Anaerobic System Research Articles

Changing Horses in Midstream: Modern Pentathlon After the 2024 Olympic Games.

The decision of the Union Internationale de Pentathlon Moderne to replace horse riding with Obstacle after the 2024 Olympic Games challenges training, testing, and recovery management in Modern Pentathlon. This commentary discusses physiological, technical, and tactical effects of rule changes in the 5 disciplines with a specific focus on the new discipline Obstacle. Modern Pentathlon requires athletes to develop specific endurance capacities relying on both the aerobic and anaerobic systems while simultaneously increasing lower- and upper-body strength capabilities. In addition, movements must be repeatedly executed in an explosive and precise manner. Running and swimming must be fast but economical. Swapping from horse riding to Obstacle will prioritize the explosive strength of the upper extremities and core while keeping high levels of endurance and precision in swimming, fencing, and shooting. Moreover, condensing the Modern Pentathlon competition to a 90-minute television-friendly format enables more competitions in the future. Athletes and coaches will thus also need to develop and maintain effective individual peri-exercise routines (before, during, and after the competition) to successfully meet the resulting tactical and physical challenges of the new format. This commentary aims to stimulate the discussion on the effect of the Union Internationale de Pentathlon Moderne's decisions to replace riding with the new Obstacle discipline and implement a more television-friendly format with a focus on physiological, technical, and tactical aspects.

Hexanoic acid production from anaerobic fermentation of Chinese cabbage waste with exogenous lactic acid as electron donor

The lack of electron donors is one of the key factors hindering hexanoic acid production from anaerobic fermentation. In this study, three different types of lactic acids were supplemented as exogenous electron donors to the anaerobic fermentation system of Chinese cabbage waste (CCW). The yields of hexanoic acid in the reactors supplemented with CCW lactic acid pre-fermentation broth (PFB), lactic acid diluent (LAD) and chemical lactic acid (LA) were 6996.8 mg COD/L, 4534.8 mg COD/L and 6777.1 mg COD/L, respectively. Compared with the reactor supplemented with LA, the electron efficiency of hexanoic acid in reactor supplemented with PFB increased by 188 %. Supplementing PFB shifted the microbial communities towards a direction favorable to hydrolysis and chain elongation, thereby facilitating the synthesis of hexanoic acid.

Metabolic mechanisms of carbon and nitrogen interactions during anaerobic digestion of coal

There was limited research on the impact of nitrogen metabolism in the process of methane production with coal, even if carbon and nitrogen metabolism were closely interconnected. Lignite was the source of carbon and nitrogen in anaerobic digestion system. The relationship between carbon and nitrogen metabolism was systematically discussed during the anaerobic digestion process. The results showed that phenolic carbon or ether carbon (C-O), pyridine-type nitrogen (N-6) and nitrogen oxide compound (N-X) in coal were decomposed under the action of Macellibacteroides, Sphaerochaeta and Trichococcus in the hydrolysis stage, respectively. In the acidogenesis stage, the stress of volatile fatty acids and ammonia produced by dissolved organic matter under the action of Syner-01 and Sphaerochaeta on hydrogenotrophic and acetoclastic methanogens was alleviated during the nitrogen cycle. In the acetogenesis stage, acetic acid produced from the decomposition of organic acids and alcohols by Synergistaceae and Sedimentibacter was competed by denitrifying bacteria and acetogenic methanogens. In the methanogenesis stage, CO2 was reduced by Methanobacterium and Methanoculleus to produce CH4, while acetic acid was decomposed by Methanosaeta to produce CH4. And methyl substances were generated into CH4 by Methanosarcina and Methanofastidiosum. This understanding will provide a basis for strengthening the favorable factors in biomethane production.

