Anaerobic Digestion Of Manure Research Articles

Denaturing Gradient Gel Electrophoresis Approach for Microbial Shift Analysis in Thermophilic and Mesophilic Anaerobic Digestions.

To determine the evolution of microbial community and microbial shift under anaerobic processes, this study investigates the use of denaturing gradient gel electrophoresis (DGGE). In the DGGE, short- and medium-sized DNA fragments are separated based on their melting characteristics, and this technique is used in this study to understand the dominant bacterial community in mesophilic and thermophilic anaerobic digestion processes. Dairy manure is known for emitting greenhouse gases (GHGs) such as methane, and GHG emissions from manure is a biological process that is largely dependent on the manure conditions, microbial community presence in manure, and their functions. Additional efforts are needed to understand the GHG emissions from manure and develop control strategies to minimize the biological GHG emissions from manure. To study the microbial shift during anaerobic processes responsible for GHG emission, we conducted a series of manure anaerobic digestion experiments, and these experiments were conducted in lab-scale reactors operated under various temperature conditions (28 °C, 36 °C, 44 °C, and 52 °C). We examined the third variable region (V3) of the 16S rRNA gene fingerprints of bacterial presence in anaerobic environment by PCR amplification and DGGE separation. Results showed that bacterial community was affected by the temperature conditions and anaerobic incubation time of manure. The microbial community structure of the original manure changed over time during anaerobic processes, and the community composition changed substantially with the temperature of the anaerobic process. At Day 0, the sequence similarity confirmed that most of the bacteria were similar (>95%) to Acinetobacter sp. (strain: ATCC 31012), a Gram-negative bacteria, regardless of temperature conditions. At day 7, the sequence similarity of DNA fragments of reactors (28 °C) was similar to Acinetobacter sp.; however, the DNA fragments of effluent of reactors at 44 °C and 52 °C were similar to Coprothermobacter proteolyticus (strain: DSM 5265) (similarity: 97%) and Tepidimicrobium ferriphilum (strain: DSM 16624) (similarity: 100%), respectively. At day 60, the analysis showed that DNA fragments of effluent of 28 °C reactor were similar to Galbibacter mesophilus (strain: NBRC 10162) (similarity: 87%), and DNA fragments of effluent of 36 °C reactors were similar to Syntrophomonas curvata (strain: GB8-1) (similarity: 91%). In reactors with a relatively higher temperature, the DNA fragments of effluent of 44 °C reactor were similar to Dielma fastidiosa (strain: JC13) (similarity: 86%), and the DNA fragments of effluent of 52 °C reactor were similar to Coprothermobacter proteolyticus (strain: DSM 5265) (similarity: 99%). To authors' knowledge, this is one of the few studies where DGGE-based approach is utilized to study and compare microbial shifts under mesophilic and thermophilic anaerobic digestions of manure simultaneously. While there were challenges in identifying the bands during gradient gel electrophoresis, the joint use of DGGE and sequencing tool can be potentially useful for illustrating and comparing the change in microbial community structure under complex anaerobic processes and functionality of microbes for understanding the consequential GHG emissions from manure.

Global potential nitrogen recovery from anaerobic digestion of agricultural residues

Meeting the anticipated 50% increase in global food demand by 2050 requires a crucial reassessment of agricultural practices, particularly in terms of nitrogen fertilizers inputs. This study analyzes the technical potential of nitrogen recovery from livestock manure and crop residues, bringing attention to the often-overlooked resource of digestate derived from anaerobic digestion. Our analysis highlights the significant capacity of the anaerobic digestion process, yielding approximately 234 ± 5 million metric tons (Mt) of nitrogen annually, sourced 93% from livestock manure and 7% from crop residues. Additionally, we estimated that substituting synthetic nitrogen with nitrogen from anaerobic digestion has the potential to reduce greenhouse gas emissions by 70% (185 Mt CO2-eq yr−1). Lastly, 2.5 billion people could be sustained by crops grown using nitrogen from anaerobic digestion of manure and crop residues rather than synthetic nitrogen fertilizers. Although agricultural residues have double the technical potential of current synthetic nitrogen fertilizer production, 30% of croplands encounter difficulties in satisfying their nitrogen needs solely through crop residues and anaerobic digestion manure. This deficiency primarily results from inefficient reuse attributed to geographical mismatches between crop and livestock systems. This underscores the urgent need to reconnect livestock and cropping systems and facilitate the transport and reuse of manure in crop production. In conclusion, the mobilization of these large amounts of nitrogen from livestock manure and crop residues will require to overcome the nitrogen from anaerobic digestion green premium with incentives and subsidies.

