Dry anaerobic digestion of chicken manure coupled with membrane separation of ammonia

Microwave-assisted organic acids and green hydrogen production during mixed culture fermentation

BACKGROUND

The integration of anaerobic digestion into bio-based industries can create synergies that help render anaerobic digestion self-sustaining. Two-stage digesters with separate acidification stages allow for the production of green hydrogen and short-chain fatty acids, which are promising industrial products. Heat shocks can be used to foster the production of these products, the practical applicability of this treatment is often not addressed sufficiently, and the presented work therefore aims to close this gap.

METHODS

Batch experiments were conducted in 5 L double-walled tank reactors incubated at 37 °C. Short microwave heat shocks of 25 min duration and exposure times of 5-10 min at 80 °C were performed and compared to oven heat shocks. Pairwise experimental group differences for gas production and chemical parameters were determined using ANOVA and post-hoc tests. High-throughput 16S rRNA gene amplicon sequencing was performed to analyse taxonomic profiles.

RESULTS

After heat-shocking the entire seed sludge, the highest hydrogen productivity was observed at a substrate load of 50 g/l with 1.09 mol H2/mol hexose. With 1.01 mol H2/mol hexose, microwave-assisted treatment was not significantly different from oven-based treatments. This study emphasised the better repeatability of heat shocks with microwave-assisted experiments, revealing low variation coefficients averaging 29%. The pre-treatment with microwaves results in a high predictability and a stronger microbial community shift to Clostridia compared to the treatment with the oven. The pre-treatment of heat shocks supported the formation of butyric acid up to 10.8 g/l on average, with a peak of 24.01 g/l at a butyric/acetic acid ratio of 2.0.

CONCLUSION

The results support the suitability of using heat shock for the entire seed sludge rather than just a small inoculum, making the process more relevant for industrial applications. The performed microwave-based treatment has proven to be a promising alternative to oven-based treatments, which ultimately may facilitate their implementation into industrial systems. This approach becomes economically sustainable with high-temperature heat pumps with a coefficient of performance (COP) of 4.3.

Organic manures enhance biomass and improve content, chemical compounds of essential oil and antioxidant capacity of medicinal plants: A review

The current farming systems strongly depend on chemical fertilizers (CF), which are widely applied to increase crop yield worldwide. However, although CF enhance crop yield in the short term, their excessive and long-term application can have adverse effects on environmental and human health. One of the most important goals of sustainable agriculture is substituting CF with organic manures. Organic manures can be used as a low-cost and safe alternative for CF. They contain essential nutrients for crop growth, improve soil conditions and nutrient availability, increase plant growth, and ultimately enhance yield. The application of organic manures to medicinal plants (MP) is more critical than to other plants, because organic manures not only enhance the growth and productivity of MP but also modify quality of their products. In this review, the effect of different types of organic manures on the biomass, content and chemical compositions of essential oil and antioxidant activity of various MP has been investigated. The included information was gathered from scientific databases such as Science Direct, Google Scholar, PubMed, and Scopus. Many of the collected studies showed that organic manures increase biomass and improve the quality of these plants. The findings of this review indicate that broiler litter (BL) and compost (C) are highly recommended as organic manures to promote biomass. Moreover, C, sheep manure, and vermicompost (VC) are suggested as the optimal organic manures for enhancing the essential oil content. Organic manures significantly changed the aroma profile of the essential oils and in many cases, they enhanced major chemical compositions. The usage of VC raised the content of the linalool of studied MP. Most of the organic manures, especially BL, VC, farmyard manure, and poultry manure increased the antioxidant activity of these plants. Hence, the utilization of organic manures can be recommended for productivity enhancement and quality improvement of MP.

