RESUMEN

Pyrolysis of animal manure at high temperature is necessary to effectively immobilize heavy metals, while the available phosphorus (P) level in biochar is relatively low, rendering it unsuitable for use as fertilizer. In this study, the pretreatment of swine manure with different potassium (K) sources (KOH, K2CO3, CH3COOK and C6H5K3O7) was conducted to produce a biochar with enhanced P availability and heavy metals immobility. The addition of all K compounds lowered the peak temperature of decomposition of cellulose in swine manure. The percentage of ammonium citrate and formic acid extractable P in biochar increased with K addition compared to undoped biochar, with CH3COOK and C6H5K3O7 showing greater effectiveness than KOH and K2CO3, however, water- extractable P did not exhibit significant changes. Additionally, the available and dissolved Si increased due to the doping of K, with KOH and K2CO3 having a stronger effect than CH3COOK and C6H5K3O7. X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed that K addition led to the formation of soluble CaKPO4 and silicate. In addition, the incorporation of K promoted the transformation of labile copper (Cu) and znic (Zn) into the stable fraction while simultaneously reducing their environmental risk. Our study suggest that the co-pyrolysis of swine manure and organic K represents an effective and valuable method for producing biochar with optimized P availability and heavy metals immobility.

Asunto(s)

RESUMEN

Microalgae biomass products are gaining popularity due to their diverse applications in various sectors. However, the costs associated with media ingredients and cell harvesting pose challenges to the scale-up of microalgae cultivation. This study evaluated the growth and nutrient removal efficiency (RE) of immobilized microalgae Tetradesmus obliquus in sodium alginate beads cultivated in swine manure-based wastewater compared to free cells. The main findings of this research include (i) immobilized cells outperformed free cells, showing approximately 2.3 times higher biomass production, especially at 10% effluent concentration; (ii) enhanced organic carbon removal was observed, with a significant 62% reduction in chemical oxygen demand (383.46-144.84 mg L-1) within 48 h for immobilized cells compared to 6% in free culture; (iii) both immobilized and free cells exhibited efficient removal of total nitrogen and total phosphorus, with high REs exceeding 99% for phosphorus. In addition, microscopic analysis confirmed successful cell dispersion within the alginate beads, ensuring efficient light and substrate transfer. Overall, the results highlight the potential of immobilization techniques and alternative media, such as biodigested swine manure, to enhance microalgal growth and nutrient RE, offering promising prospects for sustainable wastewater treatment processes.

Asunto(s)

RESUMEN

Livestock manure harbors antibiotic resistance genes (ARGs), and aerobic composting (AC) is widely adopted for waste management. However, mitigating ARG resurgence in later stages remains challenging. This work aims to curb ARGs rebounding through a Fenton-like reaction during food waste and swine manure co-composting. Results revealed that 0.025 % zerovalent iron (ZVI) + 0.5 % hydrogen peroxide (H2O2) facilitated maximum ARG, mobile genetic elements (MGEs), and 16 s rRNA removal with reductions of 2.68, 2.69, and 1.4 logs. Spectroscopic analysis confirmed Fenton-like reaction and cell apoptosis analysis indicated that 0.025 % ZVI and 0.5 % H2O2 treatment had the maximum early apoptosis, least observed, and normal cells on day 30. Redundancy analysis highlighted the influence of bacterial communities and physicochemical properties on ARGs, with MGEs playing a crucial role in Fenton treatments. Our findings suggest incorporating ZVI and H2O2 in composting can significantly reduce ARGs and enhance waste management practices.

