Vermicomposting System Research Articles

How do earthworms affect the pathway of sludge bio-stabilization via vermicomposting?

The synergy effects between earthworms and microorganisms promote nitrogen mineralization and enhance stabilization of organic matters in a vermicomposting system. However, the stabilization pathways of vermicomposting in the system remain unknown. The aim of this study was to investigate the effect of earthworms on the stabilization pathway and associated microbial population of waste activated sludge recycled by vermicomposting. The treatment of sludge with and without earthworms was conducted at 20 °C for 60 days. The trends in organic matter (OM), dissolved organic carbon (DOC), NH4+-N, electrical conductivity (EC), microbial biomass carbon (MBC), and dehydrogenase activity (DHA) were similar in both systems over time. At the end of the treatment, OM and DOC were significantly lower (p < 0.05), and EC, NH4+-N, and NO3−-N were significantly higher (p < 0.05) in the vermicomposting group than in the control. Based on the statistical results of principal component analysis (PCA), it was proposed that the stabilization pathway in both treatment systems required a sequence of reactions characterized by the degradation of organic matter, accumulation of dissolved organic carbon, ammonification, and nitrification. Vermicomposting led to greater abundance and diversity (Shannon index) of 16S rDNA microbial species, but more even distribution in microbial community composition (Simpson index) than the control. However, the opposite performance for 18S rDNA microbes was observed. Vermicomposting enhanced the abundance of microorganisms involved in organic matter degradation and nitrification, facilitating the conversion of organic matter and favoring the nitrification. In short, the pathway of sludge bio-stabilization is not altered regardless of the addition of earthworms or not, which enables us to better understand vermicomposting process of sludge.

Enumeration of synergistic relationship between carbon dioxide evaluation and nutrient budget during vermicomposting of cereal grain processing industry sludge

Despite the growing concerns about global warming issues, very little emphasis is being given to understand the dynamics of CO2 emission in a vermicomposting system. The present study was designed to investigate the synergistic relationship between nutrient budget and CO2 evaluation rate during the vermistabilization of cereal grain processing industry sludge employing Perionyx excavatus. The results obtained from Principal Component Analysis and correlation studies revealed a negative correlation among both variables indicating that a periodical increase in nutrient budget decreases the CO2 evaluation rate during vermicomposting. The vermicomposting treatment containing 5 % Cow dung was deemed superior in terms of physico-chemical, maturity, phytotoxicity as well as nutritional parameters (pH, Conductivity, Total organic carbon, exchangeable acidity, heavy metal content, BOD, COD, NPK). Finally, statistical interpretation coupled with apropos analysis was employed to conclude that enriching the raw materials prior to any vermicomposting practice is key to reducing the emission of CO2.

Significance to the Horticulture Industry

Significance to the Horticulture Industry

An Analysis of the Quality of Compost Produced from Vermicomposting Fresh Cut Flower Waste

Abstract Higher levels of pesticide applications are used when growing cut flowers when compared to other crops such as tomatoes, lettuce, and rice, much of the floriculture industry production occurs in developing countries where less environmental regulations may be in place compared to those in the United States. Therefore, special consideration should be given to cut flower disposal from floral shops due to the potential excessive leaching of pesticides into land and waterways. Most retail florists in the industry dispose of their floral waste into municipal dumpsters. There are an estimated 13,200 retail flower shop locations in the United States, comprised of single location and multiple location companies. While the United States Department of Agriculture (USDA) has stringent guidelines to prevent the importation of pests and plant diseases, there are no regulations on the disposal of spent floral crops that may contain residues of pesticides or other chemicals. Vermicomposting is a method of composting used for pollution abatement while having the added benefit of acting as an alternative waste management method to traditional landfill dumping. The castings produced are a valuable commodity for agricultural, horticultural, and related industries. The main objective of this research was to analyze the quality of compost produced from vermicomposting fresh cut floral waste. Analysis of results was based on the U.S. Composting Council's Tests Methods for the Examination of Composting and Compost used by the U.S. Composting Council's Seal of Testing Approval (STA) program. When compared to STA standards, pH, soluble salts, organic matter, total nitrogen, carbon, carbon-to-nitrogen, bioassay, and respirometry all were found to be within normal ranges for compost sold in the horticulture industry. Chemical analysis found the level of arsenic, cadmium, copper, lead, mercury, molybdenum, nickel, selenium, zinc all to be well below set industry standards. Additionally, the vermicompost was lab tested for 23 herbicides and insecticides. Of those, one herbicide (clopyralid) and two insecticides (clofentezine and lufenuron) were found in the sample in trace amounts, and well below Environmental Protection Agency (EPA) set industry standards for acceptable trace amount in U.S. products. Results indicated floral waste collected from retail flower shops can be incorporated into a vermicomposting system to create a quality compost suitable for use in the horticulture industry.