Comparative Evaluation of Methane Yield from Continuous and Batch Fermentative Processing of Selected Agrowaste

This study investigated the influence of different agrowaste compositions on methane yield in batch and continuous operational modes, highlighting the significance of substrate characteristics in determining the efficiency of methane production. It comparatively assessed the methane yield derived from continuous and batch fermentative processing of the following agrowaste; Cassava peels (A), Maize husks (B), Pig Slurry (C), and composite (D) that represents the co-digestion of the aforementioned A, B & C. Eight digesters were used in all, two anaerobic systems for each substrate, [I.e one operating in a batch mode (1) and the other in a continuous mode (2)]. The proximate properties of the substrates were determined and gas production rates were monitored over the experimental period of 45 days. Gas analysis of the generated gas revealed mainly methane and CO2, with concomitant organic compounds like; Ethanol, Methanol, Acetic Acid, Acetone, etc. Minute quantities of Phenol and Lactic Acid were mainly found in the gas generated from Cassava peels. The average percentage value of Co-digested substrates (D) yielded higher gas volume of 78.263±4.54, followed by C (74.263±4.65), B (70.240±4.38), and A (56.090±3.50). The results also revealed that the continuous fermentative process demonstrated a more stable and consistent methane production rate compared to the batch system, attributed to its steady-state operational mode and continuous substrate feed input. However, modeled graphical results showed that batch fermentation system produced higher gas yield (for all the substrates) between days 29-39 before it recorded a sharp decline curve, attributed to the reduction in substrate availability.

Anaerobic Sport-Specific Tests for Taekwondo: A Narrative Review with Guidelines for the Assessment.

The ATP-PCr system represents the main source of energy during high-intensity attack actions in taekwondo matches. In contrast, the glycolytic system supports the maintenance of these actions when repeated techniques are performed. Given the close relationship between anaerobic energy systems and attack activity in combat, the literature relating to the use of sport-specific test protocols for anaerobic assessment has experienced a remarkable increase. This narrative review aims to illustrate the sport-specific anaerobic tests available in taekwondo by retracing and examining development and validation process for each test. Forty-one articles published between 2014 and 2023 were selected via the MEDLINE and Google Scholar bibliographic databases. These tests are the Taekwondo Anaerobic Test and Adapted Anaerobic Kick Test (i.e., continuous mode testing); the 10 s and multiple Frequency Speed of Kick Tests; the chest and head Taekwondo Anaerobic Intermittent Kick Tests; and the Taekwondo-Specific Aerobic-Anaerobic-Agility test (i.e., intermittent mode testing). Coaches and strength and conditioning professionals can use all the tests described in taekwondo gyms as they feature short and easy-to-implement protocols for monitoring and prescribing specific anaerobic training. The guidelines in this review evaluate each test from several perspectives: basic (e.g., validity, reliability, and sensitivity), methodological (e.g., continuous or intermittent mode testing) and application (e.g., time-motion structure and performance parameters). This comprehensive approach aims to assist stakeholders in selecting the most appropriate test.

Uncovering the toxic effects and adaptive mechanisms of aminated polystyrene nanoplastics on microbes in sludge anaerobic digestion system: Insight from extracellular to intracellular

The impacts of polystyrene nanoplastics (PS NPs) with amino functional groups on sludge anaerobic digestion process and the underlying microbial feedbacks remains unclear. Herein, PS NPs coated with and without amino functional groups were employed to explore their impacts on the sludge digestion performance. Experimental results showed that aminated PS NPs (PS-NH2) deteriorated the methane yield and hydrolysis rate. The Derjaguin-Landau-Verwey-Overbeek theory analysis suggested that the PS-NH2 decreased the interaction energy barrier, making it easier to contact with sludge and disrupting the structure of extracellular polymeric substances. Metagenomic analysis showed that the abundance of functional microbes (e.g., Longilinea, Leptolinea, and Methanosarcina) decreased, accompanied with lower network complexity and fewer keystone taxa. Molecular docking revealed that PS-NH2 occupy the antioxidant enzyme active binding sites through hydrogen bonding and hydrophobic interactions, impairing degradation of reactive oxygen species. The severe intracellular oxidative stress up-regulated genes associated with quorum sensing (e.g., luxI and luxR) and protein biosynthesis (e.g., algA, trpG and trpE), and further inducing compact tryptophan-like proteins as a defense against NPs. These findings provide new understanding of the toxic effects from PS-NH2 in biological systems and offer valuable insights into the regulation strategies aimed at alleviating NPs inhibition.

