Sustainable treatment and nutrient recovery from leafy waste through vermicomposting

Optimization of Eisenia fetida stocking density for biotransformation during green waste vermicomposting

Appropriate stocking density plays an important role in ensuring the stability and improving the overall efficiency of the vermicomposting system. Although some studies have shown that earthworms can degrade lignocellulosic materials, relatively few studies have been conducted on the effect of earthworm stocking density on the degradation of a single green waste (GW) with high lignocellulosic content. Therefore, this study investigated the degradation effect of earthworms on GW at different stocking densities, and assessed the stability and maturity of the whole vermicomposting by comprehensively analysing the changes in physicochemical and biological properties of earthworms during vermicomposting, and by combining the growth of earthworms with a multi-dimensional assessment of the stability and maturity of the whole vermicomposting. In this study, six stocking densities (CK-T5) were set up, namely, no earthworms, 10, 20, 30, 40, and 50 worms/kg. The results showed that compared with the CK (without earthworms), when there were 30 earthworms per kg of GW (i.e. T3), the total nitrogen, total phosphorus, total potassium, organic matter decomposition, bacterial and fungal numbers, and germination index of earthworm compost products increased by 14 %, 29 %, 32 %, 35 %, 42 %, 94 %, and 125 %, respectively. T3 also enhanced the activities of cellulase and alkaline phosphatase. The results were further supported by principal component analysis. Finally, we conclude that when the stocking density of earthworms is appropriate (T3), it not only favours the growth of earthworms, but also positively affects the physicochemical properties of the vermicomposting process, which in turn significantly improves the biodegradation efficiency of GW.

Optimizing biochar addition strategies in combined processes: Comprehensive assessment of earthworm growth, lignocellulose degradation and vermicompost quality

The sustainable management of agricultural waste is essential for curtailing environmental contamination. To address the shortcomings of single treatment methods, this study evaluated the feasibility of combining membrane-covered composting (MC) with vermicomposting. Based on this, the integrated effects of different biochar addition strategies on the combined process were investigated. The aim was to improve the efficiency of vermicomposting while eliminating the negative effects of biochar on earthworms. Addition of biochar before membrane-covered composting increased total earthworm biomass by 25.6 - 31.4 % and reproduction rate by 13.4 - 23.9 %. Specifically, the electrical conductivity (EC) (1061.0 - 1112.0 uS/cm) of the vermicompost was significantly reduced, while the total nutrient content (42.3 - 42.6 mg/g) and germination index (GI) (103.9 - 108.4 %) were maximized. Additionally, reductions in the carbon-to-nitrogen ratio and volatile content were observed. Overall, combination process is a promising approach to improve the quality of vermicomposting. The study's results offer a novel perspective on the value-added treatment of agricultural waste.

Vermicompost: In situ retardant of antibiotic resistome accumulation in cropland soils

The dissemination of antibiotic resistance genes (ARGs) in soil has become a global environmental issue. Vermicomposting is gaining prominence in agricultural practices as a soil amendment to improve soil quality. However, its impact on soil ARGs remains unclear when it occurs in farmland. We comprehensively explored the evolution and fate of ARGs and their hosts in the field soil profiles under vermicompost application for more than 3 years. Vermicompost application increased several ARG loads in soil environment but decreased the high-risk bla-ARGs (blaampC, blaNDM, and blaGES-1) by log(0.04 - 0.43). ARGs in soil amended with vermicompost primarily occurred in topsoil (approximately 1.04-fold of unfertilized soil), but it is worth noting that their levels in the 40-60 cm soil layer were the same or even less than in the unfertilized soil. The microbial community structure changed in soil profiles after vermicompost application. Vermicompost application altered the microbial community structure in soil profiles, showing that the dominant bacteria (i.e., Proteobacteria, Actinobacteriota, Firmicutes) were decreased 2.62%-5.48% with the increase of soil depth. A network analysis further revealed that most of ARG dominant host bacteria did not migrate from surface soil to deep soil. In particular, those host bacteria harboring high-risk bla-ARGs were primarily concentrated in the surface soil. This study highlights a lower risk of the propagation of ARGs caused by vermicompost application and provides a novel approach to reduce and relieve the dissemination of ARGs derived from animals in agricultural production.