Microbial analysis of anaerobic digester reveals prevalence of manure microbiota

Anaerobic digestion of swine manure reduces farm greenhouse gases emissions and provides a renewable gas in the agricultural sector. The particular composition of manure, with high concentrations of ammoniacal nitrogen and volatile fatty acids, often threatens the stability of the process through inhibition of methanogens. In this work, continuous production of biogas was tested under relative short hydraulic retention time (15 days). Although a strong inhibition period was detected, adaptation of the microbiota and displacement of bacteria and archaea present in the inoculum by microorganisms present in the animal manure resulted in biogas production close to the values found in standardized batch tests in absence of inhibitions. These findings suggest that in anaerobic digestion of manure, it is not necessary to inoculate, as manure itself contains a large number of active fermentative microorganisms that can even resist long-term digestion inhibition.

Renewable natural gas: A case study of Minnesota

Renewable natural gas (RNG) often generates usable energy from waste products, reduces methane emissions, and creates new revenue streams. However, not all RNG projects are financially or technically feasible. We assessed the total RNG potential of currently available local waste feedstocks in the state of Minnesota and analyzed the financial and technical limitations for project development. We found that under ideal production conditions the RNG potential from municipal solid waste, dairy and hog farm manure, and municipal wastewater solids in the state could replace approximately 7.5% of current Minnesota natural gas use. We find that technical and financial factors such as project size, financing, and distance to an existing pipeline further reduce the number of feasible RNG project sites in Minnesota. Virtual pipelines – trucking RNG short distances to pipeline injection stations – improved the modeled profitability of 124 out of 175 projects (71%) by decreasing transmission costs. No projects are financially feasible without state or federal renewable fuel credit programs because direct sale of RNG alone does not cover project costs. Dairy manure projects have the lowest levelized cost of energy, the highest total revenue, and the shortest payback period compared to municipal solid waste landfill and wastewater treatment plant projects of similar size. This difference is because manure anaerobic digestion projects are eligible for larger credits under renewable fuel credit programs than municipal solid waste landfills and wastewater treatment plants, but this credit system limits end-use of the RNG to vehicle fuel. Our contribution helps provide an outline for the magnitude of current natural gas use in Minnesota replaceable via RNG projects.

CO2 bubbling pretreatment to remove the inhibition of lime disinfection wastewater in a swine manure anaerobic digestion system

Under the African swine fever epidemic, the extensive use of lime disinfectants has seriously inhibited anaerobic digestion (AD). In this study, the subject was swine manure containing lime disinfectant wastewater. The research set up a carbon dioxide (CO2) bubbling pretreatment device before it entered AD to explore the effect of breaking the inhibition of lime disinfectant. The results showed that the initial pulmonary hypertension (pH) of 11.0 and CO2 bubbling time of 8 h had the best effect, which could reduce calcium ion (Ca2+) by 73.0%, and the biogas production of the batch AD test increased by 28 times. In the continuous AD test, the Ca2+ of CK increased to 7.67 g/L, while the S1 pretreated by CO2 bubbling stabilized at 2.6 g/L, the biogas production in S1 was 112.4% higher than in CK. CO2 bubbling pretreatment reduces the concentration of Ca2+ in swine by utilizing the combination of exogenous CO2 and Ca2+, breaking the inhibitory effect on AD, and thereby improving the performance of the AD system. The test used CO2 in biogas to break the inhibition of lime disinfectants on AD, which was a convenient and feasible pretreatment process.