Fixing collapsed dry anaerobic digestion system of kitchen waste caused by severe VFAs accumulation

Severe inhibition by volatile fatty acids (VFAs) frequently occurs during the dry anaerobic digestion of kitchen waste at high organic load rate (OLR), leading to decreased biogas production and even the collapse of the anaerobic digestion system. In this study, VFAs accumulation was significantly reduced by adding powder-activated carbon (PAC) or alkaline additives (AA), thus restoring the collapsed system to a stable operating state. With the addition of PAC or AA, the maximal OLR reached 11.14 g VS/(L·d), which was 30 % higher than observed without any additives (control group), while the VFAs concentration was maintained below 3000 mg/L. At this OLR, the volumetric biogas production rate stabilized at 5.1 L/(L·d) in the presence of PAC and AA, while that of the control group gradually decreased to zero. The VFAs concentration with PAC addition was 86 % lower than that of the control group, possibly because PAC might stimulate the formation of direct interspecies electron transfer between syntrophic bacteria and methanogens (Methanosarcina), thereby promoting VFAs degradation. The addition of AA, which resulted in a 95 % decrease in ammonia-nitrogen concentration, can provide a good growth environment for the microorganisms involved in acidogenesis and hydrogenotrophic methanogenesis.

A novel strategy for improving ammonia resistance of acidogenesis using domesticated sludge combined with nZVI addition in an ambient anaerobic digestion system

A novel strategy for improving ammonia resistance of acidogenesis using domesticated sludge combined with nZVI addition in an ambient anaerobic digestion system

Enhancing anaerobic digestion of food waste for biogas production: Impact of graphene nanoparticles and multiwalled nanotubes on direct interspecies electron transfer mechanism

The present research investigated the effect of two carbonaceous materials, multiwalled carbon nanotubes (MWCNTs), and graphene nanoparticles (GNPs), on biogas yield from food waste (FW) in an anaerobic digestion system for 30 days. Lab scale investigations were conducted in batch mode in 250 mL glass reactor bottles and the findings were compared to the control reactor. The performance of the experimental procedure was assessed in terms of biogas output and organic matter reduction. The addition of 100 mg/L multiwalled carbon nanotubes and 100 mg/L GNPs increased the cumulative biogas production (33.55 % and 81.16 %, respectively) while decreasing the total solid content (about 25.95 % and 24.95 %, respectively). However, increasing the concentration of both carbon nanomaterials from 100 mg/L to 500 mg/L reduced the total biogas production compared to the control, which can be attributed to cytotoxic effects. A microbial diversity study was performed using 16S amplicon sequencing to understand the changes occurring in the microbial ecology. The predominant phyla found during diversity analysis were Firmicutes, Proteobacteria, Actinobacteriota, and Bacteroidota. Finally, addition of carbonaceous nanomaterials to the anaerobic reactors favours organic matter degradation through the DIET mechanism. It improves the biogas production kinetics and productivity during the anaerobic digestion of FW up to a certain dose.

Unveiling the inactivation mechanisms of different viruses in sludge anaerobic digestion based on factors identification and damage analysis

Despite anaerobic digestion having potential for pathogen reduction in sewage sludge, the behaviors of viruses as the primary health concern are rarely studied. This study investigated the inactivation kinetics and mechanisms of four typical virus surrogates with different structures in mesophilic (MAD) and thermophilic (TAD) anaerobic digestion of sludge. Virus inactivation in MAD was virus-type-dependent correspondingly to different function loss. Temperature drove the faster inactivation proceeding for enveloped Phi6, while temperature and ammonia were the critical inactivation factors for nonenveloped MS2, causing genome degradation and protein functional damage. Interaction with sludge solids played critical role in DNA viruses T4 and Phix174 inactivation via inducing host binding function damage. By comparison, TAD enhanced viral protein denaturation, bringing efficient inactivation with reducing heterogeneity among nonenveloped viruses. These insights into unique virus behaviors in anaerobic digestion systems can provide guidance for developing more effective disinfection protocols and improving sludge biosafety.

How Does Triclocarban Affect Sulfur Transformation in Anaerobic Systems?

