Search Results (503)

Anaerobic digestion (AD) is a proven and promising technology for recovering energy from biowastes, such as pig slurry (PS) from the fattening/finishing phase. The mechanisms of AD are widely studied, and nowadays, it is of the utmost importance to investigate strategies that give end-users the confidence to choose this technology and to adapt it to their reality, promoting the energy transition and circular economy. This study investigated how collection and storage period affect PS samples, and how hydraulic retention time (HRT) (15 versus 20 days) influences AD performance and stability. Seasonality was the primary factor influencing feedstock characteristics. Samples presented no significant differences during the storage period. A 20-day HRT led to higher digestate pH, total ammonia nitrogen (TAN), and free ammonia nitrogen (FAN) concentrations, which can cause process instability and methanogenesis inhibition. However, 20-day HRT led to a specific methane production that was 7% higher and to a methane quality (expressed in % v/v CH₄) that was 6% higher than 15-day HRT. Overall, methane quality, digestate pH, TAN, and FAN values may be considered key points that need to be monitored to prevent the AD system from being compromised. Nevertheless, these results provide the operational freedom to choose either HRT, allowing reduced reactor volume and investment. Full article

Anaerobic digestion (AD) of ensiled orange peel waste (OPW) offers a promising pathway for the valorisation of citrus-processing residues and the generation of renewable energy. This study evaluated the impact of two carbon-based materials, biochar and granular activated carbon (GAC), on methane yield and process stability using Biochemical Methane Potential (BMP) tests. The experimental setup consisted of two consecutive cycles, the second of which was designed to examine microbial acclimation by reusing both the digestate (as the inoculum) and the previously added carbon materials. Ensiled OPW exhibited a methane yield of 578 ± 59 mL_CH4/g_VS during the initial cycle, confirming its high biodegradability. The addition of biochar and GAC resulted in comparable yields (approximately 520–560 mL_CH4/g_VS) and did not enhance the ultimate methane potential; however, both additives proved fully compatible with the process. In the subsequent cycle, a marked increase in methane production was observed, with OPW reaching approximately 730 mL_CH4/g_VS, primarily attributed to improved microbial adaptation. Kinetic analysis revealed moderate enhancements in degradation rates, which were more pronounced when higher biochar dosages were used. Overall, ensiled OPW emerges as a highly suitable substrate for AD. At the same time, biochar and GAC did not adversely affect the AD process under the tested conditions; however, their potential benefits have yet to be fully demonstrated and warrant further investigation, particularly under continuous reactor operating conditions. Full article

Reductive soil disinfestation (RSD) is a promising strategy for mitigating soil degradation and enhancing soil health. While soil organic carbon (SOC) is crucial for soil fertility and climate regulation, the mechanisms underlying its stabilization via plant lignin and microbial humus in the RSD process remain elusive. Using a microcosm experiment, we investigated SOC dynamics by quantifying plant-derived (lignin phenols) and microbial-derived (amino sugars) C during RSD at key stages: initial (2 h), anaerobic (14 and 28 days), and aerobic (35 days). Concurrently, soil properties, microbial PLFA, and enzymatic activity were analyzed to elucidate underlying mechanisms. Over the initial 14 days, plant-derived C increased sharply by 61% before declining, yet still showed a 22% increase by the end of the RSD (35 days), a trend mirrored by bacterial-derived C. In contrast, fungal-derived C initially accumulated rapidly with a significant increase of 43%, then stabilized, and its proportion (21.63%) surpassed that of bacterial-derived C (5.56%). Over time, plant- (25.01% to 19.76%) and bacterial-derived C (7.81% to 5.56%) contributions to decreases in SOC, while fungal-derived C (about 21%) remained stable after day 14. This pattern is likely attributable to the initial anaerobic conditions, which caused a massive die-off of fungi and aerobic bacteria that utilize lignin and necromass, resulting in significant accumulation of both plant- and microbial-derived C. Subsequently, the proliferation of anaerobic bacteria consumed these plant- and bacterial-derived C sources in the soil, leading to their eventual decline. Key drivers of plant-derived C included soil pH, living fungi/bacteria, and β-1,4-glucosidase activity, whereas microbial-derived C depended on total nitrogen and living fungi. Our findings demonstrate that early SOC accumulation under RSD is driven by combined plant lignin and microbial necromass inputs, while fungal necromass becomes pivotal for long-term SOC stabilization, shaped by both abiotic and biotic factors. Full article