Metagenomic comparison of effects of mesophilic and thermophilic manure anaerobic digestion on antimicrobial resistance genes and mobile genetic elements

This study evaluated the long-term effects of mesophilic (MAD) and thermophilic (TAD) anaerobic digestion on the fate and evolution of antimicrobial resistance genes (ARGs) and mobile genetic elements (MGEs) in cattle manure following a metagenomic approach. The results indicated that MAD and TAD lowered ARG levels in fresh cattle manure by over 50 % and MGEs by over 65 %. However, no statistically significant difference was observed between the MAD and TAD processes in terms of their ability to reduce ARG and MGE. Co-occurrence analysis suggested facultative anaerobic species belonging to the Bacillota and Actinomycetota phyla as the primary potential hosts of ARGs and MGEs. Analyses of co-assembled contigs revealed the presence of transposon and toxin-antitoxin systems in close proximity to ARGs typically found in anaerobic digesters. The identification of these systems near ARGs is particularly significant, as it highlights a potential mechanism for the persistence and spread of ARGs in such environments. Overall, the results indicated that digested cattle manure (whether under mesophilic or thermophilic conditions) would pose a much lower risk of dissemination of antimicrobial resistance than untreated manures. Since TAD did not outperform MAD at reducing ARGs and MGEs, thermophilic temperatures may not be necessary to improve ARG reduction rates in cattle manure AD. These valuable insights could help develop strategies to reduce the dissemination of antibiotic resistance due to manure treatment and disposal.

Effect of reactor operation modes on mitigating antibiotic resistance genes (ARGs) and methane production from hydrothermally-pretreated pig manure

Numerous efforts have been made to enhance the performance of anaerobic digestion (AD) for accelerating renewable energy generation, however, it remains unclear whether the intensified measures could enhance the proliferation and transmissions of antibiotic resistance genes (ARGs) in the system. This study assessed the impact of an innovative pig manure AD process, which includes hydrothermal pretreatment (HTP) and a two-stage configuration with separated acidogenic and methanogenic phases, on biomethane (CH4) production and ARGs dynamics. Results showed that HTP significantly increase CH4 production from 0.65 to 0.75 L/L/d in conventional single-stage AD to 0.82 and 0.91 L/L/d in two-stage AD. This improvement correlated with a rise in the relative abundance of Methanosarcina, a key methanogenesis microorganism. In the two-stage AD, the methanogenic stage offered an ideal environment for methanogens growth, resulting in substantially faster and higher CH4 production by about 10% compared to single-stage AD. Overall, the combined use of HTP and the two-stage AD configuration enhanced CH4 production by 40% compared to traditional single-stage AD. The abundance and diversity of ARGs were significantly reduced in the acidogenic reactors after HTP. However, the ARGs levels increased by about two times in the following methanogenesis stage and reached similar or higher levels than in single stage AD. The erm(F), erm(G), ant(6)-Ia, tet(W), mef(A) and erm(B) were the six main ARGs with significant differences in relative abundances in various treatments. The two-stage AD mode could better remove sul2, but it also had a rebound which elevated the risk of ARGs to the environment and human health. Network analysis identified pH and TVFAs as critical factors driving microbial communities and ARG proliferation in the new AD process. With the results, this study offers valuable insights into the trade-offs between AD performance enhancement and ARG-related risks, pinpointing essential areas for future research and practical improvements.

