Search Results (60)

Volatile fatty acids (VFA) are valuable intermediates with growing demand in chemical, pharmaceutical, and environmental applications. Their sustainable production from organic waste is increasingly explored in the context of circular economy and biorefinery models. This study investigates the co-fermentation of waste-activated sludge (WAS) and the organic fraction of municipal solid waste (OFMSW) as a strategy for integrated VFA and biogas production. Semi-continuous experiments were carried out to assess the effect of the substrates ratio (WAS:OFMSW = 90:10 and 30:70), hydraulic retention time (HRT), and pH control (5, 9, no control) on VFA yield and composition. Results showed that higher OFMSW content and alkaline conditions favoured VFA production, with a maximum yield of 144.9 mgHAc·gVS⁻¹ at pH 9 and 70:30 ratio. Acetate dominated, while butyrate production peaked at 114.1 mgHBu·gVS⁻¹ under high sludge conditions. However, the addition of alkali required for pH control may lead to excessive accumulation of alkaline-earth metal ions, which can disrupt biological processes due to their potential toxicity. Anaerobic digestion of fermentation residues enhanced biomethane yields significantly (0.27 NL·gVS⁻¹ vs. 0.05 NL·gVS⁻¹ from raw sludge). The proposed process demonstrates potential for converting wastewater treatment plants into biorefineries, maximising resource recovery while reducing environmental impact. Full article

This study aimed to evaluate alkali-treated spent mushroom substrate (Pleurotus eryngii SMS) combined with condensed molasses solubles (CMS) as an alternative forage source for ruminants via in vitro fermentation. Pleurotus eryngii SMS was treated with different chemicals, including NaOH (at 5% in DM of SMS), H₂O₂ (at 3.5% in DM of SMS), and AHP (at 5% NaOH + 3.5% H₂O₂ in DM of SMS) to improve its fiber structure and digestibility. The NaOH and AHP treatments significantly increased the total gas production and volatile fatty acid (VFA) concentration and improved digestibility by about 1.5 to 1.8 times. CMS supplementation led to a 21% increase in microbial protein (MCP) synthesis in the NaOH treatment group. A replacement experiment involving a total mixed-ration diet indicated that CMS supplementation increased gas production while reducing dry matter digestibility in the NaOH treatment group. The AHP treatment group performed best at all substitution rates, particularly in digestibility and MCP synthesis. These results suggest that alkali treatment and CMS could improve the nutrient utilization efficiency of Pleurotus eryngii SMS, providing a feasible solution for the resource utilization of agricultural waste. Full article

This study investigates the effects of NaOH pretreatment on the microstructural distribution and biomethane released from Xyris capensis. Xyris capensis was pretreated with NaOH using 1, 2, 3, 4, and 5% w/w concentrations for 60, 45, 30, 20, and 15 min of exposure time, respectively, at a 90 °C autoclave temperature. The impacts of the pretreatment technique on microstructural arrangement, crystallinity, and functional groups were examined with a scanning electron microscope (SEM), X-ray diffraction, and Fourier transform infrared (FTIR), respectively. NaOH-pretreated and untreated feedstocks were digested at the laboratory scale at a mesophilic temperature (37 ± 2 °C) for 35 days for their biomethane potential. It was discovered from the SEM analysis that NaOH pretreatment affects the microstructural arrangement of Xyris capensis, and the sample with the longer exposure time is the most affected. The results of XRD and FTIR also indicated that NaOH pretreatment lowered the crystallinity of the feedstock and significantly influenced the functional groups at varying degrees. Biomethane yield was recorded to be 258.68, 287.80, 304.02, 328.20, 310.20, and 135.06 mL CH₄/gVS_added, representing 91.53, 113.09, 125.10, 143.00, and 129.68% more increases than the untreated feedstock. It was discovered that the optimum biomethane generation was achieved when 4% w/w of NaOH concentration was utilized for 20 min. This study shows that a higher NaOH concentration with a shorter retention time is more suitable for Xyris capensis. This pretreatment method can improve the biomethane yield of Xyris capensis and can be investigated for industrial applications and its use on other lignocellulose feedstocks, especially energy grasses. Full article

