Search Results (131)

This study aimed to evaluate the potential benefits of co-digesting rapeseed oil cake, a by-product of biodiesel production, with microalgal biomass. Anaerobic fermentation was carried out under mesophilic conditions using various doses of press residue as a co-substrate. The results demonstrate that the addition of rapeseed oil cake enhances biogas production. The highest biogas yield was achieved during co-digestion with 1 g VS·L⁻¹ of microalgal biomass and 0.5 g VS·L⁻¹ of rapeseed oil cake. The average methane content in the biogas was 62.42%. The average hydrogen sulfide concentration ranged from 400 to 700 ppm. The maximum energy yield of 3.76 kWh·kg⁻¹ DM was obtained from co-digesting microalgal and rapeseed oil cake biomass in a 2:1 ratio. Full article

The low efficiency of the microbial gasification of coal limits the application of bio-coal bed methane technology. The co-fermentation of coal and biomass provides a new approach for improving the degradation rate of coal. In this study, a co-fermentation system comprising five different coal orders with five microalgae was constructed in the laboratory, and the methanogenic characteristics of coal–algae co-fermentation and its microbiological mechanism were systematically investigated in terms of gas production, soluble organic matter, and microbial community characteristics. The results showed that the combination of lignite and Nannochloropsis exhibited optimal methane production, with a methane yield of 26.43 mL/g coal. Biogenic methane yields for lignite–Porphyra and anthracite–Porphyra were 23.43 mL and 21.28 mL, respectively, demonstrating the potential for algae to enhance gas production even in high-rank coals. pH monitoring revealed that algal species played a critical role in the acidification process. Dunaliella caused a continuous pH decrease, reaching 3.76 by day 30, while Nannochloropsis maintained a neutral pH of 6.95, optimizing the fermentation environment. Significant differences in soluble organic matter were observed between the lignite and anthracite fermentation systems, with lignite systems producing more volatile fatty acids, including acetic and butyric acids. Microbial community analysis revealed that Methanosarcina, an acetic acid-utilizing methanogen, was dominant in lignite and anthracite systems, while Syntrophomonas played a key role in lignite–Nannochloropsis co-fermentation. These findings provide valuable insights into optimizing coal microbial gasification and selecting appropriate algal species to enhance methane production efficiency. Full article

The aim of this study is an interdisciplinary assessment of the potential of cement pastes to permanently bind carbon dioxide (CO₂) under anaerobic digestion conditions, considering technological, microstructural, environmental, and economic aspects. The research focused on three types of Portland cement: CEM I 52.5N, CEM I 42.5R-1, and CEM I 42.5R-2, differing in phase composition and reactivity, which were evaluated in terms of their carbonation potential and resistance to chemically aggressive environments. The cement pastes were prepared with a water-to-cement ratio of 0.5 and subjected to 90-day exposure in two environments: a reference environment (tap water) and a fermentation environment (aqueous suspension of poultry manure simulating biogas reactor conditions). XRD, TG/DTA, SEM/EDS, and mercury intrusion porosimetry were applied to analyze CO₂ mineralization, phase changes, and microstructural evolution. XRD results revealed a significant increase in calcite content (e.g., for CEM I 52.5N from 5.9% to 41.1%) and the presence of vaterite (19.3%), indicating intense carbonation under organic conditions. TG/DTA analysis confirmed a reduction in portlandite and C-S-H phases, suggesting their transformation into stable carbonate forms. SEM observations and EDS analysis revealed well-developed calcite crystals and the dominance of Ca, C, and O, confirming effective CO₂ binding. In control samples, hydration products predominated without signs of mineralization. The highest sequestration potential was observed for CEM I 52.5N, while cements with higher C₃A content (e.g., CEM I 42.5R-2) exhibited lower chemical resistance. The results confirm that carbonation under fermentation conditions may serve as an effective tool for CO₂ emission management, contributing to improved durability of construction materials and generating measurable economic benefits in the context of climate policy and the EU ETS. The article highlights the need to integrate CO₂ sequestration technologies with emission management systems and life cycle assessment (LCA) of biogas infrastructure, supporting the transition toward a low-carbon economy. Full article