Syntrophic consortium with the aid of coconut shell-derived biochar enhances methane recovery from ammonia-inhibited anaerobic digestion

Anaerobic digestion (AD) of nitrogen-rich substrates often suffers from the issue of ammonia inhibition. Although bioaugmentation has been used to assist AD with high ammonia concentration, the combined effect of domesticated syntrophic consortium (MC) together with biochar on ammonia inhibited AD are still unknown. In the present study, MC was adapted and enriched by purposive domestication. As a novel strategy, coconut shell-derived biochar was used as a carrier to aid the MC. The results showed that the digestion system deteriorated completely without the assistance of MC and biochar when the TAN concentration exceeded 8.0 g L^-1. The combination of biochar and MC (B-MC treatment) could restore ammonia inhibition in 10 days and achieved a high methane yield of 357.5 mL g^-1 volatile solid, which was 7.5 % higher than that of MC treatment. Syntrophomonas, Syntrophobacter, and Methanoculleus in MC played a critical role in reducing propionic acid and butyric acid content and efficiently producing methane. Their abundances increased 12-fold, 10-fold, and 2-fold, respectively. With the assistance of biochar, MC had a better performance in relieving ammonia inhibition. This could be attributed to two aspects. First, biochar encouraged the growth or colonization of key microorganisms such as propionate and butyrate oxidizing bacteria and ammonia-tolerant archaea. Second, biochar induced the growth of conductive microorganisms such as Geobacter. From the perspective of enzyme genes, biochar increased the abundance of related enzyme genes in butyrate and propionate degradation, acetoclastic and hydrogenotrophic pathways. In conclusion, MC combined with biochar is a potential approach to alleviate ammonia nitrogen inhibition.

Inhibitory mechanisms on dry anaerobic digestion: Ammonia, hydrogen and propionic acid relationship

Inhibitory pathways in dry anaerobic digestion are still understudied and current knowledge on wet processes cannot be easily transferred. This study forced instability in pilot-scale digesters by operating at short retention times (40 and 33 days) in order to understand inhibition pathways over long term operation (145 days). The first sign of inhibition at elevated total ammonia concentrations (8 g/l) was a headspace hydrogen level over the thermodynamic limit for propionic degradation, causing propionic accumulation. The combined inhibitory effect of propionic and ammonia accumulation resulted in further increased hydrogen partial pressures and n-butyric accumulation. The relative abundance of Methanosarcina increased while that of Methanoculleus decreased as digestion deteriorated. It was hypothesized that high ammonia, total solids and organic loading rate inhibited syntrophic acetate oxidisers, increasing their doubling time and resulting in its wash out, which in turn inhibited hydrogenotrophic methanogenesis and shifted the predominant methanogenic pathway towards acetoclastic methanogenesis at free ammonia over 1.5 g/l. C/N increases to 25 and 29 reduced inhibitors accumulation but did not avoid inhibition or the washout of syntrophic acetate oxidising bacteria.

Prediction of methane yield and pretreatment efficiency of lignocellulosic biomass based on composition

Lignocellulosic biomass is considered a key resource for the future expansion of biogas production through anaerobic digestion (AD), and research on the development of pretreatment technologies for improving biomass conversion is an intensive and fast-growing field. Consequently, there is a need for creating tools able to predict the efficiency of a certain pretreatment on different biomass types, fast and accurately, and to assist in selecting a pretreatment technology for a specific biomass. In this study, seven different types of raw lignocellulosic biomass of industrial relevance were systematically analyzed regarding their composition (carbohydrates, lignin, lipids, ash, extractives, etc.) and subjected to a common pretreatment. The aim of the study was to identify the most important characteristics that make a biomass good receptor of the specific pretreatment prior to AD. A simple ammonia pretreatment was chosen as a case study and partial least squares regression (PLS-R) was used for modeling initially the ultimate methane yield of raw and pretreated biomass. In the sequel, PLS-R was used for modeling the efficiency of the pretreatment on increasing the ultimate methane yield and hydrolysis rate as a function of the biomass composition. The fit of the models was satisfactory, ranging from R² = 0.89 to R² = 0.97. The results showed that the most decisive characteristics for predicting the efficiency of the pretreatment were the lipid (r = -0.88), ash (r = +0.79), protein (r = -0.61), and hemicellulose/lignin (r = -0.53) content of raw biomass. Finally, the approach followed in this study facilitated an improved understanding of the mechanism of the pretreatment and presented a methodology to be followed for developing tools for the prediction of pretreatment efficiency in the field of lignocellulosic biomass valorization.