Asunto(s)

RESUMEN

Solids concentration, temperature, and digester configuration were subjected to biomethanation study to identify effective retrofitting schemes for old swine waste digesters. Batch assays were commenced to determine an appropriate scenario at 30-55 °C and total solids 1-3 %TS. Sub-thermophilic temperature (45 °C) was found desirable with an additional 11.1 % methane yield, while digestion at higher TS induced ammonium inhibition. Subsequent batch experiments lasted 72 hrs for hydrolytic-acidogenic assessment under various temperatures. Heating control at 45 °C and 55 °C for 24 hrs increased hydrolysis efficiency 4.6-5.7 folds above control but showed no significant difference (α = 0.05) between them. Limited heat supply from biogas engine dictated the continuous digestion study to operate pre-hydrolysis reactor at maximum temperature of 45 °C. The two-stage strategy demonstrated best overall performances at the sub-thermphilic combination, raising methane yield by 35.4 %. Next-Generation Sequencing indicated remarkable shifts in abundance and diversity, especially for hydrolytic organisms, which expanded from 54 to 70.2 % by sub-thermophilic temperature.

Asunto(s)

RESUMEN

This research aimed to design an integrated aerobic-anaerobic reactor with dynamic aeration that was automatically regulated based on real-time oxygen concentration and investigate the aerobic pretreatment and subsequent dry co-anaerobic digestion (co-AD) characteristics of highly solids-loaded corn stover and swine manure in terms of temperature rise, physiochemical characteristics, and methane production. The high-temperature feedstocks from the aerobic pretreatment phase rapidly entered the AD phase without transportation and effectively improved the start-up and methane production of the co-AD. Oxygen concentration range, aeration rate, and pretreatment time affected the cumulative aeration time, temperature rise, and organic matter removal interactively during aerobic pretreatment, and a low aeration rate was relatively preferable. Although the lignocellulose removal increased with the increase in pretreatment duration, the maximal lignin elimination efficiency only reached 1.30%. The inoculum injection in the transition phase from aerobic pretreatment to co-AD and the leachate reflux during co-AD were also critical for producing methane steadily apart from aerobic pretreatment. The cold air weakened the temperature rise of aerobic pretreatment, and the low-temperature leachate reduced the methane production in the co-AD process. An oxygen concentration range of 13%-17%, aeration rate of 0.10 m3/(min·m3), pretreatment time of 84 h, inoculum loading of 40%, leachate refluxing thrice per day, and double-layer inoculation were optimum for improving the integrated aerobic-anaerobic digestion system's ability to resist low temperatures and achieving high methane production. The maximal cumulative and volatile solids (VS) methane yields of corn stover and swine manure reached 444.58 L and 266.30 L/kg VS.

Asunto(s)

RESUMEN

17ß-estradiol is a naturally occurring estrogen, and livestock manure applied to agricultural fields is a major source to the environment. Liquid swine manure is widely applied to agricultural fields in the Canadian Prairies, a region where the majority of the annual runoff occurs during a brief snowmelt period over frozen soil. Transport of estrogens from manure amendments to soil during this important hydrological period is not well understood but is critical to mitigating the snowmelt-driven offsite transport of estrogens. This study quantified the concentration and load of 17ß-estradiol in snowmelt from an agricultural field with a history of manure application under manure application methods: no manure applied, manure applied on the sub-surface, and on the surface, using a laboratory simulation study with flooded intact soil cores and a field study during snowmelt. A higher concentration of 17ß-estradiol was in the laboratory simulation than in the field (mean laboratory pore water = 1.65 ± 1.2 µg/L; mean laboratory flood water = 0.488 ± 0.58 µg/L; and mean field snowmelt = 0.0619 ± 0.048 µg/L). There were no significant differences among manure application methods for 17ß-estradiol concentration. Laboratory pore water concentrations significantly increased over time, corresponding with changes in pH. In contrast, there was no significant change in the field snowmelt concentrations of 17ß-estradiol over time. However, for both laboratory simulation experiments and field-based snowmelt experiments, mean concentrations of 17ß-estradiol were higher with subsurface than surface-applied manure, and the cumulative load of 17ß-estradiol was significantly higher in the sub-surface than in surface applied. The mean cumulative load from the field study across all treatments (6.91 ± 3.7 ng/m2) approximates the magnitude of 17ß-estradiol that could be mobilized from manured fields. The sub-surface application of manure seems to increase the persistence of 17ß-estradiol in soil, thus enhancing the potential loss to snowmelt runoff.