Triclocarban (TCC), as a typical antimicrobial agent, accumulates at substantial levels in natural environments and engineered systems. This work investigated the impact of TCC on anaerobic sulfur transformation, especially toxic H2S production. Experimental findings revealed that TCC facilitated sulfur flow from the sludge solid phase to liquid phase, promoted sulfate reduction and sulfur-containing amino acid degradation, and largely improved anaerobic H2S production, i.e., 50-600 mg/kg total suspended solids (TSS) TCC increased the cumulative H2S yields by 24.76-478.12%. Although TCC can be partially biodegraded in anaerobic systems, the increase in H2S production can be mainly attributed to the effect of TCC rather than its degradation products. TCC was spontaneously adsorbed by protein-like substances contained in microbe extracellular polymers (EPSs), and the adsorbed TCC increased the direct electron transfer ability of EPSs, possibly due to the increase in the content of electroactive polymer protein in EPSs, the polarization of the amide group C═O bond, and the increase of the α-helical peptide dipole moment, which might be one important reason for promoting sulfur bioconversion processes. Microbial analysis showed that the presence of TCC enriched the organic substrate-degrading bacteria and sulfate-reducing bacteria and increased the abundances of functional genes encoding sulfate transport and dissimilatory sulfate reduction.

Gender-Specific Physiological Profiles and Performance Metrics in Young Elite Table Tennis Players

Table tennis requires a combination of anaerobic and aerobic energy systems, agility, short reaction times, and precise motor skills. The aim of this study is to investigate gender-specific physiological profiles and performance measures in young elite table tennis players. The objectives are to identify key physical and anthropometric attributes contributing to table tennis performance, compare these attributes between male and female athletes, and develop targeted training recommendations. The study involved sixteen players (8 males and 8 females) within the age range of 10 to 18 years who train regularly at Istanbul Pendik Sports Hall. Inclusion criteria required training at least three times per week and participating at championship levels. Anthropometric measurements were taken using a Seca 220R stadiometer and a Seca 710R weighing scale, with body fat percentage estimated via a Tanita scale. Performance tests included vertical jump height (Witty Microgate device), reaction times (custom device), and heart rates (Activio Sport System). Assessments were carried out between 4:00 PM and 6:00 PM. Male athletes had higher mean values in height (159.00 ± 13.29 cm), weight (50.00 ± 12.06 kg), and vertical jump height, whereas female athletes had better reaction times (1.17 ± 0.14 seconds). No statistically significant differences were found in body fat percentage and mean heart rate. t-Tests revealed that gender differences in most performance metrics were not statistically significant, but correlation analysis showed statistically significant relationships between various physical characteristics and performance outcomes (p<0.05). As a result, physical fitness and reaction time are crucial for table tennis performance. Tailored training programs should focus on these attributes to enhance performance in young elite players. Future studies should follow these metrics longitudinally to understand their impact on competitive success.

Mechanism of biochar in alleviating the inhibition of anaerobic digestion under ciprofloxacin press

The antibiotic ciprofloxacin (CIP), detected in various aqueous environments, has broad-spectrum antimicrobial properties that can severely affect methanogenic performance in anaerobic systems. In this study, a novel strategy to alleviate the inhibition of AD performance under CIP press with the direct addition of biochar (BC) prepared from corn stover was proposed and the corresponding alleviation mechanism was investigated. When the dosage of BC was 5 and 20 g/L, the cumulative methane production in AD could reach 317.9 and 303.0 mL/g COD, and the CIP degradation efficiencies reached 94.1 % and 96.6 %, significantly higher than those of 123.0 mL/g COD and 81.2 % in the Control system. BC avoided excessive reactive oxygen species in anaerobic systems and induced severe oxidative stress response, while protecting the cell membrane and cell wall of microorganisms. Microorganisms could consume and utilize more organic extracellular polymeric substances for their growth and metabolism. When BC was involved in AD, fewer toxic intermediates were generated during CIP biodegradation, reducing acute and chronic toxicity in anaerobic systems. Microbial diversity suggested that BC could enrich functional microorganisms involved in direct interspecies electron transfer like Methanosaeta, norank_f_Bacteroidetes_vadinHA17, JGI-0000079-D21 and Syntrophomonas, thus facilitating the methanogenic process and CIP degradation. Genetic analyses showed that BC could effectively upregulate functional genes related to the conversion of butyrate-to-acetate and acetyl-to-methane under CIP stress, while functional gene abundance associated with CIP degradation enhanced partially, about encoding translocases, oxidoreductases, lyases, and ligases. Therefore, BC can be added to AD under CIP press to address its inhibited methanogenic performance.