The Valorization of Wastes and Byproducts from Cruciferous Vegetables: A Review on the Potential Utilization of Cabbage, Cauliflower, and Broccoli Byproducts

The management of vegetable waste and byproducts is a global challenge in the agricultural industry. As a commonly consumed vegetable crop, cruciferous vegetables marked higher amounts of wastage during their supply chain processes, with a significant contribution from cabbage, cauliflower, and broccoli. Therefore, the sustainable and resource-efficient utilization of discarded materials is crucial. This review explores potential applications of cruciferous vegetable waste and byproducts, spotlighting cabbage, cauliflower, and broccoli in food, medicinal, and other industries. Their significance of being utilized in value-added applications is addressed, emphasizing important biomolecules, technologies involved in the valorization process, and future aspects of practical applications. Cabbage, cauliflower, and broccoli generate waste and low-processing byproducts, including leaves, stems, stalks, and rot. Most of them contain high-value biomolecules, including bioactive proteins and phytochemicals, glucosinolates, flavonoids, anthocyanins, carotenoids, and tocopherols. Interestingly, isothiocyanates, derived from glucosinolates, exhibit strong anti-inflammatory and anticancer activity through various interactions with cellular molecules and the modulation of key signaling pathways in cells. Therefore, these cruciferous-based residues can be valorized efficiently through various innovative extraction and biotransformation techniques, as well as employing different biorefinery approaches. This not only minimizes environmental impact but also contributes to the development of high-value-added products for food, medicinal, and other related industries.

Sustainable management of tea wastes: resource recovery and conversion techniques

As the demand for tea (Camellia sinensis) has grown across the world, the amount of biomass waste that has been produced during the harvesting process has also increased. Tea consumption was estimated at about 6.3 million tonnes in 2020 and is anticipated to reach 7.4 million tonnes by 2025. The generation of tea waste (TW) after use has also increased concurrently with rising tea consumption. TW includes clipped stems, wasted tea leaves, and buds. Many TW-derived products have proven benefits in various applications, including energy generation, energy storage, wastewater treatment, and pharmaceuticals. TW is widely used in environmental and energy-related applications. Energy recovery from low- and medium-calorific value fuels may be accomplished in a highly efficient manner using pyrolysis, anaerobic digestion, and gasification. TW-made biochar and activated carbon are also promising adsorbents for use in environmental applications. Another area where TW shows promise is in the synthesis of phytochemicals. This review offers an overview of the conversion procedures for TW into value-added products. Further, the improvements in their applications for energy generation, energy storage, removal of different contaminants, and extraction of phytochemicals have been reviewed. A comprehensive assessment of the sustainable use of TWs as environmentally acceptable renewable resources is compiled in this review.

Enhanced vermicomposting of rice straw and pressmud with biogas slurry employing Eisenia fetida: Production, characterization, growth, and toxicological risk assessment

The biogas plant plays a dual role: it directly provides energy and indirectly promotes organic farming through outlet slurry. However, agricultural biomass wastes such as rice straws (RS) and pressmud (PM), which can't be used as fertilizers on their own, were vermicomposted (60 days) with biogas slurry (BS), using earthworm, into four blends: T1(BS, 100%), T2(3:2, BS: RS), T3(3:2, BS: PM), and T4(3:1:1, BS: RS: PM). The characterization, elemental analysis, and toxicological risk assessment of derived vermimanure were carried out using various analytical tools, such as an organic elemental analyzer such as CHNS, FT-IR, FESEM-EDXA, XPS, and ICP-OES. The pH, electrical conductivity, and C/N values were within 7.1-7.8, 3.2-6.0 dSm-1, and 12-15, respectively, for all treatments. The proportions of N (38%), P (70%), K (58%), Mg (67%), Ca (42%), and ash (44%), increased significantly (P < 0.05) over the initial feedstocks. The ecological risks of heavy metals (Zn, Cu, Ni, Pb, Cd, and Cr) in all feedstocks were found to be under WHO-permitted levels. The growth performance of earthworms was also considerably higher (P < 0.05) over the control feedstock group. The analytical methods verified that feedstock T4 (3:1:1, BS: RS: PM) was more porous, containing NH4+, PO43-, K+, and other nutrients. Pellets of all vermimanure groups keep 65-75% of the original volume. As well, when these pellets have been employed for agronomy and dispersed in the field, they will cause less dust than traditional or powdered compost or manure. In comparison to the control group, the synergistic approach of RS, PM, and BS in vermimanure significantly (P < 0.05) enhanced seed germination (83%), vigour index (42.5%), and decreased mean germination time by 27%. Furthermore, pot trials with Abelmoschus esculentus seed indicated that seedlings cultivated with 40% vermimanure of T4 (3:1:1, BS: RS: PM) mixed soil showed high growth in shoot, root, and plant yield.

