Search Results (28)

Cattle manure accounts for approximately one-third of the total livestock manure produced in the Republic of Korea and is typically composted. To elucidate its feasibility as a renewable resource, this study evaluated the conversion of cattle manure into a solid biofuel and the nutrient recovery potential of its combustion residues. Solid fuel was prepared from cattle manure collected in Gyeongsangbuk-do, Korea, and its fuel characteristics and ash composition were analyzed after combustion. Combustion tests conducted using a dedicated solid fuel boiler showed that an average lower heating value of 13.27 MJ/kg was achieved, meeting legal standards. Under optimized combustion, CO and NO_x emissions (129.9 and 41.5 ppm) were below regulatory limits (200 and 90 ppm); PM was also within the 25 mg/Sm³ standard. The bottom ash contained high concentrations of P₂O₅ and K, and its heavy metal content was below the regulatory threshold, suggesting its potential reuse as a fertilizer material. Although the Zn concentration in the fly ash exceeded the standard, its quantity was negligible. Therefore, the solid fuel conversion of cattle manure can become a viable and environmentally sustainable solution for both bioenergy production and nutrient recycling, contributing to improved waste management in livestock operations. Full article

Recycled manure solids (RMS) are increasingly adopted in dairy farming for their economic advantages and their role in improving nutrient recycling and waste management; however, concerns regarding greenhouse gas (GHG) emissions during storage persist. This study assessed the effects of biochar supplementation at 2.5% (2.5B) and 10% (10B) compared to untreated RMS (C−) and acidified RMS (C+) on GHG emissions (measured both continuously and intermittently) and RMS characteristics during a one-month storage period. The results showed that the addition of biochar increased heavy metals concentration (with the exception of molybdenum) and the electrical conductivity of the RMS. Storage of RMS generally led to an increase in its dry matter content, except in the 10B treatment. The results showed that 10% biochar significantly reduced cumulative CO₂ and N₂O emissions, resulting in a 32% GWP reduction compared to untreated RMS. In contrast, the 2.5% dose led to higher CO₂ emissions, possibly due to microbial stimulation. Adding 10% biochar mitigated GHG emissions similarly to H₂SO₄ acidification but with fewer environmental and operational risks, making it a preferable farm-scale option. Continuous monitoring captured transient emission peaks, highlighting the importance of high-resolution assessments. Despite the emissions generated during biochar production, its application in RMS bedding systems offsets these environmental costs by mitigating GHG emissions and increasing nutrient content. Biochar’s mitigation potential, especially at higher doses, presents a safer, multifunctional alternative that aligns with EU climate goals. These findings support the integration of biochar into sustainable manure management strategies, though further research is needed to optimize application rates and assess cost-effectiveness in dairy farming. However, continued assessments at a larger scale and with different biochar addition rates are necessary to fully determine the potential of biochar supplementation to RMS. Full article

The global production of brewers’ spent grains (BSG) is 37 million tons yearly. Composting represents an eco-friendly method to manage and valorize organic by-products in a circular economy model. This project aims to compare two BSG bin-composting mixtures (BSG and wheat straw with pig slurry solid fraction, MIX1, or sheep manure, MIX2) and approaches (manual turning, MT, and static composting, ST). The two mixtures’ physicochemical characteristics and greenhouse gas (GHG) emissions were assessed during the process. The evolution of physicochemical properties is reported in detail. Headspace samples of GHG emissions were collected and analyzed with gas chromatography coupled with specific detectors. Carbon dioxide (CO₂) emissions were 34.3 ± 0.03 and 31.0 ± 0.06 g C kg⁻¹ fresh matter (FM) for MIX1-MT and MIX2-MT, and 28.8 ± 0.01 and 31.2 ± 0.02 g Ckg⁻¹ FM for MIX1-ST and MIX2-ST. Methane emissions were negligible (all conditions < 0.086 ± 0.00 mg C kg⁻¹ FM). Nitrous oxide (N₂O) emissions from composting are affected by the substrate, bulking material, pile dimension, and manure. Particularly, the total emissions of N₂O, estimated as CO₂ equivalents, were 45.8 ± 0.2 and 63.0 ± 0.4 g CO₂ eq kg⁻¹ FM for MIX1-MT and MIX1-ST, respectively. In both composting approaches, MIX2 showed a low CO₂ equivalent (1.8 ± 0.02 and 9.9 ± 0.05 g CO₂ eq kg⁻¹ FM for MT and ST), likely due to incomplete decomposition. The bin-composting process represents a solution for recycling and reusing organic waste and livestock manure in small to medium-sized breweries. The solid fraction of the pig slurry resulted in the most suitable manure. Full article