The balance of nitrogen forms and number of microorganisms of the nitrogen cycle in vermicomposts based on leaf litter and cow manure

The processes of nitrogen transformation in the vermiculture system by Eisenia fetida using cow manure and leaf litter (poplar with small birch addition) have been investigated. Vermicomposting was carried out for five months in half-cubic meter wooden containers. The Kjeldahl method and potentiometry determined the total nitrogen, NH4 + and NO3- content in vermicompost. The total nitrogen content in cow manure was 1.83%, in leaf litter - 0.73%. The nitrate and ammonium content in non-composted leaf litter was 351 and 7.3 mEq/kg of dry matter, respectively. The nitrate and ammonium content in non-composted cow manure was 18.2 and 22 mEq/kg, respectively. Both investigated substrates of vermicomposting did not influence total nitrogen content. In cow manure-based vermicomposting system, the ammonium amount decreased by 5.3 times, while the concentration of nitrates increased by 6.5 times. In the leaf litter-based vermicomposting system, the ammonium amount increased by 2.9 times, and the amount of the nitrate increased by 1.6 times. The Azotobacter bacteria actual activity in both vermicomposts was close to 100%. The sum of nitrogen cycle microorganisms in manure vermicompost was 2.4 times higher than in leaf litter vermicompost.

Changes in the nutrient dynamics and microbiological properties of grape marc in a continuous-feeding vermicomposting system.

Finding strategies to reuse and treat organic wastes is of utmost need. Biological processes offer the possibility to transform them into safer end products with benefits for both agriculture and the environment. Moreover, it represents an ecologically-sound and economically attractive alternative to landfill disposal and incineration. In this work, we evaluated the feasibility of vermicomposting to treat and process grape marc, the main solid by-product of the wine industry. The long-term changes in grape marc derived from both white and red winemaking processes were assessed throughout the process of vermicomposting from a physico-chemical and microbiological perspective. New layers of fresh marc were added sequentially in the presence and absence of earthworms (Eisenia andrei) forming an age gradient during a 42-week period. An optimal moisture level of 70% was maintained over the course of the process. The pH fell within weak-alkaline levels through the layerś profile and the electrical conductivity was between 200 and 300 µS cm-1, providing optimum conditions for earthworm growth. The mass loss caused by earthworm activity led to an increased content of macro- and micronutrients at the end of the trial. An overall decrease in microbial biomass and its activity, indicative of a stabilised material, was also recorded with depth of layer. Altogether, this points to vermicomposting as a suitable management system for processing grape marc with a dual purpose, that is fertilizer production and environment protection. This is especially relevant in the current attempts to reach a fully circular economy.

An Improved Vermicomposting System Provides More Efficient Wastewater Use of Dairy Farms Using Eisenia fetida

Dairy cattle farming produces large amounts of wastewater and it causes environmental pollution and eutrophication of rivers, but the nutrients in the waste could be recycled. Here, an improved vermicomposting system was applied to dairy farm wastewater, and wastewater with a nitrogen content of 100 mg/L and 200mg/L tested with different combinations of organic substrates such as cow manure and rice straw in rural solid waste. Results showed that earthworms could continuously grow, wastewater (N 100mg/L) mixed with rice straw corresponding to the most significant gained weight for Eisenia fetida earthworms (2.38 to 9.12-fold), and the earthworms’ weight was positively correlated with the C/N ratio, organic matter content, and pH. Compared to the initial state, the system significantly changed physicochemical parameters in nutrients, such as the percentages of total nitrogen, phosphorous, and potassium, which were found to increase in vermicomposting while organic matter content, C/N ratio, and cellulose declined as a function of the vermicomposting period, and the final vermicompost was better for the absorption of plants. These results suggest that continuous wastewater addition improved the effective transformation of organic waste to allow valorizing a broad range of organic residues, and avoid the risk of environmental pollution in dairy cattle farming.