Effect of konjac glucomannan on gut microbiota from hyperuricemia subjects in vitro: fermentation characteristics and inhibitory xanthine oxidase activity.

The disorder of uric acid metabolism is closely associated with gut microbiota and short-chain fatty acids (SCFAs) dysregulation, but the biological mechanism is unclear, limiting the development of uric acid-lowering active polysaccharides. Konjac glucomannan (KGM) could attenuate metabolic disturbance of uric acid and modulate the gut microbiota. However, the relationship between uric acid metabolism and gut microbiota is still unknown. In this study, The fecal samples were provided by healthy volunteers and hyperuricemia (HUA) patients. Fecal samples from healthy volunteers was regarded as the NOR group. Similarly, 10% HUA fecal suspension was named as the HUA group. Then, fecal supernatant was inoculated into a growth basal medium containing glucose or KGM, and healthy fecal samples were designated as the NOR-GLU and NOR-KGM groups, while HUA fecal samples were designated as the HUA-GLU and HUA-KGM groups. All samples were cultured in an anaerobic bag system. After fermentation for 24 h, the samples were collected for further analysis of composition of intestinal microbiota, SCFAs concentration and XOD enzyme activity. The results showed that KGM could be utilized and degraded by the gut microbiota from HUA subjects, and it could modulate the composition and structure of their HUA gut microbiota to more closely resemble that of a healthy group. In addition, KGM showed a superior modulated effect on HUA gut microbiota by increasing Megasphaera, Faecalibacterium, Lachnoclostridium, Lachnospiraceae, Anaerostipes, and Ruminococcus levels and decreasing Butyricicoccus, Eisenbergiella, and Enterococcus levels. Furthermore, the fermentation solution of KGM showed an inhibitory effect on xanthine oxidase (XOD) enzyme activity, which might be due to metabolites such as SCFAs. In conclusion, the effect of KGM on hyperuricemia subjects was investigated based on the gut microbiota in vitro. In the present study. It was found that KGM could be metabolized into SCFAs by HUA gut microbiota. Furthermore, KGM could modulate the structure of HUA gut microbiota. At the genus level, KGM could decrease the relative abundances of Butyricicoccus, Eisenbergiella, and Enterococcus, while Lachnoclostridium and Lachnospiraceae in HUA gut microbiota were significantly increased by the addition of KGM. The metabolites of gut microbiota, such as SCFAs, might be responsible for the inhibition of XOD activity. Thus, KGM exhibited a superior probiotic function on the HUA gut microbiota, which is expected as a promising candidate for remodeling the HUA gut microbiota.

Genome-centric metagenomic analysis reveals mechanisms of quorum sensing promoting anaerobic digestion under sulfide stress: Syntrophic metabolism and microbial self-adaptation

Sulfide stress is a common inhibition factor in anaerobic digestion systems with sulfur-rich feedstocks. Quorum sensing (QS) signaling molecule N-acyl-homoserine lactones (AHLs) possess positive effect on promoting anaerobic digestion. However, the micro-biological mechanisms of AHLs affecting syntrophic metabolism and microbial self-adaptation have not yet been deciphered in anaerobic digestion under sulfide stress. In this study, the CH4 production increased by 21.34 % at 20 μM AHLs addition in anaerobic digestion under sulfide stress. AHLs contributed to establishing potential syntrophic relationship between acidifying bacteria (unclassified_o__Bacteroidales, Lentimicrobium, Acetoanaerobium, Longilinea, and Sphaerochaetaa) and Methanothrix. AHLs promoted syntrophic metabolism by boosting microbial metabolic activity and interspecies electron transfer (IET) process under sulfide stress. For microbial metabolic activity, AHLs promoted the key enzyme synthesis in acidogenesis and methanogenesis. For IET process, AHLs promoted the assembly and synthesis of conductive pili, and synthesis and secretion of riboflavin. Furthermore, AHLs promoted microbial self-adaptation including two component system, lipopolysaccharide biosynthesis, and DNA repair, which were important evidences that microbial resistance to sulfide stress was enhanced by AHLs. Microbial self-adaptation provided favorable foundation and safeguard for syntrophic metabolisms under sulfide stress. These findings deciphered the micro-biological mechanisms of AHLs enhancing anaerobic digestion under sulfide stress.