The use of recycled manure solids (RMS) as cow bedding in dairy farms poses concerns due to its potential to harbor pathogenic and antimicrobial-resistant bacteria. This study evaluated the impact of RMS supplementation with biochar at three concentrations (2.5%, 5%, and 10%) on bacterial counts and on the antimicrobial resistance and virulence profiles of Escherichia coli and Enterococcus isolates. The results show that biochar supplementation did not promote a significant reduction in bacterial numbers. Overall, there were no significant changes in the isolates’ virulence or resistance profiles, and none of the isolates obtained were classified as high or moderate threats based on their MAR and VIR indexes. The most pathogenic Enterococcus isolates found were present in the control samples. A phylogenetic analysis of E. coli isolates allowed us to identify phylogroup D strains, predominantly in RMS supplemented with 2.5% and 10% biochar, which are associated with higher virulence and resistance. These findings indicate that the biochar concentrations tested were not effective in significantly reducing the bacterial risks associated with RMS. Further research is needed to evaluate different biochar formulations and concentrations, aiming to optimize its potential use for RMS supplementation. Full article

Ammonium inhibition is a key limiting factor for anaerobic digestion when using chicken manure as the main substrate, especially in a digestion system with biogas slurry reflux. Air stripping is usually used as a recycled biogas slurry treatment. In this study, we carried out the anaerobic co-digestion of chicken manure and corn straw. The fermentation performance was investigated with and without air stripping at different biogas slurry reflux ratios and with an increasing organic loading rate. The results show that air stripping enhanced biogas production, system stability, and volatile solid removal efficiency via the mitigation control of ammonium inhibition. The total ammonium nitrogen in the digesters with air stripping was 20.24–46.40% lower than in those without air stripping. The highest specific biogas production and volatile solid removal efficiency values were obtained in the digesters at an organic loading rate of 3.3 g volatile solid (VS)/(L·d) and a reflux ratio of 75% with air stripping, reaching 480.43 mL/gVS_add and 63.36%, respectively. Moreover, air stripping also improved the organic loading rate and reflux ratio. Stable operation was achieved at an organic loading rate of 5.3 gVS/(L·d) and a reflux ratio of 75%, with specific biogas production of 392.35 mL/gVS_add and a volatile solid removal efficiency of 50.33%. The fermentation performance deteriorated when the organic loading rate was increased to 8.0 gVS/(L·d) at a reflux ratio of 75%, even when air stripping was conducted, indicating that a slighter lower reflux ratio (50%) could be more feasible at a higher organic loading rate (8.0 gVS/(L·d). Additionally, the methanogen community structure varied according to the use of air stripping, with a shift in the methanogenic pathway from hydrogenotrophic to acetoclastic methanogens. Overall, our findings support the adoption of air stripping for ammonium mitigation in anaerobic digestion with biogas slurry reflux. Full article

Recycled manure solids (RMSs) are widely utilised as beddings due to their economic and environmentally friendly features. Internal change in RMSs plays a vital role in the stable operation and management of beddings. However, the internal microenvironment of various manure beddings has not been fully reported. Therefore, we evaluated the physicochemical properties, internal gases and changes in the microbial community of the in situ fermentation beds, which were prefermented by cow manure with sawdust (FSD), straw (FST) and sawdust–straw mixture (FM), at a farm in Jiangsu, China, from June to September 2022. The results indicated that the FSD and FM beds were more capable of degrading organic matter (OM), accumulating total nitrogen and processing a more stable pH environment. FSD bed promoted the conversion of nitrate–nitrogen and ammonium–nitrogen (NH₄⁺-N). Different treatments and times had significant effects on bacterial and fungal communities. FSD enriched Chloroflexi, and FST enriched Actinobacteriota in the early stage, while FM enriched Proteobacteria in the late stage. Bacterial communities were more sensitive to NH₄⁺-N and OM, while fungal communities were more sensitive to temperature and pH. FSD had potential advantages concerning N conversion and C emission reduction. The results of the study revealed the microenvironmental dynamics during bedding use, providing a theoretical basis for the use of a compost bedding system for managing recycled dairy manure. Full article