Bio-hydrogen and bio-methane co-production was a promising way to enhance the energy conversion efficiency, and enzyme loading and pH are key factors influencing anaerobic fermentation processes. Therefore, in this study, the co-production process of bio-hydrogen and bio-methane was evaluated based on the effect of enzyme loading (20%, 30%, and 40%) combined with initial pH (6.0, 7.0, 8.0, and 9.0). The results indicated that, compared with other conditions, 30% enzyme loading with an initial pH of 8.0 was more feasible for bio-hydrogen and bio-methane co-production from duckweed, achieving a bio-hydrogen yield of 114.56 mL/g total solid (TS) and a bio-methane yield of 260.32 mL/g TS. Under optimum condition, the energy conversion efficiency was 71.4%, which was 6-fold and 4.8-fold higher than that of the single bio-hydrogen production stage (pH 8, 40% and 10.2%) and single methane production stage (control group with 12.30%), respectively. Full article

Methane (CH₄) is the second largest greenhouse gas (GHG) after carbon dioxide (CO₂), and ruminant production is an important source of CH₄ emissions. Among the six types of livestock animal species that produce GHGs, cattle (including beef cattle and dairy cows) are responsible for 62% of livestock-produced GHGs. Compared to beef cattle, continuous lactation in dairy cows requires sustained energy intake to drive rumen fermentation and CH₄ production, making it a key mitigation target for balancing dairy production and environmental sustainability. Determining how to safely and efficiently reduce CH₄ emissions from dairy cows is essential to promote the sustainable development of animal husbandry and environmental friendliness and plays an important role in improving feed conversion, reducing environmental pollution, and improving the performance of dairy cows. Combined with the factors influencing CH₄ emissions from dairy cows and previous research reports, this paper reviews the research progress on reducing the enteric CH₄ emissions (EMEs) of dairy cows from the perspectives of the CH₄ generation mechanism and emission reduction strategies, and it summarizes various measures for CH₄ emission reduction in dairy cows, mainly including accelerating genetic breeding, improving diet composition, optimizing feeding management, and improving fecal treatment. Future research should focus on optimizing the combination of strategies, explore more innovative methods, reduce EME without affecting the growth performance of dairy cows and milk safety, and scientifically and effectively promote the sustainable development of animal husbandry. Full article

Given the increasing volume of selectively collected bio-waste and the requirement to increase waste treatment system energy efficiency, dry anaerobic digestion (DAD) represents a more sustainable choice for the treatment of municipal organic fraction instead of conventional technologies. The current paper provides an overview of the existing knowledge on DAD of green waste or kitchen waste collected selectively. Key substrates characteristics (chemical composition, methane potential), novel reactor design and process conditions relevant to effective digestion at elevated dry matter content are considered. Of special interest is the process intensification techniques, impact of contamination and co-fermentation opportunity with other biodegradable wastes. This article also discusses energy and economic performance of DAD plants and puts their environmental burden in perspective versus other bio-waste treatment processes. The current legislation and DAD’s role in the circular economy are also considered. Selectively collected biowaste has significant energy potential and dry anaerobic digestion is an effective technology, especially in areas with limited water availability, offering both waste volume reduction and minimized energy losses. The aim of this work is to introduce the potential of this technology as a sustainable option within the context of renewable energy and modern waste management. Full article

