Biogas Slurry Research Articles

Physiological and transcriptomic responses of microalgal-bacterial co-culture reveal nutrient removal and lipid production during biogas slurry treatment.

Microalgal-bacterial consortia can treat biogas slurry and produce high-value products. This study found that co-cultures of Desmodesmus sp. and Bacillus megaterium improved nutrient removal, biomass production, and lipid accumulation in Desmodesmus sp. Dual transcriptomic analyses revealed that B. megaterium upregulated genes associated with glycolysis, the Calvin cycle, tricarboxylic acid cycle, indole acetic acid synthesis, and fatty acid biosynthesis in Desmodesmus sp. Under a high C/N ratio, key genes involved in fatty acid degradation were downregulated, promoting lipid accumulation in co-cultured Desmodesmus sp. Effective NH4+-N removal in the co-culture under a high C/N ratio was attributed to microbial interactions. Desmodesmus sp. downregulated the URE gene in bacteria, inhibiting urea hydrolysis, while B. megaterium upregulated the URE and gdhA genes in microalgae, promoting urea utilization and NH4+-N assimilation. This study provides new insights into the transcriptional regulation in nutrient assimilation and lipid metabolism in microalgal-bacterial consortia.

Combined effect of flocculation and ammonia stripping on different biogas slurries

The combined use of flocculation and ammonia stripping could be an efficient method for treating biogas slurry (BS). In this study, the operating parameters of ammonia stripping after flocculation were optimized. Swine manure biogas slurry (SMBS) and chicken manure biogas slurry (CMBS) were used as raw materials, and the flocculation efficiency and ammonia nitrogen removal rate (ANRR) were the main indices to evaluate the process performance. The bioflocculant (BF), polyaluminium chloride (PAC), ferric chloride (FC), and calcium oxide (CaO) were used as flocculants for the different biogas slurry flocculation. The results showed that CaO was more suitable for SMBS; the flocculation efficiency reached 56.63 % at the additive concentration of 5 g/L. Moreover, the ANRR was significantly improved by over 80 % after flocculation. However, the best flocculation potential on CMBS was achieved at an additive concentration of 0.3 g/L, and the flocculation efficiency reached 44.44 %. The ANRR reached 94.42 % at 45 ℃. This study provides a scientific basis and feasible scheme for treating different BS.

Penggunaan Slurry sebagai Pupuk Organik terhadap Kualitas dan Fermentabilitas Rumput Setaria (Setaria splendida Stapf) di Rumen

Biogas slurry is an organic product derived from livestock manure and produced through an aerobic fermentation process that can be used to improve soil fertility, forage production, and quality. This study aimed to investigate the effect of slurry organic fertilizer on crude protein content, crude fiber, and total fermentation gas production in the rumen in vitro . The study was conducted in a completely randomized design (CRD), consisting of five treatments of slurry levels as organic fertilizer and four replications consisting of two experimental units. The treatments consisted of S0 = without slurry, S1 = slurry 20 g/polybag, S2 = slurry 25 g/polybag, S3 = slurry 30 g/polybag, and S4 = slurry 35 g/polybag. The variables measured in this study were crude protein content, crude fiber, and total fermentation gas production. The data obtained were analyzed using a variance analysis (ANOVA). Duncan’s test was used to determine the effect of different levels of slurry on the measured parameters. The results showed that the use of slurry as an organic fertiliser increases crude protein content by an average of 16.06%, increases crude protein production from 1.47 g/poly bag to 96.38 g/poly bag and improves fermentability in the rumen by an average of 8.08% of setaria grass (Setaria splendida Stapf). The use of slurry at the level of 35 g/poly bag is recommended for the cultivation of setaria grass (Setaria splendida Stapf).