A novel high-rate vermicomposting machine for downstream processing of biorefinery waste and other forms of organic solid waste

A novel machine, with the acronym HEVSTOW (high-efficiency vertically stacked vermicomposting system for treating organic waste), of which a patent has recently been granted, is described. It is capable of rapid, inexpensive, and emission-free processing of biorefinery waste and other forms of organic solid waste. The machine is based on the paradigm of high-rate vermicomposting earlier developed by the authors. It makes it possible to rapidly process biorefinery waste of plant origin, as also paper, which the conventional vermireactors are not able to handle without elaborate pre-treatment and/or augmentation of animal manure. The machine also makes it possible to simultaneously vermicompost different forms of biowaste as also use different species of earthworms in such a manner that each batch operates independently without one batch interfering with the other. The applicability of the machine has been demonstrated by its application in simultaneous yet independent processing of a biorefinery waste, and paper waste, each with two epigeic species of earthworms Eisenia andrei and Lumbricus rubellus.

The non-negligibility of greenhouse gas emission from a combined pre-composting and vermicomposting system with maize stover and cow dung.

The acceptance of combined pre-composting and vermicomposting systems is increasing because of the advantage in rapidly stabilizing organic wastes and reducing emission of greenhouse gasses (GHG). However, GHG emission during the pre-composting phase is often neglected when evaluating the system. This study aimed to quantify GHG emission from a combined pre-composting and vermicomposting system and to investigate the effects of earthworms on GHG emission. A combined system using Eisenia fetida was employed to stabilize maize stover and cow dung (mixing ratio 60:40). The inoculating densities were 60 (T1), 120 (T2), and 180 (T3) earthworms per kilogram of substrate. A traditional composting system without earthworms was set as a control (T0). The results indicated that earthworms increased CO2 while decreased CH4 and N2O emissions compared to the control. Higher emission of CO2 suggested that the earthworms promoted the degradation of the substrates. Lower emission of CH4 and N2O showed the advantage of the combined system because CH4 and N2O possess extremely higher global warming potential than that of CO2. T2 is recommended for stabilizing maize stover and cow dung when making a tradeoff between stabilization rate and reduction of GHG. The percentages of GHG emission during pre-composting relative to total GHG emission in T1, T2, and T3 were 34%, 35%, and 30%, respectively. GHG emission is non-negligible when using a combined system, especially the emission of GHG during the pre-composting phase cannot be ignored.

Potential utilization of various organic waste additives in vermicomposting using two different earthworm species

The aim of the present study is to test the null hypothesis that the composting potential of the adult earthworm is mainly species-specific processes. In order to realize this hypothesis, two different species of earthworms; one epigeic; Eisenia fetida, and the other edaphic; Aporrectodea caliginosa were chosen in this study. Different organic additives were used consisting of (rice straw, leaf litter, sawdust, kitchen waste, and banana peel) to enrich bedding for vermicomposting systems in addition to cow dung. Vermicompost formed were assessed across different periods during vermicomposting process. The obtained results revealed that the addition of organic additives to vermicomposting system increase the moisture content and nutrient concentrations (N, P, K and Ca) in produced vermicompost. Contrarily, pH, OM, OC and C/N ratio decreased significantly during vermicomposting process. The quality of vermicompost was higher in vermicomposting processed by E. fetida than in case of A. caliginosa. Moreover, organic additives enhanced the characteristics of end product of vermicomposting process.

Nutrients Recovery during Vermicomposting of Cow Dung, Pig Manure, and Biochar for Agricultural Sustainability with Gases Emissions

