Long-term influence of trace element deficiency on anaerobic mono-digestion of chicken manure

CO2 agitation combined with magnetized biochar to alleviate "ammonia inhibited steady-state": Exploring the mechanism by combining metagenomics with macroscopic indicators

The "ammonia inhibited steady-state" phenomenon is frequently observed in the anaerobic digestion (AD) process of nitrogen-rich substrates. Reconfiguring microbial ecosystems has proven to be an effective strategy for mitigating ammonia inhibition. In the current study, biochars were screened and targeted for modification. CO2 agitation combined with magnetized biochar was used to aid the semi-continuous AD systems with "ammonia inhibited steady-state." The results indicated that coconut shell biochar had the best stimulating effect on AD performance. The content of oxygen-containing functional groups (OCFGs), which had a positive correlation with the electron donating capacity (EDC), was targeted to be regulated. This strategy significantly increased the CH4 yield by 31.7 % (from 344 to 278 mL/g VS) (p < 0.05). Isotope tracing and KEGG gene annotation indicated that this strategy stimulated the efficiency of the hydrogenotrophic pathway. Simultaneously, it accelerated the attachment of microorganisms, which made the DIET pathway between bacteria and archaea efficient. Under CO2 agitation, the attachment of functional microorganisms to the biochar accelerated. Biochar weakened the synthesis of bioelectronic carriers (Cyt-c and chemosensory pili), while the electroactivity of the AD system was enhanced. This means that biochar replaced bioelectronic carriers and improved the DIET efficiency. In addition, the strategy had a positive effect on the colonization of simultaneous nitrification-denitrifying bacteria (Georgenia), which led to a decrease in ammonia nitrogen concentrations. This study revealed the mechanism by which this strategy alleviates ammonia inhibition and provided a promising strategy for the efficient AD of nitrogen-rich substrates.

Residual ciprofloxacin in chicken manure inhibits methane production in an anaerobic digestion system

Anaerobic digestion (AD) is commonly used to dispose of laying hen manure. However, veterinary antibiotic residues present in chicken manure may affect the AD process. Here, the effects of three types of veterinary antibiotics commonly used in laying hen breeding on AD were explored. Manures containing antibiotics at two different concentrations were continuously added during AD for 5 days: amoxicillin (HAMX: 145.06 mg/kg, LAMX: 57.88 mg/kg), doxycycline (HDOC: 183.61 mg/kg, LDOC: 98.00 mg/kg), and ciprofloxacin (HCIP: 96.34 mg/kg, LCIP: 40.43 mg/kg). Compared with a control with no veterinary antibiotics, the amoxicillin and doxycycline groups presented no significant effects on biogas production, methane production, VFA concentration, acetic acid concentration or the pH of the AD system (P > 0.05). However, compared with the control, the ciprofloxacin groups presented significantly inhibited biogas and methane production during AD (P < 0.05), and the HCIP and LCIP groups presented significantly decreased biogas (47.82% and 45.37%, respectively) and methane (58.24% and 52.55%, respectively) production (P < 0.05). Moreover, the VFA and acetic acid concentrations of the ciprofloxacin groups were significantly higher than those of control during the entire AD period (P < 0.05), and the pH value at the withdrawal stage was significantly lower than that of the control group (P < 0.01), with no significant difference between the HCIP and LCIP groups (P > 0.05). Our results suggest that ciprofloxacin causes VFA and acetic acid accumulation in AD systems, thereby reducing the pH of the systems and inhibiting methanogen growth, ultimately reducing methane production in the AD systems. These findings contribute to a deeper understanding of the impact of ciprofloxacin on methane production in AD systems and offer some considerations for the application of AD systems.

Enhancement of Biodegradability of Chicken Manure via the Addition of Zeolite in a Two-Stage Dry Anaerobic Digestion Configuration