Application of organic manure on farmland is one of the most important tasks in agricultural recycling. However, few studies have investigated the potential impact of different solid–liquid separation (SLS) technologies on soil porosity and greenhouse gas (GHG) emissions as a result of the application of liquid fractions (LFs). A microcosm experiment was conducted to track the emissions of ammonia (NH₃), nitrous oxide (N₂O), carbon dioxide (CO₂), and methane (CH₄) from soils (1) without liquid manure application (CK), (2) with a raw dairy slurry (RM), (3) with the liquid fractions of mechanical solid–liquid separation (MS) technologies, and (4) with the LF of an enhanced solid–liquid separation technology including a flocculant (tannic acid, Ta) (MS + Ta). Soil porosities of different treatments were measured using computed tomography (CT). The saturated water conductivities of the RM and MS treatments were 53.38% and 78.63%, respectively, lower than that of the CK. The application of raw slurry and LFs reduced the gas diffusion due to the strong decrease in pore sizes >500 μm and increased gas emissions compared to the CK. Compared with RM, MS had greater N₂O and lower CH₄ emissions, whereas MS + Ta had lower NH₃ and N₂O emissions. MS had the greatest CO₂-e emissions, mainly owing to high N₂O emissions, followed by RM and MS + Ta. The implementation of a simple SLS led to an increase in nitrogen (N) loss and GHG emissions when the resultant LFs were applied to farmlands, whereas high emissions were reduced when a simple SLS was combined with a flocculant, such as Ta. Further research is required to elucidate the reduction mechanism and its effectiveness under field conditions. Full article

Recycling of solid biowaste and manure would reduce the dependence of agriculture on synthetic products. Most of the available studies on the effects of exogenous organic matter (EOM) application to soil were focused on nutrients and crop yield, with much less attention to microbiological processes in soil, especially using modern molecular methods. The aim of this study was to evaluate the effects of various types of manure, sewage sludge and bottom sediment on the biochemical activity and biodiversity of soil and plant yield in a pot experiment. The soil was treated with a range of EOM types: six types of manure (cattle, pig, goat, poultry, rabbit and horse manure; two bottom sediments (from urban and rural systems); and two types of municipal sewage sludge. All EOMs stimulated dehydrogenases activity at a rate of 20 t ha⁻¹. Alkaline phosphatase was mostly stimulated by poultry manure and one of the sludges. In general, the two-fold greater rate of EOMs did not further accelerate the soil enzymes. The functional diversity of the soil microbiome was stimulated the most by cattle and goat manure. EOMs produce a shift in distribution of the most abundant bacterial phyla and additionally introduce exogenous bacterial genera to soil. Poultry and horse manure introduced the greatest number of new genera that were able to survive the strong competition in soil. EOMs differentiated plant growth in our study, which was correlated to the rate of nitrate release to soil. The detailed impacts of particular amendments were EOM-specific, but in general, no harm for microbial parameters was observed for manure and sludge application, regardless of their type. There was also no proof that the PAH and pesticide contents measured in manure or sludge had any effect on microbial activity and diversity. Full article

The appropriate use of manure is important for the sustainable development of dairy farms. To identify more advantageous ways of using manure and key factors in the recycling process, this study investigated differences in soil fertility between solid and liquid manure waste recycling at an integrated farm. Both types of manure waste recycling promote soil fertility. However, solid manure exerted a more pronounced effect on soil fertility, especially on available phosphorus (P), which increased by 93.83%, but only 26.67% with liquid manure. As the amount of solid manure was increased, a clear logarithmic relationship (correlation coefficient = 0.90) formed between manure use and available P, indicating that P was a key index for manure recycling. Solid manure had a more positive influence on soil fertility in terms of microbial community change, as revealed by redundancy analysis and Pearson’s correlation analysis. The results of this study can be applied to most large-scale breeding farms, that the combination of solid and liquid manure fertilizer can be used to meet sustainable development goals. And the findings highlight solid manure as a key component for improving soil fertility. Full article