Methane (CH₄), originating from ruminants, is a major source of greenhouse gas emissions in the agriculture industry. This study aimed to determine the potential of red seaweed Gracilaria lemaneiformis (G. lemaneiformis) as an anti-methanogenic feed additive for cattle. Three supplementation levels of seaweed (2%, 5%, and 10% of dry matter) were evaluated for their effects on gas production and rumen fermentation characteristics during 48 h in vitro fermentation. The results revealed a significant decrease in total gas production (TGP), CO₂, CH₄, ammonia nitrogen (NH₃-N), and volatile fatty acid (VFA) concentrations, with no differences in pH or dry matter disappearance (DMD). Notably, compared with the control group without seaweed, supplementation with 2% G. lemaneiformis effectively reduces CH₄ emissions by 27.5% (p < 0.05). Supplementation with 2% G. lemaneiformis decreased the abundance of methanogens g_norank_f_Methanomethylophilaceae, responsible for CH₄ generation, and increased the populations of bacteria (Kandleria and Succinivibrio) that compete with methanogens for substrates. Furthermore, upregulating the levels of 13(S)-HOTrE and 9(S)-HOTrE (polyunsaturated fatty acids) could inhibit methanogenic activity. Additionally, lower VFA concentrations will provide less raw materials for methane synthesis, thus further inhibiting methanogenesis. In summary, G. lemaneiformis, as a red seaweed with important economic value, can not only be applied to enhance marine carbon sinks but can also serve as a promising candidate for mitigating biomethane emissions in cattle. Full article

This study evaluated the effects of replacing SBM with CWYWEP on in vitro rumen fermentation, nutrient degradability, and gas production kinetics. Citric waste was co-fermented with yeast waste and a multi-enzyme complex for 14 days, then sun-dried and pelleted. The final CWYWEP product contained 50.4% crude protein (DM basis). A completely randomized design tested seven diets in which SBM was replaced by CWYWEP or non-enzymatic citric waste–yeast waste pellets (CWYWP) at 0%, 33%, 66%, or 100% inclusion. Replacing SBM with CWYWEP significantly increased cumulative gas production at 96 h, with the 100% CWYWEP group achieving 93.7 mL/0.5 g DM—a 14% increase over the control (p < 0.01). Microbial lag time was reduced to 0.17 h vs. 0.28 h in the control (p < 0.05), suggesting faster microbial colonization. The highest in vitro DM degradability (IVDMD) at 48 h was observed in the 100% CWYWEP group (64.5%), outperforming both the SBM control and all CWYWP treatments (p < 0.01). Notably, CWYWEP increased total volatile fatty acids by 5% at 4 h and propionate by 9% at 2 h, while reducing methane production by 5% (p < 0.05). Other parameters, including pH, ammonia nitrogen, organic matter digestibility, and protozoal counts, were unaffected (p > 0.05). In contrast, CWYWP without enzymes showed minimal improvement. These findings indicate that CWYWEP is a promising high-protein alternative to SBM, enhancing fermentation efficiency and reducing methane under in vitro conditions. Further in vivo studies are warranted to validate these effects. Full article

While the Ankom RF system facilitates efficient high-throughput in vitro fermentation studies, its high cost and limited flexibility constrain its broader applicability. To address these limitations, we developed and validated a low-cost, modular gas monitoring system (FerME), assembled from commercially available components. To evaluate its performance and reproducibility relative to the Ankom RF system (Ankom Technology, Macedon, NY, USA), in vitro rumen fermentation experiments were conducted under strictly controlled and identical conditions. Whole rumen contents were collected approximately 2 h post-feeding from individual mid- or late-lactation dairy cows and immediately transported to the laboratory. Each fermenter received 50 mL of processed rumen fluid, 100 mL of anaerobically prepared artificial saliva buffer, and 1.2 g of the donor cow’s diet. Bottles were sealed with the respective system’s pressure sensors, flushed with CO₂, and incubated in a 50 L water bath maintained at 39 °C. FerME (New Taipei City, Taiwan) and Ankom RF fermenters were placed side-by-side to ensure uniform thermal conditions. To assess the effect of filter bag use, an additional trial employed Ankom F57 filter bags (Ankom Technology, Macedon, NY, USA; 25 μm pore size). Trial 1 revealed no significant differences in cumulative gas production, volatile fatty acids (VFAs), NH₃-N, or pH between systems (p > 0.05). However, the use of filter bags reduced gas output and increased propionate concentrations (p < 0.05). Trial 2, which employed filter bags in both systems, confirmed comparable results, with the FerME system demonstrating improved precision (CV: 4.8% vs. 13.2%). Gas composition (CH₄ + CO₂: 76–82%) and fermentation parameters remained consistent across systems (p > 0.05). Importantly, with 12 pressure sensors, the total cost of FerME was about half that of the Ankom RF system. Collectively, these findings demonstrate that FerME is a reliable, low-cost alternative for real-time rumen fermentation monitoring and could be suitable for studies in animal nutrition, methane mitigation, and related applications. Full article