Mitigating the irreversible consequences of climate change necessitates the application of sustainable energy resources. Hereby, we investigated the biological anaerobic fermentation of Azolla filiculoides biomass for biohydrogen production as a clean renewable energy source. Azolla filiculoides is a widely growing aquatic plant in polluted freshwater streams. However, the high non-biodegradable organic matter content in Azolla filiculoides biomass remains challenging in efficiently producing renewable energy, especially when it is being used as the sole donor substrate. In order to overcome this challenge, different pretreatment scenarios (namely, alkali, autoclaving, and ultrasonication) have been employed for enhancing the hydrolysis of Azolla filiculoides biomass to maximize the anaerobic fermentation and, consequently, the biohydrogen production potential. The biohydrogen production potential was 250.5, 398, 414.5, and 439.5 mL-H₂, giving a hydrogen yield of 60.1, 89.6, 92.9, and 107.9 mL-H₂/g-VS, respectively. Gompertz kinetics were applied to estimate the growth parameters of the process, which revealed a good fit with R² ranging from 0.96 to 0.98. The produced digestate was valorized for biochar production, a material that could be applied for water treatment purposes. The produced biochar was characterized using different physical analyses, including FTIR, SEM, EDX, and TEM. The physicochemical characterizations of biochar demonstrate a successful formation of biochar with a highly porous structure and a rough surface, as evidenced by the emergence of significant functional groups (e.g., O-H, C-H, C=C, and C=O) existing on the surface of the biochar. In conclusion, this study harnesses a sustainable approach for the treatment of organic waste streams, which represents a circular economy model by transforming waste materials into valuable products and reducing the reliance on non-renewable resources. Full article

Different fertilization measures affect the soil’s physical and chemical properties and bacterial community structure, which in turn affects the growth environment and yield of maize seed production. Therefore, rational fertilization measures are important in maintaining and improving soil fertility and promoting maize crop growth. Research on fertilization practices in maize fields for seed production can help to increase agricultural productivity while protecting and enhancing soil health and achieving sustainable agricultural development. To clarify the effects of different fertilization measures on soil bacterial communities in seed corn fields, 16S rRNA high-throughput sequencing technology and PICRUSt method were used to explore the soil under different fertilization measures (CK as control, effects of single application of liquid organic fertilizer (M), single application of bacterial agents (BF), and combined application of liquid organic fertilizer and bacterial agents (M + BF)) on soil bacterial community structure characteristics and ecological functions. Proteobacteria (20.14–25.30%), Actinobacteriota (18.21–20.47%), Actinobacteriota (13.55–22.00%), and Chloroflexi (14.24–17.59%) were the dominant phyla. Bacillus, RB41, Arthrobacter, and Sphingomonas were the dominant genera. M + BF treatment significantly increased the relative abundance of Planctomycetota. The relative abundance of Bacillus and PaeniBacillus in M treatment decreased considerably, while the relative abundance of Turicibacter increased significantly. The relative abundance of Sphingomonas was reduced considerably in M and M + BF treatments. The relative abundance of Subgroup 10 decreased significantly after BF and M + BF treatments. BF treatment significantly increased the relative abundance of Skermanella. Redundancy analysis showed that alkali-hydrolyzed nitrogen (p = 0.044) was the main environmental factor affecting soil bacterial communities under different fertilizer treatments. PICRUSt function prediction results showed that metabolism was the main functional component of bacteria, accounting for 78.45–78.94%. The abundance of functional genes for terpenoid and polyketone metabolism, the endocrine system, the excretory system, and the immune system of the soil bacterial community was significantly increased under M treatment, while the abundance of functional genes for the digestive system was decreased considerably. Different fertilizer cultivation measures changed soil bacterial community composition and ecological function in maize fields. These results can provide a theoretical reference for the study of bacterial community succession characteristics in maize fields and the determination of appropriate fertilizer cultivation measures. Full article

Marginal lands have been proposed to produce non-food crop biomass for energy or green materials. For this purpose, the selection, implementation, and growth optimization of plant species on such lands are key elements to investigate to achieve relevant plant yields. Stinging nettle (Urtica dioica) is a herbaceous perennial that grows spontaneously on contaminated lands and was described as suitable to produce fibers for material applications. Two mercury-contaminated soils from industrial wastelands with different properties (grassland soil and sediment landfill) were used in this study to assess the potential growth of stinging nettle in a greenhouse mesocosm experiment. Two organic amendments were studied for their impact on nettle growth. The solid digestate from organic food wastes significantly doubled plant biomass whereas the compost from green wastes had a lower impact. The highest doses of organic amendments significantly increased the number of fibers, which doubled following digestate application, while reducing leaf Hg concentration. Both amendments significantly improved soil respiration and enzymatic activities linked to the microbial biomass in the soil from the sediment landfill by the end of the experiment. In the context of a phytomanagement scenario, solid digestate would be a preferred amendment resource to improve nettle production on industrial wastelands. Full article