The sustainable management of brewer’s spent grain (BSG) is critical for advancing circular bioeconomy strategies in the brewing industry; however, its efficient conversion to bioenergy remains limited by lignocellulosic recalcitrance. In this study, subcritical water hydrolysis (SWH) is systematically evaluated under mild conditions as an environmentally friendly pretreatment to simultaneously enhance the solubilization of carbohydrates and proteins and improve the anaerobic digestion (AD) performance of BSG. Under relatively low-severity conditions (130 °C, 15 MPa), SWH promoted extensive depolymerization of BSG, releasing up to 146 mg g⁻¹ of total reducing sugars and 18 mg albumin g⁻¹ of soluble proteins, while generating organic acids that influenced hydrolysate pH. Unlike previous studies that primarily focused on solid BSG digestion or high-severity pretreatments, this work directly compares the biomethane potential of SWH-derived hydrolysate and solid BSG under controlled BMP assays. The hydrolysate supported stable microbial activity and efficient degradation of volatile fatty acids, achieving a maximum methane yield of 712 L CH₄ kg⁻¹ TVS, significantly exceeding the yield obtained at 12.5% solid BSG loading (469 L CH₄ kg⁻¹ TVS). These results demonstrate that mild SWH substantially enhances BSG biodegradability and methane recovery while revealing critical trade-offs between organic loading, conversion efficiency, and process stability. Overall, this study provides new process-level insights into the integrated use of SWH and AD for BSG valorization, positioning SWH as a scalable, low-chemical, and sustainable pretreatment strategy for maximizing renewable biogas production from agro-industrial residues. Full article

The global output of organic solid residues (e.g., crop straw) is substantial, creating an urgent sustainability need for low-impact pathways that avoid open burning or disposal while recovering renewable energy. Dry anaerobic digestion (AD) offers a water-saving, high-solids valorization route for straw-rich substrates, but its deployment is often constrained by acidification that suppresses methanogenesis, reducing reliability and limiting practical adoption. Here, at laboratory scale, we formulated a co-digestion substrate dominated by wheat straw (50%) with swine manure and household organic waste, and evaluated whether co-supplementation of trace metals (Fe, Ni, Co) can enhance process stability and energy recovery, thereby strengthening the sustainability of high-solids straw treatment. System performance was assessed by pH, biogas production, volatile fatty acids (VFAs), functional genes, and microbial community profiles to elucidate micronutrient effects and microbial responses. Micronutrient addition stabilized pH (minimum 6.5) and enhanced biogas output. Specific yields in the supplemented digester were 260.64 ± 11.83 mL g⁻¹ TS and 319.89 ± 14.27 mL g⁻¹ VS, compared with 220.31 ± 9.45 mL g⁻¹ TS and 270.33 ± 11.72 mL g⁻¹ VS in the control; cumulative gas production was higher by 18.33%. Community analyses showed marked enrichment of Methanosarcina, increasing from 7.28% on day 10 to 44.00% on day 30. Molecular ecological network analysis indicated a transition from a sparse, fragmented configuration to a highly connected, centralized one: the number of nodes decreased from 74 to 70; the number of edges increased from 46 to 223 (a 4.85-fold rise); network density increased from 0.0170 to 0.0923; mean degree increased from 1.24 to 6.37; the number of modules declined from 39 to 5; and the proportion of positive versus negative links shifted from 85%/15% to 70%/30%, evidencing stronger interspecies coupling and functional robustness. Consistently, methyl-coenzyme reductase subunit A gene copy numbers were about 1.60-fold higher on day 30 and about 1.51-fold higher on day 50 than in the control. Overall, Fe-Ni-Co co-supplementation enhances methane potential and suppresses acidification in straw-rich dry anaerobic digestion, providing a low-input and practical strategy to stabilize high-solids systems. By improving microbial robustness, this approach enables efficient renewable energy recovery with reduced water demand and lower risk of process failure, thereby supporting scalable straw valorization and advancing circular bioeconomy pathways for agricultural and organic solid residues. Full article

