23.56b 14.31b 23.67b
Total earthworm populations (adult + hatchlings) at the end 56.0 60.33 155.67 112.0 78.33
± ± ± ± ±
9.85a 14.48a 6.35b 44.68ab 1.53a
Mean value followed by different letters is statistically different (ANOVA; Tukey’s t-test, p < 0.05).
3.2. Biomass, cocoon production and earthworm population in different vermibeds During vermicomposting there was a significant change in earthworm numbers, total biomass and survival in different waste mixtures. The earthworm mortality was observed for initial critical period of establishment (Suthar, 2010) in vermibeds. Statistically, there was significant difference among different vermibeds for total live weight of earthworms (ANOVA: F = 6.242, p = 0.009), total end population of earthworm (ANOVA: F = 11.024, p = 0.001) and earthworm mortality rate (ANOVA: F = 8.048, p = 0.004). The maximum mean total earthworm biomass was 59.60 ± 27.96 g in T4 , while T1 exhibit the minimum value of total earthworm biomass (18.40 ± 4.11 g). The earthworm total biomass was in the order: T4 > T3 > T5 > T2 > T1 . As compared to initial values there was manifold increase in live weight of earthworms in all vermibeds. The maximum increase in total weight of earthworms was in T4 (6.1fold) followed by T3 (5.6-fold), T5 (3.8-fold), T2 (2.4-fold) and T1 (1.7-fold) than initial values at the end (Table 4). The earthworm growth is directly related with quality of feedstock used for earthworm culture. The excellent growth rate in T3 and T4 (containing 50–75% HPIW) could be due to its’ palatability and more acceptability as food by worms. In general, plant wastes have different C:N ratios, particle size, protein and crude fiber contents and even some special plant metabolites, i.e. polyphenols and related substances (Ganesh et al., 2009) which affects the earthworm feeding rate in vermibeds. Relatively lower growth in T5 supports the above hypothesis that herbal pharmaceutical waste cause adverse impact on earthworm biomass production at higher concentrations. It is hypothesized that a better worm growth pattern in E. fetida was due to a good supply of easily metabolizable organic matter, non-assimilated carbohydrates, and even low concentration of growth-retarding substances in vermibeds. There was a statistical significant difference among different vermibeds for total cocoon numbers (ANOVA: F = 26.358, p < 0.001) during vermicomposting. E. fetida produced cocoon in the ranges of 81.0 ± 9.54 (T1 )–306.33 ± 14.31 (T4 ) in all vermibeds during vermicomposting. The maximum cocoons were obtained from T4 vermibed followed by T3 (238.67 ± 23.56), T5 (234.0 ± 23.67), T2 (142.67 ± 8.83) and T1 (81.0 ± 9.54) (Table 4). The difference T3 , T4 and T5 was not statistically significant (ANOVA: Tukey’s t-test, p > 0.05). The reproduction rate in earthworm is mainly determined by feedstock quality and microclimatic viabilities. The cocoon production rate increased with increasing proportion of HPIW in feedstock. It could be due to some stimulatory impact of any plant chemical present in herbal waste. The results clearly suggested that herbal pharmaceutical waste may acts as suitable substrate for earthworm propagation but at higher concentration it can acts as retarding agent for reproduction in epigeic earthworms. The important difference between the rates of cocoon production in the two organic wastes must be related to the quality of the wastes.
4. Conclusions This work provides an opportunity to explore the potential of vermicomposting to manage solid waste generated from herbal pharmaceutical industries. The results of this study clearly suggest that HPIW may be a valuable source of nutrients for sustainable land restoration programme if proper technology is applied to recover the valuable nutrients from such industrial wastes. The ready material at the end showed significant increase in all chemical characteristics of wastes and C:N also reduced up to its acceptable limit for agronomic uses. Results thus suggested that vermicomposting can be an efficient tool to convert the noxious community wastes into value-added materials for sustainable human development. References Aira, M., Monroy, F., Dominguez, J., 2007. Eisenia fetida (Oligochaeta, Lumbricidae) modifies the structure and physiological capabilities of microbial communities improving carbon mineralization during vermicomposting of pig manure. Microbial Ecol. 54, 662–671. Anon, 2011. Herbal Industry in India, http://www.herbal.co.in/herbal-industry-inindia.html (assessed on 12-6-2011). Diaz, L.F., Savage, G.M., Eggerth, L.L., Golueke, C.G., 1996. Solid Waste Management for Economically Developing Countries. International Solid Waste Association, Copenhagen. Dominguez, J., Edwards, C.A., 2004. Vermicomposting organic wastes: a review. In: Hanna, S.H.S., Milkhail, W.Z.A. (Eds.), Soil Zoology for Sustainable Development in the 21st Century. Edwards, C.A., Bohlen, P.J., 1996. Biology and Ecology of Earthworms, 3rd ed. Chapman and Hall, New York/London. Ganesh, P.S., Gajalakshmi, S., Abbasi, S.A., 2009. Vermicomposting of the leaf litter of acacia (Acacia auriculiformis): possible roles of reactor geometry, polyphenols, and lignin. Bioresour. Technol. 100 (5), 1819–1827. Gomez-Brandon, M., Lazcano, C., Lores, M., Dominguez, J., 2011. Short-term stabilization of grape marc through earthworms. J. Hazard. Mater. 187, 291–295. Hait, S., Tare, V., 2011. Vermistabilization of primary sewage sludge. Bioresour. Technol. 