47 Feeding Pigs with Low Crude Protein Diets: Impact of Pig Manure Nitrogen Content on Biogas Production and Digestate Quality

Abstract Lowering dietary crude protein levels is a nutritional strategy recognized to both decrease the use of high-impact feed ingredients and reduce nitrogen (N) excretion. Improved pig manure management practices can further mitigate the environmental impacts associated with pig production towards net-zero emissions. Anaerobic digestion (AD) is a promising technology for transforming pig manure into energy as biogas and into bio-based fertilizers (i.e., digestate from AD). However, little is known about the effects of pig manure N content on AD. Thus, this study aimed to evaluate the impact of pig manure N content on biogas production and digestate quality through the AD of manure from pigs fed low crude protein diets. Three pig manure N concentrations were tested: T1 = 5873, T2 = 5421, and T3 = 5149 total Kjeldahl nitrogen (TKN, mg/L). Throughout 5 sequential fed-batch cycles (25 ± 4 days/cycle), biogas production and its composition (CH4, CO2, and H2S) were measured, while raw manure and weekly digestate samples were analyzed for total solids (TS, %), volatile solids (VS, %), pH, chemical oxygen demand (COD, mg/L), TKN, and ammoniacal nitrogen (NH3-N, mg/L). In a temperature-controlled room (20 ± 1ºC), 6 digesters (3 treatments x 2 replicates) were operated as single-stage reactors to digest pig slurry (mixture of urine and feces, TS: 5.6%) inoculated with a liquid inoculum (TS: 2.3%) to improve manure-microbe interactions. Data were analyzed by ANOVA using PROC MIXED with repeated measures and comparison of means through the Tukey test (SAS software). In addition, both correlation and regression analyses were performed with R to evaluate the relationship among variables. Decreasing pig manure N content showed a tendency to reduce biogas (-20% in T3 vs T1; P = 0.0782) and methane (-22% in T3 vs T1; P = 0.0576) production per cycle, as shown in Table 1. Regarding biogas composition, CH4/biogas and CH4/CO2 decreased with N content (-3 and -4% in T3 vs T1; P ≤ 0.0082). There were strong positive correlations between the N content of pig manure and the amount of NH3-N (linear: r = 0.94, R2 = 0.88) and TKN (linear: r = 0.90, R2 = 0.81) present in the digestate at the end of each cycle. These results suggest that a reduction in pig manure N content reduces biogas production and its quality (ratio of CH4 to CO2). This latter variable is important for biogas efficiency; thus, reducing crude protein in pig diets may impair the production of biogas in AD. However, a decreased N content may cause less emissions into the environment, but when using the digestate as fertilizer, it may not entirely fulfill the N requirements of fast-growing crops for a given application rate.

Biogas and biomethane production potential via anaerobic digestion of manure: A case study of Portugal

Anaerobic digestion is a promising technology that can be part of the solution to meet the increasing energy demand while reducing the harmful effects on the environment. The objective of this work is to assess Portugal’s potential to produce biogas or biomethane via anaerobic digestion of manure. First, a spatial analysis of manure availability was done using ArcGIS. Then, a thermodynamic model of the production system was created in MATLAB, which includes three proposed production paths. The outputs of the thermodynamic model served as inputs for an economic analysis, also performed in MATLAB, and a life cycle assessment done using SimaPro software. Findings from the spatial analysis revealed that the centre and south areas (excluding Algarve) of Portugal have the highest manure availability, 73.6% of the national amount, and the Azores archipelago has high availability of cattle manure, 17.88% of the national amount. The total possible amount of production plants was estimated as 743. The thermodynamic model results show that the region of Lezíria do Tejo has the highest biogas and biomethane production potential, at 557172 t/year and 352364 t/year. Furthermore, the total potential biogas and biomethane production in Portugal was estimated as 3561947.05 t/year and 1791402.48 t/year. Regarding energy, the calculated efficiencies of biogas and biomethane production were 62.96% and 51.82%. The economic analysis yielded national average selling prices of 0.8174 €/kg and 1.290 €/kg for biogas and biomethane. The life cycle assessment showed that the main concerns regarding this type of systems are toxicity impacts and resource consumption.

Characterization of Proteus mirabilis and associated plasmids isolated from anaerobic dairy cattle manure digesters.