Urbanization and population rise considerably increase the generation of solid wastes. The recycling of solid wastes through vermicomposting is a sustainable approach. The current study aimed to investigate the effect of earthworm (Eisenia fetida and Eugilius euganiae)-processed/mixed solid waste manure (vermicompost) on the development, productivity, and chemical characteristics of chili and brinjal in different wooden reactors (R). A mixture of palash leaf litter, biogas slurry, food wastes from a hostel kitchen and households, and municipal solid waste (MSW) were used during the study. The effects of different reactors; process parameters; earthworm cultures, such as R1–R9 with different widths and lengths at a constant height (30 cm); pH, salt, and moisture content; temperature; C:N ratios; N, P, K, and pathogen content; and the type of mono/-polyculture on vermicompost were tested with respect to chili and brinjal production. The average net increase in the worms’ zoomass in reactor R1 at different mixed worm densities (E. fetida + E. eugeniae) under optimum conditions was observed. Compared to a monoculture reactor, the yield of both chili and brinjal were significantly greater in the polyculture reactor with vermicompost soil. Full article

This study focuses on the feasibility of the dry anaerobic digestion of solid agricultural biomass for efficient renewable-energy production and nutrient recycling. Methane production and the amount of nitrogen in the digestates were measured in pilot- and farm-scale leach-bed reactors. In the pilot scale, with a digestion time of 133 days, the methane production of a mixture of whole crop fava bean and horse manure corresponded to 94% and 116%, respectively, of the methane potentials of the solid substrates. The mono-digestion of fava beans resulted in relatively low methane production (production/potential ratios of 59% and 57%). In two full-scale experiments, the methane production of mixtures of clover-grass silage, chicken manure, and horse manure corresponded to 108% and 100% of their respective methane potentials with digestion times of 117 and 185 days. In co-digestion, the production/potential ratios were similar in the pilot and farm experiments. High nitrogen loss was observed in the farm scale when the digestate was stored in a stack covered with a tarpaulin during summertime. Thus, although the technology seems promising, attention needs to be paid to management practices to minimise nitrogen losses and greenhouse gas emissions. Full article

Manure is considered a by-product or organic waste in cattle, pig, chicken or other animal breeding farms, which can be a valuable product as compost or feedstock for biogas production. The production of biomethane from biogas always copes with the formation of carbon dioxide (CO₂) as a by-product. This CO₂ may be recycled through the feedstock as a pretreatment to maximize homogeneity, and improve biogas yield and biogas quality. The CO₂-pretreatment process of cow manure (CoM), chicken manure (ChM) and pig manure (PM) was performed in the continuously fed agitated reactor at 25 °C temperature and ambient barometric pressure. Biogas yield and composition exploration were performed in an anaerobic continuous feeding digester with controlled mesophilic (37 °C) environmental conditions. The CO₂ pretreated PM, CoM and ChM yielded 234.62 ± 10.93 L/kg_VS, 82.01 ± 3.19 L/kg_VS and 374.53 ± 9.27 L/kg_VS biomethane from feedstock volatile solids, respectively. The biomethane yield from CO₂ pretreated CoM, ChM and PM achieved was higher over untreated manure by +33.78%, +28.76% and +21.78%, respectively. The anaerobic digestion process of tested feedstocks was stable, and the pH of the substrate was kept steady at a pH of CoM 7.77 ± 0.02, PM 8.07 ± 0.02 and ChM 8.09 ± 0.02 during all the experiment. The oxidation-reduction potential after pretreatment was within the optimal range (−255 ± 39.0 to −391 ± 16.8 mV) for anaerobic digestion. This process also had a positive effect on the energy generated from the feedstock, with ChM showing the greatest increase, from 2.38 MJ/kg to 3.06 MJ/kg. Full article