102, 2812–2820. Hung, R.T., 1993. The Practical Handbook of Compost Engineering. Levis Publishers, Boca Raton, FL. Jackson, M.L., 1975. Soil Chemical Analysis. Prentice Hall of India, New Delhi. Morais, F.M.C., Queda, C.A.C., 2003. Study of storage influence on evolution of stability and maturity properties of MSW composts. In: Proceeding of the fourth International Conference of ORBIT association on Biological Processing of Organics: Advances for a Sustainable Society, Part II, Perth, Australia. Kaur, A., Singh, J., Vig, A.P., Dhaliwal, S.S., Rup, P.J., 2010. Cocomposting with and without Eisenia fetida for conversion of toxic paper mill sludge to a soil conditioner. Bioresour. Technol. 101, 8192–8198. Kaviraj, Sharma, S., 2003. Municipal solid waste management through vermicomposting employing exotic and local species of earthworms. Bioresour. Technol. 90, 169–173. Khwairakpam, M., Bhargava, R., 2009. Bioconversion of filter mud using vermicomposting employing two exotic and one local earthworm species. Bioresour. Technol. 100, 5846–5852. Moreno, R., Benitez, E., Meglar, R., Polo, A., Gomez, M., Nogales, R., 2000. Vermicomposting as an alternative for reusing by-products from the olive oil industry. Fresenius Environ. Bull. 9, 1–8. Nelson, D.W., Sommers, L.E., 1996. Total carbon and organic carbon and organic matter. In: Page, A.L., Miller, R.H., Keeney, D.R. (Eds.), Method of Soil Analysis. American Society of Agronomy, Madison, pp. 539–579. Olsen, S.R., Cole, C.V., Watanabe, F.S., Dean, L.A., 1954. Estimation of Available Phosphorus in Soils by Extraction with Sodium Bicarbonate. Circ. US Dept. Agric, 939.
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Prakash, M., Karmegam, N., 2010. Dynamics of nutrients and microflora during vermicomposting of mango leaf litter (Mangifera indica) using Perionyx ceylanensis. Int. J. Global Environ. 10, 339–353. Pramanik, P., Ghosh, G.K., Ghosal, P.K., Banik, P., 2007. Changes in organic – C, N, P and K and enzymatic activities in vermicompost of biodegradable organic wastes under liming and microbial inoculants. Bioresour. Technol. 98, 2485–2495. Pramanik, P., Chung, Y.R., 2011. Changes in fungal population of fly ash and vinasse mixture during vermicomposting by Eudrilus eugeniae and Eisenia fetida: documentation of cellulose isozymes in vermicompost. Waste Manage., doi:10.1016/j.wasman.2010.12.017. Simard, R.R., 1993. Ammonium acetate extractable elements. In: Martin, R., Carter, S. (Eds.), Soil Sampling and Methods of Analysis. Lewis Publisher, FL, USA, pp. 39–43. Suthar, S., 2009. Vermicomposting of vegetable market solid waste using Eisenia fetida: impact of bulking material on earthworm growth and decomposition rate. Ecol. Eng. 35, 914–920.
Suthar, S., 2010. Recycling of agro-industrial sludge through vermitechnology. Ecol. Eng. 36, 1028–1036. Suthar, S., 2011. Utilizing livestock waste solids as bioresource for socio-economic sustainability: a report from rural India. Rev. Environ. Sci. Biotechnol., doi:10.1007/s1157-011-92240-0. Suthar, S., Singh, S., 2008. Comparison of some novel polyculture and traditional monoculture vermicomposting reactors to decompose organic wastes. Ecol. Eng. 33, 210–219. Suthar, S., Singh, S., 2009. Bioconcentrations of metals (Fe, Cu, Zn, Pb) in earthworms (Eisenia fetida), inoculated in municipal sewage sludge: do earthworms pose a possible risk of terrestrial food chain contamination? Environ. Toxicol. 24 (1), 25–32. Vinotha, S.P., Parthasarthi, K., Rangnathan, L.S., 2000. Enhanced phosphatase activity in earthworm casts is more of microbial origin. Curr. Sci. 79 (9), 1158–1159. Yadav, A., Garg, V.K., 2009. Feasibility of nutrient recovery from industrial sludge by vermicomposting technology. J. Hazard. Mater. 168, 262–268.
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Ecological Engineering journal homepage: www.elsevier.com/locate/ecoleng
Short communication
Vermicomposting of herbal pharmaceutical industry solid wastes Deepika Singh, Surindra Suthar ∗ School of Environment & Natural Resources, Doon University, Dehradun 248001, India
a r t i c l e
i n f o
Article history: Received 14 June 2011 Received in revised form 2 September 2011 Accepted 28 October 2011 Available online 19 December 2011 Keywords: Eisenia fetida Industrial waste Vermicompost Composting Waste recycling
a b s t r a c t The efforts were made in this study to decompose the herbal pharmaceutical industrial waste (HPIW) using earthworm Eisenia fetida (Savigny) under laboratory conditions. To achieve the objectives HPIW was mixed with cow dung (CD) in different ratios to produce five different waste mixtures for vermicomposting: T1 – CD (100%), T2 – HPIW (25%) + CD (75%), T3 – HPIW (50%) + CD (50%), T4 – HPIW (75%) + CD (25%) and T5 – HPIW (100%). Vermicomposting caused significant changes in vermibed characteristics. In all waste mixtures, a decrease in pH, organic C, C:P ratio and C:N ratio, but increase total N, available P and exchangeable K was recorded. C:N ratio of end material (vermicompost) was within the agronomic preferable limit (>15). T3 and T4 vermibeds showed better mineralization and waste decomposition rate during vermicomposting. E. fetida produced cocoons in the ranges of 81.0 ± 9.54 (T1 )–306.33 ± 14.31 (T4 ) in all vermibeds. Results clearly suggested that vermicomposting could be an efficient technology to convert HPIW into some value-added products for ecological restoration practices. © 2011 Elsevier B.V. All rights reserved.
