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Abstract To identify potential linkages between specific bacterial populations and process performance in anaerobic digestion, the dynamics of bacterial community structure was monitored with high-throughput sequencing in triplicate anaerobic digesters treating animal waste. Firmicutes and Bacteroidetes were found as the two most abundant populations, however, with contrasting population dynamics in response to organic overloading. Firmicutes dominated the bacterial community during stable process performance at low organic loading rate, representing over 50 % of the bacterial abundance. In contrast, the onset of organic overloading raised the relative abundance of Bacteroidetes from 20 ± 2.6 to 44 ± 3.1 %. In addition to the significant negative correlation between the relative abundance of Firmicutes and Bacteroidetes, populations of Firmicutes and Bacteroidetes were found to be linked to process parameters including organic loading rate, volatile fatty acids concentration, and methane production. Therefore, the population abundance ratio of Firmicutes to Bacteroidetes (F/B ratio) was suggested as a potential indicator for process performance. The interactions between Firmicutes and Bacteroidetes populations could be exploited to develop strategies for the prevention of performance perturbation in anaerobic digestion processes.

Toxic pollutants in the form of heavy metals are added through various anthropogenic activities daily into the aquatic ecosystem beyond their permissible limits, and their bioaccumulation capacity makes them hazardous substances for the survival of all organisms. Thus, their removal from aquatic ecosystems is the need of the hour. Treatment of wastewater containing heavy metals through biosorption is gaining popularity and is being explored all around the world due to its various advantages over conventional methods of treatment. Utilization of animal waste as a biomaterial could be the best solution to remove it from the ecosystem. Such treatment methods are a blessing for developing and underdeveloped countries due to their low cost. This paper provides in-depth details about heavy metals, their health implications, mechanisms of toxicity, modes of transportation, and conventional treatment approaches. A comprehensive understanding of the biosorption process, encompassing its world scenario, evolution, mechanisms, factors affecting the process, and advantages, will also be covered. Finally, animal wastes and their applicability in the removal of heavy metal pollutants from wastewater shall also be thoroughly reviewed, followed by their future utility and recommendations.

Animal feeding practices in the United States have changed considerably over the past century. As large-scale, concentrated production methods have become the predominant model for animal husbandry, animal feeds have been modified to include ingredients ranging from rendered animals and animal waste to antibiotics and organoarsenicals. In this article we review current U.S. animal feeding practices and etiologic agents that have been detected in animal feed. Evidence that current feeding practices may lead to adverse human health impacts is also evaluated. We reviewed published veterinary and human-health literature regarding animal feeding practices, etiologic agents present in feed, and human health effects along with proceedings from animal feed workshops. Data were extracted from peer-reviewed articles and books identified using PubMed, Agricola, U.S. Department of Agriculture, Food and Drug Administration, and Centers for Disease Control and Prevention databases. Findings emphasize that current animal feeding practices can result in the presence of bacteria, antibiotic-resistant bacteria, prions, arsenicals, and dioxins in feed and animal-based food products. Despite a range of potential human health impacts that could ensue, there are significant data gaps that prevent comprehensive assessments of human health risks associated with animal feed. Limited data are collected at the federal or state level concerning the amounts of specific ingredients used in animal feed, and there are insufficient surveillance systems to monitor etiologic agents \"from farm to fork.\" Increased funding for integrated veterinary and human health surveillance systems and increased collaboration among feed professionals, animal producers, and veterinary and public health officials is necessary to effectively address these issues.

Healthy soils are essential for progressive agronomic activities. Organic fertilization positively affects agro-ecosystems by stimulating plant growth, enhancing crop productivity and fruit quality and improving soil fertility. Soil health and food security are the key elements of Organic Agriculture 3.0. Landfilling and/or open-dumping of animal wastes produced from slaughtering cause environmental pollution by releasing toxic substances, leachate and greenhouse gases. Direct application of animal carcasses to agricultural fields can adversely affect soil microbiota. Effective waste management technologies such as thermal drying, composting, vermicomposting and anaerobic digestion transform animal wastes, making them suitable for soil application by supplying soil high in organic carbon and total nitrogen. Recent agronomic practices applied recycled animal wastes as organic fertilizer in crop production. However, plants may not survive at a high fertilization rate due to the presence of labile carbon fraction in animal wastes. Therefore, dose calculation and determination of fertilizer application frequency are crucial for agronomists. Long-term animal waste-derived organic supplementation promotes copiotrophic microbial abundance due to enhanced substrate affinity, provides micronutrients to soils and protects crops from soil-borne pathogens owing to formation of plant-beneficial microbial consortia. Animal waste-derived organically fertilized soils possess higher urease and acid phosphatase activities. Furthermore, waste to fertilizer conversion is a low-energy requiring process that promotes circular bio-economy. Thus, considering the promotion of soil fertility, microbial abundance, disease protection and economic considerations application of animal-waste-derived organic fertilizer should be the mainstay for sustainable agriculture.