Asunto(s)

RESUMEN

Treatment of swine manure by hydrothermal carbonization (HTC) with the aid of different surfactants was first explored in this study. PEG 400 (polyethylene glycol 400) and Tween 80 facilitated the formation of bio-oil. SLS (sodium lignosulfonate) and SDS (sodium dodecyl sulfate) promoted the formation of water-soluble matters/gases. Span 80 enhanced the formation of hydrochar, which resulted in a 50.19 % mass yield, 92.39 % energy yield, and a caloric value of 28.68 MJ/kg. The hydrochar obtained with Span 80 presented a similar combustion performance to raw swine manure and the best pyrolysis performance. The use of Span 80 promoted the transfer of degradation products to hydrochar, especially hydrophobic ester and ketone compounds. Notedly, Span 80 suppressed the synthesis of PAHs during the HTC process, which was reduced to 0.92 mg/kg. Furthermore, the hydrochar produced with Span 80 contained lower contents of heavy metals. On the whole, Span 80 has shown great potential in enhancing the HTC of swine manure. The acting mechanisms of surfactants in the HTC of swine manure included adsorption, dispersion, and electrostatics repulsion.

Asunto(s)

RESUMEN

Escherichia coli is one of the key bacteria responsible for a variety of diseases in humans and livestock-associated infections around the globe. It is the leading cause of mortality in neonatal and weaned piglets in pig husbandry, causing diarrhea and significant harm to the industry. Furthermore, the frequent and intensive use of antimicrobials for the prevention of diseases, particularly gastrointestinal diseases, may promote the selection of multidrug-resistant (MDR) strains. These resistant genotypes can be transmitted through the excrement of animals, including swine. It is common practice to use porcine manure processed by biodigesters as fertilizer. This study aimed to examine the antimicrobial susceptibility, the presence of virulence genes frequently associated with pathotypes of intestinal pathogenic E. coli (InPEC), and antimicrobial resistance genes (ARGs) of 28 E. coli isolates collected from swine manure fertilizers. In addition, the enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR) technique was used to investigate the genetic relationship among the strains. Using disk diffusion, the antimicrobial susceptibility profiles of the strains were determined. Using polymerase chain reaction (PCR), 14 distinct virulence genes associated with the most prevalent diarrhea and intestinal pathogenic E. coli (DEC/InPEC) and five ARGs were analyzed. All isolates tested positive for multidrug resistance. There was no detection of any of the 14 virulence genes associated with InPECs, indicating the presence of an avirulent commensal microbiota. Molecular classification by ERIC-PCR revealed that the majority of isolates (27 isolates) coalesced into a larger cluster with a genetic similarity of 47.7%; only one strain did not cluster in this cluster, indicating a high level of genetic diversity among the analyzed isolates. Thus, it is of the utmost importance to conduct epidemiological surveillance of animal breeding facilities in order to determine their microbiota and formulate plans to reduce the use of antimicrobials and improve animal welfare.

Asunto(s)

RESUMEN

Although the promotive effect of direct interspecies electron transfer (DIET) on methane production has been well-documented, the practical applicability of DIET in different scenarios have not yet been systematically studied. This study compared the effects of magnetite-mediated DIET with conventional biogas mixing-driven interspecies hydrogen transfer (IHT) on anaerobic digestion (AD) of swine manure (SM). Compared with control, magnetite supplementation, biogas circulation, and their integration enhanced the CH4 yield by 19.3%, 25.9%, and 26.2%, respectively. Magnetite mainly enriched DIET-related syntrophic bacteria (Anaerolineae and Synergistia) and methanogens (Methanosarcina) to accelerate acidification and establish DIET, while biogas circulation mainly enriched hydrolytic bacteria (Clostridia) and hydrogenotrophic methanogens (Methanolinea and Methanobacterium) to promote hydrolysis and accelerate IHT. Coupling magnetite addition with biogas circulation led to the enrichment of the above six microorganisms to different extents. The effectiveness of the strategies for lowering the H2 pressure followed: magnetite + biogas circulation ≈ biogas circulation > magnetite. Under stress-free environment, the enhancement effect of magnetite-induced DIET was not even as pronounced as biogas circulation-a simple and common mixing strategy in commercial AD plants, and the promotion effect of magnetite was insignificant in the well-mixed digesters. In short, the magnetite-mediated DIET is not always effective in improving AD of SM.