Quorum-sensing molecules regulate biochar-assisted anaerobic digestion system for methane production: Single-stage vs. two-stage digestion

Promoting methane production performance from waste activated sludge is of great significance for energy self-sufficiency operation of wastewater treatment plants. This study evaluated the methane production enhancement strategies of biochar and quorum-sensing molecules like N-acylated homoserine lactone (AHL) in single-stage and two-stage anaerobic digestion systems. The methane yield increased to 134.9 mL/g volatile suspended solids in single-stage digestion system, which was 41.7 % higher than that of control group, while it in two-stage digestion system was not only lower than that obtained in single-stage digestion system but also less than that observed in groups adding AHL either at the beginning or on the third day of experiment period. The mechanism studies indicated that the single-stage digestion strategy promoted solubilization, hydrolysis, acetogenesis, and methanogenesis stages and improved the conversion and utilization of organic matters with the enhanced syntrophic metabolisms between microorganisms. In addition, the electron transfer activity between microorganisms was promoted, with an increase ratio of 54.7 %, meanwhile, the syntrophic relationships between methanogens such as Methanosarcina and electroactive bacteria such as norank_f__Bacteroidetes_vadinHA17 were promoted. As a result, both acetotrophic and hydrogenotrophic methanogenesis pathways were improved. This study provided some novel approaches for promoting anaerobic digestion performance while using biochar as the additive.

High rate methanogenesis and nitrogenous component transformation in the high-solids anaerobic digestion of chicken manure enhanced by biogas recirculation ammonia stripping

High-solids anaerobic digestion is a promising technology for treating animal manure. However, the high nitrogen content in chicken manure leads to severe ammonia inhibition, thereby hindering the application of this technology for chicken manure. This study operated a high-solid anaerobic system feeding the reactor with 20 % total solids (TS) chicken manure for 650 days to investigate whether the anaerobic metabolic performance could be enhanced by adopting biogas recirculation ammonia stripping. The results show that, with ammonia stripping, the total ammonia nitrogen (TAN) was reduced from 8.2 to 3.0 g/L. The methanogenic activity was enhanced 1.3 – 2.9 fold. This led to a low level of volatile fatty acids (VFA, 0.6 g/L) and a high methane yield of 0.3 L/g-volatile solids (VS). Protein decomposition was facilitated under stripping conditions and correlated with a higher abundance of protein decomposition bacteria and enhanced methane production. The dynamics of ammonium formation and removal were illustrated for different stripping conditions. The ability to maintain low ammonium and the carbon and nitrogen balance was also verified. The proven effectiveness observed in this long continuous experiment may provide a foundation for further demonstrating the high-solids anaerobic digestion of chicken manure.

Methanogenic degradation of long-chain fatty acids associated with syntrophic microbial dynamics during thermophilic AnMBR treatment of lipid-rich dairy wastes