Background: In Egypt, calcareous soils represent a large part of desert soils suffering from a shortage of nutrients and organic matter, affecting production and biological diversity in agroecosystems. Organic wastes, negatively affect the environment, recycling it as a promising technology in different farming systems, and its impact on crop productivity and soil fauna is largely unknown. In this study, the effects of integrating poultry manure (PM) alone or combined with vinasse (V) at rates of 4.2 g kg − 1 and 6.3 g kg − 1 in pots, on improving soil fauna diversity, soil fertility, soil consistency and yield of barley ( Hordeum aestivum L.) grown in a calcareous soil were investigated. Results: The results showed that the addition of PM alone or combined with V at different rates led to a significant increase in the microbial biomass carbon (MBC), organic matter (OM), NPK soil availability and yield of barley. The addition of 6.3 g PM and 4.2 g V kg − 1 soil have the best results in OM with 65.0% compared to control, and V contributes more than 16% of them. Prostigmata and Collembola were the dominant groups and accounted for 43.3% and 50.0% in the PM1 and 50.0% and 20.0% in the PM2 of the total individuals, respectively. Shannon and Evenness indices increased significantly with the soil amended by PM alone or combined with V. Soil fauna plays a key role in soil consistency because of a significant relationship between soil fauna and soil OM, MBC and soil fertility index. The addition of 6.3 g PM and 4.2 g V kg − 1 soil gave the best results in grain yield by 76.90% compared to the control. Conclusion: In conclusion, the interaction between PM and V can be used as a promising organic amendments to increase barley yield and improve efficiency of a recycled PM and V on soil fauna and soil fertility of calcareous soil.

The feasibility of the anaerobic ammonium oxidation (anammox) process to treat synthetic swine wastewater containing antibiotics and heavy metals was studied in this work. Nitrogen removal performance and granule characteristics were tracked by continuous-flow monitoring to evaluate the long-term joint effects of Cu and Zn and of Cu and oxytetracycline (OTC). Cu and Zn with a joint loading rate (JLR) of 0.04 kg m⁻³ day⁻¹ did not affect the performance, while a JLR of 0.12 kg m⁻³ day⁻¹ caused a rapid collapse in performance. Cu and OTC addition with a JLR of 0.04 kg m⁻³ day⁻¹ for approximately 2 weeks induced significant nitrite accumulation. Granule characteristic analysis elucidated the disparate inhibition mechanisms of heavy metals and antibiotics: the internalization of heavy metals caused metabolic disorders, whereas OTC functioned as a growth retarder. However, anammox reactors could adapt to a JLR of 0.04 kg m⁻³ day⁻¹ via self-regulation during the acclimatization to subinhibitory concentrations, which had a stable nitrogen removal rate (>8.5 kg m⁻³ day⁻¹) and removal rate efficiency (>75 %) for reactors with Cu-OTC addition. Therefore, this study supports the great potential of using anammox granules to treat swine wastewater.

Increased demand for animal protein is met by increased food animal production resulting in large quantities of manure. Animal producers, therefore, need sustainable agricultural practices to protect environmental health. Large quantities of antimicrobials are used in commercial food animal production. Consequently, antimicrobial-resistant bacteria and the resistance genes emerge and are excreted through feces. Manure management is essential for the safe disposal of animal waste. Lagoons, with or without covers, and anaerobic digesters, with the primary purpose of methane production, and composting, with the primary purpose of producing organic fertilizer, are widely used methods of manure treatment. We reviewed manure management practices and their impact on tetracycline resistance genes. Lagoons are maintained at ambient temperatures; especially uncovered lagoons are the least effective in removing tetracycline resistance genes. However, some modifications can improve the performance of lagoons: sequential use of uncovered lagoons and the use of covered lagoons resulted in a one-log reduction, while post-treatments such as biofiltration following covered lagoon treatment resulted in 3.4 log reduction. Mesophilic digestion of animal manure did not have any significant effect; only a 0.7 log reduction in tet(A) was observed in one study. While thermophilic anaerobic digesters are effective, if properly operated, they are expensive for animal producers. Aerobic thermophilic composting is a promising technology if optimized with its economic benefits. Composting of raw animal manure can result in up to a 2.5 log reduction, and postdigestion composting can reduce tetracycline resistance gene concentration by >80%. In general, manure management was not designed to mitigate antimicrobial resistance; future research is needed to optimize the economic benefits of biogas or organic fertilizer on the one hand and for the mitigation of foodborne pathogens and antimicrobial resistance on the other.

