Assessment of the use of organic composts derived from municipal solid waste for the adsorption of Pb, Zn and Cd

Effects of biochar and compost on microbial community assembly and metabolic processes in glyphosate, imidacloprid and pyraclostrobin polluted soil under freezethaw cycles

Biochar and organic compost are widely used in agricultural soil remediation as soil immobilization agents. However, the effects of biochar and compost on microbial community assembly processes in polluted soil under freezingthawing need to be further clarified. Therefore, a freezethaw cycle experiment was conducted with glyphosate (herbicide), imidacloprid (insecticide) and pyraclostrobin (fungicide) polluted to understand the effect of biochar and compost on microbial community assembly and metabolic behavior. We found that biochar and compost could significantly promote the degradation of glyphosate, imidacloprid and pyraclostrobin in freezethaw soil decrease the half-life of the three pesticides. The addition of immobilization agents improved soil bacterial and fungal communities and promoted the transformation from homogeneous dispersal to homogeneous selection. For soil metabolism, the combined addition of biochar and compost alleviated the pollution of glyphosate, imidacloprid and imidacloprid to soil through up-regulation of metabolites (DEMs) in amino acid metabolism pathway and down-regulation of DEMs in fatty acid metabolism pathway. The structural equation modeling (SEM) results showed that soil pH and DOC were the main driving factors affecting microbial community assembly and metabolites. In summary, the combined addition of biochar and compost reduced the adverse effects of pesticides residues.

A systematic review on garbage enzymes and their applications in environmental processes

Understanding the new insight on conversion of organic waste into value-added products can improve the environmental activities driven by microorganisms and return the nutrients to environment and earth. Here, we comprehensively review the available knowledge on application of garbage enzyme (GE) for different environmental activities including waste activated sludge, composting process, landfill leachate treatment, soil remediation and wastewater treatment with special focus on their efficiency. To identify peer-reviewed studies published in English-language journals, a comprehensive search was performed across multiple electronic databases including Scopus, Web of Science, Pubmed, and Embase. The search was conducted systematically using relevant keywords. The eligible studies were analyzed to extract data and information pertaining to components of GE, fermentation process operational parameters, type of hydrolytic enzymes and improved environmental performance. The findings derived from this current review demonstrated that GE produced from the fruit and vegetable peels, molasses or brown sugar (carbon source), and water within fermentation process contain different hydrolytic enzymes in order to facilitate the organic waste degradation. Therefore, GE can be considered as a promising and efficient pathway in order to improve the environmental activities depended on microorganism including, composting, wastewater and leachate treatment and bioremediation process.

Overview of municipal solid waste management in sub-tropical climatic region of North Eastern India

Municipal solid waste management (MSWM) is perceived as a global issue regardless of the place of waste generation. The amount of unmanaged waste is increasing rapidly, along with its impact on the environment and human health. In hilly areas, specifically the North Eastern Region (NER) states of India, due to the unique topography coupled with socio-economic factors, there are inadequate waste management practices marked by insufficient infrastructure, minimal research studies, and limited data availability. This paper comprehensively reviews the existing status of MSWM practices and waste treatment technologies, identifies the challenges, and discusses the prospective approaches for MSWM in NER states of India. NER, is characterized by its hilly terrain and has the most diverse demographic profile in the country. The study highlights the notable increase in waste generation in the urban population in NER. The total amount of waste generated in NER is about 2907 tons per day, with a collection rate of 86.96%, treatment at 31.09%, and landfilling at 33.67%. The biodegradable fraction makes up the majority of waste composition (more than 50%) in NER, followed by recyclables and inert. The existing MSWM consists of waste collection, transportation, and disposal with limited source segregation and treatment. All the states of NER practice open dumping and burning as the primary waste treatment and disposal system. The study discusses the challenges and prospects to ensure effective MSWM in NER. This review is a region-specific study that considers cultural diversity, topography, and socio-economic dynamics. The outcome of this review will be helpful to the researchers and policymakers in making appropriate waste management plans and improve the MSWM system in NER.

