Bauxite residue, an industrial alkaline solid waste, has a low organic carbon content which hinders plant growth. Dissolved organic matter (DOM) drives many biogeochemical processes including carbon storage and soil formation in soils. Input of exogenous organic materials may provide organic carbon and accelerate soil formation processes in bauxite residue. However, the potential effects of ameliorants on the quantity and quality of DOM in bauxite residue are still poorly understood. Here, the integration of ultraviolet–visible (UV–Vis) spectra, fluorescence spectra, and parallel factor (PARAFAC) analysis were used to investigate the vertical characteristics of DOM in bauxite residue treated by PV (the combined addition of 2% phosphogypsum and 4% vermicompost, w/w) and BS (6% w/w including 4% bagasse and 2% bran) with 2-year column experiments. The content of DOM in untreated residues ranged from 0.064 to 0.096 g/kg, whilst higher contents of DOM were observed in PV (0.13 g/kg) and BS (0.26 g/kg) treatment. Meanwhile, with the increase of residue depth, the aromaticity and hydrophobic components of DOM in residue decreased, which indicated that the degree of humification of the treated residues in the upper layer was higher than that in the lower layer. Compared with BR, BS and PV treatment accumulated the related content of fulvic acid-like substance from 36.14% to 71.33% and 74.86%, respectively. The incorporation of vermicompost and biosolids increased the content of humic-like substances, whilst decreasing the content of protein-like substances in the surface layer, which may be due to the enrichment of the microbial community. During soil formation processes, the application of organic amendments reduced both salinity and alkalinity, enhanced microbial community diversity, and changed the quantity and quality of DOM in bauxite residue. These findings improve our understanding of the dynamics of DOM and response of DOM to soil formation processes in bauxite residue.

Coexistence of antibiotics/heavy metals and the overexpression of resistance genes in the vermicompost has become an emerging environmental issue. Little is known about the interaction and correlation between chemical pollutants and biological macromolecular compounds. In this study, three typical vermicompost samples were selected from the Yangtze River Delta region in China to investigate the antibiotic, heavy metal and corresponding antibiotic resistance genes (ARGs) and heavy metal resistance genes (HRGs). The results indicated the prevalence of tetracycline (TC), copper (Cu), zinc (Zn), cadmium (Cd), corresponding TC-resistance genes (tetA, tetC, tetW, tetM, tetO, and tetS) and HRGs (copA, pcoA, cusA, czcA, czcB, and czcR) in the three vermicompost samples. In addition, the ARG level was positively associated with the water-soluble TC fraction in the vermicompost, and it was same between the HRG abundance and exchangeable heavy metal content (p < 0.05). Moreover, a positive correlation was found between ARG and HRG abundance in the vermicompost samples, suggesting a close regulation mechanism involving the expression of both genes. The result obtained here could provide new insight into the controlling risk of heavy metals, TC, and relevant resistance genes mixed contamination in the vermicompost.

Vermicomposting is a green technology used in the recycling of sewage sludge using the joint action of earthworms and microorganisms. Although tetracycline is present in abundance in sewage sludge, little attention has been given to its influence on vermicomposts. This study investigated the effects of different tetracycline concentrations (0, 100, 500 and 1000 mg/kg) on the decomposition of organic matter, microbial community and antibiotic resistance genes (ARGs) during vermicomposting of spiked sludge. The results showed that 100 mg/kg tetracycline could stimulate earthworms’ growth, accompanied by the highest humification and decomposition rates of organic matter in the sludge. The abundance of active microbial cells and diversity decreased with the increase in tetracycline concentrations. The member of Bacteroidetes dominated in the tetracycline spiked treatments, especially in the higher concentration treatments. Compared to its counterparts, the addition of tetracycline significantly increased the abundances of ARGs (tetC, tetM, tetX, tetG and tetW) and Class 1 integron (int-1) by 4.7–186.9 folds and 4.25 folds, respectively. The genera of Bacillus and Mycobacterium were the possible bacterial pathogen hosts of ARGs enriched in tetracycline added group. This study suggests that higher concentration of tetracycline residual can modify microbial communities and increase the dissemination risk of ARGs for final sludge vermicompost.