Asunto(s)

RESUMEN

Livestock manure is one of the most important pools of antibiotic resistance genes (ARGs) in the environment. Aerobic composting can effectively reduce the spread of antibiotic resistance risk in livestock manure. Understanding the effect of aerobic composting process parameters on manure-sourced ARGs is important to control their spreading risk. In this study, the effects of process parameters on ARGs during aerobic composting of pig manure were explored through data mining based on 191 valid data collected from literature. Machine learning (ML) models (XGBoost and Random Forest) were utilized to predict the rate of ARGs changes during pig manure composting. The model evaluation index of the XGBoost model (R2 = 0.651) was higher than that of the Random Forest (R2 = 0.490), indicating that XGBoost had better prediction performance. Feature importance was further calculated for the XGBoost model, and the XGBoost black box model was interpreted by Shapley additive explanations analysis. Results indicated that the influencing factors on the ARGs variation in pig manure were sequentially divided into thermophilic period, total composting period, composting real time, and thermophilic stage average temperature. The findings gave an insight into the application of ML models to predict and decipher the ARG changes during manure composting and provided suggestions for better composting manipulation and optimization of process parameters.

Asunto(s)

RESUMEN

Anaerobic co-fermentation is a favorable way to convert agricultural waste, such as swine manure (SM) and apple waste (AW), into lactic acid (LA) through microbial action. However, the limited hydrolysis of organic matter remains a main challenge in the anaerobic co-fermentation process. Therefore, this work aims to deeply understand the impact of cellulase (C) and protease (P) ratios on LA production during the anaerobic co-fermentation of SM with AW. Results showed that the combined use of cellulase and protease significantly improved the hydrolysis during the enzymatic pretreatment, thus enhancing the LA production in anaerobic acidification. The highest LA reached 41.02 ± 2.09 g/L within 12 days at the ratio of C/P = 1:3, which was approximately 1.26-fold of that in the control. After a C/P = 1:3 pretreatment, a significant SCOD release of 45.34 ± 2.87 g/L was achieved, which was 1.13 times the amount in the control. Moreover, improved LA production was also attributed to the release of large amounts of soluble carbohydrates and proteins with enzymatic pretreated SM and AW. The bacterial community analysis revealed that the hydrolytic bacteria Romboutsia and Clostridium_sensu_stricto_1 were enriched after enzyme pretreatment, and Lactobacillus was the dominant bacteria for LA production. This study provides an eco-friendly technology to enhance hydrolysis by enzymatic pretreatment and improve LA production during anaerobic fermentation.

Asunto(s)

RESUMEN

Using swine manure biochar and biogas slurry in agriculture proves to be an effective strategy for soil improvement and fertilization. In this study, a pot trial on the growth of lotus root was conducted to investigate the persistent effects of applying 350°C swine manure biochar (1% and 2%) and biogas slurry (50% and 100%) on soil nitrogen nutrient and lotus root quality. The results showed that compared to chemical fertilizer alone (A0B0), swine manure biochar significantly increased soil nitrogen content after one year of application. The contents of total nitrogen (TN), alkali-hydrolyzed nitrogen (AHN), ammonium nitrogen (NH4 +-N), and nitrate nitrogen (NO3- -N) increased by 17.96% to 20.73%, 14.05% to 64.71%, 17.76% to 48.68% and 2.22% to 8.47%, respectively, during the rooting period. When swine manure biochar was present, the application of biogas slurry further elevated soil nitrogen content. The co-application of swine manure biochar and biogas slurry significantly increased soil nitrogen content, and the 100% nitrogen replacement with biogas slurry combined with 2% swine manure biochar (A2B2) treatment exhibited the most significant enhancement effect during whole plant growth periods. Soil enzyme activities, including soil protease (NPT), leucine aminopeptidase (LAP), b-glucosidase (ß-GC) and dehydrogenase (DHA), showed a tendency to increase and then decrease with the prolongation of lotus root fertility period, reaching the maximum value during the rooting period. Compared to A0B0, the treatment with 2% swine manure biochar had the most significant effect on enzyme activities and increased the lotus root's protein, soluble sugar, and starch contents. Nitrate content decreased with the application of 2% swine manure biochar as the amount of biogas slurry increased. In conclusion, swine manure biochar effectively improved soil nitrogen content, enzyme activity, and lotus root quality. Even after one year of application, 2% swine manure biochar had the best enhancement effect.