The increasing atmospheric concentration of carbon dioxide (CO₂) poses a critical threat to global climate stability, highlighting the need for efficient carbon capture technologies. While amine-based solvents such as monoethanolamine (MEA) are widely used for industrial CO₂ capture, they are subject to limitations such as high energy requirements for regeneration, solvent degradation, and environmental concerns. This study investigates potassium carbonate/bicarbonate system as an alternative solution for CO₂ absorption. The absorption mechanism and reaction kinetics of potassium carbonate in the presence of bicarbonates were reviewed. A rate-based model was developed in Aspen Plus, using literature kinetics, to simulate CO₂ absorption using 20 wt% potassium carbonate (K₂CO₃) solution with 10% carbonate-to-bicarbonate conversion under different industrial conditions. Three flue gas compositions were evaluated: cement industry, biomass combustion, and anaerobic digestion, each at 3000 m³/h flow rate. The simulation was conducted to determine minimum column height and solvent loading requirements with a target output of 90% CO₂ removal from the gas streams. Results demonstrated that potassium carbonate systems successfully achieved the target removal efficiency across all scenarios. Column heights ranged from 18 to 25 m, with molar K₂CO₃/CO₂ ratios between 1.41 and 4.00. The biomass combustion scenario proved most favorable due to lower CO₂ concentration and effective heat integration. While requiring higher column heights (18–25 m) compared to MEA systems (6–12 m) and greater solvent mass flow rates, potassium carbonate demonstrated technical feasibility for CO₂ capture. The findings of this study provide a foundation for technoeconomic evaluation of potassium carbonate systems versus amine-based technologies for industrial carbon capture applications. Full article

Coronary artery bypass grafting (CABG) remains the gold standard for patients with advanced multivessel coronary artery disease. Optimal myocardial protection versus ischemia during reversible and controlled cardiac arrest is a cornerstone of successful outcomes. Myocardial ischemia represents a state of reduced coronary perfusion with oxygenated blood, insufficient to meet the metabolic demands of the myocardium. Conventional cardioplegic solutions offer controlled and reversible cardiac arrest while actively modulating the molecular and cellular mechanisms that mediate ischemia–reperfusion injury. Cardioplegia dramatically elongates the reversible period of ischemic injury and restricts cardiomyocyte death by shutting down electromechanical activity, lowering metabolic demand, stabilizing ionic homeostasis, protecting mitochondrial integrity, and slowing oxidative stress and inflammatory signaling. During ischemia, cardiomyocytes shift from aerobic to anaerobic metabolism, resulting in adenosine triphosphate (ATP) depletion, loss of ionic homeostasis and calcium overload that activate proteases, phospholipases and membrane damage. Reperfusion restores oxygen supply and prevents irreversible necrosis but paradoxically initiates additional injury in marginally viable myocardium. The reoxygenation phase induces excessive production of reactive oxygen species (ROS), endothelial dysfunction and a strong inflammatory response mediated by neutrophils, platelets and cytokines. Mitochondrial dysfunction and opening of the mitochondrial permeability transition pore (mPTP) further amplify oxidative stress and inflammation, and trigger apoptosis and necroptosis. Understanding these intertwined cellular and molecular mechanisms remains essential for identifying novel therapeutic targets aimed at reducing reperfusion injury and improving myocardial recovery after ischemic events, particularly in coronary surgery. Full article