Our preliminary study identified dairy cow placenta extract (CPE) as a mixture of peptides with potent antioxidant activity both in vivo and in vitro. However, the specific antioxidant peptides (AOPs) responsible for this activity were not yet identified. In the current study, we employed virtual screening and chromatography techniques to isolate two peptides, ANNGKQWAEVF (CP1) and QPGLPGPAG (CP2), from CPE. These peptides were found to be less stable under extreme conditions such as high temperature, strong acid, strong alkali, and simulated digestive conditions. Nevertheless, under normal physiological conditions, both CP1 and CP2 exhibited significant antioxidant properties, including free-radical scavenging, metal chelating, and the inhibition of lipid peroxidation. They also up-regulated the activities of intracellular antioxidant enzymes in response to hydrogen-peroxide-induced oxidative stress, resulting in reduced MDA levels, a decreased expression of the Keap1 gene and protein, and increased levels of the Nrf2 and HO-1 genes and proteins. Furthermore, CP1 demonstrated superior antioxidant activity compared to CP2. These findings suggest that CP1 and CP2 hold potential for mitigating oxidative stress in vitro and highlight the efficacy of virtual screening as a method for isolating AOPs within CPE. Full article

Concentrating organic matter in sludge and converting it into methane through anaerobic bioconversion can improve resource recovery from domestic wastewater. Enhanced membrane coagulation (EMC) is highly efficient at concentrating organic matter, but residual coagulants (aluminum salts) can obstruct bioconversion by blocking microbial access. Limited research exists on evaluating EMC sludge bioconversion performance and addressing coagulant inhibition. This study proposes alkaline pre-fermentation to break down HO-Al-P backbones in coagulated sludge flocs, thereby improving hydrolysis and organic acid production for anaerobic digestion. Among the tested alkaline conditions (pH 9, pH 10, pH 11), pre-fermentation at pH 11 released the most organic matter (4710.0 mg/L SCOD), 20.4 times higher than without alkaline treatment. At pH 11, phosphate (61 mg/L PO₄³⁻–P) and organic acid production (2728.1 mg COD/L, with nearly 50% acetic acid) peaked, resulting in superior volatile solids removal (65.2%) and methane production (185.8 mL/g VS) during anaerobic digestion. Alkaline pre-fermentation favored alkali-tolerant bacteria such as Firmicutes and Actinobacteria, especially at pH 11, while neutrophilic Proteobacteria were suppressed. Trichococcus and Bifidobacterium, known acid producers, dominated under all conditions, with their abundance increasing at higher pH levels. Anaerobic digestion enriched fermentative bacteria like Chloroflexi and Synergistota (e.g., Thermovirga), especially in high pH reactors. Methanothrix, an acetoclastic methanogen, became the dominant methanogenic archaeon, indicating that methane production from EMC sludge primarily followed the acetoclastic methanogenesis pathway. Our findings demonstrate that alkaline pre-fermentation at pH 11 significantly enhances the hydrolysis efficiency of EMC sludge for methane recovery. Full article

Green and sustainable economies have recently become a key issue in long-term growth and well-being. Co-digestion of various waste materials in an eco-friendly way through biogas production has become the preferred method for their utilization and valorization. The possibility of hydrogen and methane yield maximization depends on the most suitable alkali reagent for pretreatment of waste lignocellulosic material, which was revealed in batch tests to determine the hydrogen production potential. The mixture for digestion consisted of pretreated wheat straw mixed with waste algal biomass in a ratio of 80:20 (w/w). The maximum hydrogen yield was achieved after applying sodium hydroxide thermoalkaline pretreatment, with a two-fold higher yield than the untreated control. Hydrogen production was stable and methane was not present in the resultant gas. The influence of the hydraulic retention time (HRT) on the maintenance of cascade installation was studied. The maximum daily concentration of hydrogen was achieved at an HRT of 2 days—42.5% H₂—and the maximum concentration of methane was 56.1% at an HRT of 6 days. Accumulation of volatile fatty acids was registered in the first step and their depletion was noted in the second one. The obtained values of the cellulose content demonstrated that it was utilized by up to 2.75% in the methanogenic bioreactor at the end of the process. Metagenomics analyses revealed the bacteria Thermocaproicibacter melissae (44.9%) and Clostridium cellulosi (41.9%) participated in the consortium, accomplishing substrate hydrolysis and acidogenesis in the first stage. Less in abundance were Thermoanaerobacterium butyriciformans, Calorimonas adulescens, Pseudomonas aeruginosa and Anaerocolumna chitinilytica. Methanogenesis was performed by an archaeon closely related to Bathyarchaeota (99.5%) and Methanobacterium formicicum. The most abundant bacterial strains in the methanogenic fermenter were Abyssalbus ytuae (30%), Proteiniphilum acetatigenes (26%) and Ruficoccus amylovorans (13%). Full article