In recent years, biofuels and bioenergy derived from algae have gained increasing attention, fueled by the growing demand for renewable energy sources and the urgent need to lower CO₂ emissions. This research examines the generation of bioethanol and biomethane using freshly harvested and sedimented algal biomass. Employing a factorial experimental design, various trials were conducted, with ethanol yield as the primary optimization target. The findings indicated that the sodium hydroxide concentration during pretreatment and the amylase dosage in enzymatic hydrolysis were key parameters influencing the ethanol production efficiency. Under optimized conditions—using 0.3 M NaOH, 25 μL/g starch, and 250 μL/g cellulose—fermentation yielded ethanol concentrations as high as 2.75 ± 0.18 g/L (45.13 ± 2.90%), underscoring the significance of both enzyme loading and alkali treatment. Biomethane potential tests on the residues of fermentation revealed reduced methane yields in comparison with the raw algal feedstock, with a peak value of 198.50 ± 25.57 mL/g volatile solids. The integrated process resulted in a total energy recovery of up to 809.58 kWh per tonne of algal biomass, with biomethane accounting for 87.16% of the total energy output. However, the energy recovered from unprocessed biomass alone was nearly double, indicating a trade-off between sequential valorization steps. A comparison between fresh and dried feedstocks also demonstrated marked differences, largely due to variations in moisture content and biomass composition. Overall, this study highlights the promise of integrated algal biomass utilization as a viable and energy-efficient route for sustainable biofuel production. Full article

The objective of this study was to assess the effects of gallic acid (GA) on nutrient degradability, gas production, rumen fermentation, and the microbial community and its functions using in vitro fermentation methods. An in vitro experiment was conducted to test GA dose levels (0, 5, 10, 20, and 40 mg/g DM) in the cow’s diet. Based on the results of nutrient degradability, gas production, and rumen fermentation, the control group (0 mg/g DM, CON) and the GA group (10 mg/g DM, GA) were selected for metagenomic analysis to further explore the microbial community and its functions. The degradability of dry matter and crude protein, as well as total gas production, CH₄ production, CH₄/total gas, CO₂ production, and CO₂/total gas, decreased quadratically (p < 0.05) with increasing GA doses, reaching their lowest levels at the 10 mg/g DM dose. Total volatile fatty acid (VFA) (p = 0.004), acetate (p = 0.03), and valerate (p = 0.03) exhibited quadratic decreases, while butyrate (p = 0.0006) showed a quadratic increase with increasing GA doses. The 10 mg/g DM dose group had the lowest levels of total VFA, acetate, and valerate, and the highest butyrate level compared to the other groups. The propionate (p = 0.03) and acetate-to-propionate ratio (p = 0.03) linearly decreased with increasing gallic acid inclusion. At the bacterial species level, GA supplementation significantly affected (p < 0.05) a total of 38 bacterial species. Among these, 29 species, such as Prevotellasp.E15-22, bacteriumP3, and Alistipessp.CAG:435, were less abundant in the GA group, while 9 species, including Aristaeella_lactis and Aristaeella_hokkaidonensis, were significantly more abundant in the GA group. At the archaeal species level, the relative abundances of Methanobrevibacter_thaueri, Methanobrevibacter_boviskoreani, and Methanobrevibactersp.AbM4 were significantly reduced (p < 0.05) by GA supplementation. Amino sugar and nucleotide sugar metabolism, Starch and sucrose metabolism, Glycolysis/Gluconeogenesis, and Pyruvate metabolismwere significantly enriched in the GA group (p < 0.05). Additionally, Alanine, aspartate and glutamate metabolism was also significantly enriched in the GA group (p < 0.05). GA use could potentially be an effective strategy for methane mitigation; however, further research is needed to assess its in vivo effects in dairy cows over a longer period. Full article