Mixing Compost and Biochar Can Enhance the Chemical and Biological Recovery of Soils Contaminated by Potentially Toxic Elements

Biochar and compost are able to influence the mobility of potentially toxic elements (PTEs) in soil. As such, they can be useful in restoring the functionality of contaminated soils, albeit their effectiveness can vary substantially depending on the chemical and/or the (micro)biological endpoint that is targeted. To better explore the potential of the two amendments in the restoration of PTE-contaminated soils, biochar, compost (separately added at 3% w/w), and their mixtures (1:1, 3:1, and 1:3 biochar-to-compost ratios) were added to contaminated soil (i.e., 2362 mg kg-1 of Sb and 2801 mg kg-1 of Zn). Compost and its mixtures promoted an increase in soil fertility (e.g., total N; extractable P; and exchangeable K, Ca, and Mg), which was not found in the soil treated with biochar alone. All the tested amendments substantially reduced labile Zn in soil, while biochar alone was the most effective in reducing labile Sb in the treated soils (-11% vs. control), followed by compost (-4%) and biochar-compost mixtures (-8%). Compost (especially alone) increased soil biochemical activities (e.g., dehydrogenase, urease, and β-glucosidase), as well as soil respiration and the potential catabolic activity of soil microbial communities, while biochar alone (probably due to its high adsorptive capacity towards nutrients) mostly exhibited an inhibitory effect, which was partially mitigated in soils treated with both amendments. Overall, the biochar-compost combinations had a synergistic effect on both amendments, i.e., reducing PTE mobility and restoring soil biological functionality at the same time. This finding was supported by plant growth trials which showed increased Sb and Zn mineralomass values for rigid ryegrass (Lolium rigidum Gaud.) grown on biochar-compost mixtures, suggesting a potential use of rigid ryegrass in the compost-biochar-assisted phytoremediation of PTE-contaminated soils.

Competitive sorption and desorption of cadmium, lead, and zinc onto peat, compost, and biochar

Soil and water contamination by potentially toxic metals (PTMs) has exerted adverse environmental impacts, which justifies studies of promising remediation alternatives. This article investigated the competitive sorption of cadmium (Cd), lead (Pb), and zinc (Zn) onto peat, compost, and biochar derived from the organic fraction of municipal solid waste (OFMSW), but its main innovation was the post-sorption assessment. The effects of contact time on competition between contaminants were systematically analyzed by batch experiments and the effectiveness of the sorption process was evaluated in desorption tests (H2O, HCl, NaOH, and NaCl) and sequential extraction. Kinetic data were well-fitted to pseudo-first-order (PFO) and pseudo-second-order (PSO) models and the intra-particle diffusion model revealed the existence of multiple linear regions, indicating the sorption process was controlled by a multi-step mechanism. The sorption capacities followed a biochar > compost > peat order, with biochar retaining more than 99% of Cd, Pb, and Zn in all samples. The general order of desorption percentage was peat > compost > biochar, with a below 0.60% biochar release, suggesting the importance of chemical processes. HCl solution (more acid pH) showed the highest release of previously sorbed contaminants and, therefore, can be employed for the reuse of sorbents (sorption/desorption cycles). The only exception was Pb desorption on biochar, with maximum release in NaOH solution. A negative Pearson correlation with F1 (acid-soluble/exchangeable fraction) for Cd and Zn and a positive one with the other steps were reported. Pb exhibited an opposite behavior, showing the highest sorption performances and the lowest desorption rates for all sorbents, justified by positive correlations with F4 (residual fraction) and negative ones with desorption. The findings suggest the evaluated sorbents, especially compost and biochar, can be effective materials in the simultaneous sorption of Cd, Pb, and Zn in wastewater, as well as an amendment for PTMs immobilization in contaminated soils.

Effect of humic compost on the adsorption of cadmium (II) in aqueous medium

The humic compost obtained from the treatment of tobacco from smuggled cigarettes (SCT) and industrial sewage sludge (ISS) was evaluated as adsorbent for Cd (II) in aqueous solution, for possible decontamination of water resources. Optimum conditions were found at pH 5 and a 3 g/L adsorbent concentration, which presented 92% Cd (II) removal and maximum adsorption capacity of 28.546 mg/g. The pseudo-second-order kinetic model presented the best fit, pointing 120 min as the time needed to attain a steady state. FTIR and EDX results suggest the formation of coordinated Cd (II) bonds by functional groups between the compost and the solution. The results obtained in real samples showed that, even under different environmental conditions, the Cd (II) adsorption varied between 80.05 and 91.61%. The results indicated that the compost evaluated can be used for remediation of Cd (II)-contaminated water resources.