1. Introduction The herbal pharmaceutical and cosmetic industry in India is probably the oldest medical care system in the world. The use of herbs to cure general health disorders and complex diseases has been mentioned in the Vedas, an ancient religious work of the Hindus. The ancient herbal healing methods of Ayurveda and Unani deal with the use of herbs and natural products to tackle health conditions (Anon, 2011). In recent years there is growing concern over adverse impact of synthetic chemicals and therefore, people are now moving towards traditional herbal based medical care system. The demand of herbal products and raw materials has been many folds during last two decades and Indian and China both share more than one-third markets of herbal products in the worlds. The total market of Ayurvedic products in India is about one billion dollar (US). An estimation suggests about 400,000–500,000 MT consumption of key raw material in domestic market for herbal product manufacturing. Solid waste generated from these herbal manufacturing industries is an emerging pollutant for terrestrial environment. However such industries (processing units and product manufacturing) produce a large quantity of spent wastes after pre-processing and/or extracting or distillation of active ingredients from raw materials. Such industrial wastes not only spoil aesthetics sense of local habitats but at the same time also create issues of all types of environmental pollution, if proper disposal is
∗ Corresponding author. Tel.: +91 135 2255103. E-mail address: sutharss [email protected] (S. Suthar). 0925-8574/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ecoleng.2011.10.015
not made. In majority of cases such plant-origin waste is dumped openly either at landfill sites or at open space nearby to industrial areas. The emission of green house gases, nutrient enrichments in surface water bodies, nitrate leaching to groundwater, prolification and breeding of disease vectors are the major disadvantages of open dumping of organic wastes (Suthar, 2011). The stabilization of industrial wastes prior to use of disposal could reduce the environmental problems associated with its management (GomezBrandon et al., 2011). There is emerging concern over using waste as resources for land restoration and energy production. The recycling, reuse and resource recovery has been considered as one of the best options for sustainable solid waste management programme. In nature, a variety of decomposers or detritus feeders (fungi, actinomycetes, protozoa, nematodes, annelids, arthropods, etc.) are available which not only decomposes the complex organic substances of wastes but at the same time also enhances the quality of end products. The earthworms have been recommended as potential decomposer to recycle a variety of organic wastes generated from different sectors of human society. Utilization of earthworms for waste decomposition is called vermicomposting. Vermicomposting is emerging as a most appropriate alternative to convert aerobic composting (Hait and Tare, 2011). The vermicomposting is stabilization of organic material through the joint action of earthworms and microorganisms. While, microbes are responsible for biochemical degradation of organic matter, earthworms are the important drivers of the process, conditioning the substrate and altering the biological activity (Dominguez and Edwards, 2004). Earthworm’s foregut acts as mechanical blenders and modifies the physical status of ingested organic wastes and
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consequently increases the surface area for digestive enzyme actions. In earthworm, the gut-associated-microbes provide several essential enzymes (exogenous) required for rapid digestions of ingested organic fractions. Further mineralization of nutrients is carried out by microbial communities associated with freshly deposited worm casts (Aira et al., 2007). Vermicomposting has several advantages over conventional thermophilic composting systems in terms of process time, nutrients recovery, microbial richness and phytotoxicity. The traditional composting and vermicomposting methods operate under very different conditions and can produce very different composted products. The potential of vermitechnology in stabilization of a variety of industrial wastes is well documented in published literature. Few earlier author reported the successful utilization of epigeic earthworms for decomposition of food processing industry sludge (Yadav and Garg, 2009), vinasse (Pramanik and Chung, 2011), paper mill sludge (Kaur et al., 2010), distillery sludge (Suthar and Singh, 2009), sugar factory waste (Khwairakpam and Bhargava, 2009), Olive oil mill sludge (Moreno et al., 2000), etc. In majority of previous studies E. fetida was used as candidate species for vermicomposting operation because it can tolerate wide pH range, temperature, moisture and a wide range of putrescible substances and biotoxic compounds (Ganesh et al., 2009). The aim of this study was to investigate the decomposition of herbal pharmaceutical industrial waste spiked with cow dung in different ration using composting earthworm E. fetida under laboratory condition. 2. Methods 2.1. Earthworm, herbal pharmaceutical waste collection and pre-processing The vermicomposting earthworm species: E. fetida used for experimentation was procured from vermiculture unit, Indian Veterinary Research Institute, Izatnagar, India. For stock earthworms were cultured in a circular plastic container containing of 30 L capacity in waste mixtures (cow dung mixed with leaf litter), under laboratory conditions. The stock was further used for laboratory studies on vermicomposting. The herbal pharmaceutical industrial waste (HPIW) was procured from spent material disposing unit of The Himalaya Drug Company, Dehradun which is one of the leading herbal pharmaceutical product manufacturing or processing unit in India. The waste was of mixed type containing spent material after extraction/distillation of herbs and unused part of the plant. The partially composted mixture of HPIW was collected in large-sized cleaned polythene containers and brought to laboratory. In lab the material was shed dried and then stored in dry plastic containers for further vermibed preparation. The cow dung was used as bulky agent for preparation of vermibeds/feed materials for earthworms. Freshly deposited cow dung (CD) was obtained from a local cowshed, Mothrawala, Dehradun. The cow dung was partially dried in shed and stored for further experimentations. The chemical characteristic of fresh HPIW and CD is described in Table 1. 