Membrane Technologies for Nitrogen Recovery from Waste Streams: Scientometrics and Technical Analysis

The concerns regarding the reactive nitrogen levels exceeding the planetary limits are well documented in the literature. A large portion of anthropogenic nitrogen ends in wastewater. Nitrogen removal in typical wastewater treatment processes consumes a considerable amount of energy. Nitrogen recovery can help in saving energy and meeting the regulatory discharge limits. This has motivated researchers and industry professionals alike to devise effective nitrogen recovery systems. Membrane technologies form a fundamental part of these systems. This work presents a thorough overview of the subject using scientometric analysis and presents an evaluation of membrane technologies guided by literature findings. The focus of nitrogen recovery research has shifted over time from nutrient concentration to the production of marketable products using improved membrane materials and designs. A practical approach for selecting hybrid systems based on the recovery goals has been proposed. A comparison between membrane technologies in terms of energy requirements, recovery efficiency, and process scale showed that gas permeable membrane (GPM) and its combination with other technologies are the most promising recovery techniques and they merit further industry attention and investment. Recommendations for potential future search trends based on industry and end users' needs have also been proposed.

Bioaugmentation with methanogenic culture to improve methane production from chicken manure in batch anaerobic digestion

This study sought to investigate the effect of bioaugmentation on batch anaerobic digestion of chicken manure. The digestion performance with and without bioaugmentation and bioaugmented efficiency under different dosages were compared. The results demonstrated that bioaugmentation increased the methane yield and shortened the methane production time in batch reactors. Compared to the un-bioaugmented control, the methane yield of bioaugmented digesters was increased by 1.2-, 1.7-, 2.2-, 3.4-, and 3.6-fold at addition ratios of 0.07, 0.14, 0.21, 0.27, and 0.34 g VS _{bioaugmentation seed (BS)}/g VS_CM, respectively. However, higher bioaugmentation doses (0.34 g VS_BS/g VS_CM) did not exhibit significantly improved bioaugmentation efficiency, thus, the recommended dose is 0.27 g VS_BS/g VS_CM for biomethane conversion of CM. Moreover, whole genome pyrosequencing revealed that Methanoculleus and Methanobrevibacter predominated the non-bioaugmentation digesters, whereas Methanothrix, Methanobacterium, and Methanomassiliicoccus were the dominant methanogens in bioaugmentation digesters. The increased methane may be explained by an increase in the Methanothrix population, which accelerated acetic acid degradation. With bioaugmentation the mainly methanogenic pathways have become more diverse. From gene function perspective, bioaugmentation enhanced metabolic activities in digestor which function better in metabolism.

Ammonia recovery from acidogenic fermentation effluents using a gas-permeable membrane contactor

A gas-permeable membrane (GPM) contactor was used to recover ammoniacal nitrogen from a synthetic and a biowaste fermentation broth under different pH (from 6 to 11) and temperatures (35 and 55 °C). Ammonia mass transfer constant (K_m) increased as pH and temperature increased. For synthetic broth, pH 10 provided the best results, when considering the K_m (9.2·10^-7 m·s^-1) and the reagents consumption (1.0 mol NaOH·mol^-1 TAN and 0.6 mol H₂SO₄·mol^-1 TAN). Biowaste fermentation generated a broth with a high concentration of ammoniacal nitrogen (4.9 g N·L^-1) and volatile fatty acids (VFA) (41.1 g COD·L^-1). Experiments using the biowaste broth showed a lower K_m (5.0·10^-7 m·s^-1 at pH 10) than the synthetic broth, related to the solution matrix and other species interference. VFAs were not detected in the trapping solution. Overall, these results show that GPM is a suitable technology to efficiently separate ammoniacal nitrogen and VFA from fermentation broths.