Quantitative transport and immobilization of cadmium in saturated-unsaturated soils with the combined application of biochar and organic fertilizer

In this study, cadmium (Cd) transport and immobilization on passivators (biochar, organic fertilizer) and soils under saturated-unsaturated conditions were independently analyzed. The results showed that the Cd adsorption capacities of biochar and organic fertilizer were comparable in acidic soils. But in alkaline soils, the Cd adsorption capacity of organic fertilizer was significantly larger than that of biochar. In acidic soils, passivators effectively immobilized Cd, and the total net effects were in the order: combination (44.05-58.13%) > 3% biochar (31.96-46.88%) > 3% organic fertilizer (28.78-41.82%). In alkaline soils, all treatments had negative effects on Cd immobilization. For acidic soils, the immobilization of Cd was mainly attributed to the passivators, and the positive contribution percentages of relatively stable Cd increase by passivators were 81.05-100%, while those by soils were 0-18.95%. For alkaline soils, after the treatments of passivators, although a considerable amount of Cd was immobilized inside the passivator, Cd was activated more inside the soil. Therefore, it is noteworthy that soil conditions must be fully considered when applying biochar and organic fertilizers for Cd remediation.

Sorption and post-sorption performances of Cd, Pb and Zn onto peat, compost and biochar

The development of waste-derived sorbents to immobilize potentially toxic elements (PTEs) is a promising strategy, contributing to the achievement of sustainable development goals (SDGs). Therefore, this study aimed to assess the sorption performance of cadmium (Cd), lead (Pb) and zinc (Zn), comparing sorbents derived from organic fraction of municipal solid waste (composts and biochars) with peat. The physicochemical characterization, equilibrium of sorption, post-sorption analyzes and bioaccessibility were investigated. Results showed that the sorbents have distinct characteristics; however, each material have their particularities favorable to sorption. For instance, peat and composts have the highest cation exchange capacity (800-1100 mmol_c kg^-1), while biochar produced at 700 °C has the highest specific surface area (91.21 m² g^-1). The sorption equilibrium data revealed the actual sorption capacity and was well explained by the Freundlich and Langmuir isotherms and, in some cases, by the Dubinin-Radushkevich model. Post-sorption analyzes indicated the occurrence of several sorption mechanisms, driven by the physicochemical properties. Electrostatic interaction stood out for peat and compost. The FTIR spectrum for peat proved the complexation with oxygenated functional groups. The composts showed variations in the released cations (e.g. Ca²⁺ and K⁺), indicating cation exchange. Differently, for biochars, the XRD patterns showed that precipitation or coprecipitation seems to be one of the main mechanisms, especially for Cd and Pb. Regarding human bioaccessibility, the results of the gastric phase simulation (pH∼1.20) revealed lower percentages of Pb (33-81%) than Cd (91-99%) or Zn (82-99%), especially for the highest concentrations. Nevertheless, in numerical terms, all bioaccessible concentrations inspire care. In conclusion, among the sorbents, composts and biochars presented the best sorption performances and, therefore, have great potential for environmental applications. Furthermore, the bioaccessibility findings indicate that these assays, still little used in experiments with sorbents, are an important tool that should be better explored in the assessment of the environmental risk associated with contamination.

Management of the Organic Fraction of Municipal Solid Waste in the Context of a Sustainable and Circular Model: Analysis of Trends in Latin America and the Caribbean

The main objective of this research is to analyze the most relevant aspects of the management of the organic fraction of municipal solid waste (OFMSW) and the Sustainable and Circular Production Models (SCPMs) in Latin America and the Caribbean (LAC). The bibliometric method was used for the analysis of 190 studies obtained from the Scopus and Latin America and The Caribbean on Health Sciences (LILACS) databases. The systematic review provided information on the main research approaches: identification and characterization; quantification; strategic and interdisciplinary management; and processes for treatment or valorization. Finally, an evaluation of public policies and strategies was performed. The results show that Brazil, Mexico, and Colombia have the highest number of publications on OFMSW. The findings also indicate that both research and policy strategies on SCPMs prioritize bioenergy and biofuels as the leading alternatives for the valorization of OFMSW. It also reflects the relevance of the Circular Economy (CE) and Bioeconomy (BE) as the main drivers of waste recovery and/or valorization in LAC. These aspects are of great interest to governments that are still in the process of implementing SCPMs. However, for those more advanced in this area, it provides valuable information on progress, policy effectiveness, and future actions for improvement.