2.2. Treatment design and observations The HPIW was mixed with CD in different ratios (dry weight proportions) to produce five different combinations of waste mixtures: The details of experimental vermibeds are described as: T1 – CD (100%), T2 – HPIW (25%) + CD (75%), T3 – HPIW (50%) + CD (50%), T4 – HPIW (75%) + CD (25%) andT5 – HPIW (100%). Two treatments
Table 1 Chemical characteristics of herbal pharmaceutical industrial waste (HPIW) and cow dung (CD) used for experimentation (mean ± SD, n = 3). Parameters
CD
pH EC Total organic carbon Available P Sulphate Exchangeable K Na+ Total N
9.02 0.877 743.3 580.0 12.96 452.0 18.76 15.20
HPIW ± ± ± ± ± ± ± ±
0.01 0.02 34.4 2.0 0.07 15.87 0.15 0.26
8.08 0.264 641.26 678.0 14.44 187.67 23.99 46.8
± ± ± ± ± ± ± ±
0.22 0.20 12.2 2.65 0.22 7.37 0.61 1.71
were composed of pure CD and HPIW (without any dilutions). The waste mixture acts as bedding as well as feed for the composting earthworms. For vermicomposting experimentation, 300 g waste mixture (dry weight basis) was filled in plastic circular containers of 2 L capacity (one for each mixture). The waste mixtures moistened with distilled water to maintain appropriate moisture level for initial decomposition of waste mixtures. These bedding were kept for 1 week for initiation of microbial degradation and softening of waste mixture). For vermicomposting experiments, 20 earthworms were collected from the stock culture and released into each different container containing 300 g of substrate material. The experimental beddings were kept in triplicate for each waste mixture. The moisture content was maintained at 55–65%, throughout the study period by periodic sprinkling of adequate quantity of water. The containers were placed in a humid and dark place at room temperature (27–28 ◦ C). In order to measure the changes in chemical characteristics of waste mixture during vermicomposting, the homogenized samples were drawn at 0, 10, 20, 20, 40, 50 and 60 days from each experimental container. The samples were oven dried (48 h at 60 ◦ C), and stored in sterilized plastic airtight containers for further physico-chemical analysis. The chemical characteristics of all waste mixtures used for experimentation were described in Table 2. During first observation (after 10 days) the inoculated earthworms in waste mixtures were counted to assess the overall mortality (%) in vermibed. The changes in earthworm population, growth and live weight were measured during vermicomposting experiment in all vermibeds by following method as described by Suthar (2009). Total earthworm population and total cocoon numbers (fresh and residual) in each experimental container were measured at the end. Earthworms and cocoons were separated from the parental waste mixture by hand sorting method, after which worms were washed in tap water to remove adhering material from their body and subsequently weighed live weight basis without voiding their gut. Separated cocoons were counted at the end and then introduced in separate bedding containing partially decomposed cod dung. On the basis of observed information other data sets: biomass change (%), growth rate, reproduction rate (cocoon worm−1 day−1 ), mortality, etc. were produced for different waste mixtures. 2.3. Chemical analysis The pH was measured using a digital pH meter (Metrohm, Swissmade) in 1:10 (w/v) aqueous solution (deionized water). Electrical conductivity (EC) was measured using a digital conductivity meter. Total organic carbon (TOC) was measured after igniting the sample in a Muffle furnace at 550 ◦ C for 60 min by the method of Nelson and Sommers (1996). Extractable phosphorous was measured using the method described by Olsen et al. (1954). Total exchangeable cations (K+ and Na+ ) were determined after extracting the sample using ammonium acetate (Simard, 1993). Total Kjeldahl nitrogen (TKN) was measured using the method described
D. Singh, S. Suthar / Ecological Engineering 39 (2012) 1–6
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Table 2 Chemical characteristics of initial and vermicomposted waste mixture from different treatments (mean ± SD, n = 3). Treatmenta
pH
Initial waste mixture T1 9.02 ± 0.017 8.79 ± 0.90 T2 8.72 ± 0.03 T3 T4 8.67 ± 0.04 T5 8.08 ± 0.22 Vemicomposted waste mixture 8.75 ± 0.23 T1 7.50 ± 0.05 T2 8.09 ± 0.04 T3 T4 7.41 ± 0.05 T5 8.24 ± 0.06
TOC
0.877 ± 0.02 0.396 ± 0.04 0.550 ± 0.10 0.340 ± 0.02 0.264 ± 0.20
743.3 754.47 730.40 643.46 641.26
± ± ± ± ±
34.35 9.34 6.39 6.07 12.20
15.20 24.10 33.0 37.9 46.8
± ± ± ± ±
0.26 0.33 0.77 1.24 1.71
580.0 610.0 531.76 585.9 678.0
± ± ± ± ±
2.0 2.0 2.54 3.43 2.65
452.0 281.3 315.3 324.3 187.67
15.87 7.09 7.76 4.5 7.37
18.76 20.68 20.90 21.9 23.99
± ± ± ± ±
0.15 0.31 0.44 0.87 0.61
426.10 608.8 542.2 535.6 540.9
± ± ± ± ±
35.9 10.21 27.88 15.6 7.19
22.60 42.45 52.40 49.76 59.94
± ± ± ± ±
0.39 0.33 1.04 1.55 2.11
614.3 635.3 562.0 634.3 712.67
± ± ± ± ±
5.51 4.16 4.36 5.51 15.37
526.1 ± 7.49 414.0 ± 7.81 342.1 ± 9.84 374.67 ± 15.27 213.67 ± 5.67
16.25 14.53 16.22 19.33 19.66
± ± ± ± ±
1.43 0.57 0.69 1.53 0.74
0.99 0.69 0.82 0.80 0.70
± ± ± ± ±
0.03 0.05 0.06 0.06 0.05
Ntot
Pavail
Na+
EC
Kexch ± ± ± ± ±
Units of all the parameters except pH and EC are in g kg−1 . The EC values are in S/cm. a For treatment compositions see text.