Leach bed reactors (LBRs) are dry anaerobic systems that can handle feedstocks with high solid content, like chicken manure, with minimal water addition. In this study, the chicken manure was mixed with zeolite, a novel addition, and packed in the LBR to improve biogas production. The resulting leachate was then processed in a continuous stirred tank reactor (CSTR), where most of the methane was produced. The supernatant of the CSTR was returned to the LBR. The batch mode operation of the LBR led to a varying methane production rate (MPR) with a peak in the beginning of each batch cycle when the leachate was rich in organic matter. Comparing the MPR in both systems, the peaks in the zeolite system were higher and more acute than in the control system, which was under stress, as indicated by the acetate accumulation at 2328 mg L-1. Moreover, the presence of zeolite in the LBR played a crucial role, increasing the overall methane yield from 0.142 (control experiment) to 0.171 NL CH4 per g of volatile solids of chicken manure entering the system at a solid retention time of 14 d. Zeolite also improved the stability of the system. The ammonia concentration increased gradually due to the little water entering the system and reached 3220 mg L-1 (control system) and 2730 mg L-1 (zeolite system) at the end of the experiment. It seems that zeolite favored the accumulation of the ammonia at a lower rate (14.0 mg L-1 d-1) compared to the control experiment (17.3 mg L-1 d-1). The microbial analysis of the CSTR fed on the leachate from the LBR amended with zeolite showed a higher relative abundance of Methanosaeta (83.6%) compared to the control experiment (69.1%). Both CSTRs established significantly different bacterial profiles from the inoculum after 120 days of operation (p < 0.05). Regarding the archaeal communities, there were no significant statistical differences between the CSTRs and the inoculum (p > 0.05).

Stimulating anaerobic digestion to degrade recalcitrant organic pollutants: Potential role of conductive materials-led direct interspecies electron transfer

This review aims to provide a comprehensive understanding of the potential of CMs-dominated DIET in the degradation of recalcitrant organic pollutants in AD. The review covers the mechanisms and efficiencies of recalcitrant organic pollutant degradation by CMs-dominated DIET, the comparison of degradation pathways between DIET and chemical treatment, recent insights on DIET-enhanced degradation, and the evaluation of the potential and future development of CMs-dominated DIET. The review emphasizes the importance of coupled syntrophic microorganisms, electron flux, and physicochemical properties of CMs in enhancing the degradation performance of AD. Additionally, it highlights the advantages of DIET-led syntrophic metabolism over traditional oxidation technologies in terms of environmental friendliness and efficiency. Finally, the review acknowledges the potential risks associated with introducing CMs into AD systems and provides guidance for waste treatment and energy recovery.

Trace elements' deficiency in energy production through methanogenesis process: Focus on the characteristics of organic solid wastes

Excessive or insufficient supplementation of trace elements (TEs) limits the progression of anaerobic digestion. The main reason for this is the lack of sufficient understanding of digestion substrate characteristics, which significantly affects the demand for TEs. In this review, the relationship between TEs requirements and substrate characteristics is discussed. We mainly focus on three aspects. 1) The basis for TE optimization and existing problems: The optimization of TEs often based on the total solids (TS) or volatile solids (VS) of substrates, does not fully consider substrate characteristics. 2) TE deficiency mechanisms for different types of substrates: nitrogen-rich, sulfur-rich, TE-poor, and easily hydrolyzed substrates are the four main types of substrates. The mechanisms underlying TEs deficiency in the different substrates are investigated. 3) Regulation of TE bioavailability: characteristics of substrates affect digestion parameters, which disturb the bioavailability TE. Therefore, methods for regulating bioavailability of TEs are discussed.

Conductive materials as fantastic toolkits to stimulate direct interspecies electron transfer in anaerobic digestion: new insights into methanogenesis contribution, characterization technology, and downstream treatment

Direct interspecies electron transfer (DIET) stimulated by conductive materials (CMs) enables intercellular metabolic coupling that can address the unfavorable thermodynamical dilemma inherent in anaerobic digestion (AD). Although the DIET mechanism and stimulation have been extensively summarized, the methanogenesis contribution, characterization techniques, and downstream processes of CMs-led DIET in AD are surprisingly under-reviewed. Therefore, this review aimed to address these gaps. First, the contribution of CMs-led DIET to methanogenesis was re-evaluated by comparing the effect of various factors, including volatile fatty acids, free ammonia, and functional enzymes. It was revealed that AD systems are usually intricate and cannot allow the methanogenesis stimulation to be singularly attributed to the establishment of DIET. Additionally, considerable attention has been attached to the characterization of DIET occurrence, involving species identification, gene expression, electrical properties, cellular features, and syntrophic metabolism, suggesting the significance of accurate characterization methods for identifying the syntrophic metabolism interactions. Moreover, the type of CMs has a significant impact on AD downstream processes involving biogas purity, sludge dewaterability, and biosolids management. Finally, the central bottleneck consists in building a mathematical model of DIET to explain the mechanism of DIET in a deeper level from kinetics and thermodynamics.