Insides into molecular structural elucidation on the pesticidal and herbicidal potency of AD biogas slurry

Biogas slurry is the residue liquid after anaerobic fermentation of biomass. The bio-slurry has the potential to promote plant growth and control pests. This study explores the pesticidal potency of anaerobic digestate focusing on structural elucidation through gas chromatography–mass spectrometry analysis. Samples were collected from three anaerobic digesters processing cow dung, mixed substrates, and pig waste. Physicochemical parameters such as pH, electrical conductivity, total dissolved solids, and nitrogen content were measured. The slurries exhibited slightly basic pH values (7.5–7.8) and electrical conductivity (13.8–21.9 mS/m). GC–MS analysis revealed diverse phytochemical compounds in the bio-slurries, such as gramine, 2,2-dimethoxybutane, and 4-methyl-3-penten-2-one, with potential pesticidal properties. Gramine exhibited insecticidal, herbicidal, and algaecidal effects, while 2,2-dimethoxyethane demonstrated fungicidal and herbicidal properties. Gramine was identified and possesses its potential as a natural biopesticide. The identified compounds offer promising alternatives to synthetic pesticides, emphasizing the potential of biogas slurry as a sustainable biopesticide resource.

CO2 absorption performance of biogas slurry enhanced by biochar as a potential solvent in once-through CO2 chemical absorption process

Carbon capture, utilization, and storage (CCUS), offers a promising avenue for mitigating CO2 emissions, in which the big challenge is the high CO2 capture cost. A novel CCUS technology called once-through CO2 chemical absorption using biogas slurry, could potentially reduce the CO2 capture cost through decreasing the energy consumption greatly during CO2 capture. This technology, however, is constrained by the CO2 absorption capacity of biogas slurry. To enhance the CO2 capture capacity of this innovative technology, we proposed a method to enhance CO2 absorption by integrating biochar into biogas slurry. Results indicated that the CO2 absorption capacity of biogas slurry improved by biochar varied with the type of biochar adopted. Among all the investigated biochar, the wood biochar like sea buckthorn and sand willow exhibited the lowest CO2 capture enhancement, with 0.82±0.19 mmol/g and 0.81±0.30 mmol/g, respectively. Biochar from C4 plants like corn stalks and cobs demonstrated the highest enhancement, with 2.11±0.24 mmol/g and 2.47±0.86 mmol/g, respectively. The enhancement driven by C3 plant biochar like millet stalks and shells was intermediate, with 1.62±0.47 mmol/g and 1.62±0.46 mmol/g, respectively. The primary factor for promoting CO2 absorption in the biochar-based biogas slurry was the increase in pH of biogas slurry. The total pore volume of biochar was the principal material property that enhanced CO2 absorption, followed by the EC and BET surface areas of biochar. Increasing the carbonization temperature of biochar could also enhance the CO2 absorption capacity by biogas slurry. In CO2-rich biochar-based biogas slurry, CO2 primarily existed as HCO3− and carbamate. However, for the influence of the biochar's pore structure, CO2 in the CO2-rich biochar-based biogas slurry was more stable than that in CO2-rich biogas slurry.

The effects of influent 5-Deoxystrigol concentrations on integral biogas upgrading and nutrient removal by different algal-fungal-bacterial consortium

The low quality of biogas and the difficulties in treating biogas slurry are important bottlenecks that limit the development of the fermentation industry. The effects of 5-deoxystrigol (5DS) on the growth rate, daily productivity, and photosynthetic performance of different algal-fungal-bacterial consortia were investigated, and the auxiliary activities of endophytic bacteria (S395–2), Ganoderma lucidum (G. lucidum), Bacillus licheniformis (B. licheniformis), and activated sludge in these systems were examined. The consortium Chlorella vulgaris (C. vulgaris) + G. lucidum + S395–2 was found to be the most effective combination for both biogas upgrading and nutrient removal. Removal efficiencies of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorous (TP) were approximately 82.94 ± 7.88 %, 81.36 ± 7.79 %, and 83.27 ± 8.09 %, respectively, and the CO2 removal efficiency was observed to be about 69.89 ± 6.57 % at the optimum 5DS concentration of 10−11 M. On day 7 of the treatment, the CH4 content was elevated from 66.07 ± 4.84 % to 86.24 ± 8.44 %. The effect of 5DS treatments in different algal-fungal-bacterial consortia was positive in terms of growth performance and photosynthetic rate. The present study provides a framework for efficient biogas upgrading and nutrient removal by the three-phase symbionts.