An experimental vermicomposting system was established in purple soil present in Sichuan Basin, China. The purpose of vermicomposting (VC) was to recycle and manage organic waste materials; for instance, animal manure and crop residues are present in great quantity. A particular use of earthworms for VC is a valuable method for retrieving essential plant nutrients. Experimental vermicomposting followed by monitoring was conducted for two months in summer with an interval of fifteen days. Four treatments, COM (compost without earthworms), VCM (using cow manure), VPM (through pig manure), and VBC (using biochar), were applied with agricultural wastes such as rapeseed and wheat straw in combination with cow dung, pig manure, and biochar, respectively. One-way analysis of variance (ANOVA) was used to statistically analyze and interpret the nutrient change among different treatments. Post hoc analysis was done using Tukey’s test. The experimental vermicomposting results revealed that VCM gives increased plant nutrients with a minimum C: N ratio (from 22.13 to 14.38) and a maximum increase in nitrogen concentrations (1.77 to 29.15 g kg−1). A significant decrease in ammonia volatilization was observed in the order VCM &gt; VBC &gt; VPM when compared to COM. It was experimentally established that vermicomposting is the most suitable method for converting organic waste into nutrient-rich fertilizer with the least environmental pollution load.

Vermicomposting of sludge from a malt house

Malting sludge is waste that could be used as a good soil conditioner after proper treatment. In the current study, the feasibility of vermicomposting malting sludge and its mixtures with straw pellets on the basis of physico-chemical and biological properties was verified. A vermicomposting system with continuous feeding of earthworms Eisenia andrei was used. The greatest number and biomass of earthworms was found in the variant with 25% malt house sludge + 75% straw pellets (on average of all layers: 320 earthworms/kg and 35 g/kg, respectively), followed by a variant with 50% malt house sludge + 50% straw pellets (on average of all layers: 47 earthworms/kg and 13 g/kg, respectively), indicating that a minimum of 50% (vol.) straw pellets is necessary for successful vermicomposting of malting sludge. Most earthworms lived in the youngest upper layer (42% and 52% of total number and earthworm biomass, respectively). On the contrary, the oldest bottom layers (final vermicomposts) after 180 days of vermicomposting were characterized by maturity, indicating lesser contents of microorganisms and enzyme activity. These vermicomposts had favorable agrochemical properties (pH = 7.8, EC = 1.2 mS cm−1, C/N = 11, Ptot = 1.23%, Ktot = 2.55%, Mgtot = 0.42%). The proportion of the available contents in the total contents were 10%, 59%, and 19% for P, K, and Mg, respectively.

Assessment of a Cattle Manure Vermicomposting System Using Material Flow Analysis: A Case Study from Uganda

Growth in cattle population is associated with increased manure generation whose current management in low-income countries is associated with health and environmental problems as well as low utilization rates. This trend can be reversed by promoting better manure management technologies. This study assessed vermicomposting as one of the technologies to manage organic wastes, using the case study in Uganda. A vermicomposting system using cattle manure and earthworms (Eudrilus euginea) was monitored for one year with the harvesting of products (compost, earthworm biomass) after every three months. Vermicompost samples from the beginning of the experiment and after every harvest were analyzed for the following parameters: pH, ash content, volatile and total solids, nutrients N, P, K, and C. Emissions of CO2, CH4, NH3, and N2O were also measured. Material flow analysis was used to determine the flows and retention of nutrients within the system. Results showed that total solids, ash, N, P, and K content significantly increased, while contents of volatile solids and C, as well as the pH, significantly decreased over time. Of the materials that entered the vermicomposting system, 46% went to vermicompost, 2% into earthworms, and 52% was lost to the atmosphere. Substance flow analysis showed that 30% of C went to vermicompost, 69% was emitted to the atmosphere, and 2% ended up in earthworms while 75% of N was transferred to vermicompost, 7% went to earthworms, and 18% escaped into the atmosphere. The cumulative emissions were 102 g CO2 kg−1 waste, 7.6 g CH4 kg−1 waste, and 3.943 × 10−5 g N2O kg−1 waste on a dry basis, while NH3 was not detected throughout the measurement time. Compared to other manure management methods, vermicomposting demonstrated good potential in conserving nutrients as well as reducing greenhouse gas emissions.