Volatile Fatty Acids (VFA) Production and Recovery from Chicken Manure Using a High-Solid Anaerobic Membrane Bioreactor (AnMBR)

Acidogenic fermentation of chicken manure (CM) for production and recovery of volatile fatty acids (VFA) is an interesting biological waste-to-value approach compared to benchmark organic waste management strategies. Considering the wide range of high value applications of VFA, a semi-continuous immersed anaerobic membrane bioreactor (AnMBR) was applied to boost VFA productivity and yield, while reducing downstream processing stages assisting the recovery of VFA. In this regard, the effect of parameters such as pH and organic loading rates (OLR) on the overall bioconversion and filtration performance was investigated. Thermal-shocked CM was applied both as inoculum and substrate. A very high VFA yield (0.90 g-VFA/g-VS) was obtained in the treatment with no pH control (~8.2) at an OLR of 2 g-VS/(L·d), presenting 24% higher yield compared to that of the controlled pH. Batch assays further demonstrated the enhanced hydrolysis and acidogenesis activities at weak alkaline conditions. A long-term (78 days) fermentation and filtration was successfully performed, where stable membrane filtration performance was experienced for about 50 days under high-solid (suspended solid of 37-45 g/L) and high flux (20 L/(m²·h)) conditions. Results suggest that AnMBR of CM is a feasible and promising process for VFA production and recovery.

The role of biochar on alleviating ammonia toxicity in anaerobic digestion of nitrogen-rich wastes: A review

This paper reviewed the mechanisms of biochar in relieving ammonia inhibition. Biochar affects nitrogen-rich waste's anaerobic digestion (AD) performance through four ways: promotion of direct interspecies electron transfer (DIET) and microbial growth, adsorption, pH buffering, and provision of nutrients. Biochar enhances the DIET pathway by acting as an electron carrier. The role of DIET in relieving ammonia nitrogen may be exaggerated because many related studies don't provide definite evidence. Therefore, some bioinformatics technology should be used to assist in investigating DIET. Biochar absorbs ammonia nitrogen by chemical adsorption (electrostatic attraction, ion exchange, and complexation) and physical adsorption. The absorption efficiency, mainly affected by the properties of biochar, pH and temperature of AD, can reach 50 mg g^-1 on average. The biochar addition can buffer pH by reducing the concentrations of VFAs, alleviating ammonia inhibition. In addition, biochar can release trace elements and increase the bioavailability of trace elements.

Syntrophic propionate-oxidizing bacteria in methanogenic systems

The mutual nutritional cooperation underpinning syntrophic propionate degradation provides a scant amount of energy for the microorganisms involved, so propionate degradation often acts as a bottleneck in methanogenic systems. Understanding the ecology, physiology and metabolic capacities of syntrophic propionate-oxidizing bacteria (SPOB) is of interest in both engineered and natural ecosystems, as it offers prospects to guide further development of technologies for biogas production and biomass-derived chemicals, and is important in forecasting contributions by biogenic methane emissions to climate change. SPOB are distributed across different phyla. They can exhibit broad metabolic capabilities in addition to syntrophy (e.g. fermentative, sulfidogenic and acetogenic metabolism) and demonstrate variations in interplay with cooperating partners, indicating nuances in their syntrophic lifestyle. In this review, we discuss distinctions in gene repertoire and organization for the methylmalonyl-CoA pathway, hydrogenases and formate dehydrogenases, and emerging facets of (formate/hydrogen/direct) electron transfer mechanisms. We also use information from cultivations, thermodynamic calculations and omic analyses as the basis for identifying environmental conditions governing propionate oxidation in various ecosystems. Overall, this review improves basic and applied understanding of SPOB and highlights knowledge gaps, hopefully encouraging future research and engineering on propionate metabolism in biotechnological processes.

Impact of electro-conductive nanoparticles additives on anaerobic digestion performance - A review

Anaerobic digestion (AD) is a biochemical process that converts waste organic matter into energy-rich biogas with methane as the main component. Addition of electric electro-conductive, such as that nanoparticles (NP), has been shown to improve biogas generation. Interspecies electron transfer and direct interspecies electron transfer (DIET) using conductive materials is one of the mechanisms responsible for observed increases in CH₄. This article discusses the effect of the type and size of electro-conductive NPs on improving microbial degradation within AD systems, as well as the effect of electro-conductive NPs on microbial community shifts and syntrophic metabolism. Limitations and future perspectives of using NPs in an AD system is also discussed.