Silage is a core roughage resource for ruminant production, but aerobic deterioration caused by microorganisms severely reduces its nutritional value and increases microbial risk. This study aimed to isolate and identify specific spoilage organisms (SSOs) from Napier grass silages during aerobic deterioration and evaluate their spoilage capability. Based on morphological observation, physiological and biochemical tests, and ITS rDNA sequence analysis, four SSOs were obtained as Trichosporon asahii (TA32), Nakaseomyces glabratus (NG38), Candida tropicalis (CT39), and Pichia kudriavzevii (PK41) with high lactate-assimilating and spoilage capacity. All four strains were facultative anaerobic yeast and exhibited robust growth within the range of 25–40 °C and pH 3.5–6.5. To verify their spoilage capability, these purified strains were inoculated into Napier grass silage and exposed to air. Fermentation and chemical parameters were monitored at 0, 2, 5, and 9 days. Results showed that silages inoculated with PK41 or TA32 exhibited the lowest aerobic stability with most rapid increase in pH (p < 0.05), while the control (CON) remained the highest aerobic stability (p < 0.05). These results provide a theoretical basis for developing targeted preservation technologies to extend the shelf-life of silage. Full article

Non-invasive acidic pretreatments using acetic acid (1–5 mM) and citric acid (0.02–0.1 g g⁻¹ TS) were investigated to enhance anaerobic digestion (AD) of waste-activated sludge (WAS). Both pretreatments improved short-term process stability, with pH (6.5–7.1) and alkalinity (1000–5000 mg CaCO₃ L⁻¹) remaining within optimal ranges during 10-day digestion. Acetic acid markedly enhanced solubilization and acidification, increasing volatile fatty acids to ~2500 mg L⁻¹ (+67% vs. control), whereas citric acid achieved ~2000 mg L⁻¹ (+37%). EPS analysis revealed pronounced redistribution of polysaccharides and proteins, with acetic acid inducing stronger disruption of the EPS matrix (SB-EPS polysaccharides up to 34.1 mg eq Glc mL⁻¹). Specific methane yield increased from 28.5 mL CH₄ g⁻¹ VS (control) to 101.7 mL CH₄ g⁻¹ VS with acetic acid (3.6-fold) and to 73.8 mL CH₄ g⁻¹ VS with citric acid (2.5-fold). Gompertz modeling confirmed higher maximum methane potential, ~68% higher maximum methane production rates, and reduced lag phases for both pretreatments. In contrast, pharmaceutical concentrations (31 compounds) were largely unaffected by acid pretreatment, with significant reductions observed only for selected biodegradable molecules. Full article

The untreated discharge of dairy industry wastewater, characterized by high organic and nutrient loads, poses a severe eutrophication threat, leading to oxygen depletion and the disruption of aquatic ecosystems, which necessitates advanced treatment strategies. Anaerobic digestion (AD) represents an effective and sustainable alternative, converting organic matter into biogas while minimizing sludge production and contributing to Circular Economy strategies. This study investigated the effects of fat concentration and operational temperature on the anaerobic digestion of dairy effluents. Three types of effluents, skimmed, semi-skimmed, and whole substrates, were evaluated under mesophilic 35 °C and thermophilic 55 °C conditions to degrade substrates with different fat content. Low-fat effluents exhibited higher COD removal, shorter lag phases, and stable activity under mesophilic conditions, while high-fat substrates delayed start-up due to accumulation of fatty acids and brief methanogen inhibition. Thermophilic digestion accelerated hydrolysis and methane production but demonstrated increased sensitivity to lipid-induced inhibition. Kinetic modeling confirmed that the modified Gompertz model accurately described mesophilic digestion with rapid microbial adaptation, while the Cone model better captured thermophilic, hydrolysis-limited kinetics. The thermophilic operation significantly enhanced methane productivity, yielding 105–191 mL CH₄ g⁻¹VS compared to 54–70 mL CH₄ g⁻¹VS under mesophilic conditions by increasing apparent hydrolysis rates and reducing lag phases. However, the mesophilic process demonstrated superior operational stability and robustness during start-up with fat-rich effluents, which otherwise suffered delayed methane formation due to lipid hydrolysis and volatile fatty acid (VFA) inhibition. Overall, the synergistic interaction between temperature and fat concentration revealed a trade-off between methane productivity and process stability, with thermophilic digestion increasing methane yields up to 191 mL CH₄ g⁻¹ VS but reducing COD removal and robustness during start-up, whereas mesophilic operation ensured more stable performance despite lower methane yields. Full article