Proteus mirabilis is an opportunistic pathogen associated with a variety of human infections, including urinary tract infections. The prevalence of P. mirabilis in foods of animal origin and in the manure by-products created in animal production is not well documented. Further, the prevalence and persistence of extended-spectrum cephalosporin (ESC) resistant P. mirabilis is largely unknown. In this study, we characterized ESC-resistant P. mirabilis recovered from various stages of dairy manure anaerobic digestion. Isolates were screened by PCR for blaCTX-M, blaCMY and blaSHV, and antimicrobial susceptibility testing was performed. Fifty-six P. mirabilis carrying CTX-M were sequenced with short and long read sequencing technologies, and the assembled chromosomes and plasmids were compared. ESC-resistant Proteus was found in four of the six manure digesters, an indication that not all digesters were colonized with resistant strains. Both CTX-M-1 and CTX-M-15 plasmids were found in P. mirabilis isolates. Transfer of plasmid DNA by conjugation was also explored, with ESC-resistance plasmids able to transfer to Escherichia coli at high frequency. We concluded that P. mirabilis can harbour and transfer ESC-resistance genes and plasmids, and may be an overlooked reservoir of antimicrobial resistance.

Improvement of cow manure anaerobic digestion performance by three different crop straw biochars

Anaerobic digestion (AD) is an effective bioconversion technology widely used to treat agricultural waste and reduce environmental pollution. Although AD has been commonly applied to practical social needs, low yield and reactor instability limit its performance. In this study, potato, rape, and wheat straw were pyrolyzed to biochar at 600 °C and added to a batch AD system to improve biogas yield. Biochemical methane potential test was used to assess the methane production. The results showed that the three straw biochar had similar efficiency that increased cumulative methane production (35.45%–52.66%) compared with that in the control group (818.5 mL). Potato straw biochar presented the highest cumulative methane production (1249.5 mL). Significant differences in microbial communities between biochar and control groups were noticed. The microbial community structure in the AD system was significantly related to the biochar properties. The addition of biochar increased the abundance of Methanobrevibacter in the biochar group by 2–147 times. This study provides reference for the application of straw biochar to promote methane production.

Use of reverse osmosis concentrate for mitigating greenhouse gas emissions from pig slurry.

Due to the high global warming potential (GWP) in a short time scale (GWP100 = 28 vs. GWP20 = 86), mitigating CH4 emissions could have an early impact on reducing current global warming effects. The manure storage tank emits a significant amount of CH4, which can diminish the environmental benefit resulting from the anaerobic digestion of manure that can generate renewable energy. In the present study, we added the reverse osmosis concentrate (ROC) rich in salt to the pig slurry (PS) storage tank to reduce CH4 emissions. Simultaneously, pure NaCl was tested at the same concentration to compare and verify the performance of ROC addition. During 40 days of storage, 1.83 kg CH4/ton PS was emitted, which was reduced by 7-75% by the addition of ROC at 1-9 g Na+/L. This decrease was found to be more intensive than that found upon adding pure sodium, which was caused by the presence of sulfate rich in ROC, resulting in synergistic inhibition. The results of the microbial community and activity test showed that sodium directly inhibited methanogenic activity rather than acidogenic activity. In the subsequent biogas production from the stored PS, more CH4 was obtained by ROC addition due to the preservation of organic matter during storage. Overall, 51.2 kg CO2 eq./ton PS was emitted during the storage, while 8 kg CO2 eq./ton PS was reduced by biogas production in the case of control, resulting in a total of 43.2 kg CO2 eq./ton PS. This amount of greenhouse gas emissions was reduced by ROC addition at 5 g Na+/L by 22 and 65 kg CO2 eq./ton PS, considering GWP100 and GWP20 of CH4, respectively, where most of the reduction was achieved during the storage process. To the best of our knowledge, this was the first report using salty waste to reduce GHG emissions in a proper place, e.g., a manure storage tank.