by Jackson (Jackson, 1975). Biodegradability coefficient indicated the organic matter (OM) contents: OM % = (100 − Ash content %). Biodegradability coefficient (Kb ) was calculated using the following equation (Diaz et al., 1996): Kb =
(OMi − OMf ) × 100 OMi (100 − OMf )
where OMf is the organic matter content at the end of process and OMi is the organic matter content at the beginning of the process. 2.4. Statistical analysis One-way ANOVA was used to analyze the differences between treatments. A Tukey’s t-test was also performed to identify the homogeneous type of the data sets. SPSS® statistical package (Window Version 13.0) was used for data analysis. All statements reported in this study are at the p < 0.05 levels. 3. Results and discussion 3.1. Physico-chemical changes in waste mixture during vermicomposting The earthworm caused significant changes in the chemical characteristics of waste mixtures during vermicomposting process. The worm-worked material was more stabilized, odor-free, and dark brown substance with high range of plant available forms of soil nutrients. There was significant reduction in pH value of all waste mixtures after vermicomposting process (Table 2). The range of pH in vermicomposted material was 7.41–8.75 (Table 2). pH of relatively higher in initial substrate materials, especially in CD vermibed. In worm-worked waste mixtures pH shifted towards to downward scale and this could be due to the production of CO2 , ammonia, NO3 − and other intermediate organic acids during waste decomposition processes. Pramanik et al. (2007) suggested that decomposition of organic material leads to the formation of ammonium (NH4 + ) and humic acids. The combined effect of these two oppositely charged groups actually regulates the pH of vermicomposting substrates. The difference in pH for different experimental containers may be attributed to degree of mineralization and microbial activities which directly affects the production of intermediate compounds during waste stabilization process. pH of substrate also importance because it directly affects the colonization of major decomposer (bacteria and fungi) in decomposing waste feed stocks. Electrical conductivity (EC) showed significant changes after vermicomposting process in all waste mixtures. The EC in wormworked waste mixture ranged from 0.70 ± 0.20 S/cm (T5 ) to
0.99 ± 0.03 S/cm (T1 ). EC was relatively higher in vermicomposted material than initial materials in all vermibeds. Overall, the increase in EC was in the ranges of 12.9 (T1 )–165.2 (T5 )% for different waste mixtures. The EC increase was in the order: T5 > T4 > T2 > T3 > T1 (Table 2). EC increased in CD vermibed but to a lesser extent. The increase in EC could be to reduction of organic matter and release of different mineral salts: phosphate, ammonium, potassium, etc. The results indicate that mineralization rate was higher in T5 and T4 waste mixtures than other waste mixtures. Hait and Tare (2011) reported average increase in EC of about 35.4–56.4% in vermistabilized sewage sludge. Ash contents indicate the organic matter mineralization and waste stabilization. In this study there was significant increase in the content of ash in all vermibeds. In vermicomposted material the maximum ash content was in T1 (573.9 g kg−1 ) followed by T4 (464.4 g kg−1 ), T5 (459.1 g kg−1 ), T3 (457.8 g kg−1 ) and T2 (391.2 g kg−1 ). As compared to initial contents ash content increased in the ranges of 28–123.5% in all vermibeds. Total organic carbon (TOC) showed decrease than initial contents in all vermibeds after decomposing wastes through earthworms. The maximum decrease was 42.6% in T1 followed by 25.74% (T3 ), 19.31% (T2 ), 16.77 (T4 ) and 15.62% (T5 ). The loss of carbon as CO2 due to microbial respiration and assimilation of simple carbohydrates leads to TOC reductions from waste mixtures. Moreover, carbohydrates and other polysaccharides which are considered major source of carbon are digested rapidly by earthworms and some fraction of digested substances is then assimilated into worm biomass. The greater TOC reduction in CD (T1 ) may be due to microbial richness of substrate materials. In such beddings the microbial respiration may leads to rapid C loss through CO2 production. Also, earthworm fragments the waste feedstock into fine fractions which results in increased sites for microbial hydrolytic enzyme actions. The biological mutuality between earthworms and associated microbes is primarily responsible for C loss from the organic wastes. Kaviraj and Sharma (2003) reported 20–45% reduction in TOC contents of vermicomposted municipal solid waste mixed with CD. Similar observations have been reported by Prakash and Karmegam (2010) during vermicomposting of press-mud from sugar industry. There was increase in total N contents in all vermibeds as compared to initial levels after completion of vermicomposting process (Table 2). The total N content in vermicomposted waste mixture was in the range of 22.60 g kg−1 (T2 )–59.94 g kg−1 (T4 ). The maximum increase in total N content was in T2 (76.5% higher than initial) followed by T3 (58.8%), T1 (48.7%), T4 (31.3%) and T5 (28.1%). The N enrichment process during vermicomposting depends upon the microbial populations and proportion of industrial wastes which contains microbial growth retarding
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Table 3 C:N and C:P ratios of initial and vermicomposted waste mixtures from different treatment vermibeds (mean ± SD, n = 3). Treatmenta