Application of neem waste vermicompost in compensating nematode induced stress and upregulating physiological markers of tomato plants under glass house conditions after 10 days of exposure

Farming, food processing, animal husbandry and other agro-based activities contribute to global environmental degradation by producing millions of tons of organic and inorganic solid waste. In terms of sustainable agriculture, agricultural waste management and conversion into useful products are essential. In addition, plants are facing various kinds of biotic stress, which ultimately affects their defense system. Altered defense systems in plants ultimately lead to the death of plants and a reduction in crop production. The present study is designed to keep the abovementioned fact in mind, which mainly focuses on the reuse of agricultural waste and its application to the antioxidant potential and structural components of tomato plants during nematode stress. In the present study, neem leaves were collected and mixed with cattle dung for the preparation of vermicompost. Then, tomato seeds were pre-treated with vermicompost extract before being germinated in earthen pots. After germination, they were transplanted to separate pots and inoculated with freshly hatched juveniles of Meloidogyne incognita. The experiments were conducted for 10 days under glass house conditions, and after that, plants were harvested and various physiological (antioxidant capacity, percent electrolyte leakage) and structural markers (carbohydrate content, Fourier transform infrared spectroscopy) were analyzed. Results revealed that all physico-chemical properties make vermicompost superior as compared to soil and pre-compost material. Further, nematode stress leads to altered physiological and structural markers as compared to uninfected seedlings. However, treatment with vermicompost significantly increases carbohydrate content and antioxidative capacity in a concentration dependent manner. In addition, electrolyte leakage was found to be decrease with an increase in the concentration of vermicompost. All these findings conclude that vermicompost has strong potential to limit the damage caused by nematodes and boost the antioxidant potential of the host plants. Further, this study provides strong evidence for using vermicompost as an eco-friendly alternative to chemical nematicides and a potential strategy for agricultural waste management. This is the first study in which the tomato plant's structural and physiological markers were assessed during nematode stress after being supplemented with vermicompost under glass house conditions for an initial 10 days of nematode exposure.

Physiological, biochemical and structural changes in tomato plants by vermicompost application in different exposure periods under glass house conditions

In modern era, various inorganic fertilizers and pesticides are used as plant growth supplements in a variety of crop in order to gain maximum output and also reported as hazardous to mankind as well as environment. In addition, some of the plants died in initial phase of the growth after germination due to poor nutrient content of the soil or exposure to biotic stresses. In the beginning of sustainable agriculture, these chemical fertilizers were replaced with some alternative growth boosters such as organic fertilizers. In the present study, vermicompost was prepared using garden waste and cattle dung followed by analysis of various physico-chemical properties. Then tomato seeds were allowed to germinate in soil and supplemented with different doses of vermicompost (0-100%). The plants were harvested after 10 and 45 days of their germination and tissues were subjected to analysis of various morphological and biochemical parameters. Morphological parameters included root length, shoot length, root fresh weight, shoot fresh weight and number of leaves. Whereas biochemical parameters such as protein content, antioxidative enzymes (catalase, superoxide dismutase, ascorbate peroxidase, polyphenol oxidase), non-enzymatic antioxidants (ascorbic acid, glutathione, tocopherol), osmolytes (proline, carbohydrate), photosynthetic pigments (chlorophyll, carotenoid) and secondary metabolites (phenol, flavonoid, anthocyanin) were estimated on UV-visible spectrophotometer using standard protocols. Further, structural analysis of plant tissue was done using fourier transform infrared spectroscopy spectra (FTIR) and carbon hydrogen nitrogen (CHN) elemental analyzer. Results obtained from the present study revealed significant difference in all morphological and biochemical markers at both 10 and 45 days intervals of time. Further, growth of all plants was found to be directly proportional to the concentration of vermicompost and exposure duration. FTIR spectra and CHN analyses reveal the breakdown of various complex compounds and their transformation from Vcom amended soil to roots of plants. This is the first study in which significant changes were observed in growth, physiology and structural composition of tomato plants at two different exposure periods (10 and 45 days) under glass house conditions which further concluded that vermicompost has a significant potential for increasing plant growth.