Recent advances in the characterization of metasomatic iron and alkali-calcic (MIAC) systems with associated iron-oxide apatite (IOA) prospects and iron-oxide–copper–gold (IOCG) and metasomatic cobalt deposits of the Great Bear magmatic zone were used to determine if the geochemistry of glacial sediments can unveil pathfinder elements indicative of mineralization and associated alteration. Analysis of variance within bedrock lithogeochemical (n = 707 samples) and till geochemical datasets (n = 92 samples) are compared. Results show that Fe, Co, Ni, Cu, As, Mo, Bi, La, Th, U, and W were identified as potential vectoring elements in different fractions of till due to their anomalous concentrations down-ice of various mineralized outcrops within the study area. For instance, Fe, Co, Cu, and Mo were established as the most useful vectoring elements in the locally derived till (<2 km down-ice) near the Sue Dianne IOCG deposit, and Fe, Co, Ni, Cu, Mo, W, Bi, and U near the Fab IOCG prospect. At the Sue Dianne deposit, the ratios of near-total (4-acid digestion) versus partial (modified aqua regia digestion) concentrations in the silt + clay-sized till fraction (<0.063 mm) for both La and Th reflect the mineralization alteration signature and define a more consistent dispersal train from mineralization compared to element concentrations mapped alone. Additional testing in an area of continuous till cover near an isolated point source is recommended to further develop the elemental ratio method for exploration of MIAC systems. Full article

The extraction and utilization of sugars from readily available and cost-effective sewage sludge increases the economic potential of this residue, contributing to sustainable urban development. The work presented here presents a novel method in which sugars can be directly extracted from sewage sludge following an ultrasound + thermal–alkali pretreatment. The best results indicated that by subjecting the sludge to a 240 W ultrasound for 20 min, followed by alkali digestion using 6 mL of a 2 M NaOH solution at 48 °C for 60 min, it was possible to maximize the yield of crude sugar (34.22 wt.% dry) with the purity of crude sugar at 46.80%, reaching an extraction efficiency of 99.84%. Response surface methodology was used to optimize the crude sugar yields based on experimental data, reaching a value of 34.67 wt.% dry when employing an ultrasound exposure time of 12.5 min and 6 mL of the NaOH solution for a digestion time of 57.5 min; these results were considered consistent with the experimental data. Full article

Anaerobic co-digestion of waste wheat straw and horse manure in two steps was revealed as a promising option for renewable energy production in the form of hydrogen and methane. Addition of waste cooking oils, disposal of which could cause damage to health or the environment, as a third substrate for digestion, is suggested as an approach not only to help handle the increasing volume of food waste worldwide but also to improve process performance. In the present study, waste cooking oil, in a concentration of 5%, appeared to be a positive modulator of anaerobic digestion with the production of hydrogen and did not lead to inhibition of the hydrolysis phase. The overall efficiency of the two-stage anaerobic digestion of the mixture, which contains mainly lignocellulose waste, is positively dependent on thermochemical pretreatment with the alkali reagent (Ca(OH)₂), but elevated temperature (55 °C) and cooking oil addition revealed the opportunity to omit the pre-treatment step. Nevertheless, the overall energy production was lower due to the methane production step. However, the addition of waste cooking oils to the process in which lig-nocellulose is not pretreated (V3) led to an increase in the methane production and energy yield compared to V1. The anaerobic digestion of lignocellulosic waste is a complex process and comprises successive degradation pathways and syntrophic microbial associations’ activities, so the division in two reactors ensured suitable conditions for the microorganisms residing in each of them. In this study, along with the production of hydrogen and methane and the separation of the hydrolysis and methanogenesis stages, utilization of agriculture- and kitchen-generated wastes was realized in the context of waste-to-energy sustainable production methods. Full article