Initial
Final
C:N ratio T1 T2 T3 T4 T5 a b c d
48.8 26.6 22.1 17.0 16.1
± ± ± ± ±
1.47b 0.83 0.35 0.56 0.76
C:P ratio 57.37 64.32 56.82 50.3 44.41
± ± ± ± ±
Acceptable (C:N ratios < 20)
C:N ratio 2.67 1.26 0.96 1.05 1.32
18.9 12.7 10.4 10.8 10.2
± ± ± ± ±
1.73 0.07 0.62 0.30 0.53
Preferable (C:N ratios < 15)c
Preferable (C:P ratio <15)d
– √ √ √ √
× √ √ √
C:P ratio 21.85 13.97 13.06 13.56 21.79
± ± ± ± ±
1.22 0.49 0.62 1.89 0.10
√ – – – –
×
For treatment compositions see text. Mean value followed by different letters is statistically different (ANOVA; Tukey’s t-test, P < 0.05). Morais and Queda (2003). Edwards and Bohlen (1996).
substances (Suthar, 2010). Earthworm enhances the N level of vermibed by adding excreta and other secretions. Also, mucus a polysaccharide is secreted by earthworm to moisten the body surface also important to enrich vermibeds with nitrogen fixers. Earthworm also alters the microclimatic conditions of vermibeds which consequently promotes microbial populations responsible for N enrichment. Better microbial population in vermicomposting system (Aira et al., 2007) may an advantage over traditional composting system. Moreover, earthworm adds N-rich substances (excretory products, mucus, body fluid, enzymes, etc.) in substrates during vermicomposting process. Earlier studies have also reported the N enrichment in vermicomposted waste mixtures (Khwairakpam and Bhargava, 2009; Prakash and Karmegam, 2010; Hait and Tare, 2011). There was significant increase in the contents of available P (phosphate) in all vermibeds than initial levels (Table 2). The level of phosphate in end material was in the ranges of 562.0 ± 4.36 g kg−1 (T3 )–712.67 ± 15.37 g kg−1 (T5 ) for different waste mixtures. The maximum PO4 3− enhancement was in T4 (8.25%) followed by T1 (5.92%), T3 (5.68%), T5 (5.12%) and T2 (4.15%) than initial level. The high available P (plant available form of phosphorus) in vermicompost suggests the agronomic potential of vermicompost as potential plant growth media. The phosphorous mineralization is performed partly by earthworm gut phosphatases, and further release of P might be attributed to the microbial activities in deposited casts (Vinotha et al., 2000). Few author suggested the role of P-solubilizing bacteria in phosphorous enhancements in deposited casts of earthworms (Pramanik et al., 2007; Prakash and Karmegam, 2010). PO4 3− enhancement showed drastic variations among different experimental waste mixtures. The highest P mineralization in T4 suggests the suitability of waste substrate for earthworm feed and microbial propagation. The vermicomposted waste mixtures were rich in exchangeable K contents (Table 2). The end material showed higher level of exchangeable and total available potassium contents than initial levels. Exchangeable K was the ranges of 213.67 ± 5.67 g kg−1 (T5 )–526.1 ± 7.49 g kg−1 (T1 ) in end product of vermicomposting process. The maximum increase in exchangeable K was in T2 44.17 (% more than initial) followed by T1 (16.44%), T4 (15.49%), T5 (14.0%), and T3 (8.46%) vermibeds. The waste mineralization mainly depends upon the earthworm activity and microbial population in waste mixture. In general, when organic waste passes through the gut of worm some fraction of organic minerals is then converted into more available species of nutrients (i.e. exchangeable forms) due to the action of endogenic and/or exogenic enzymes (Suthar, 2010). The high range of potassium in vermicomposted material further indicates the agronomic importance of end products. Sodium contents showed slight decrease after processing waste through earthworms. Total sodium in vermicomposted material
was in the ranges of 14.53 ± 0.57 g kg−1 –19.66 ± 0.74 g kg−1 in different vermibeds. The maximum decrease in sodium was in T5 (29.7%) while T4 showed the minimum decrease (11.8%) in total sodium content at the end of process (Table 2). Overall changes (decrement) in sodium were in the order: T2 > T3 > T5 > T1 > T4 . The results of sodium mineralization of this study are corroborated by the findings of other workers who have reported similar results (Kaur et al., 2010) of sodium loss in vermibeds. They attributed the results of sodium loss to chemical binding. However use of available fractions of salts by earthworm itself could be another important reason for sodium loss from substrates. Biodegradability is considered an important parameter for assessment of rate of waste decomposition in composting processes (Hung, 1993). Yadav and Garg (2009) applied this parameter in vermicomposting trials to measure the organic matter conversion during vermicomposting. The biodegradability coefficient (Kb ) was calculated for different waste mixtures in this study. Kb was in the ranges of 0.34–0.74 for different waste mixtures. The Kb for different experimental container was in the order: 0.74 (T1 ) > T3 (0.56), T5 (0.49), T4 (0.36) > 0.34 (T2 ). Data clearly suggested that the proportion of herbal pharmaceutical industrial waste directly affects the rate of biodegradability. There was significant reduction in C:N rations of vermibeds after completion of vermicomposting. It was due to increase in N content and simultaneously decrease in TOC contents of waste mixtures. The C:N ratio of vermicomposted material was in the ranges of 10.2 ± 0.53 to 18.90 ± 1.73 in different vermibeds. The C:N ratio of