Anaerobic digestion for biogas production represents a crucial approach to achieving the high-value utilization of agricultural solid waste. The adoption of multi-material co-digestion offers a viable solution to overcome the inherent constraints associated with single-substrate digestion, thereby significantly enhancing the efficiency of resource utilization. This study explored a co-digestion system using dairy manure and cucumber vines as substrates, uncovering how total solids (TS) influence the methane yield and microbial community characteristics. All treatments exhibited swift methane fermentation, with daily production initially increasing before declining. Cumulative methane production increased with the increasing TS contents. These results may be linked to pH value and the concentration of volatile fatty acids (VFAs). Except for the 6% TS treatment, digesters across different TS levels maintained a favorable final pH of 7.4–8.4, while VFA concentrations exhibited a downward trend as TS contents increased. The treatment with the highest TS concentration (25%) demonstrated superior performance, achieving the maximum volumetric methane yield. This yield was 1.6 to 9.1 times higher than those obtained at low (6–10%) and medium (12–18%) TS concentrations. Microbial community analysis revealed that during the peak methane production phase, Firmicutes and Methanoculleus were the predominant bacterial and archaeal phyla, respectively. The microbial community structure changed with different TS levels. This study offers valuable scientific insights for enhancing biogas production efficiency in co-digestion systems. Full article

Anaerobic fermentation has been recognized as an effective approach to harness livestock manure resources. In the present study, cow dung and pig manure were employed as fermentation substrates. These were subjected to co-fermentation experiments with sodium hydroxide-pretreated corn straw. Additionally, biochar derived from artificial wetland substrate was introduced as a conditioner to investigate the impact of varying addition quantities on the pretreated anaerobic co-fermentation process. Our findings indicate that for the anaerobic co-fermentation of cow dung, an optimal addition of 4% biochar reduced the gas production cycle by 35–45%, although the total methane yield remained relatively unchanged. Conversely, in the anaerobic co-fermentation of pig manure, a 6% biochar addition proved most effective. This adjustment, while not significantly altering the gas production cycle, led to a marked increase in the total methane content, ranging from 18.53% to 150.18%. The PCA analysis results of the cow manure experimental group showed a significant positive correlation between the addition of biochar and ammonia nitrogen. For the pig manure fermentation system, the addition of biochar can increase the final methane production potential, from 47.43 mL/g VS to 122.24 mL/g VS in the P2C experimental group. Biochar mainly regulates the activity of anaerobic bacteria through changes in pH and conductivity, thereby affecting methane production. Full article

The growing need to reduce methane emissions from ruminants while enhancing feed utilization has driven the development of innovative in vitro measurement techniques. This review examines the Gas Endeavour (GES), an automated volumetric apparatus that quantifies both total gas and methane production in real time during rumen fermentation. Utilizing the principles of liquid displacement and buoyancy, the GES integrates a thermostatically controlled water bath, specialized gas flow cells, and an alkaline CO₂ absorption unit to deliver precise kinetic data on fermentation. Compared to conventional methods—which often rely on manual measurements and post-incubation gas chromatography—the GES provides continuous monitoring and immediate data acquisition, reducing labour and potential errors. This review discusses the system’s design, operational challenges such as controlling headspace pressure and ensuring consistent inoculum preparation, and its applications in both animal nutrition and biomethane potential assessments. The findings suggest that, with further standardization and protocol refinement, the GES could significantly advance research aimed at optimizing feed digestibility and mitigating methane emissions in ruminant production systems. Full article

The limited usage of fermentation residues, due to increasingly stringent legal requirements, demands novel routes of utilization for these feedstocks. To the best of our knowledge, for the first time, a mixture of fermentation residues and wood chips is used as feedstock in a fixed-bed gasifier, using only O₂/CO₂ mixtures as gasifying agent. The maximum O₂ concentration achieved was 31.6 Vol.-%. Pronounced process stability was achieved with a cold gas efficiency of about 94%, possibly due to CO₂ conversion within the process. The heating value of the produced synthesis gas was 8.5 MJ/m³_i.N.dry, with increased amounts of carbon monoxide and methane when compared to air-blown operations. Full article