The adsorption of phenol and Pb2+ from aqueous solutions was achieved using calcined animal waste (cow dung) as a low-cost adsorbent. Fourier transform infrared analysis confirmed the involvement of hydroxyl, carbonate, and possibly silicate functional groups in the adsorption process. Scanning electron microscope images revealed the presence of distinct rod-like fibers on the adsorbent surface. Adsorption kinetics revealed an increase in pollutant uptake over time, with the effect being more pronounced at a higher initial concentration of 280 mg/L. The optimal pH for maximum adsorption was identified as 6.5 for phenol and 4.5 for lead. Langmuir isotherm analysis indicated a higher adsorption affinity for lead, with a maximum adsorption capacity of 101 mg/g, compared to 89.3 mg/g for phenol. Conversely, the Freundlich isotherm model demonstrated a better fit for phenol adsorption. Thermodynamic evaluations showed negative ΔG° values, confirming the spontaneous nature of the sorption process for both pollutants. The enthalpy change (ΔH°) values of 11.6 kJ/mol for phenol and 21.7 kJ/mol for lead validated the endothermic nature of the adsorption. These results underscore the effectiveness of calcined animal waste as a sustainable and efficient adsorbent for eliminating phenol and lead from wastewater.

Improper disposal of animal waste is responsible for several environmental problems, causing eutrophication of lakes and rivers, nutrient overload in the soil, and the spread of pathogenic organisms. Despite the potential to cause adverse ecological damage, animal waste can be a valuable source of resources if incorporated into a circular concept. In this sense, new approaches focused on recovery and reuse as substitutes for traditional processes based on removing contaminants in animal manure have gained attention from the scientific community. Based on this, the present work reviewed the literature on the subject, performing a bibliometric and scientometric analysis of articles published in peer-reviewed journals between 1991 and 2021. Of the articles analyzed, the main issues addressed were nitrogen and phosphorus recovery, energy generation, high-value-added products, and water reuse. The energy use of livestock waste stands out since it is characterized as a consolidated solution, unlike other routes still being developed, presenting the economic barrier as the main limiting factor. Analyzing the trend of technological development through the S curve, it was possible to verify that the circular economy in the management of animal waste will enter the maturation phase as of 2036 and decline in 2056, which demonstrates opportunities for the sector’s development, where animal waste can be an economic agent, promoting a cleaner and more viable product for a sustainable future.

Animal waste can be converted into a renewable energy source using biogas technology. This process has an impact on greenhouse gas emissions and is a sustainable source of energy for countries. It can reduce the effects of climate change and protect the planet for future generations. Tier1 and tier2 approaches are commonly used in the literature to calculate emissions factors. With boosting algorithms, this study estimated each animal category’s biogas potential and CH 4 emissions (tier1 and tier2 approach) for 2004–2021 in all of Turkey’s provinces. Two different scenarios were created in the study. For scenario-1, the years 2020–2021 were predicted using data from 2004 to 2019, while for scenario-2, the years 2022–2024 were predicted using data from 2004 to 2021. According to the scenario-1 analysis, the eXtreme Gradient Boosting Regressor (XGBR) algorithm was the most successful algorithm with an R 2 of 0.9883 for animal-based biogas prediction and 0.9835 and 0.9773 for animal-based CH 4 emission predictions (tier1 and tier2 approaches) for the years 2020–2021. When the mean absolute percentage error was evaluated, it was found to be relatively low at 0.46%, 1.07%, and 2.78%, respectively. According to the scenario-2 analysis, the XGBR algorithm predicted the log10 values of the animal-based biogas potential of five major cities in Turkey for the year 2024, with 11.279 for Istanbul, 12.055 for Ankara, 12.309 for Izmir, 11.869 for Bursa, and 12.866 for Antalya. In the estimation of log10 values of CH 4 emission, the tier1 approach yielded estimates of 3.080, 3.652, 3.929, 3.411, and 3.321, respectively, while the tier2 approach yielded estimates of 1.810, 2.806, 2.757, 2.552 and 2.122, respectively. Graphical Abstract