Ammonia recovery from real biogas slurry in the up-scaled Donnan Dialysis-Osmotic Distillation membrane-based system: Performance and potentials

Recovering ammonia from wastewater is crucial for building a circular economy and achieving carbon neutrality. Some innovative ammonia recovery technologies have shown great potential yet lacking theoretical guidance for up-scaling from laboratory to practical applications. Based on our previously-proposed Donnan dialysis-osmotic distillation (DD-OD) hybrid process for selective ammonia recovery at nearly zero energy input, two challenges as modelling/prediction and product application were solved in this study. Under the guide of the tailor-made mass transfer model, a reasonable design of the reactor and operating parameters was fixed, whose performance in recovering ammonia from real biogas slurry and the feasibility of the recovered product as irrigation water was then investigated. The up-scaled DD-OD reactor achieved efficient and stable ammonia removal and recovery (∼75 % and ∼ 65 %, respectively) and excellent impurity retention efficiency (∼95 %) in 360 h continuous run. Impurities deposited on the cation-exchange membrane did not affect ammonium transfer and were effectively removed by water washing, and no fouling was found for the hydrophobic membrane, highlighting its long-term capability for ammonia recovery. Moreover, the cost-effectiveness of the process was analyzed, which could be greatly improved given the future improved membrane materials. A proper dilution of the recovered product for irrigating cabbage and radish promoted plant growth, recycled product containing a moderate ammonia concentration (136 mg/L) was highlighted and well-rounded, multi-element nutrient profile was recommended. The above results provide theoretical guidance for the scaling-up of ammonia recovery module and a reference basis for the application of recycled products in agricultural irrigation.

Assessment of Physico-Chemical Properties of Biogas Slurry as an Organic Fertilizer for Sustainable Agriculture

Chemical fertilizers have been extensively used for growing crops and controlling plant diseases, but they pose potential hazards to the environment, soil health, plants, and people. The current world situation highlights the need to implement eco-friendly agricultural practices for sustainable crop production. Using environmentally friendly manure, such as biogas slurry, can help reduce the negative effects of chemical fertilizers. Biogas slurry is an efficient waste material and organic fertilizer, making it an ideal supplement for sustainable crop production and waste management. An experiment was conducted at IARI, New Delhi, to explore the nutrient potential of biogas slurry. The main objective of this study was to assess biogas slurry's physico-chemical characteristics and nutrient contents. Samples of biogas slurry were collected in three replications and analyzed using standard methods for macro and micronutrients. The data revealed that biogas slurry has a pH of 7.2-8.5, EC of 1.06 to 1.12 dS/m, and organic carbon content of 41.7 to 45.8%. In terms of fertility, it contains significant amounts of nitrogen (1.98-2.17%), phosphorus (0.97 to 1.15%), and potassium (1.98 to 2.17%). Additionally, biogas slurry contains micronutrients such as Zn (0.023-0.027 ppm), Cu (0.005-0.009 ppm), Fe (0.32-0.38 ppm), and Mn (0.089-0.094 ppm). Statistical analysis using ANOVA and Post Hoc tests indicated that the mean data values among all three replications do not differ significantly. Therefore, it can be concluded that the nutritive value of biogas slurry is sufficient to reduce the reliance on chemical fertilizers in agriculture. It represents an optimal long-term organic remedy for developing fertile soil, ensuring enduring agricultural productivity, and mitigating the negative environmental impacts associated with waste management.

Reducing nitrogen fertilizer usage coupled with organic substitution improves soil quality and boosts tea yield and quality in tea plantations.

The utilization of chemical fertilizers is a key measure for maintaining tea yield and quality, but excessive use has negative environmental impacts. The substitution of chemical fertilizer with organic fertilizer has been promoted to sustain crop yield and soil quality. However, knowledge gaps regarding the effects of organic substitution on soil quality and tea yield in tea plantations still exist. A field experiment was conducted to investigate the influence of organic substitution treatments (i.e. 25% partial substitution: biogas slurry + green manure + formula fertilizer, BFG; sheep manure + formula fertilizer, OFF; 100% complete substitution: sheep manure + green manure, OG) on the soil quality, tea yield and quality, and nitrogen utilization efficiency in southwestern China. Results showed that all organic substitution treatments slightly increased soil pH, and significantly increased soil organic matter by 13.22-14.88% compared to conventional fertilization (CF). The BFG treatment was the most effective in enhancing the soil quality index, showing increases of 16.80%, 8.37% and 24.87% higher than the CF, OFF and OG treatments, respectively. Tea yield significantly increased under the BFG, OFF and OG treatments by 11.97%, 13.58% and 5.90% compared to CF, respectively. The BFG treatment increased the amino acid content by 7.78% and decreased the tea polyphenol/amino acid ratio by 6.87%. Additionally, the BFG, OFF and OG treatments greatly increased the nitrogen utilization efficiency of young sprouts by 70.71%, 82.54% and 34.28%, respectively. Overall, partial organic substitution could effectively improve soil quality while maintaining tea yield. © 2024 Society of Chemical Industry.