Drivers of Residents’ Home Composting Intention: Integrating the Theory of Planned Behavior, the Norm Activation Model, and the Moderating Role of Composting Knowledge

Home composting is judged as an effective municipal waste management option in which household contribution is essential, but it has a low adoption. The objectives of the study were to determine the factors that influence home composting intention and identify the moderating role of composting knowledge in the model, using the combined model of the theory of planned behavior (TPB) and norm activation model (NAM). A structured questionnaire was applied to a sample of 367 residents of Isfahan city, Iran, randomly selected. Data were analyzed using cluster analysis, discriminant analysis, PLS-SEM, and PLS-MGA. Cluster analysis grouped the three clusters based on the constructs of the integrated model, and this result was confirmed by discriminant analysis. Findings show that attitude, subjective norm, and perceived behavior control can predict the intention to compost. Study results confirmed the positive effect of awareness of the consequences of composting on ascribed responsibility to compost at home, of responsibility to the personal norm, and of the personal norm on intention to compost at home. Furthermore, it was observed that composting knowledge moderates the relationship between subjective norm and behavioral intention, and the one between perceived behavioral control and behavioral intention. The integrated model had more predictive power than the TPB model. The fit statistic of the integrated model was good and 71% of the variance for intention behavior toward home composting. The insights on factors affecting residents’ intention to compost obtained from this study can be used in measures and programs that reinforce and stimulate home composting.

Assisted phytostabilization of Pb-spiked soils amended with charcoal and banana compost and vegetated with Ricinus communis L. (Castor bean)

A greenhouse experiment was performed to elucidate the potency of Prosopis juliflora charcoal (PJC) and banana waste compost (BWC) to improve soil fertility and enhance plant growth rate. Plantlets of Ricinus communis were grown in 0, 400, and 800 mg kg^-1 Pb-spiked soil ameliorated with P. juliflora charcoal and banana waste compost at 0, 5%, and 10% (w/w) for 60 days. PJC and BWC significantly (p < 0.05) increased plant growth parameters, that is, number of leaves, node number, plant height, and leaf diameter and reduced oxidative stress manifested by the lesser production of proline, hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) with respect to control plants. Soil usage of PJC at 10% decreased the Pb accumulation by 61%, whereas BWC decreased Pb concentration in roots by 56% concerning control. Field emission scanning electron microscope (FE-SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) showed high macro and microspores on the surface of charcoal while banana compost showed significant raise in the nutrient content (N, P, K, Zn, Ca, Fe, and Mg). Thermogravimetric (TG) and Fourier-transform infrared spectroscopy (FTIR) analysis of banana compost showed enhanced molar convolution of carbohydrate composites and nitrogen content. These findings pave a clear understanding that PJC and BWC are recalcitrant for Pb phytotoxicity and can also be used as nutrient-rich composites for increased crop production.

Exploring the synergic effect of fly ash and garbage enzymes on biotransformation of organic wastes in in-vessel composting system

The aim of the present work was to study the synergic effect of fly ash (FA) and garbage enzymes (GE) on biotransformation of organic wastes in in-vessel composting system. In-vessel composting of organic waste (household + brown in vessel 1) was performed with fly ash (mixed 5% in vessel 2; 10% in vessel 3; 15% in vessel 4; and 20% in vessel 5) by addition of extra carbon source (5%) and garbage enzyme in a fixed-dose (5%) for 15 days and changes in chemical properties (C: N ratio, nitrates, sulphates, phosphates and macro-elements) were analyzed at maturity. Vessel 5 showed better results in terms of organic matter degradability and C: N ratio (13.68) of mature compost. Principal Component Analysis (PCS) also confirmed vessel 5 as the best performing among other vessels. FTIR analysis indicated a major shift in chemical structure of organic waste due to the composting action.

Effect of immobilizing reagents on soil Cd and Pb lability under freeze-thaw cycles: Implications for sustainable agricultural management in seasonally frozen land

Agricultural soil contamination in seasonally frozen land threatens food security. It is necessary to investigate the effects of freeze-thaw cycles on heavy metal bioavailability so as to select suitable immobilization agents. In this study, the soil was collected from a mid-latitude agricultural site in Liaoning Province, China, which was spiked with cadmium (Cd²⁺) and lead (Pb²⁺). Four immobilization treatments were set up, including (i) corn stover biochar, (ii) organic fertilizer, (iii) combined biochar and organic fertilizer, and (iv) the control group. The immobilized soils were subjected to 16 freeze-thaw cycles to temperatures of -10 °C, -20 °C, and -30 °C. It was found that freeze-thaw cycling increased the labile cadmium (Cd) and lead (Pb) content in the soil (i.e., exchangeable). The organic fertilizer treatment performed best in short-term immobilization, which was demonstrated by the amount of diethylenetriaminepentaacetic acid (DTPA) extractable lead (Pb) being 17.3-53.3% lower than that of the other treatments, and 7.2-31.5% lower for cadmium (Cd). Biochar, on the other hand, displayed better long-term performance under freeze-thaw cycling. This is probably because the biochar's organic carbon content is relatively stable, and therefore, releases relatively little dissolved organic carbon (DOC) which could re-mobilize heavy metals. Furthermore, additional sorption sites are formed and the abundance of oxygen-containing functional groups increased when biochar breaks down during freeze-thaw cycles. Overall, the joint application of biochar and organic fertilizer had the greatest immobilization effect, which inhibited the cracking of soil aggregates, reduced the labile metal content, and displayed both short- and long-term immobilization effectiveness. It is suggested that combined biochar and organic fertilizer may offer an effective strategy for the sustainable agricultural management of cadmium (Cd) and lead (Pb) contaminated in seasonally frozen land.