Managing the Effluents of Anaerobic Fermentations by Bioprocess Schemes Involving Membrane Bioreactors and Bio-Electrochemical Systems: A Mini-Review

Anaerobic bioprocesses, such as anaerobic digestion and dark fermentation, provide energy carriers in the form of methane and hydrogen gases, respectively. However, their wastewater-type residues, that is, the fermentation effluents, must be treated carefully due to the incomplete and non-selective conversion of organic matter fed to the actual system. For these reasons, the effluents contain various secondary metabolites and unutilized substrate, in most cases. Only a fraction of anaerobic effluents can be directly applied for fertilization under a moderate climate. Conventional wastewater treatment technologies may be used to clean the remainder, but that approach leads to a net loss of energy and of potentially useful agricultural input materials (organic carbon and NPK fertilizer substitutes). The rationale of this paper is to provide an overview of promising new research results in anaerobic effluent management strategies as a part of technological downstream that could fit the concept of new-generation biorefinery schemes aiming towards zero-waste discharge, while keeping in mind environmental protection, as well as economical perspectives. According to the literature, the effluents of the two above processes can be treated and valorized relying either on membrane bioreactors (in case of anaerobic digestion) or bio-electrochemical apparatus (for dark fermentation). In this work, relevant findings in the literature will be reviewed and analyzed to demonstrate the possibilities, challenges, and useful technical suggestions for realizing enhanced anaerobic effluent management. Both membrane technology and bio-electrochemical systems have the potential to improve the quality of anaerobic effluents, either separately or in combination as an integrated system.

Material characterization and conditioning of cattle feedlot manure as feedstock for dry batch anaerobic digestion

The focus of the study was to determine the suitability of cattle feedlot manure originating from clay-pack feedlots as a possible feedstock material for dry batch anaerobic digestion. Oedometer tests were carried out that measure the permeability and compressibility of the feedstock under practical conditions experienced in large-scale dry batch anaerobic digestion plants. Material characterization tests showed that feedlot manure was impermeable under compression and therefore unsuitable for percolation. Mixtures of feedlot manure, wood chips (3 %ww) and wheat straw (6 %ww) showed superior permeability under compression compared to feedlot manure alone with an 56% increased permeability. Further practical tests showed that dry digestion of feedlot manure mixtures led to methane yields of 99 mL/g VS which equals 86% of the material biochemical methane potential (BMP). High percolation rate and low inoculum recycle led to the highest specific methane yield (SMY) and digester productivity with implications on process design to reduce capital investment costs.

Moisture content and aeration control mineral nutrient solubility in poultry litter

Poultry litter waste is typically land-applied as a soil amendment but repeated application in the vicinity of poultry houses has led to phosphorus accumulation in soil. Such application can also lead to runoff that causes eutrophication. Most farmers store litter under dry conditions or compost the litter prior to land application, but it is not clear if these approaches are best from a nutrient management-perspective. The objective of this study was to investigate the effects of moisture content and active aeration on soluble mineral forms of nitrogen and phosphorus in poultry litter incubated for roughly one month. Mineral forms of nutrients are immediately plant-available upon field application and also most conducive to low-cost stripping and recovery methods. Litters were incubated at 50% and 70% moisture content with and without active aeration. Litter aeration led to significant ammonia losses and a consequent decline in litter pH but it had no effect on phosphate solubility. Moisture content during litter incubation governed the levels of plant-available phosphate and nitrification. High (70%) moisture led to 41%-78% higher plant-available phosphate (4.2-4.8 mg/g litter) compared to litters with 50% moisture content (2.7-3.0 mg/g litter). In contrast, the 50% moisture litters experienced 5-6 fold higher levels of nitrification (0.11-0.12 mg NO₃-N/g litter) than litters with 70% moisture content (0.02 mg NO₃-N/g litter), regardless of aeration. The implication is that lower-moisture litter storage is likely best for field application because phosphate is less soluble under neutral-alkaline conditions and therefore less likely to end up in runoff. In contrast, higher-moisture litter storage may be amenable to low-cost processes to leach and recover phosphate from litter.