RESUMEN

The production of biogas from organic waste has attracted considerable interest as a solution to current energy and waste management challenges. This study explored the methane (CH4) production potential of swine manure (SM), food waste (FW), and tomato waste (TW) and the changes in the microbial community involved in the anaerobic digestion process. The results revealed that the CH4 production potentials of the four kinds of SM samples were influenced by the characteristics of SM (e.g., age and storage period). Among the four kinds of SM samples, the CH4 yield from the manure directly sampled from primiparous sows (SM3) was the highest. The CH4 yield was significantly improved when SM3 was co-digested with FW, but not with TW. The addition of SM fostered a stable CH4 production community by enhancing the interaction between methanogens and syntrophic bacteria. Furthermore, the addition of FW as a co-substrate may improve the functional redundancy structure of the methanogenesis-associated network. Overall, the characteristics of SM must be considered to achieve consistent CH4 yield efficiency from anaerobic digestion since CH4 production potentials of SM can be different. Also, the contribution of co-substrate to the synergistic relationship between methanogens and syntrophic bacteria can be considered when a co-substrate is selected in order to enhace CH4 yield from SM.

Asunto(s)

RESUMEN

Antibiotic resistance genes (ARGs) are emerging pollutants that enter the farm and surrounding environment via the manure of antibiotic-treated animals. Pretreatment of livestock manure by composting decreases ARGs abundance, but how antibiotic residues affect ARGs removal efficiency remains poorly understood. Here, we explored the fate of the resistome under different doxycycline residue levels during aerobic swine manure composting. Metagenomic sequencing showed that the presence of high levels of doxycycline generally had a higher abundance of tetracycline ARGs, and their dominant host bacteria of Firmicutes, especially Clostridium and Streptococcus, also had limited elimination in composting under high levels of doxycycline stress. Moreover, high levels of doxycycline impaired the removal of the total ARGs number in finished composts, with a removal rate of 51.74 % compared to 63.70 % and 71.52 % for the control and low-level doxycycline manure, respectively. Horizontal gene transfer and strengthened correlations among the bacterial community fostered ARGs preservation at high doxycycline levels during composting. In addition, ARGs carried by both plasmids and chromosomes, such as multidrug ARGs, showed wide host characteristics and rebound during compost maturation. Compared with chromosomes, a greater variety of ARGs on plasmids suggested that the majority of ARGs were characterized by horizontal mobility during composting, and the cross-host characteristics of ARGs during composting deserve further attention. This study provided deep insight into the fate of ARGs under residual antibiotic stress during manure composting and reminded the associated risk for environmental and public health.

Asunto(s)