Optimal Application of Biogas Slurry in Paddy Fields under the Dual Constraints of Agronomy and Environment in the Yangtze River Delta Region

The production of huge amounts of biogas slurry during livestock breeding has resulted in pressing environmental issues. Although paddy fields can be potential sinks for the disposal of biogas slurry, the impacts of biogas slurry on rice production, grain quality, and relevant environmental risks in the Yangtze Delta region remain unclear. Herein, we conducted a field trial from 2021 to 2023 which involved different gradients of biogas slurry utilization, including CK (no fertilizer), CN (100% chemical nitrogen (N) of 240 kg ha−1), NBS (biogas slurry replacing 50% chemical N), BS1 (replacing 100% chemical N), BS1.5 (replacing 150% chemical N), and BS2 (replacing 200% chemical N). The results showed that there were no significant differences in average rice yields between CN, NBS, BS1.5, and BS2 over the three-year study period, with an average yield of 8283 kg ha−1, and the average yields of BS1 and CK were 7815 kg ha−1 and 6236 kg ha−1, respectively. However, heavy utilization of biogas slurry (BS1.5 and BS2) not only significantly reduced the rice seed-setting rate, the 1000-grain weight, and the processing quality, but also significantly increased the protein, amylose, Cu, and Zn content in rice grains; additionally, higher N losses occurred via surface water and increased NH3 volatilization was observed, finally resulting in lower nitrogen-use efficiency. Meanwhile, moderate utilization of biogas slurry (NBS and BS1) led to better rice quality and nitrogen-use efficiency, lower potential food safety risk, and N loss. Further, compared to BS1, NBS showed higher yield, harvest index, processing quality, gel consistency, palatability scores, and nitrogen-use efficiency, but lower N losses were present. Overall, the NBS treatment balanced the agronomic benefits and environmental risks in the Yangtze River Delta region. In the future, more attention should be paid to food safety and environmental risks when using biogas slurry.

Calcium silicate hydrate complex konjac glucomannan-based hydrogel selectively adsorbed phosphate in low alkalinity solution

The selective recovery of phosphate from wastewater can manage nutrients and realize the recycling of phosphorus resources. In this study, a novel konjac glucomannan/pectin/calcium silicate composite hydrogel (KP-CSH) was developed for efficient recovery of phosphate in aqueous solution. The amount of alkali released after the reaction of KP-CSH in a neutral solution was small (the pH of the solution after the reaction was < 9). In a wide initial pH range (3–10), the adsorption capacity of KP-CSH in 50 mg-P/L phosphate solution reached 39∼45 mg-P/g. Besides, even if the pH of the solution after the reaction was less than 8, it could still well adsorb phosphate. The kinetic and isothermal adsorption experiments indicated that the adsorption process of phosphate by KP-CSH was chemical adsorption, and the maximum adsorption capacity was 61.2 mg-P/g. KP-CSH preferentially adsorbed phosphate even in the presence of high concentrations of competitive ions. In the actual biogas slurry, KP-CSH also exhibited the strongest selectivity/affinity for phosphate, and its distribution coefficient (Kd) was significantly higher than that of other co-existing anions and cations. The adsorption mechanism analysis indicated that Ca was the main adsorption site of KP-CSH, and that the adsorption process of target pollutants mainly involved ligand exchange and the intra-sphere complexation. Further plant seed germination and seedling growth experiments suggested that KP-CSH after phosphate recovery did not exert a negative effect on the growth of plant seedlings, and increased the chlorophyll content of seedling leaves. These results demonstrate that KP-CSH is a potential adsorbent for efficient phosphate recovery, which can be used as a slow-release phosphate fertilizer after recovering phosphate.