Anaerobic membrane reactors (AnMBRs) have been applied to effectively treat dairy wastes because they can address the drawbacks of sludge flotation and biomass washout. However, when dairy wastes contain considerable proportion of lipids, any anaerobic systems will likely encounter challenges with long-chain fatty acid (LCFA) inhibition. In this study, a thermophilic AnMBR was operated to treat dairy processing wastewater (DPW) plus ice cream waste (ICW). To evaluate the impact of LCFAs, the lipid-rich ICW was gradually introduced at different levels (0, 5, 10, and 20 %) into the AnMBR, along with a stepwise increase in lipid loading rate (LLR) from 0.22 to 11.24 g lipid/L/d. The results of biomethanation revealed that the AnMBR could be successfully operated when the LLR was maintained at 5.73 g lipid/L/d with a lipid/VS ratio of 50.22 % in the feedstock. However, at ultra-high LLR of 11.24 g lipid/L/d (20 % ICW added), a significant inhibitory effect on methane yields was observed, resulting in a reduction of 56.90 %. Dynamic analysis of the LCFAs profiled that a lower degradation rate was an important factor contributing to LCFA accumulation, and the inhibition concentration of various LCFAs was identified. Based on microbial evolution and co-occurrence network results, potential syntrophic partnerships between LCFA-degrading bacteria and methanogens were proposed. The responsible enzyme genes in the LCFA-degrading, acetoclastic, and hydrogenotrophic methanogenic pathways played crucial roles in LCFA inhibition and degradation. These findings offer practical insights for the efficient methanogenic treatment of lipid-rich wastes.

From pollution to resource: advancing swine waste treatment in the USA

Concentrated animal feeding operations (CAFOs) have led to environmental challenges, specifically waste management. Swine CAFOs generate large amounts of waste, requiring proper treatment to avoid air and water pollution. Conventional waste management technologies, such as lagoon and spray field systems, do not prevent air and water pollution impacts. Research for the past few decades led to recommendations for waste treatment technologies superior to lagoons and spray fields. Private environmental sustainability initiatives focused on reducing greenhouse gas emissions in the food supply chain have implemented biogas digester projects for capturing methane in covered swine lagoons to reduce greenhouse gas emissions. However, research indicates that methane capture alone does not solve the broader pollution issues associated with lagoon and spray field systems still in use at these CAFOs to dispose of digested effluents. The Environmentally Superior Technologies (EST) initiative in North Carolina set public standards to eliminate waste discharge, reduce atmospheric emissions, and control odors and pathogens. Research has confirmed that technologies coupling solids separation with water treatments to remove volatile organic carbon, pathogens, and reactive forms of nitrogen can meet EST standards. A designated EST—the Super Soil System—substantially reduced odor by 99.9%; pathogens by 99.99%, nutrients (phosphorus and nitrogen) by >90%, and heavy metals (cooper and zinc) by 99%. The ammonia emissions were reduced by 94.4% for the warm and 99.0% for the cool season with respect to a conventional lagoon system. Corresponding greenhouse gas emission reductions were 96.7%. Components of designated EST can be applied to retrofit covered lagoons and anaerobic digestion systems with significant environmental benefits. Recommendations are proposed, based on the collective experience with EST and current trends in animal production concentration, for environmentally safe technologies to handle excess manure produced in the USA.

Deciphering the microbial interactions and metabolic shifts at different COD/sulfate ratios in electro-assisted anaerobic digestion

This research aims to investigate the influence of sulfate on the performance of microbial electrolysis cell-assisted anaerobic digester (MEC-AD) across varying sulfate conditions, including no sulfate and reduced COD/sulfate ratios from 20 to 1. The principal results indicate a gradual decline in methane yield in the MEC-AD from 78.7 ± 2.3 % under no sulfate conditions to 56.2 ± 2.0 % at a COD/sulfate ratio of 1, contrasting with a more substantial decrease in the control reactor (69.9 ± 3.6 % to 32.8 ± 1.5 %). The MEC-AD reactor exhibits heightened resilience to sulfide toxicity, showcasing higher specific methanogenic activities. Key findings suggest that the MEC-AD reactor maintains lower free sulfide concentrations, attributed to its higher pH and potential anodic sulfide oxidation. Additionally, the study reveals the promotion of syntrophic partnerships in the MEC-AD reactor, particularly between sulfate-reducing bacteria (SRB) such as Desulfovibrio, Desulfomicrobium, and Desulfobulbus, and other microbial groups, including hydrogenotrophic methanogens and electroactive bacteria. The integration of these mechanisms highlights the MEC-AD reactor's ability to effectively mitigate sulfate-induced challenges and enhance overall anaerobic digestion performance. This study presents a significant step forward in the development of resilient anaerobic digestion systems capable of efficiently handling sulfate stress.