Synergistic effect of biochar amendment in milk processing industry sludge and cattle dung during the vermiremediation

The effective and sustainable management of fast growing and large quantities of industrial waste is a serious issue. The purpose of the present study was to assess the synergistic effect of biochar (BC) amended in milk processing industry sludge (MS) mixed with cattle dung (CD) in different ratios through vermiremediation. The MS₂₅ and MS₂₅BC₁₀ (25:75 + 10 % BC) showed the least mortality and greatest earthworm growth and development. The final product from all feed mixtures recorded a decrease in pH, total organic carbon and C/N ratio. Other parameters viz., electrical conductivity, total available phosphorus, total Kjeldahl nitrogen, total sodium, total potassium and ash content was observed to be increased after vermicomposting. Significantly lower heavy metal content was found in all biochar amended feed mixtures than in mixtures without biochar. The germination index of Trigonella foenum-graecum showed a value ranging from 89.14 to 131.46 % for mixtures without BC and 115.18-153.47 % for biochar amended mixtures.

Biochar improves compost humification, maturity and mitigates nitrogen loss during the vermicomposting of cattle manure-maize straw

Maintaining humidification and inhibiting nitrogen losses during vermicomposting process have emerged to be key factors for high-quality productions. Previous data have showed outstanding functions of biochar addition in improving vermicomposting quality. In this study, the influence of bamboo biochar (BB) and rice husk biochar (RHB) addition on compost maturity, humification and nitrogen loss was evaluated in the vermicomposting of cattle manure and maize straw. Results revealed that BB or RHB amendment improved organic matter decomposition, enhanced humification and maturity of compost, particularly in the 10% BB treatment, which exerted the highest humic acids content and GI value. Furthermore, BB or RHB addition significantly reduced nitrogen losses, in which the volatilization of NH₃ and N₂O were reduced by 24.93%-66.23% and 14.91%-55.12%. The fewest nitrogen loss was detected in the treatment of 10% BB. Biochar inhibited nirK, nirS but promoted AOB-amoA, nosZ expression; fewer N₂O producing bacteria (Pseudomonas, Devosia, Luteimonas genus) were observed in the biochar treatment, and thereby decreased the N₂O emission. Therefore, 10% BB addition for co-vermicomposting cattle manure and maize straw is an efficient way to increase humification, maturity, and reduce nitrogen loss, and future applications following this strategy is believed to generate better productions.

The synergistic effect between biofertility properties and biological activities in vermicomposting: A comparable study of pig manure

Vermicomposting is a resource technology for managing animal excreta, whereas the internal relationships of the process are vital for its wide applications. The present study examined how macronutrient and micronutrient concentrations, microbial communities, and enzymatic activity of pig manure (PM) changed during the composting and vermicomposting processes and their internal interactions. The vermicomposting process increased macronutrients more significantly than composting (32.40% of total available nitrogen, 21.70% of total available phosphorous, and 12.70% of total available potassium). The vermicomposting reduced total organic carbon (7.91%), C/N ratio (61.35%), and humification index (56.47%) more than composting due to the quick decomposition of PM. After continual fertility optimization, the total microbial population, with the exception of total fungi, rose significantly to accelerate organics mineralization and improve macronutrients in vermicomposting compared to composting. Moreover, earthworm addition favored the stabilization of the PM containing higher concentrations of micronutrients after being catalyzed by the enhanced catalase activity and reduced sucrase activity after 90 days of vermicomposting. Principal component analysis and chord plots found that the generated vermicomposting products had higher fertility properties and biological activities induced by the synergistic effect of microorganisms and earthworms. These findings highlight vermicomposting is an eco-friendly management technology for processing PM and can be scaled up for agricultural applications.