Biogas slurry: A potential substance that synergistically enhances rapeseed yield and lodging resistance

Biogas slurry (BS) plays a vital role in improving the efficiency of crop production. On the flip side, the impact of BS on plant lodging factors and yield related traits is still obscure. Hence, we aimed to study the effects of pig and cow BS applications on yield formation, morpho-anatomical, mechanical, physiological properties and transcript expression patterns. The results showed that the yield and lodging resistance of rapeseed were synergistically improved via applying full BS dosage versus nitrogen fertilizer (CK). In addition, the seed yield was significantly increased by 23.9 % by promoting the dry matter accumulation and transport-ability, increasing number of pods by 8.4 % and 1000-seed weight by 5.1 %, respectively. Moreover, BS developed the stem mechanical strength by decreasing lodging index by 34.2 %, which was manifested by an increase in stem thickness and stiffness and a reduction in plant height. Besides, it enhanced the photosynthesis through promoting chlorophyll synthesis, delaying plant senescence, and accumulating N and K concentration. Anatomical observations revealed that BS increased greater number and area of stem vascular bundles, vessels, and maintained a dense microstructure than CK. Also, it boosted pectin, Ca2+ and K+ contents, which were significantly positively correlated with stem mechanical strength and reduced cellulose, lignin and hemicellulose contents. Meanwhile, correlation and structural equation modeling analysis validated the above results. Additionally, the differentially expressed genes were enriched in cell wall formation pathway, especially about the biosynthesis of pectin (PME, PG and PL), cellulose (CesA and CSL), lignin (PAL, POD, CCR, LAC and COMT) and hemicellulose (XTH and Xyl) were identified under BS. The above-mentioned results indicated that BS simultaneously affected lodging behavior by altering structural carbohydrates and modified yield composition by regulating dry-matter accumulation and allocation. This is the first comprehensive strategy on synchronizing rapeseed yield increase and lodging resistance under optimized BS management.

Development of an efficient pretreatment process and multi-functional acetate co-metabolism strategy for the treatment of high strength biogas slurry using a newly isolated Chlorella sorokiniana

The efficient treatment of biogas slurry (BS) to meet the government’s discharge standards is a major challenge for most livestock and poultry enterprises. Although microalgae-based wastewater treatment has many significant benefits over traditional technologies, the poor ammonium tolerance of regular algal species, the pH imbalance during microalgae cultivation, and the complex and expensive BS pretreatment process greatly limit its application in BS treatment. Aimed at these issues, this study firstly isolated a robust Chlorella sp. with strong ammonium and acidic tolerance, as well as heterotrophy ability. To facilitate optimal pH stability and growth enhancement, a co-metabolism cultivation strategy based on the addition of 0.1 g·L-1 acetate in the form of fed-batch was developed. In addition, an efficient pretreatment process integrating ammonia reduction by air stripping with turbidity and chromaticity reduction by acidic precipitation was developed for the elimination of inhibitory factors of microalgal growth in BS. The isolated Chlorella sp. was capable of growing in the pretreated real BS and no growth inhibition was observed even in the undiluted BS. The acetate co-metabolism cultivation strategy obviously enhanced cell growth and pollutant removal and both NH4+ and total phosphorus were reduced to meet the discharge standards of China via 2.5-fold dilutions of BS. The accumulation of high-value biomass could not only fully cover the cost of wastewater treatment, but also bring significant returns. The net profit from treating 1 m3 of BS reached $ 116.2. This study provides a simple and efficient packaged process for the treatment of high strength BS and is expected to greatly reduce the process cost of BS.

Influence of Biomass Amendments on Soil CO2 Concentration and Carbon Emission Flux in a Subtropical Karst Ecosystem

Soil in karst areas is rare and precious, and karst carbon sinks play an important role in the global carbon cycle. Therefore, the purpose of karst soil improvement is to improve soil productivity and a carbon sink effect. Biomass amendment experiments in this study included three schemes: filter mud (FM), filter mud + straw + biogas slurry (FSB), and filter mud + straw + cow manure (FSC). The characteristics of soil CO2 production, transport, and the effect on soil respiration carbon emissions in two years were compared and analyzed. The results were as follows: 1. The rate, amount, and depth of CO2 concentration were affected by the combinations with biogas slurry (easy to leach) or cow manure (difficult to decompose). 2. The diurnal variation curves of soil respiration in the FSB- and FSC-improved soils lagged behind those in the control soil for three hours. While the curves of FM-improved soil and the control soil were nearly the same. 3. Soil–air carbon emissions increased by 35.2 tCO2/(km2·a−1) under the FM scheme, decreased by 212.9 tCO2/(km2·a−1) under the FSB scheme, and increased by 279.5 tCO2/(km2·a−1) under the FSC scheme. The results were related to weather CO2 accumulation in the deep or surface layers under different schemes.