final product was in the order: T1 > T2 > T4 > T3 > T5 (Table 3). The maximum reduction in C:N ratio was in T1 (61.3%) followed by T3 (52.9%), T2 (52.3%), T5 (36.6%) and T4 (36.5%). In general, C:N ratio of vermicompost reflects the waste mineralization rate and N enrichment process of ready material (Suthar and Singh, 2008). It is suggested that in vermicomposting sub system, the loss of carbon as carbon dioxide due to respiratory activities of earthworms and associated microflora, and simultaneously adding of nitrogen in substrate material by inoculated earthworms (through production of mucus, enzymes and nitrogenous excrements) lowers the C:N ratio of waste mixtures. The parameter traditionally considered determining the degree of maturity of compost and to define its agronomic quality is the C:N ratio. The C:N ratio below 20 is indicative of acceptable maturity, while a ratio of 15 or lower being preferable for agronomic use of composts. In this study the C:N ratio of all vermicomposted waste mixtures were within the preferable range (<15) for agriculture use. C:P ratio of vermicomposted material was in the ranges of 13.06 ± 0.62 (T3 )–21.79 ± 0.10 (T5 ). Data clearly suggested that C:P ratio of vermicomposted material was within the acceptable limit as suggested by Edwards and Bohlen (1996), i.e. <15:1, except in T1 and T5 (Table 3). The C:P ratio of 15:1 of vermicompost is considered ideal for better assimilation by plants.
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Table 4 Earthworm productions during vermicomposting process (mean ± SD, n = 3). Vermibeds
Mean initial total earthworm weight (g)
T1 T2 T3 T4 T5
11.04 10.88 10.54 9.80 9.51
± ± ± ± ±
0.14 0.58 1.08 0.90 1.97
Net earthworm total biomass at the end (g) 18.40 26.40 59.39 59.60 35.76
± ± ± ± ±
4.11a 6.06ab 3.92b 27.62b 2.82ab
% change in total earthworm biomass during vermicomposting 66.98 144.0 470.4 495.2 284.04
± ± ± ± ±
39.6a 64.2a 100.0b 220.9ab 58.1b
Total cocoon production
81.0 142.67 238.67 306.33 234.0
± ± ± ± ±
9.54a 8.83a 23.56b 14.31b 23.67b
Total earthworm populations (adult + hatchlings) at the end 56.0 60.33 155.67 112.0 78.33
± ± ± ± ±
9.85a 14.48a 6.35b 44.68ab 1.53a
Mean value followed by different letters is statistically different (ANOVA; Tukey’s t-test, p < 0.05).
3.2. Biomass, cocoon production and earthworm population in different vermibeds During vermicomposting there was a significant change in earthworm numbers, total biomass and survival in different waste mixtures. The earthworm mortality was observed for initial critical period of establishment (Suthar, 2010) in vermibeds. Statistically, there was significant difference among different vermibeds for total live weight of earthworms (ANOVA: F = 6.242, p = 0.009), total end population of earthworm (ANOVA: F = 11.024, p = 0.001) and earthworm mortality rate (ANOVA: F = 8.048, p = 0.004). The maximum mean total earthworm biomass was 59.60 ± 27.96 g in T4 , while T1 exhibit the minimum value of total earthworm biomass (18.40 ± 4.11 g). The earthworm total biomass was in the order: T4 > T3 > T5 > T2 > T1 . As compared to initial values there was manifold increase in live weight of earthworms in all vermibeds. The maximum increase in total weight of earthworms was in T4 (6.1fold) followed by T3 (5.6-fold), T5 (3.8-fold), T2 (2.4-fold) and T1 (1.7-fold) than initial values at the end (Table 4). The earthworm growth is directly related with quality of feedstock used for earthworm culture. The excellent growth rate in T3 and T4 (containing 50–75% HPIW) could be due to its’ palatability and more acceptability as food by worms. In general, plant wastes have different C:N ratios, particle size, protein and crude fiber contents and even some special plant metabolites, i.e. polyphenols and related substances (Ganesh et al., 2009) which affects the earthworm feeding rate in vermibeds. Relatively lower growth in T5 supports the above hypothesis that herbal pharmaceutical waste cause adverse impact on earthworm biomass production at higher concentrations. It is hypothesized that a better worm growth pattern in E. fetida was due to a good supply of easily metabolizable organic matter, non-assimilated carbohydrates, and even low concentration of growth-retarding substances in vermibeds. There was a statistical significant difference among different vermibeds for total cocoon numbers (ANOVA: F = 26.358, p < 0.001) during vermicomposting. E. fetida produced cocoon in the ranges of 81.0 ± 9.54 (T1 )–306.33 ± 14.31 (T4 ) in all vermibeds during vermicomposting. The maximum cocoons were obtained from T4 vermibed followed by T3 (238.67 ± 23.56), T5 (234.0 ± 23.67), T2 (142.67 ± 8.83) and T1 (81.0 ± 9.54) (Table 4). The difference T3 , T4 and T5 was not statistically significant (ANOVA: Tukey’s t-test, p > 0.05). The reproduction rate in earthworm is mainly determined by feedstock quality and microclimatic viabilities. The cocoon production rate increased with increasing proportion of HPIW in feedstock. It could be due to some stimulatory impact of any plant chemical present in herbal waste. The results clearly suggested that herbal pharmaceutical waste may acts as suitable substrate for earthworm propagation but at higher concentration it can acts as retarding agent for reproduction in epigeic earthworms. The important difference between the rates of cocoon production in the two organic wastes must be related to the quality of the wastes.