Pennycress (Thlaspi arvense L.) is an annual cover crop known for its exceptional cold tolerance and high oil and protein yields. Pennycress can be integrated into a corn–soybean rotation in the U.S. However, the utilization of pennycress biomass remains largely unexplored, including assessing compositional changes through its growth and organic matter digestibility. This study harvested pennycress at three growth stages, characterized the biomass for anaerobic digestion (AD), and tested the effects of concurrent alkali pretreatment and ensiling on the biomass methane yield. Results showed that the biomass harvested when the plants were undergoing senescence (“third-harvest”) had higher contents of acid detergent fiber, neutral detergent fiber, and lignin, while the biomass harvested when 80–90% of the pods were fully-sized (“second-harvest”) had the highest protein content. The AD experiments showed that the first-harvest biomass (90% of flowers opened) failed to produce biogas due to a drop in the pH and alkalinity, the second-harvest biomass was inhibited for methane production (45.74 ± 0.20 L/kg-VS), and the third-harvest biomass had a methane yield of 171.80 ± 4.82 L/kg-VS. After the alkali pretreatment and ensiling, a methane yield of 270.4 ± 3.10 L/kg-VS was obtained from the second-harvest biomass, representing a significant 4.5-fold increase (adjusted for the organic matter loss) relative to the untreated second-harvest biomass. Full article

Microplastic (MP) pollution is a serious global issue affecting freshwater systems, coastal regions, and oceans. These non-biodegradable materials have a detrimental impact on marine species and ecosystems, disrupting their feeding, breathing, and reproduction. In this study, 120 samples of two species of shrimp, Penaus monodon and Penaus indicus, from ten locations in the Negombo lagoon in Sri Lanka were analyzed. MPs were extracted from gastrointestinal tracts (GI) and gills (GL) by alkali digestion followed by vacuum filtering. Stereomicroscopy coupled with advanced micro-imaging and analysis software was employed for analyzing the isolated MPs. A total of 415 items were identified as MPs with an average of 8.29 ± 4.63 items per gram of GI and GL in Penaus monodon and 5.52 ± 3.78 items per gram of GI and GL in Penaus indicus. The majority of MPs identified were fibers (93%), and the remaining ones were fragments. Most of the MPs were >1000 μm, and the most prevalent color was blue (61%), followed by red (15%), black (9%), and others, comprising polystyrene, polyamide, polyester, polypropylene, and rayon, as revealed by FTIR spectroscopy. This study highlights the prevalence of MPs in shrimps harvested from the Negombo lagoon and displays missing baseline data before the effects of fragmented nurdles from the X-Press Pearl incident. Full article

Egypt faces significant challenges in managing its sewage sludge generated in large quantities from wastewater treatment plants. This study investigates the feasibility of utilizing sewage sludge as a renewable resource for hydrogen production through anaerobic digestion at the 100 L bioreactor level. Hydrogen is considered a promising alternative energy source due to its high energy content and environmental benefits. To optimize the microbial degradation process and maximize hydrogen production from sewage sludge, a specialized pretreatment is necessary. Various pretreatment methods have been applied to the sewage sludge, individually and in combination, to study the bio-hydrogen production from sewage sludge. The four methods of treatment were studied in batch assays as a pilot scale. Thermal pretreatment of sewage sludge significantly increases bio-hydrogen production yield compared to other sewage sludge pretreatment methods, producing the highest H₂ yield (6.48 LH₂/g VS). In general, the hydrogen yield of any type of pretreated inoculum was significantly higher than the untreated inoculum. At the same time, alkaline pretreatment improved the hydrogen yield (1.04 LH₂/g VS) more than acid pretreatment (0.74 LH₂/g VS), while the hydrogen yield for the combination of pretreatments (shock alkali pretreatment) was higher than both (1.73 LH₂/g VS), On the other hand, untreated sewage sludge (control) had almost no hydrogen yield (0.03 LH₂/g VS). The self-fermented anaerobic bioreactor improved sewage sludge utilization, increased bioenergy yields, and seems to be promising for treating complex wastes at this scale. Full article