Characterization of humic acids in a continuous-feeding vermicomposting system with horse manure

The increasing numbers of kept horses create problems with processing horse manure as important local waste. This work was focused on horse manure vermicomposting in a real-field continuous-feeding system under controlled conditions, and on the complex study of the maturity and stability of the produced vermicompost. Commonly used simple indicators such as the C/N ratio, N-NH4+/N-NO3− ratio, DOC or ion exchange capacity, and also more advanced spectroscopic and thermoanalytic techniques were used and applied on the humic substances isolated from the vermicompost during its maturation (12 months in total). When compared with the original horse manure, vermicomposting decreased the aliphatic, protein-like, and polysaccharide humic components, whereas vermicomposting increased the aromaticity and contents of oxygen-containing functional groups. The typical tryptophan-like fluorophores in the manure, corresponding to the freshly produced organic matter of biological or microbial origin, were progressively transformed to humic-like fluorophores during vermicomposting. The most thermally labile humic fraction disappeared quickly during the very early vermicomposting stages. The results of spectroscopic and thermogravimetric analyses suggest that stable and mature vermicompost was produced after 6–9 months of vermicomposting, which was also supported by biologically-based maturity indicators.

Effects of Different Concentrations of Tetracycline in Sludge on Ammonia Oxidizers During Vermicomposting

Dewatered sludge often contains abundant antibiotics, and such contaminants can potentially affect the nitrogen fertilizer value of sludge-derived vermicompost. For this purpose, the aims of this study were to investigate the effects of different tetracycline concentrations in sludge on the nitrification rate and abundance and community characteristics of ammonia oxidizers during vermicomposting. Four sludge treatments with different concentrations of tetracycline (0, 100, 500, and 1000 mg·kg-1) were used, and data were collected to reveal the mechanism regarding the ammonia oxidization of sludge in the vermicomposting system. The results showed that the high concentration of tetracycline (1000 mg·kg-1) significantly inhibited the nitrification rate of vermicomposting (P<0.05), but no significant effect was observed in the low concentration treatments. Compared with ammonia-oxidizing bacteria (AOB), ammonia oxidizing archaea (AOA) were detected as the dominant microorganisms involved in the ammonia oxidation process during vermicomposting. In addition, the abundances of amoA genes were significantly elevated (P<0.05) in the treatments with 100 mg·kg-1 tetracycline, but values significantly decreased with the further increments of tetracycline concentrations (P<0.05). The results obtained from high-throughput sequencing revealed that the community diversity and structure of AOA and AOB were strongly modified by tetracycline concentrations, and a negative correlation relationship was detected between the tetracycline concentrations and the α diversity of AOA.

Removal of High Concentrations Decachlorobiphenyl of Earthworm Eisenia fetida and its Symbiotic Bacteria in a Vermicomposting System

The persistent organic pollutants decachlorobiphenyl (DCB) are a group of synthetic substances of high risk to human and environmental health. This study was aimed to evaluate the potential removal of DCB by earthworm Eisenia fetida and its symbiotic bacteria in a vermicomposting system for a period of 72 days using a complete randomized design. The results showed that the vermicomposting system was able to significantly remove high concentrations decachlorobiphenyl (DCB) from the polluted substrate. The addition of a concentration of 1000 mg L−1 during vermicomposting were a removal of 230.28 mg L−1 DCB and the results obtained from adding a concentration of 1500 mg L−1 DCB were 424.11 mg L−1. The earthworms bioaccumulated less than 5 mg L−1 of DCB without an apparent toxic effect. The earthworm weight decreased during vermicomposting and DCB concentration compared to the control (non-polluting); however, earthworms survived until the end of experiment. Phylogenetic analysis of 16S rDNA gene sequences of Eisenia fetida gut strains grown in the presence of 1500 mg L−1 DCB were identified as Bacillus, Paenibacillus, Pseudomonas, Solibacillus, and Staphyloccocus at zero time (0-days). At 7 days of culture, the genera, Acinetobacter, Bacillus, Enterobacter, Klebsiella, and Staphylococcus were identified, and at 72 days, the symbiotic bacteria isolated were classified into the genera, Bacillus, Enterobacter, Klebsiella, and Staphylococcus. The strains Pseudomonas extremaustralis ADA-5 and Staphylococcus sciuri ADA-12 showed higher potential of removal from the DCB (219.7 and 162.74 mg L−1, respectively) at an initial concentration of 1500 mg L−1. Both vermicomposting system and degrading bacteria from Eisenia fetida worms are useful to remove high concentrations of decachlorobiphenyl from contaminated soils.