The Antibiotics Degradation and Its Mechanisms during the Livestock Manure Anaerobic Digestion.

Antibiotics are administered to livestock at subtherapeutic levels to promote growth, and their degradation in manure is slow. High antibiotic concentrations can inhibit bacterial activity. Livestock excretes antibiotics via feces and urine, leading to their accumulation in manure. This can result in the propagation of antibiotic-resistant bacteria and antibiotic resistance genes (ARGs). Anaerobic digestion (AD) manure treatment technologies are gaining popularity due to their ability to mitigate organic matter pollution and pathogens, and produce methane-rich biogas as renewable energy. AD is influenced by multiple factors, including temperature, pH, total solids (TS), substrate type, organic loading rate (OLR), hydraulic retention time (HRT), intermediate substrates, and pre-treatments. Temperature plays a critical role, and thermophilic AD has been found to be more effective in reducing ARGs in manure compared to mesophilic AD, as evidenced by numerous studies. This review paper investigates the fundamental principles of process parameters affecting the degradation of ARGs in anaerobic digestion. The management of waste to mitigate antibiotic resistance in microorganisms presents a significant challenge, highlighting the need for effective waste management technologies. As the prevalence of antibiotic resistance continues to rise, urgent implementation of effective treatment strategies is necessary.

СЕТЕВОЕ МОДЕЛИРОВАНИЕ ПРОЦЕССА АНАЭРОБНОГО СБРАЖИВАНИЯ НАВОЗА

The article discusses the technological complex of anaerobic digestion of manure (ASN). Thanks to biogas plants, it is possible to mitigate the harmful effects on reservoirs and their inhabitants, reduces pollution with ammonium salts and restores the natural oxygen saturation of waters. The effectiveness of the functioning of such systems can be ensured with the help of modern methods of information processing, using methods of system analysis of complex objects based on a mathematical description of the technological process. Based on the review of the main methods of modeling discrete-continuous chemical-technological systems (CTS), the expediency of using the apparatus of the theory of Petri nets (SP) for process modeling (ASN) is substantiated. To describe the system, we propose the use of N–schemes based on the mathematical apparatus of Petri nets, one of the advantages of which is the possibility of presenting the network model both in analytical form, with the possibility of automating the analysis process, and in graphical form to ensure the visibility of the model being developed. When analyzing chemical-technological schemes, the main limitation of the N–scheme formalism should be taken into account, which is that they do not take into account the time characteristics of the simulated systems, since the transition response time is considered to be zero. Taking into account these conditions, we have proposed modified Petri nets focused on modeling and analysis of discrete-continuous CTS by including priority transitions, delay time of labels in positions and transitions. A model in the form of a modified Petri net (SME) is constructed. By means of the TRACE MODE SCADA technology, a software package of the process control system (ASN) has been developed. The process control system allows you to perform dispatching control of the main elements of the control system, stop the system (ASN) and analyze its condition, both as a whole and in order to predict the development of emergency situations.

Circularity indicators and added value to traditional LCA impact categories: example of pig production