4. Conclusions This work provides an opportunity to explore the potential of vermicomposting to manage solid waste generated from herbal pharmaceutical industries. The results of this study clearly suggest that HPIW may be a valuable source of nutrients for sustainable land restoration programme if proper technology is applied to recover the valuable nutrients from such industrial wastes. The ready material at the end showed significant increase in all chemical characteristics of wastes and C:N also reduced up to its acceptable limit for agronomic uses. Results thus suggested that vermicomposting can be an efficient tool to convert the noxious community wastes into value-added materials for sustainable human development. References Aira, M., Monroy, F., Dominguez, J., 2007. Eisenia fetida (Oligochaeta, Lumbricidae) modifies the structure and physiological capabilities of microbial communities improving carbon mineralization during vermicomposting of pig manure. Microbial Ecol. 54, 662–671. Anon, 2011. Herbal Industry in India, http://www.herbal.co.in/herbal-industry-inindia.html (assessed on 12-6-2011). Diaz, L.F., Savage, G.M., Eggerth, L.L., Golueke, C.G., 1996. Solid Waste Management for Economically Developing Countries. International Solid Waste Association, Copenhagen. Dominguez, J., Edwards, C.A., 2004. Vermicomposting organic wastes: a review. In: Hanna, S.H.S., Milkhail, W.Z.A. (Eds.), Soil Zoology for Sustainable Development in the 21st Century. Edwards, C.A., Bohlen, P.J., 1996. Biology and Ecology of Earthworms, 3rd ed. Chapman and Hall, New York/London. Ganesh, P.S., Gajalakshmi, S., Abbasi, S.A., 2009. Vermicomposting of the leaf litter of acacia (Acacia auriculiformis): possible roles of reactor geometry, polyphenols, and lignin. Bioresour. Technol. 100 (5), 1819–1827. Gomez-Brandon, M., Lazcano, C., Lores, M., Dominguez, J., 2011. Short-term stabilization of grape marc through earthworms. J. Hazard. Mater. 187, 291–295. Hait, S., Tare, V., 2011. Vermistabilization of primary sewage sludge. Bioresour. Technol. 102, 2812–2820. Hung, R.T., 1993. The Practical Handbook of Compost Engineering. Levis Publishers, Boca Raton, FL. Jackson, M.L., 1975. Soil Chemical Analysis. Prentice Hall of India, New Delhi. Morais, F.M.C., Queda, C.A.C., 2003. Study of storage influence on evolution of stability and maturity properties of MSW composts. In: Proceeding of the fourth International Conference of ORBIT association on Biological Processing of Organics: Advances for a Sustainable Society, Part II, Perth, Australia. Kaur, A., Singh, J., Vig, A.P., Dhaliwal, S.S., Rup, P.J., 2010. Cocomposting with and without Eisenia fetida for conversion of toxic paper mill sludge to a soil conditioner. Bioresour. Technol. 101, 8192–8198. Kaviraj, Sharma, S., 2003. Municipal solid waste management through vermicomposting employing exotic and local species of earthworms. Bioresour. Technol. 90, 169–173. Khwairakpam, M., Bhargava, R., 2009. Bioconversion of filter mud using vermicomposting employing two exotic and one local earthworm species. Bioresour. Technol. 100, 5846–5852. Moreno, R., Benitez, E., Meglar, R., Polo, A., Gomez, M., Nogales, R., 2000. Vermicomposting as an alternative for reusing by-products from the olive oil industry. Fresenius Environ. Bull. 9, 1–8. Nelson, D.W., Sommers, L.E., 1996. Total carbon and organic carbon and organic matter. In: Page, A.L., Miller, R.H., Keeney, D.R. (Eds.), Method of Soil Analysis. American Society of Agronomy, Madison, pp. 539–579. Olsen, S.R., Cole, C.V., Watanabe, F.S., Dean, L.A., 1954. Estimation of Available Phosphorus in Soils by Extraction with Sodium Bicarbonate. Circ. US Dept. Agric, 939.
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