Vermicomposting by Eisenia fetida is a Sustainable and Eco-Friendly Technology for Better Nutrient Recovery and Organic Waste Management in Upland Areas of China

Management and recycling of organic waste materials such as agricultural crops (wheat straw, rapeseed) and animal manure (pig manure, cow dung) is becoming an important issue in rapidly growing population. Vermicomposting by earthworms (Eisenia fetida) is useful technique to recover nutrients of plants such as NPK (nitrogen, phosphorus, calcium). A vermicomposting system using the earthworm species (Eisenia fetida) and treating it with cattle dung, pig manure and biochar with crop (wheat straw and rapeseed) waste was established in upland areas of China. It was monitored for two months. Four treatments (T1 to T4) were prepared using crop residues i.e. wheat straw, rapeseed and cow manure in different concentrations. Vermicomposting through biochar (Biochar 50%, rapeseed residues 20% and Biochar with earthworms) gave maximum increase in soil fertility with maximum decrease (39.63%) in C:N ratio. Significant increase of N content in nutrients and reduction in C: N ratios during this process shows conversion of harmful wastes into useful fertilizer.

Vermicomposting of Distillery Residues in a Vertical-Flow Windrow System

The present study evaluated the feasibility and processes occurring in a vertical-flow windrow vermicomposting system of distillery residues together with wheat straw. There were differences between the very top and lower layers. The top and so youngest layer showed the greatest humidity and electrical conductivity among the layers. It was characterized by partially decomposed organic matter with a great amount of earthworm biomass (2.5 g kg−1), which was confirmed by parameters such as Ctot (34%), Ntot (2.25%), and C/N (15.3). On the other hand, the lower layers were characterized by greater maturity, which was documented by a lower content of microbial biomass and activity of hydrolytic enzymes, as well as a slightly alkaline pH (7.6–7.9), and lesser values for N–NH4+ (22–84 mg kg−1) and dissolved organic carbon (5228–6564 mg kg−1), which was indirectly proportional to the ion-exchange capacity (57–60 mmol+ 100 g−1). Among the examined macronutrients, potassium showed the greatest content. The total contents of P and Mg increased directly with the age of the vermicomposted material, which was related to the loss of organic matter. The proportion of the available contents of P, K, and Mg constituted on average in all of the layers 11, 64, and 10%, respectively, of the total content. On the basis of the detected parameters, the top layer is suitable for a new windrow and for the preparation of aqueous extracts. The older layers are suitable for use as an organic fertilizer.

Change of the parameters of layers in a large-scale grape marc vermicomposting system with continuous feeding.

The main by-product of wine-making is grape marc. With proper treatment, grape marc may return to the vineyard as a fertiliser. This study deals with the vermicomposting of grape marc in a continuous feeding system in outdoor conditions for more than 12 months. The N-NH4+, dissolved organic carbon (DOC), and N-NH4+/N-NO3- contents were greater in the top layers. The pH value was about 8 in all the layers. The electrical conductivity was the greatest in the bottom layer. The ion-exchange capacity did not modify significantly during vermicomposting. The microbial biomass was the greatest in the upper layer, as well as the number and the biomass of the earthworms. The process of vermicomposting seems to be an ideal way of processing residues from the winemaking industry. This vermicompost has very good properties for use as a fertiliser, and for returning the nutrients and organic matter to the soil, for example, in a vineyard.

A novel FLippable Units Vermireactor Train System ─ FLUVTS ─ for rapidly vermicomposting paper waste to an organic fertilizer

Abstract The design and testing of a novel vermicomposting system, acronymed FLUVTS ─ FLippable Units Vermireactor Train System ─ is presented. It enables rapid vermicomposting of paper waste without the need of pre-composting and requires animal manure supplementation to the extent of only 10:1 paper: manure mass ratio in contrast to reported systems which must have 50% or more of the feed mass as animal manure. Moreover, the system enables the vermicomposting to be accomplished at a high rate, achieving near-total convertion of feed to vermicast at solid retention times of just 30 days in comparison to conventional systems which take 90–120 days for the same process. Uninterrupted vermireactor operation for 6 months, during which the feed was put in and its vermicompost harvested once in 30 days, demonstrates the robustness and the consistency of the system. The suitability of the paper-waste vermicompost as an organic fertilizer was then tested in terms of it's effect on seed germination and early growth of four food plants chilly (Capsicum annuum), ladies finger, (Abelmoschus esculentus), cucumber (Cucumis sativus), and tomato (Lycopersicon esculentum). In general, the paper waste vermicompost when applied at levels