Enhancement of alkaline pretreatment-anaerobically digested sludge dewaterability by chitosan and rice husk powder for land use of biogas slurry

Alkaline pretreatment can improve the methane yields and dewatering performance of anaerobically digested sludge, but it still needs to be coupled with other conditioning methods in the practical dewatering process. This study utilized four different flocculants and a skeleton builder for conditioning of alkaline pretreatment-anaerobically digested sludge. Chitosan was found to be the most effective in dewatering the sludge. Chitosan coupled with rice husk powder further improved the dewatering performance, which reduced normalized capillary suction time, specific resistance to filtration, and moisture content by 98.7%, 82.0%, and 12.1%. For land use of biogas slurry as a fertilizer, chitosan conditioning promoted the growth of corn seedlings, while the other three flocculants diminished the growth of corn seedlings. Chitosan coupled with rice husk powder further promoted the growth of corn seedlings by 103.5%, 65.0%, and 53.7% in fresh weight, dry weight, and root length, respectively. Overall, chitosan coupled with rice husk powder not only enhanced the dewaterability of alkaline pretreatment-anaerobically digested sludge but also realized the resource utilization of agricultural waste.

Nitrogen recovery from biogas slurry with high ammonia nitrogen concentration through struvite precipitation utilizing acid leaching solution of collophanite tailings

ABSTRACT The high concentration of ammonia nitrogen (NH4+) and chemical oxygen demand (COD) in biogas slurry pose great challenges to the efficiency of traditional wastewater treatment systems. Collophanite tailings are solid waste, characterized by significant concentrations of phosphorus (PO43-) and magnesium (Mg2+), represent a potential resource for the reduction and recovery of NH4+ in biogas slurry via struvite precipitation. This study systematically explored the optimal leaching parameters employing sulfuric acid for the extraction of PO43− and Mg2+ from collophanite tailings. The effect of [PO43-]:[NH4+] molar ratio and pH on the recovery of NH4+ in biogas slurry was investigated. The physicochemical properties of the precipitates were confirmed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and chemical analysis. Results suggested that the highest removal efficiency of NH4+ (88.5%) was achieved when employing a [PO43-]:[NH4+] molar ratio of 1.0 at pH 9.5. Evaluation of effluent quality demonstrates a significant enhancement in the biodegradability of the treated biogas slurry, evidenced by an increase in the COD/TN ratio increased from 2.1 to 10.4. Economic analysis shows that the net income would be approximately 21.33 USD/m3 for proposed produces. These findings underscore the potential of utilizing collophanite tailings for NH4+ recovery from biogas slurry.

Efficient treatment of actual biogas slurry by Chlorella sorokiniana: Nutrient recovery and biomass production

Microalgae have received widespread attention for their effectiveness in treating highly concentrated organic wastewater, not only for the effective removal of pollutants, but also for the preparation of biofuels and high-value products. This study investigated that the efficient purification process and mechanism of Chlorella sorokiniana on actual biogas slurry, including nutrient removal and biomass production. The results showed the C. sorokiniana grew well with a biomass of 742.35 ± 1.72 mg/L at pH 9, an inoculum concentration of 60 mg/L and 24 h of continuous light for 12 days. The recirculating experiments showed that after three incubations of the biogas slurry, the removal efficiency of COD, TN, NH4+-N, TP and PO43−-P were 89.11 %, 89.30 %, 97.26 %, 95.39 % and 96.43 %, respectively, and the total biomass of microalgae was 1015.87 mg/L. The contents of lipids, proteins, carbohydrates and photosynthetic pigments in C. sorokiniana cultured in biogas slurry were 26.36 %, 31.34 %, 30.26 % and 16.31 mg/L, respectively. It was increased by 6.21 %, 7.24 %, 2.74 % and 12.82 mg/L compared to the control, respectively. SEM results showed that the surface of C. sorokiniana mosaic with a large number of bacteria, and the cultivation of C. sorokiniana promoted the relative abundance for Proteobacteria, Cyanobacteria and Bacteroidota. Cultivation of C. sorokiniana in the actual biogas slurry constituted a good algae-bacterial symbiosis system, which effectively promoted the process of wastewater purification. This study provided an applied reference for the efficient treatment of actual wastewater by microalgae and its potential for resources utilization.