Vermiremediation of allopathic pharmaceutical industry sludge amended with cattle dung employing Eisenia fetida

The present study aims to vermiremediate allopathic pharmaceutical industry sludge (AS) amended with cattle dung (CD), in different feed mixtures (AS:CD) i.e (AS₀) 0:100 [Positive control], (AS₂₅) 25:75, (AS₅₀) 50:50, (AS₇₅) 75:25 and (AS₁₀₀) 100:0 [Negative Control] for 180 days using earthworm Eisenia fetida. The earthworms could thrive and grow well up to the AS₇₅ feed mixture. In the final vermicompost, there were significant decreases in electrical conductivity (29.18-18.70%), total organic carbon (47.48-22.39%), total organic matter (47.47-22.36%), and C: N ratio (78.15-54.59%). While, significant increases in pH (9.06-16.47%), total Kjeldahl nitrogen (69.57-139.58%), total available phosphorus (30.30-81.56%), total potassium (8.92-22.22%), and total sodium (50.56-62.12%). The heavy metals like Cr (50-18.60%), Cd (100-75%), Pb (57.14-40%), and Ni (100-50%) were decreased, whereas Zn (8.37-53.77%), Fe (199.03-254.27%), and Cu (12.90-100%) increased significantly. The toxicity of the final vermicompost was shown to be lower in the Genotoxicity analysis, with values ranging between (76-42.33%). The germination index (GI) of Mung bean (Vigna radiata) showed a value ranging between 155.02 and 175.90%. Scanning electron microscopy (SEM) analysis showed irregularities with high porosity of texture in the final vermicompost than in initial mixtures. Fourier Transform-Infrared Spectroscopy (FT-IR) spectra of final vermicompost had low peak intensities than the initial samples. The AS₅₀ feed mixture was the most favorable for the growth and fecundity of Eisenia fetida, emphasizing the role of cattle dung in the vermicomposting process. Thus, it can be inferred that a cost-effective and eco-friendly method (vermicomposting) with the proper amendment of cattle dung and employing Eisenia fetida could transform allopathic sludge into a nutrient-rich, detoxified, stable, and mature vermicompost for agricultural purposes and further could serve as a stepping stone in the allopathic pharmaceutical industry sludge management strategies in the future.

Exploring agricultural waste biomass for energy, food and feed production and pollution mitigation: A review

Globally agricultural production system generates a huge amount of solid waste. Improper agri-waste management causes environmental pollution which resulted in economic losses and human health-related problems. Hence, there is an urgent need to design and develop eco-friendly, cost-effective, and socially acceptable agri-waste management technologies. Agri-waste has high energy conversion efficiency as compared to fossil fuel-based energy generation materials. Agri-waste can potentially be exploited for the production of second-generation biofuels. However, composted agri-waste can be an alternative to energy-intensive chemical fertilizers in organic production systems. Furthermore, value-added agri-waste can be a potential feedstock for livestock and industrial products. But comprehensive information concerning agri-waste management is lacking in the literature. Therefore, the present study reviewed the latest advancements in efficient agri-waste management technologies. This latest review will help the researchers and policy planners to formulate environmentally robust residue management practices for achieving a green economy in the agricultural production sector.

Enhancement of soil physical properties and soil water retention with biochar-based soil amendments

The soil physical properties are deteriorating due to changing rainfall patterns and intensities, as well as climate change-induced temperature fluctuations. Pot experiments were carried out to examine the impacts of synthesized soil amendments on soil water retention and plant growth. Soil amendments (biochar, polyacrylamide (PAM), and moringa) were used at different rates (0 (control), 2.1, 4.2, and 8.3 g kg^-1) to improve the physical properties of the soil. As a result of soil amendment application, it was found that the mean weight diameter of soil aggregate increased by 188% during the 8.3 g kg^-1 treatment, forming stable soil particles. Soil water retention improved by up to 128.9% during the 8.3 g kg^-1 treatment, and it was analyzed that it was due to the high surface area of biochar, porosity, and high molecular weight of PAM. Pellet treatment increased all plant growth parameters (height, stem diameter, leaf number, and fresh and dry weight) for both beans and maize. The dry weight of beans (C₃ plant) and maize (C₄ plant) increased by 92.9 and 146.4%, respectively in an 8.3 g kg^-1 pot. The soil physical condition was stabilized by the high carbon content of biochar and the improvement of soil coagulation between PAM and moringa. This had a positive effect on the C₄ plant. The findings of this study indicate that if the soil amendments are properly mixed and applied based, they will improve soil stability and plant productivity.