Organic waste has great potential for use as an amendment to immobilize heavy metals in the environment. Therefore, this study investigates various properties of cow manure (CM) and its derived vermicompost (CV), including the pH, cationic exchangeable capacity (CEC), elemental composition and surface structure, to determine the potential of these waste products to remove Pb2+ and Cd2+ from solution. The results demonstrate that CV has a much higher pH, CEC and more irregular pores than CM and is enriched with minerals and ash content but has a lower C, H, O and N content. Adsorption isotherms studies shows that the adsorption of Pb2+ and Cd2+ onto either CM or CV follows a Langmuir model and presents maximum Pb2+ and Cd2+ adsorption capacities of 102.77 mg g−1 and 38.11 mg g−1 onto CM and 170.65 and 43.01 mg g−1 onto CV, respectively. Kinetic studies show that the adsorption of Pb2+ onto CM and CV fits an Elovich model, whereas the adsorption of Cd2+ onto CM and CV fits a pseudo-second-order model. Desorption studies indicate that CV is more effective than CM in removing Pb2+ and Cd2+. FTIR analysis demonstrates that the adsorption of Pb2+ and Cd2+ onto CM mainly depends on existed aliphatic alcohol, aromatic acid as well as new produced carbonates, whereas that onto CV may be contributed by the existed aliphatic alcohol, aromatic acids as well as some carbonates and phosphates. Thus, vermicomposting disposal of cow manure with destination mineral addition may broaden the way of its recycle and environmental usage.

The current review reports the importance and significance of cattle solid waste in vermicomposting technology concerning biowaste pollution in the environment. Needy increasing population evokes livestock production resulting in the massive generation of livestock wastes, especially cattle dung. Improper disposal and handling of biowastes originating from agriculture, industries, forests, rural and urban areas lead to nutrient loss, environmental pollution and health risks. Among the organic waste disposal methods available, vermicomposting is regarded as an environmentally friendly technology for bioconversion of agricultural, industrial, rural and urban generated organic solid wastes which are serving as reservoirs of environmental pollution. In vermicomposting of organic wastes, cattle dung plays a central role in mineralization, nutrient recovery, earthworm and microbial activity leading to vermifertilizer production. Even though the vermicomposting studies use cattle dung invariably as an amendment material, its importance has not been reviewed to highlight its central role. Hence, the present review mainly emphasizes the key role played by cattle dung in vermicomposting. Vermiconversion of cattle dung alone and in combination with other biowaste materials of environmental concern, mechanisms involved and benefits of vermicompost in sustainable agriculture are the major objectives addressed in the present review. The analysis reveals that cattle dung is indispensable amendment material for vermicomposting technology to ensure agricultural and environmental sustainability by reducing pollution risks associated with biowastes on one hand, and nutrient-rich benign vermifertilizer production on the other hand.

A long-term case of residual pollution is studied after 20 years since the largest mining accident in Spain (the Aznalcóllar spill) happened. This pollution is manifested through a surface zoning consisting of bare soils (B0), sparsely vegetated soils (B1), and densely vegetated and recovered soils (B2). A biopiles treatment with a mixture of contaminated soils (B0 and B1) with recovered soils (B2) at 50% (w/w), and vermicompost addition (50 tons ha-1) was evaluated. To assess the effectiveness of treatments, total, water-soluble, and bioavailable fractions of the most polluting elements in the zone (Cu, Zn, As, Pb, Cd, and Sb) was analyzed. To evaluate the potential risk of contamination for the ecosystem, a bioassay with earthworm Eisenia andrei was carried out. Twenty years after the accident, there are still soils where total As and Pb exceed the regulatory levels and water-soluble Zn and As exceed the toxicity guidelines. According to toxicity bioassay, weight variation and juvenile production of earthworms showed an improvement after biopiles treatment, with values that trend to be similar to those of recovered soils. The only bioaccumulated element in earthworms was Cd (BAF>1), both in polluted as in treated soils, which indicates the possible existence of exclusion mechanisms of the other pollutants by earthworms. The comparison between biopiles and polluted soils showed no significant differences for the bioaccumulation factor of trace elements, with the exception of Zn and Cu, which slightly increased after treatment. According to our results, biopiles treatment combined with vermicompost addition is a good technique for the recovery of residual contaminated areas, by the improvement of soil properties and the reduction of the potential toxicity; anyway, monitoring of soils and organisms is needed to prevent the increase of bioavailability of some potentially pollutant elements over time.