Environmental risks in swine biogas slurry-irrigated soils: A comprehensive analysis of antibiotic residues, resistome, and bacterial pathogens

Simple anaerobic digestion is insufficient to completely remove residual parent antibiotics and antibiotic resistance genes (ARGs) from animal manure. ARG prevalence in swine biogas slurry-irrigated soils threatens human health. However, comprehensive analysis of antibiotic residues, high-resolution resistance gene profiles, and pathogenic microbiomes in biogas slurry-irrigated soils is very limited. Here, we comprehensively determined the antibiotics, resistome, and potential pathogens distribution in these soils, using high-performance liquid chromatography-tandem mass spectrometry, high-throughput quantitative PCR, and 16S rRNA gene sequencing. The results revealed a significant enrichment of tetracyclines and fluoroquinolones antibiotics and ARGs in soils with prolonged biogas slurry irrigation, with a total of 12 antibiotics, 175 unique ARGs, and 9 mobile genetic elements (MGEs) detected. Quantification of veterinary antibiotic residues (especially chlortetracycline) showed significant correlations with multiple ARGs. The abundance of ARGs and MGEs was highest in the biogas slurry-irrigated soils, denoting a tight link between the application of biogas slurry and the spread of antibiotic resistance. The presence of 50 potential pathogenic bacterial genera, including 13 with multidrug resistance, was identified. Variation partitioning, combined with hierarchical partitioning analysis, indicated that Firmicutes, MGEs, and tetracyclines were the key drivers shaping the ARG profiles in biogas slurry-irrigated soils. The findings offer insights into the mechanisms of antibiotic residue and ARGs spread from the agricultural practice of biogas slurry irrigation, underscoring the necessity of sustainable soil management to mitigate the spread of antibiotic resistance.

Enhancement of Fermentation Performance in the Anaerobic Co-Digestion of Chicken Manure and Corn Straw under Biogas Slurry Reflux via Air Stripping of the Digestate

Enhancement of Fermentation Performance in the Anaerobic Co-Digestion of Chicken Manure and Corn Straw under Biogas Slurry Reflux via Air Stripping of the Digestate

Effect of hydrochar from biogas slurry co-hydrothermal carbonization with biomass on anaerobic digestion performance of food waste

Anaerobic digestion is a promising method for converting food waste into renewable methane-rich biogas. However, challenges, such as significant biogas slurry generation, poor stability, and low methane production, limit its widespread adoption. This study produced 15 types of hydrochars by co-hydrothermal carbonization of biogas slurry with sugarcane leaves, cellulosic ethanol residue, or food waste digestate at 180–260 °C to enhance anaerobic digestion performance and methane yield. The methane yield was influenced by both the raw materials and hydrothermal carbonization temperature. The hydrochar derived from sugarcane leaves at 180 °C exhibited the highest methane yield of 461.59 mL/g VS, which is a 13.69 % increase over the food waste group. Additionally, different doses of SL-180 were tested for their effects on the anaerobic digestion performance in food waste. The cumulative methane yield increased from 379.68 mL/g VS to 543.26 mL/g VS with SL-180 dosages ranging from 5 g/L to 40 g/L, enhancing cumulative methane yield by 3.90–48.66 % compared to the food waste group. The primary factor influencing methane yield was hydrochar degradation, whereas secondary factors included maintaining system stability and enriching methane-producing microorganisms, particularly Methanosaeta and Methanomassiliicoccus. Energy assessment and economic analysis indicate that combining hydrothermal carbonization with anaerobic digestion can achieve high energy output and economic benefits. This study offers insights and recommendations for managing biogas slurry, resource recovery, and improving the stability and methane yield in the anaerobic digestion of food waste.