Anaerobic digestion of organic waste: Recovery of value-added and inhibitory compounds from liquid fraction of digestate

Anaerobic digestion, as an eco-friendly waste treatment technology, is facing the problem of low stability and low product value. Harvesting value-added products beyond methane and removing the inhibitory compounds will unleash new vitality of anaerobic digestion, which need to be achieved by selective separation of certain compounds. Various methods are reviewed in this study for separating valuable products (volatile fatty acids, medium-chain carboxylic acids, lactic acid) and inhibitory substance (ammonia) from the liquid fraction of digestate, including their performance, applicability, corresponding limitations and roadmaps for improvement. In-situ extraction that allows simultaneous production and extraction is seen as promising approach which carries good potential to overcome the barriers for continuous production. The prospects and challenges of the future development are further analyzed based on in-situ extraction and economics.

Improvement of solid-state anaerobic digestion of broiler farm-derived waste via fungal pretreatment

Fungus, Trichoderma longibrachiatum, was used for the pretreatment of broiler farm derived-lignocellulosic bedding material (rice husk) to enhance the subsequent solid-state anaerobic digestion (SS-AD). Fungal pretreatment efficacy was evaluated through a series of batch studies with respect to carbon-to-nitrogen (C/N) ratio and pretreatment time. Lignocellulosic outer layer structure disruption of the rice husk was prominent under the best fungal pretreatment condition evaluated (C/N ratio of 18.9 and pretreatment time of 7 days). Consequently, the resulting methane yield of 438.1 ± 20.0 NmL/gVS_added was obtained which was ~2.0-folds higher than that of the control (without pretreatment). Furthermore, in semi-continuous SS-AD, fungal pretreatment could significantly enhance digestibility of organic substance in high solid loading (30% total solids) AD process by 3.2-folds and improve microbial kinetic parameters with subsequent daily methane yield improvement by 2.4-folds. Thus, fungal pretreatment could be an environmentally-friendly and effective low-cost approach for broiler farm-derived waste management to enhance SS-AD efficacy.

Obstacles faced by methanogenic archaea originating from substrate-driven toxicants in anaerobic digestion

Anaerobic digestion (AD) is used to treat waste and produce bioenergy. However, toxicants, which originate from the substrate, can inhibit or damage the digestion process. Methanogenic archaea (MA), which are the executor in the methanogenesis stage, are more sensitive than bacteria to these toxicants. This review discusses the effects of substrate-driven toxicants, namely, antibiotics, H₂S and sulfate, heavy metals (HMs), long-chain fatty acids (LCFAs), and ammonia nitrogen, on the activity of MAs, methanogenic pathways, and the inter-genus succession of MAs. The adverse effects of these five toxicants on MA include effects on pH, damages to cell membranes, the prevention of protein synthesis, changes in hydrogen partial pressure, a reduction in the bioavailability of trace elements, and hindrance of mass transfer. These effects cause a reduction in MA activity and the succession of MAs and methanogenic pathways, which affect AD performance. Under the stress of these toxicants, succession occurs among HA (hydrogenotrophic methanogen), AA (acetoclastic methanogen), and MM (methylotrophic methanogen), especially HA gradually replaces AA as the dominant MA. Simultaneously, the dominant methanogenic pathway also changes from the aceticlastic pathway to other methanogenic pathways. A comprehensive understanding of the impact of toxicants on MA permits more specific targeting when developing strategies to mitigate or eliminate the effects of these toxicants.