Prediction of methane production from co-digestion of lignocellulosic biomass with sludge based on the major compositions of lignocellulosic biomass

In the present study, the simplex lattice mixture design method was adopted to design the artificial biomass with different ratios of three major components (cellulose, hemicellulose, lignin). The methane yield from the co-digestion of the artificial/ natural biomass (corn stover, wheat stover, rice straw, and peanut stalk) samples with the mixed sludge at the mixture ratio of 1:1 based on total solid (TS) content was recorded for 50 days. The original mathematical prediction models for estimating the cumulative methane production, maximum methane production rate, and lag phase time were established based on the experimental results from the co-digestion of artificial biomass with sludge. To investigate the influence of the structural features of biomass and interactions among the components of biomass which contributing to the inhibition of methane production, the macroscopic factor (MF) was proposed. The mathematical models which revealed the relationship between MF and the methane production parameters were developed by the combination of the prediction results from the original mathematical prediction model and experimental results from the co-digestion of natural biomass with sludge. Modification of the original mathematical prediction models was carried out by considering MF. After modification, the relative error (RE) and root mean square error (RMSE) of the prediction model for cumulative methane production were declined from 19.00 to 30.18% and 42.38 mL/g VS_added to that of - 1.93~7.14% and 4.36 mL/g VS_added, respectively.

Effect of metal nanoparticles in anaerobic digestion production and plant uptake from effluent fertilizer

Nanoparticle (NP) use can increase biological activity and adversely impact the environment. This study was the first to quantify biogas increases with NP mixtures during continuous anaerobic digestion (AD) of poultry litter and NP uptake in crops through tracking: 1) CH₄ and H₂S production from a NP mixture (Fe, Ni, and Co) in 30 L continuous digester (AD1) for 278 days compared to a control digester (AD2) without NP addition, 2) NP degradation during digestion, 3) using AD effluent with and without NP addition as a fertilizer, and 4) plant uptake of NPs. With NP inclusion, CH₄ production increased by 23.7%, and H₂S was reduced by 56.3%. The AD1 effluent had 1,160-19,400% higher NP concentrations and the lettuce biomass had 21.0-1,920% more NPs than lettuce fertilized with the AD2 effluent. This study showed that the effects of NPs remaining in the AD effluent must be considered.

Trace Element Supplementation and Enzyme Addition to Enhance Biogas Production by Anaerobic Digestion of Chicken Litter

Anaerobic digestion (AD) of chicken litter (CL) is a viable alternative to disposal. However, methane yields from this primarily organic waste are quite low when mono-digested. This paper discusses the effect of an enzyme cocktail, trace element (TE) supplementation and selenium (Se) addition in small-scale batch biomethane potential (BMP) assays to enhance the AD of CL. Eleven different assays were set up in triplicate including assays containing only inoculum (blank), only CL (negative control) and cellulose and inoculum (positive control). The results indicate that both enzyme treatment and trace element supplementation enhanced the biogas and methane yield. The highest specific biogas and methane yields were noted for 1% enzyme-treated CL of 835.2 L/kg volatile solids (VS) and 460.8 L/kg VS, respectively. Usually, mono-digestion of CL is low due to high nitrogen content and the presence of recalcitrant lignocellulosic material from the bedding material. Enzyme treatment performed better than the addition of the TE mix and Se.

Metabolic performance of anaerobic digestion of chicken manure under wet, high solid, and dry conditions

The anaerobic digestion (AD) of chicken manure as a solo substrate has been challenging due to the ammonium inhibition effects when adopting a high organic loading rate (OLR). In this study, through increasing both the total solid in the feeding materials from 5% to 20%, and the OLR from 1.7 to 7.1 g-volatile solids (VS)/(L·d), the AD of chicken manure under wet, high solid, and dry conditions, with a fixed hydraulic retention time of 20 days, was investigated. The results obtained indicated that the wet AD system could achieve a methane yield of 0.28 L/g-VS and a low volatile fatty acid level. However, the process deteriorated under dry conditions, and methane formed mainly through acetate oxidation and methanogenesis. Methanosarcina and Methanoplasma were found to be more tolerant But, whether the dry AD of chicken manure can survive an ammonia-stressed environment when the OLR is lowered, still needs investigation.

Implications of poultry litter usage for electricity production

Poultry litter has the potential to cause water quality problems if it is not applied properly to the land as a crop nutrient. Based on the data available from a survey of Louisiana poultry producers, we find that it is not cost effective to transport poultry litter farther than 38.6 km from the production facilities for crop nutrient purposes. This limited breakeven distance restricts the movement of poultry litter and points to a need to identify an alternative disposal method. We review common methods of producing electricity from poultry litter. We identify the minimum cost solution for assigning poultry litter when one large or three small electric reactors are chosen to be built for electricity production in the poultry production region. We calculate the cost-return analysis of building electric reactors and expand it to find the economic impact of starting such electric reactors to the local and regional economies.