Background: Aggregatibacter actinomycetemcomitans is a Gram-negative, facultative anaerobic, immobile oral bacterium responsible for the secretion of virulence factors, namely leukotoxin (LtxA), a large exotoxin of the RTX family that enables the bacterium to evade the immune system by destroying leukocytes, resulting in aggressive periodontitis (AP) leading to tooth loss. Methods: This study aimed to screen 106 molecules derived from Moroccan propolis in order to identify potential inhibitors of the active sites of LtxA based on molecular docking, ADMET property evaluation, and molecular dynamics (MD) simulation. Results: Epigallocatechin gallate (EGCg), used as a reference compound, showed binding energies of −6.9 kcal/mol, −6.1 kcal/mol, −6.5 kcal/mol, and −5.9 kcal/mol with the four active sites P1, P2, P3, and P4, respectively. By establishing conventional hydrogen bonds, pi-alkyl bonds, and non-covalent pi–pi bonds. Chrysin and luteolin showed favorable binding affinities with the four active sites, named as follows: P1–P4 (P1–chrysin = −7.5 kcal/mol; P2–chrysin = −7.9 kcal/mol; P3–chrysin = −8.1 kcal/mol; P4–chrysin = −6.9 kcal/mol; P1–luteolin = −7.3 kcal/mol; P2–luteolin = −7.6 kcal/mol; P3–luteolin = −8.1 kcal/mol; P4–luteolin = −7.3 kcal/mol). The binding affinity of these two propolis derivatives was stabilized by pi−sigma bonds, pi−alkyl bonds, conventional hydrogen bonds, pi-cation interactions, non-covalent pi–pi bonds, and carbon–hydrogen bonds. According to free energy calculations performed with Prime MM-GBSA, the complexes formed by chrysin demonstrated the most stable interactions due to Van der Waals and lipophilic forces. Luteolin formed significant interactions, but slightly weaker than those of chrysin. These results reveal the inhibitory potential of chrysin and luteolin with protein active sites. MD simulations corroborated the excellent stability of complexes formed by chrysin, as indicated by low RMSD values, suggesting favorable dynamic behavior. Conclusions: These results highlight the potential of chrysin as a versatile inhibitor capable of interacting with the four active sites. These findings are a strong foundation for further experimental confirmations. Full article

Tuna-processing facilities produce substantial amounts of concentrated organic residues and sludges containing high levels of proteins, lipids, and nitrogen, which are not easily handled by conventional waste treatment methods. In this work, the anaerobic digestion (AD) performance of tuna-processing by-products (TPB1–2) and associated wastewater sludges (TWS1–3) was investigated using a combination of biochemical methane potential (BMP) tests, theoretical methane yield calculations based on the Buswell–Boyle equation, semi-continuous mono-digestion experiments, and 16S rRNA gene-based microbial analyses. Among the evaluated materials, TWS2 produced the highest methane yield (554.6 N mL CH₄/g VS) and, when its annual production volume was taken into account, showed the greatest estimated energy recovery (approximately 1.88 × 10⁶ kWh per year). By contrast, TWS3 exhibited the lowest methane yield (239.8 N mL CH₄/g VS), which was attributed to the presence of lignocellulosic sawdust and its limited biodegradability. TWS1 showed a moderate level of performance, with an estimated biodegradability of 62.3%, which may have been influenced by the addition of ferric salts and polymeric coagulants during sludge conditioning. In the semi-continuous digestion experiments, reactors that were initiated under relatively high total ammonia nitrogen (TAN) concentrations achieved stable operation within a shorter period, with the acclimation phase reduced by approximately one hydraulic retention time. These trends were supported by the microbial community data, where an increase in Bacillota-associated families, such as Tissierellaceae and Streptococcaceae, was detected along with a clear shift in dominant methanogens from Methanothrix to the more ammonia-tolerant Methanosarcina. Taken together, it is suggested that, when ammonia levels are appropriately managed, mono-digestion of tuna-processing sludges can be operated at a moderate organic loading rate. The process stabilization and energy recovery in nitrogen-rich industrial wastes are closely linked to gradual microbial adaptation rather than immediate improvements in methane yield. Full article