Transitions of microbial communities in the solid and liquid phases during high-solids anaerobic digestion of organic fraction of municipal solid waste

This study presents a microbiological diagnosis of a mesophilic high-solids anaerobic digestion (HSAD) system with percolate recirculation. The results demonstrated a significant decrease in microbial diversity in both the solid digestate and the liquid percolate. Also, the digestate from the top and middle sections of the digester had similar diversity, whereas the digestate from the bottom of the tank had a slightly lower diversity. These results suggest that despite percolate recirculation, substrate gradients might have developed across the system. Archaeal communities showed shifts towards known hydrogenotrophic and ammonia-tolerant methanogens (genera Methanocelleus, Methanolinea, Methanosarcina, vadin CA11, etc.), which was a consequence of decreased volatile fatty acids and increased ammonia-nitrogen levels over time. Compared to initial solid and liquid inoculum, the relative abundances of some bacteria (phyla Proteobacteria and Firmicutes) and archaea of the genus Methanosarcina changed between two phases in the opposite direction, indicating a shift of microbes between two phases.

Material Characterization and Substrate Suitability Assessment of Chicken Manure for Dry Batch Anaerobic Digestion Processes

Chicken manure is an agricultural residue material with a high biomass potential. The energetical utilization of this feedstock via anaerobic digestion is an interesting waste treatment option. One waste treatment technology most appropriate for the treatment of stackable (non-free-flowing) dry organic waste materials is the dry batch anaerobic digestion process. The aim of this study was to evaluate the substrate suitability of chicken manure from various sources as feedstock for percolation processes. Chicken manure samples from different housing forms were investigated for their chemical and physical material properties, such as feedstock composition, permeability under compaction and material compressibility. The permeability under compaction of chicken manure ranged from impermeable to sufficiently permeable depending on the type of chicken housing, manure age and bedding material used. Porous materials, such as straw and woodchips, were successfully tested as substrate additives with the ability to enhance material mixture properties to yield superior permeability and allow sufficient percolation. In dry anaerobic batch digestion trials at lab scale, the biogas generation of chicken manure with and without any structure material addition was investigated. Digestion trials were carried out without solid inoculum addition and secondary methanization of volatile components. The specific methane yield of dry chicken manure was measured and found to be 120 to 145 mL/g volatile solids (VS) and 70 to 75 mL/g fresh matter (FM), which represents approximately 70% of the methane potential based on fresh mass of common energy crops, such as corn silage.

Influence of Aerobic Pretreatment of Poultry Manure on the Biogas Production Process

Anaerobic digestion of poultry manure is a potentially-sustainable means of stabilizing this waste while generating biogas. However, technical, and environmental protection challenges remain, including high concentrations of ammonia, low C/N ratios, limited digestibility of bedding, and questions about transformation of nutrients during digestion. This study evaluated the effect of primary biological treatment of poultry manure on the biogas production process and reduction of ammonia emissions. Biogas yield from organic matter content in the aerobic pretreatment groups was 13.96% higher than that of the control group. Biogas production analysis showed that aerobic pretreatment of poultry manure has a positive effect on biogas composition; methane concentration increases by 6.94–7.97% after pretreatment. In comparison with the control group, NH3 emissions after aerobic pretreatment decreased from 3.37% (aerobic pretreatment without biological additives) to 33.89% (aerobic pretreatment with biological additives), depending on treatment method.