Valorization of Orange Peel Waste Using Precomposting and Vermicomposting Processes

The industrialization process of oranges generates waste, which is inadequately disposed of; this produces adverse effects on the environment. Among the alternatives for valorization is the vermicomposting process, which consists of the degradation of organic waste through the action of earthworms and microorganisms. Therefore, this research aimed to study this process using orange peel (OP) waste at the laboratory level. For this purpose, it was necessary to determine the degradation conditions through the monitoring of physicochemical parameters (temperature, pH, humidity, organic matter (OM), total organic carbon (TOC), total nitrogen (TN) and the carbon/nitrogen (C/N) ratio). To balance the substrate’s nutrients, load material (LM) that included vegetable waste and eggshells was added to three different mixtures: M1 (50% OP + 50% LM), M2 (40% OP + 60% LM) and M3 (60% OP + 40% LM). To condition the substrate for earthworm (Eisenia fetida) activity, a previous precomposting process was performed. The results showed that all the mixtures fulfilled the requirements for a quality and mature vermicompost; however, the highest concentrations for TN were in the mixtures M1 and M2. The total time required for degradation of the OP waste was 13 weeks.

Comparison of the effects of different maturity composts on soil nutrient, plant growth and heavy metal mobility in the contaminated soil

Numerous studies on the remediation of metal-contaminated soil by compost focus on the remediation efficiency of compost, however, they have not delved into the issue of nutrients and metal speciation. In this study, the application of municipal solid wastes primary compost (MSW-C), secondary compost (MSW-SC) and the aging compost (MSW-AC) has been conducted in heavy metal contaminated soil remediation. Eight different treatments were carried out to compare the effect of three different maturity composts and their addition ratio (i.e. 0, 25%, 50%) on the changes of physical properties, nutrient content and metal morphology distribution of soil. The enhancement of Sedum aizoon growth was also compared. The results showed that the treatments applied with composts increased the nutrient, organic carbon and the cation exchange capacity. In overall, the most effective treatment method was to use MSW-AC to improve soil physicochemical properties and reduce the heavy metals immobilization, and the addition of 25% MSW-AC showed significant promotion on plant biomass accumulation and root growth. The ability of compost to improve the conditions of the contaminated soil and increase the plant stress resistance was demonstrated by analyzing the root membrane lipid peroxidation, which was lower in the soil treatments with compost, especially with MSW-AC. Based on the compost maturity indexes, soil properties, and efficiency of metal activity reduction, the treatment of 25% MSW-AC is suggested for efficient soil remediation.

An explanation of soil amendments to reduce cadmium phytoavailability and transfer to food chain

Cadmium contamination in soil, water and food has become a global problem since last century's industrial and agricultural revolution. It is a highly toxic metal with serious consequences on human and animal health. Different natural and anthropogenic sources are responsible for Cd release in the soil which ultimately leads to the food chain. Cd persists in soil for long durations due to its minimal microbial or chemical loss. There are various physical, chemical or biological techniques which are helpful to minimize Cd risk in food chain. Among them, in-situ immobilization with organic, inorganic or clay amendments is a cost-effective and an environment friendly strategy to remediate Cd polluted sites. Lime, biochar, organic wastes, phosphorus fertilizers, sepiolite, zeolite, hydroxyapatite and bentonite are commonly used amendments for amelioration of Cd contaminated soils. These amendments reduce Cd uptake and enhance immobilization by adsorption, complexation, and precipitation processes. This review is aimed to provide a comprehensive note on Cd toxicity in humans and environment, its immobilization by different agents through variety of processes, and comparison of technologies for Cd removal from contaminated sites.