Lying is a high priority behavior for dairy cows. As the quality of cubicles can influence their lying time, the interest in finding objective methods to assess the quality of floors has increased substantially over recent decades. This study aimed to evaluate a technical device for measuring elastic properties of floors for the application to bedding materials for cows. Ten different floor types were used: horse manure, recycled manure solids, bark mulch, sand, sawdust, and three different rubber mats. Horse manure and bark mulch were additionally tested with chopped straw as a top layer. Two devices of the same kind and two examiners were available for performing comparative measurements. Regression analyses and an ANOVA were conducted to compare the devices, examiners, and different surfaces. Most of the floors differed significantly from each other. Sawdust was the softest material, followed by sand and recycled manure solids. The agreement between the devices (Lin’s concordance correlation coefficient (CCC) > 0.99, Spearman’s rank correlation coefficient (r_S) = 0.99) and examiners (CCC = 0.99, r_S = 0.99) was almost perfect. These findings indicate that this device can be used as a new method for assessing the softness of bedding materials for dairy cows objectively. Full article

The overapplication of manure on agricultural soils leads to nitrogen and phosphorus discharge into the aquatic environment, resulting in serious eutrophication problems and decreased water quality. Piggery wastewater (PWW) can be treated by microalgae to recycle nutrients, but the toxic levels of ammonia and organic matter hinder their growth. Fresh water is usually used to dilute PWW, but it is a scarce resource. The implementation of a pretreatment step before microalgae-based treatment could make PWW suitable for microalgae growth. Electrocoagulation, ammonia stripping, photo-Fenton, and constructed wetlands were evaluated as pretreatment methods to reduce ammonia, chemical oxygen demand (COD), color, and total suspended solids. Moreover, the pretreated PWWs were tested to grow the microalga Tetradesmus obliquus. Photo-Fenton showed the best results among the other pretreatments, achieving removal efficiencies above 90%, except for ammonia. This resulted in T. obliquus being capable of growing on undiluted PWW, even at higher ammonia levels, achieving similar biomass productivity to synthetic medium (66.4 ± 17.8 mg·L⁻¹·day⁻¹ and 60.1 ± 10.4 mg·L⁻¹·day⁻¹, respectively) almost doubling with pH control (116.5 mg·L⁻¹·day⁻¹). Thus, this pretreatment seems to be the most promising one to incorporate into microalgae-based treatment systems and must be further explored. Full article

Anaerobic co-digestion technology (AcoD) can be used to process rice straw (RS) and cow manure (CoM) to produce energy and a digestate rich in nutrients, while the improper disposal of RS and CoM causes environmental problems. The overall effectiveness of the anaerobic digestion technology can be improved by utilizing the nutrients available in the digestate. It is also a way to reduce the usage of mineral fertilizer by recycling the nutrients available in the digestate. The co-digestion of RS with CoM was performed in a newly developed digester (F1) and in a mesophilic digester (F2) used as a reference. The mass balance of C, macronutrients (N, P, K, Ca, Mg, and S), and their distribution into a liquid digestate (LD) and a solid digestate (SD) was investigated in both digesters. The mass balance was used to evaluate the carbon available in the biogas and in the digestate. It was also used to investigate the recovery potential of the macronutrients after the AD process. Moreover, the assessment of the resulting digestate was carried out to suggest its potential use in agriculture. The amount of C measured in the biogas was the same in both digesters (41.0% and 38.0% of the initial C). Moreover, the conversion efficiency of C from the substrate into methane was 23.4% for F1 and 21.0% for F2. The Ca, Mg, K, and P were conserved in the digestate because their recovery rates (RR) were close to 100%. However, a relatively low RR was observed for N (84.1% in F1 and 86.8% in F2) and S (87.1% in F1 and 86.5% in F2) in both the digesters. After separation n of the SD, from 79.1 to 83.4% (in F1) and 75.0 to 82.4% (in F2) of the final nutrients were available in the LD. The assessment of the SD suggested its use in agriculture not only for soil amendment but also as a K-providing organic fertilizer. Full article