Two-stage anaerobic digestion of food waste coupled with in situ ammonia recovery using gas membrane absorption: Performance and microbial community

A two-stage GAs Membrane Absorption anaerobic Reactor (GAMAR) was developed by combining the gas membrane absorption (GMA) system with two-stage anaerobic digestion. The two-stage configuration consisted of an acidogenic reactor (AR) and a methanogenic reactor (MR) with GMA. With the application of GMA, the ammonia concentration of MR was maintained at 2200 mgN L^-1 to alleviate potential ammonia inhibition. The setup of AR enhanced hydrolysis and acidogenesis of FW and alleviated volatile fatty acids (VFA) accumulation in MR. Two-stage GAMAR could be operated stably at 6.1 kg VS m^-3 d^-1 and the volumetric biogas production rate was 3.21 m³ m^-3 d^-1. The different environmental conditions caused a significant shift in the microbial community. Lactobacillus and Aeriscardovia became predominant in AR under low pH, while Syntrophomonas was dominant in MR when the reactor was stable. The dominant archaea genus in MR was Methanothrix and it greatly decreased when MR was acidified.

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.

Microbial community response to ammonia levels in hydrogen assisted biogas production and upgrading process

Biological conversion of carbon dioxide into methane using hydrogen derived from surplus renewable energy (wind power) as reducing power is a novel technology for biogas upgrading. High ammonia concentrations are toxic to the biogas upgrading process, however the mechanisms behind the inhibition as well as the microbial stress response in such unique upgrading system have never been reported. Thus, the effect of high ammonia concentrations on microbial community during hydrogen induced biogas upgrading process was evaluated here. The results showed that a change from aceticlastic pathway to hydrogenotrophic pathway occurred when ammonia level increased (1-7 g NH₄⁺-N L^-1). In addition, the bacteria, potentially syntrophic associated with hydrogenotrophic methanogens, were enriched at high ammonia concentrations. Moreover, growth of some bacteria (e.g., Halanaerobiaceaeen and Leucobacter) which were vulnerable to ammonia toxicity was restored upon hydrogen injection. Furthermore, hydrogen injection under high ammonia concentration could promote growth of some hydrolytic and fermentative bacteria.

Enhanced biogas production and in situ ammonia recovery from food waste using a gas-membrane absorption anaerobic reactor

A novel GAs-Membrane Absorption anaerobic Reactor (GAMAR) was developed by combining gas-membrane absorption system with anaerobic digestion. A gas-permeable expanded polytetrafluoroethylene (ePTFE) membrane was submerged in the anaerobic reactor. Free ammonia could transfer through the gas-permeable membrane and be recovered by acidic solution. The free ammonia concentration was lower than 40 mgN L^-1 in GAMAR, which alleviated ammonia inhibition. Meanwhile free ammonia concentration up 70 mgN L^-1 in the reference reactor inhibited methanogens and led to unstable operation. The volumetric biogas production rate of GAMAR was 2.83 m³ m^-3 d^-1, and 58% higher than the reference reactor. Long term use of membrane led to membrane fouling and hydrophobicity loss. The contact angle of membrane decreased from 105.9 ± 1.2° to 97.6 ± 6.3° after 43 d. The abundance of methanogens in GAMAR was 1.8-2.1 times higher than that in the reference reactor, which was in accordance with the higher biogas production rate in GAMAR.

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.

Feasibility of dry anaerobic digestion of beer lees for methane production and biochar enhanced performance at mesophilic and thermophilic temperature

This study investigated the feasibility of dry anaerobic digestion using beer lees as substrate and the effect of cow manure-derived biochar addition on dry anaerobic digestion performance at mesophilic and thermophilic temperature, respectively. With TS content of 25%, maximum cumulative methane production and yield were achieved to be 5230 ± 91 mL d^-1 and 220.1 ± 7.7 mL g^-1 VS at mesophilic condition and 7386 ± 134 mL d^-1 and 310.4 ± 9.2 mL g^-1 VS at thermophilic condition in the control cultures. The biochar addition has a positive effect in improving dry anaerobic digestion performance. The maximum cumulative methane production and yield in the cultures with 10 g L^-1 biochar were substantially improved by 82.9% and 82.6% at mesophilic condition and 47.2% and 46.8% at mesophilic condition when compared to the control.