RESUMEN

Livestock manure is a major source of veterinary antibiotics and antibiotic resistance genes (ARGs). Elucidation of the residual characteristics of ARGs in livestock manure following the administration of veterinary antibiotics is critical to assess their ecotoxicological effects and environmental contamination risks. Here, we investigated the effects of enrofloxacin (ENR), a fluoroquinolone antibiotic commonly used as a therapeutic drug in animal husbandry, on the characteristics of ARGs, mobile genetic elements, and microbial community structure in swine manure following its intramuscular administration for 3 days and a withdrawal period of 10 days. The results revealed the highest concentrations of ENR and ciprofloxacin (CIP) in swine manure at the end of the administration period, ENR concentrations in swine manure in groups L and H were 88.67 ± 45.46 and 219.75 ± 88.05 mg/kg DM, respectively. Approximately 15 fluoroquinolone resistance genes (FRGs) and 48 fluoroquinolone-related multidrug resistance genes (F-MRGs) were detected in swine manure; the relative abundance of the F-MRGs was considerably higher than that of the FRGs. On day 3, the relative abundance of qacA was significantly higher in group H than in group CK, and no significant differences in the relative abundance of other FRGs, F-MRGs, or MGEs were observed between the three groups on day 3 and day 13. The microbial community structure in swine manure was significantly altered on day 3, and the altered community structure was restored on day 13. The FRGs and F-MRGs with the highest relative abundance were qacA and adeF, respectively, and Clostridium and Lactobacillus were the dominant bacterial genera carrying these genes in swine manure. In summary, a single treatment of intramuscular ENR transiently increased antibiotic concentrations and altered the microbial community structure in swine manure; however, this treatment did not significantly affect the abundance of FRGs and F-MRGs.

Asunto(s)

RESUMEN

This study evaluated the effect of zero-valent iron nanoparticles (NZVI) on the anaerobic digestion of swine manure. A wide range of doses of NZVI was evaluated (5, 10, 15, 20, 25, 50, and 100 mgFe°/gVS). The maximum methane yield of 0.4506 L/gVSremoved was obtained with the concentration of 10 mgFe°/gVS representing an increase of 58.99% than the control system with 0.2834 L/gVSremoved, indicating that Fe° improves the methanogenic activity. However, when using doses greater than 20 mgFe°/gVS, there were decreases in the methane yield of 34.4-47.98%. Also, to observe the effect of NZVI in anaerobes was evaluated the activity in the electron transport system (ETS), where the control reactor showed an activity of 31.91 µg INTred/gVS•h, while in reactors with NZVI showed values of 39.48 µg INTred/gVS•h (10 Fe°mg/gVS), observing a stimulation of Fe° in microbial activity. However, the dose of 100 mgFe°/gVS showed the greatest decrease in methane yield (0.1474 L/gVSremoved) and a reduction in ETS was observed by 8.5% compared to the control. The effect on the composition of the volatile fatty acids was observed, where the control system obtained a maximum production of acetic acid of 639 mg/L, which was exceeded with the dose of 10 mg Fe°/gVS by 215% and a decrease of 41.15% with the inhibitory concentration of 100 mg Fe°/gVS. As a result, higher doses of NZVI affect the metabolic activity of anaerobes as well as the acetoclastic pathway causing a decrease in the methane production.

RESUMEN

In this study, the first field-scale application of a bio-foam spray (a mixture of microbes and a surfactant) for the reduction of ammonia emitted from manure was investigated on six field swine manure piles. The objective of this study was to evaluate the odor suppression ability of bio-foam and odor degradation ability of odor-degrading bacteria loaded in the surfactant foam after covering manure piles. The size of field manure piles tested in this study ranged from 27 to 300 m3. Bio-foam spraying completely suppressed the release of the major odor component, ammonia (NH3), and odor-degrading bacteria in the bio-foam aided in the degradation of NH3 in field swine manure piles. On average, 85.7-100% of NH3 was reduced after 24-48 h of serial bio-foam spray application on the swine manure surface, while the control showed 25-42%. The reduction efficiency of NH3 by the bio-foam application was affected by the bio-foam spray frequency, ambient temperature, ventilation of the field facility, and upward airflow to the pile. The reduction in surface emission of NH3 also reduced the ambient air concentration of NH3 at the gate of the compost facility. NH3 gas measurements at a depth of 50 cm indicated that NH3-degrading bacteria infiltrated the manure and were active in biodegradation. Finally, the measured effectiveness of bio-foam application as shown by this study indicates that sprinkling bio-foam via specialized rotating sprinklers may be an efficient and uniform method for the delivery of bio-foam to wide field areas within composting facilities.