Enhanced methanogenic performance and metabolic pathway of high solid anaerobic digestion of chicken manure by Fe2+ and Ni2+ supplementation

High solid anaerobic digestion (AD) is a promising technology for the treatment of organic waste in terms of efficient bioenergy production and digestate volume reduction. However, the high solid AD of chicken manure has been a challenge due to the inhibition effects caused by high ammonia levels. In this study, the addition of 280 mg/L Fe²⁺ and 2 mg/L Ni²⁺ has been proven to enhance the microbial activity and to overcome inhibition under the stressed environment. The mesophilic digesters feeding with total solid around 150 g/kg operated at an organic loading rate of 4.8 g/(L d) based on volatile solid and a 20-day hydraulic retention time. The total ammonia-nitrogen reached around 6.8 g/L in control and Fe-Ni digesters. The results from the 147-day continuously-fed experiment provided an increment of 34% methane production and a 29% reduction of volatile fatty acids against control. The acetoclastic and hydrogenotrophic methanogenic activity was increased by 89% and 40% respectively. The high throughout sequencing results showed an increased percentage of Methanosarcina sp., which may have contributed to the shifting of the methanogenic pathway towards acetoclastic methanogenesis. The positive effects of Fe²⁺ and Ni²⁺ supplementation obtained in this study lay the foundation for its use in AD of nitrogen rich materials.

Impact of metal nanoparticles on biogas production from poultry litter

The effects of metal nanoparticle (NP) addition during anaerobic digestion (AD) of poultry litter was tested using two sequential experiments: Exp. A) four NPs (Fe, Ni, Co, and Fe₃O₄) at three concentrations; and Exp. B) NP combinations (Fe, Ni, and Co) at four concentrations. Scanning electronic microscopy (SEM) and elemental analysis were used to confirm NP inclusion after dispersion (before AD) and track nanoparticles post-AD, and new technique for NP extraction post-AD was developed. Before AD, NPs ranged from 30.0 to 80.9 nm for Fe, Ni, and Co, and 94.3 to 400 nm for Fe₃O₄. Methane production increased with NPs addition compared to poultry litter-only, with the highest increases observed with NPs concentrations (in mg/L) of 12 Ni (38.4% increase), 5.4 Co (29.7% increase), 100 Fe (29.1% increase), and 15 Fe₃O₄ (27.5% increase). Nanoparticle mixtures greatly decreased H₂S production. The SEM post-AD detected Fe, Ni, and Fe₃O₄ at concentrations ≥100 mg/L.

Leaching and anaerobic digestion of poultry litter for biogas production and nutrient transformation

Anaerobic digestion of poultry litter is a potentially sustainable means of stabilizing this waste while generating biogas. However, technical challenges remain including seasonality of litter production, low C/N ratios, limited digestibility of bedding, and questions about transformation of nutrients during digestion. This study investigated biogas production and nutrient transformations during anaerobic digestion of poultry litter leachate and whole litter. Use of fresh litter collected from within the house was also compared to waste litter cake that was stored outdoors on the farm. The results showed that litter leachates had higher biomethane potential (0.24-0.30 L/gVS) than whole litter (0.15-0.16 L/gVS) and the insoluble bedding material left after leaching (0.08-0.13 L/gVS). Leachates prepared from waste litter cake had lower uric acid and higher acetic acid concentrations than fresh litter indicating that decomposition had occurred during storage. Consequently, waste litter cake had faster initial biogas production but lower final biogas yields compared to fresh litter. In all reactors, uric and acetic acids were completely consumed during digestion, phosphate levels decreased but ammonium levels increased. The results demonstrate that poultry litter leachate is amenable to digestion despite a low C/N ratio and that the remaining insoluble bedding material has been partially stripped of its nutrients. Moreover, litter can be stored prior to digestion but some losses in biomethane potential should be expected due to decomposition of organics during storage.

Anaerobic digestion of chicken manure: Influence of trace element supplementation

In this study, anaerobic digestion of nitrogen-rich chicken (egg-laying hen) manure at different trace element (TE) mix doses and different total ammonia nitrogen (TAN) concentrations was investigated in batch digestion experiments. With respect to nonsupplemented TE sets, addition of TE mixture containing 1 mg/L Ni, 1 mg/L Co, 0.2 mg/L Mo, 0.2 mg/L Se, 0.2 mg/L W, and 5 mg/L Fe at TAN concentrations of 3000 mg/L and 4000 mg/L, cumulative CH₄ production and CH₄ production rate improved by 7-8% and 5-6%, respectively. The results revealed that at a very high TAN concentration of 6000 mg/L, the effect of TE addition was significantly high and the cumulative CH₄ production and production rate were increased by 20 and 39.5%, respectively. Therefore, it is concluded that at elevated TAN concentrations the CH₄ production that was stimulated by TE supplementation was presumably occurred through syntrophic acetate oxidation.