Solid-State Anaerobic Digestion for Waste Management and Biogas Production

Solid-state anaerobic digestion (SS-AD) is commonly used to treat feedstocks with high solid content such as municipal solid waste and lignocellulosic biomass. Compared to liquid state anaerobic digestion (LS-AD), SS-AD has multiple advantages including high organic loading, minimal digestate generated, and low energy requirement for heating. However, the main disadvantages limiting the efficiency of SS-AD are long solid retention time, incomplete mixing, and an accumulation of inhibitors. For a successful and efficient SS-AD, it is important to control operation parameters such as nutrient levels, C/N ratio, feedstock-to-inoculum ratio, pH, temperature, and mixing. Biogas production in SS-AD performance can be enhanced by feedstock pretreatment, co-digestion, and supplement of additives such as biochar. The aim of this chapter is to provide a comprehensive summary of the current development in SS-AD as an effective way for treating solid waste materials. Graphical Abstract.

Ammonia removal from chicken manure digestate through vapor pressure membrane contactor (VPMC) and phytoremediation

Ammonia removal from synthetic ammonia solutions and chicken manure digestate via vapor pressure membrane contactor through Polytetrafluoroethylene (PTFE) membrane was investigated. The highest ammonia mass flux, separation factor, and removal efficiencies of 28.6 ± 0.2 g N/m² h, 53.9 ± 10.7, and 97.6 ± 0.7% were observed for synthetic solutions, respectively. Ammonia removal efficiency of 93.6 ± 1.9% through membrane contactor was observed for chicken manure digestate decreasing the total ammonia concentration from 3643.5 ± 67.2 to 230.9 ± 46.2 mg N/L. Phytoremediation via Lemna minor species was used as a polishing step to remove remaining ammonia from the membrane contactor effluent. Total ammonia concentration was then decreased below 2 mg N/L through evaporation, nitrification, and plant uptake processes occurring in the phytoremediation containers. This study reveals that ammonia can be successfully removed via VPMC and phytoremediation systems and the process is implementable as it can be coupled to anaerobic digestion processes to recover ammonia and to prevent ammonia inhibition.

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.

Improving exploitation of chicken manure via two-stage anaerobic digestion with an intermediate membrane contactor to extract ammonia

This study describes a modified process of ammonia release through pre-hydrolysis - ammonia removal via membrane contactor - methanization for counteracting ammonia inhibition in anaerobic digestion of chicken manure. In the pre-hydrolysis step, ammonia was rapidly released within the first 3-5 days. 78%-83% of the total nitrogen was finally converted into total ammonia/ammonium (TAN) with volatile fatty acids concentration of approximately 300 g/kg·VS. In the ammonia removal process, diluting the hydrolyzed chicken manure to 1:2, the TAN could be reduced to 2 g/kg in 21 h when pH was increased to 9. The final BMP test of chicken manure verified that lower TAN concentration (decreased to 2 g/kg) significantly reduced inhibitory effects, obtaining a high methane yield of 437.0 mL/g·VS. The investigations underlined several advantages of this modified process.

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

Recent findings showed that some trace elements essential for anaerobic digestion might be deficient in chicken (laying hens) manure. In this study, the long-term influence of trace element deficiency on anaerobic mono-digestion of chicken manure was investigated. Three bench-scale anaerobic reactors were operated with or without trace element supplementation. As trace element, only Se or a mix containing Co, Mo, Ni, Se, and W was added to the reactors. The results revealed that in anaerobic digestion of chicken manure at total ammonium nitrogen concentrations over 6000 mg L^-1, Se supplementation was critical but not sufficient alone for long-term stable CH₄ production. Addition of a mix consisting of Co, Mo, Ni, Se and W resulted in a more stable digestion performance. Daily trace element mix supplementation promoted the hydrogenotrophic Methanoculleus bourgensis, which is an ammonia tolerant methanogen. The decrease in the relative abundance of Methanoculleus detected after termination of trace element addition and resulted in accumulation of acetate and propionate that followed by a significant decrease in CH₄ production.