Asunto(s)

RESUMEN

This research aimed to investigate the alterations in extracellular (eARGs) and intracellular (iARGs) antibiotic resistance genes in response to oxytetracycline (OTC), and unravel the dissemination mechanism of ARGs during composting. The findings revealed both low (L-OTC) and high contents (H-OTC) of OTC significantly enhanced absolute abundance (AA) of iARGs (p < 0.05), compared to CK (no OTC). Composting proved to be a proficient strategy for removing eARGs, while AA of eARGs was significantly enhanced in H-OTC (p < 0.05). OTC resulted in an increase in AA of mobile genetic elements (MGEs), ATP levels, antioxidant and DNA repair enzymes in bacteria in compost product. Structural equation model further demonstrated that OTC promoted bacterial DNA repair and antioxidant enzyme activities, altered bacterial community and enhanced MGEs abundance, thereby facilitating iARGs dissemination. This study highlights OTC can increase eARGs and iARGs abundance, underscoring the need for appropriate countermeasures to mitigate potential hazards.

Asunto(s)

RESUMEN

Hydrothermal carbonization is an efficient technique for the disposal of livestock manure, enabling its harmless treatment, quantity reduction, and resourceful utilization. Co-hydrothermal of modified materials facilitates the production of more valuable carbonaceous materials. However, further exploration is needed to understand their potential impact on the environmental risks associated with livestock manure disposal and the application of products derived from it. Therefore, the carbonization degree, heavy metals stabilization, and phosphorus retention during the hydrothermal treatment of swine manure were systematically investigated in this study under the influence of in-situ formed MgFe2O4. The results revealed that the in-situ formation of MgFe2O4 improved the dehydration and decarboxylation of organic components in swine manure, thereby improving its carbonization degree. Furthermore, both hydrothermal carbonization and MgFe2O4 modified hydrothermal carbonization resulted in an enhanced stabilization of heavy metals, leading to a significant reduction in their soluble/exchangeable fraction and reducible fraction. Phosphorus was predominantly retained in the hydrochars, with the highest retention rate reaching 88%, attributed to the significant decrease in soluble and exchangeable phosphorus fractions facilitated by the in-situ formation of MgFe2O4. Moreover, MgFe2O4 modified hydrochars exhibited remarkable adsorption capacity for Pb(II) and Cu(II) without any leaching of heavy metals. Overall, the findings indicated that the in-situ formation of MgFe2O4 positively influenced the hydrothermal of swine manure, improving certain economic benefits in its practical application.

Asunto(s)

RESUMEN

Hydrothermal carbonization (HTC) is considered a promising technology for biomass waste management without pre-drying. This study explores the potential for swine manure management by comparing batch and continuous processes, emphasizing the benefits of the continuous mode, particularly for its potential full-scale application. The continuous process at low temperature (180 °C) resulted in a hydrochar with a lower degree of carbonization compared to the batch process, but similar characteristics were found in both hydrochars at higher operating temperatures (230-250 °C), such as C content (∼ 52 wt%), fixed carbon (∼ 24 wt%) and higher calorific value (21 MJ kg-1). Thermogravimetric and combustion analyses showed that hydrochars exhibited characteristics suitable as solid biofuels for industrial use. The process water showed a high content of organic matter as soluble chemical oxygen demand (7-22 g L-1) and total organic carbon (4-10 g L-1), although a high amount of refractory species such as N- and O-containing long aromatic compounds were detected in the process water from the batch process, while the process water from the continuous process presented more easily biodegradable compounds such as acids and alcohols, among others. The longer time required to reach operating temperature in the case of the batch system (longer heating time to reach operating temperature) resulted in lower H/C and O/C ratios compared to hydrochar from the continuous process. This indicates that the dehydration and decarboxylation reactions of the feedstock play a more important role in the batch process. This study shows the efficiency of the continuous process to obtain carbonaceous materials suitable for use as biofuel, providing a solution for swine manure management.

Asunto(s)