In light of the persistently mounting pressure on urban and rural waste management, developing efficient, low-carbon, and resource-oriented waste treatment technologies represents a critical challenge demanding urgent breakthroughs. Thermophilic anaerobic digestion (TAD), possessing these advantages, demonstrates unique application prospects in food waste treatment. However, its inherent instability constrains its engineering-scale implementation. This paper systematically reviews existing laboratory and pilot-scale research, focusing on: (1) Thecomplex interactions and synergistic effects of primary inhibitory factors; (2) The dynamic characteristics of microbial communities and their adaptive restructuring mechanisms under thermophilic stress; (3) The efficacy and underlying mechanisms of co-digestion, process control, and two-phase system strategies. This study aims to establish a clear pathway from mechanistic understanding to engineering optimisation, providing a theoretical framework for enhancing the operational stability and scalability of the TAD process. Full article

The global floriculture industry generates massive organic residues that pose environmental risks but offer untapped bioenergy potential. This review evaluates the feasibility of valorizing flower waste through anaerobic digestion (AD) by synthesizing experimental data on substrate characterization, pretreatment efficacy, and reactor performance. Results indicate that biochemical methane potentials (BMP) vary significantly, ranging from 89 to 412 mL_CH4·g⁻¹_VS, depending on plant species and tissue composition. Major bottlenecks include high lignocellulosic recalcitrance (lignin content up to 0.28 g·g⁻¹_TS) and the presence of inhibitory phenolic compounds. Analysis reveals that while alkaline pretreatments effectively disrupt lignocellulosic structures, co-digestion strategies are essential to mitigate inhibition and balance nutrient ratios. However, current research is predominantly limited to laboratory-scale batch assays, leaving a critical knowledge gap regarding long-term process stability and inhibition dynamics in continuous systems. To transform this laboratory concept into a scalable technology, future efforts must focus on pilot-scale continuous reactor trials, standardized testing protocols, and comprehensive techno-economic and life cycle assessments. Full article

Salinity shock severely impairs the partial denitrification/anammox (PD/A) process, leading to prolonged functional deterioration and slow reactivation of anaerobic ammonium-oxidizing bacteria (anammox). To develop an effective strategy for mitigating salinity-induced inhibition, this study systematically examined the role of exogenous hydroxylamine (NH₂OH) in accelerating PD/A recovery using short-term batch assays and long-term reactor operation. Hydroxylamine exhibited a clear concentration-dependent effect on system reactivation. In batch tests, low-dose hydroxylamine (10 mg/L) markedly enhanced anammox activity, increasing the ammonium oxidation rate to 5.5 mg N/(g VSS·h), representing a 42.5% increase, indicating its potential to stimulate key nitrogen-transforming pathways following salinity stress. During continuous operation, hydroxylamine at 5 mg/L proved optimal for restoring reactor performance, achieving stable nitrogen removal with 87% NH₄⁺-N removal efficiency. The nitrite transformation ratio (NTR) reached approximately 80% within 13 cycles, 46 cycles ahead of the control, while simultaneously promoting the enrichment of key functional microbial taxa, including Thauera and Candidatus Brocadia. Hydroxylamine addition also triggered the production of tyrosine- and tryptophan-like proteins within extracellular polymeric substances, which enhanced protective and metabolic functionality during recovery. In contrast, a higher hydroxylamine dosage (10 mg/L) resulted in persistent NO₂⁻-N accumulation, substantial suppression of Candidatus Brocadia (declining from 0.67% to 0.09%), and impaired system stability, highlighting a dose-sensitive threshold between stimulation and inhibition. Overall, this study demonstrates that controlled low-level hydroxylamine supplementation can effectively reactivate salinity-inhibited PD/A systems by enhancing nitrogen conversion, reshaping functional microbial communities, and reinforcing stress-response mechanisms. These findings provide mechanistic insight and practical guidance for improving the resilience and engineering application of PD/A processes treating saline wastewater. Full article