Increasing inorganic fertilizer and pesticide use has been linked to increased health risks for humans and cattle, as well as substantial water and soil contamination. In recent years, vermicomposting has shown to be a viable alternative to chemical pesticides. Vermicompost and vermicompost products such as extract and leachate assist plants in a number of ways. According to recent studies, vermicompost extract (VCE), when used as a supplement, is thought to work as a growth and stress tolerance booster for plants. These liquid supplements also help to suppress a range of pests, such as root knot nematodes. In the present study, neem- and cattle dung-based vermicompost extracts of different concentrations (0, 20, 40, 60, 80 and 100%) were prepared and used for their application against nematode infection in tomato seedlings under laboratory conditions. Apart from its antagonistic action against Meloidogyne incognita, the influence of VCE on plant growth was investigated by analyzing its morphological characteristics in tomato seedlings infected and uninfected with M. incognita. Seeds were pre-soaked in VCE for the seed priming process before being allowed for germination. After 10 days of nematode inoculation, biochemical parameters like protein content, activity of antioxidative enzymes, non-enzymatic antioxidants, stress indices, photosynthetic pigments, proline content and secondary metabolites were also analyzed. The results revealed that neem-based VCE was fatal to second-stage juveniles, with an 82% mortality rate following exposure to the highest dose. When eggs were exposed to 100% VCE, 33.8% of hatching was suppressed, indicating that VCE had an antagonistic effect on nematode egg hatching. Further, all the morphological and biochemical parameters were significantly enhanced in VCE-treated tomato seedlings as compared to untreated seedlings. Stress indices were also found to be significantly lowered by the VCE treatments in the infected plants. The effect of VCE on seedling growth and physiology was shown to be concentration dependent. As a result, the current findings show that VCE has the potential to be used as a plant growth accelerator as well as an environmentally friendly biocontrol agent against nematode pathogenesis in tomato plants.

Consumption of natural resources and waste generation continues to rise as the human population increases. Ever since the industrial revolution, consumers have been adopting a linear economy model based on the ‘take-make-dispose’ approach. Raw materials are extracted to be converted into products and finally discarded as wastes. Consequently, this practice is unsustainable because it causes a massive increase in waste production. The root problems of the linear system can be addressed by transitioning to a circular economy. Circular economy is an economic model in which wastes from one product are recycled and used as resources for other processes. This literature review discovers the potential of vermicompost as a sustainable strategy in circular economy and highlights the benefits of vermicompost in ensuring food security, particularly in improving agricultural yield and quality, as well as boosting crop’s nutritional quality. Vermicompost has the potential to be used in a variety of ways in the circular economy, including for agricultural sustainability, managing waste, pollutant remediation, biogas production and animal feed production. The recycling of organic wastes to produce vermicompost can benefit both the consumers and environment, thus paving the way towards a more sustainable agriculture for the future.

Organic substrates are gaining popularity as a means of mitigating the negative effects of cadmium (Cd) stress on plant growth. The aim of the present study was to investigate the physio-biochemical attributes of Berberis integerrima bunge under Cd-contaminated soil. The pot experiment was carried out based on a completely randomized design (CRD) with six replicates. Cd stress was used as cadmium chloride (CdCl₂) at 10, 20, and 30 mg Cd kg⁻¹ dry soil. Biochar was applied at the doses of 125 g per pot, and vermicompost was used at the doses of 250 g per pot separately, and for their combination, they were used as 125 g per pot of BC + 250 g per pot of VC. The results showed higher Cd accumulation in both roots and leaves when the soil was polluted with Cd concentrations, but both BC and VC decreased the Cd accumulation in plant tissues. Although chlorophyll content and relative water content (RWC) decreased at 20 and 30 mg Cd kg⁻¹ soil, BC and VC, particularly their combination, increased these traits. The highest total phenolic content (TPC) was observed in plants exposed to 20 mg Cd kg⁻¹ soil and combined BC and VC. The total flavonoid content (TFC) was increased to 20 mg Cd kg⁻¹ soil and then decreased to 30 mg Cd kg⁻¹ soil. In addition, organic fertilizer promoted the plants’ high accumulation of TFC. The greater activities of antioxidant enzymes including superoxide dismutase (SOD) and phenylalanine ammonia-lyase (PAL) were observed at 30 mg Cd kg⁻¹ soil when organic substrates were added. The present study suggests the use of combined BC and VC lead to alleviate the adverse effects of Cd stress in B. integerrima.

The remediation of Pb, Cd, and Zn contaminated soil by ex situ EDTA washing was investigated in two pot experiments. We tested the influence of (i) 0, 0.5, 1.0, and 1.5%wt zero-valent iron (ZVI) and (ii) a combination of 5%wt vermicompost, 2%wt biochar, and 1%wt ZVI on the metal availability in EDTA-washed soil using different soil extracts (Aqua regia, NH₄NO₃) and plant concentrations. We found that EDTA soil washing significantly reduced the total concentration of Pb, Cd, and Zn and significantly reduced the Cd and Zn plant uptake. Residual EDTA was detected in water extracts causing the formation of highly available Pb-EDTA complexes. While organic amendments had no significant effect on Pb behavior in washed soils, an amendment of ≥ 1%wt ZVI successfully reduced EDTA concentrations, Pb bioavailability, and plant uptake. Our results suggest that Pb-EDTA complexes adsorb to a Fe oxyhydroxide layer, quickly developing on the ZVI surface. The increase in ZVI application strongly decreases Zn concentrations in plant tissue, whereas the uptake of Cd was not reduced, but even slightly increased. Soil washing did not affect plant productivity and organic amendments improved biomass production.