Abstract Purpose The purpose of using circularity indicators is to show the effect of changes from linear to more circular systems. This paper contributes to highlighting the importance of methodological aspects of circularity indicators in the agricultural sector when using a life cycle thinking approach. Selected circularity indicators have been explored and compared with LCA impact categories by using them to evaluate the circularity of a livestock system. Methods Circularity indicators were tested on a theoretical pig production system where several circularity strategies and associated mitigation actions were applied. The strategies and mitigation actions were as follows: anaerobic digestion of manure (closing resource loops), anaerobic digestion of bread waste (closing resource loops), precision fertilization (narrowing resource loops), use of cover crops in feed production (regenerating resource flows), and use of bread waste as feed (slowing resource loops). The functional unit was 1 kg pork as carcass weight, and the treatment of 1.1 kg bread waste for all impact categories and indicators. For each mitigation action, relevant circularity indicators were tested. Based on this, the functionality and suitability of these indicators were discussed. Results and discussion Four of the circularity indicators were based on nitrogen (N) or phosphorus (P) substances: N recycling index, partial N balance, consumption of fossil-P fertilizers, and emissions to water bodies (P). Even if the indicators do not capture the impact of emissions of N and P as the eutrophication impact categories, they provide a useful indication of the circularity of a system. The other three circularity indicators tested were as follows: renewable energy production, soil organic carbon, and land use ratio. The renewable energy production indicator is easy to understand and communicate and provides unique information. Soil organic carbon presents a potential for soil carbon sequestration. Land use ratio is based on the same data as land occupation but provides an assessment of whether feed production competes for the suitable area for food production by including production of human-digestible protein. Conclusions Circularity indicators provide valuable information about the circularity of an agricultural product system. The circularity indicators and LCA impact categories can be used either separately or together, or to complement each other. The choice of indicators depends on the questions raised, i.e., goals and scope, and it is therefore important to have a number of circular indicators to choose from in order to achieve a comprehensive assessment.

Evaluation of the methanogenic potential of anaerobic digestion of agro-industrial wastes

Waste management technologies have become a way to generate value-added products. Anaerobic digestion (AD) allows biogas generation by treating organic wastes. In this work, the methanogenic potentials of anaerobic digestion of rumen and chicken manure, two typical agro-industrial wastes from the Colombian Caribbean region, were evaluated. On a first stage, the effect of temperature on anaerobic digestion of manure inoculated with liquid rumen was measured. Results revealed that the thermophilic digestion produces more biogas (up to 47% higher than the mesophilic digestion), but the mesophilic digestion has better biogas quality (up to 20% more methane than the thermophilic digestion). On the second experimental stage, it was assessed the effect of temperature regimen and the addition of fat-oil-grease (FOG) on cumulative biogas production, methane percentage, and physicochemical parameters. It was found that the anaerobic digestion of the rumen with FOG in mesophilic conditions had the best performance in terms of quantity and quality of biogas (2520 NL CH4/kg VS, CH4 93%, H2S 1 mg/L, H2O 16 mg/L). Finally, rumen and manure had methane concentrations above 40% in all cases studied, after 60 days of anaerobic digestion. It was concluded that rumen and manure are good candidates for biogas generation.

Effects of limed manure digestate application in sandy soil on plant nitrogen availability and soil N2O emissions

Anaerobically-digested manure is frequently applied to agricultural soil to enhance plant growth and reduce the need for chemical fertilizers. This practice also stimulates microbial nitrogen transformations and often results in N2O emissions. A single mesophilic anaerobic digestion is insufficient for pathogen removal or inactivation and therefore, a post treatment is required for its stabilization and hygienization. Here, we examined the effects of limed manure-digestate as a nitrogen source for plant growth and on N2O emission compared with compost. A plant growth experiment was conducted in a sandy soil and N2O emissions were monitored throughout the experiment. Plants were irrigated with freshwater or liquid-N fertilizer. The combination of compost application and liquid-N fertilizer resulted in surface N2O fluxes over 0.7 ​mg ​m−2 d−1, which were correlated with ammonium concentration in the soil. The presence of N2O in the rhizosphere was only detected in compost-amended soil 2–10 days after plantation. A significantly-lower surface N2O flux of 0.4 ​mg ​m−2 d−1 was recorded with application of limed-digestate, probably due to its effects on nitrogen-transforming microorganisms. Both compost and limed-digestate enhanced plant growth, with a more distinct effect in the freshwater treatment. Our observations demonstrate that limed-digestate can be an efficient substitute for compost as it effectively supports plant growth with substantially-lower N2O emissions.

Utilization of Biomass for Production of Biogas –An Overview

India is a developing country comprising more than one-sixth of the world’s population. Solely due to this reason there is a large dependence on energy resources for meeting the daily requirements particularly the fossil fuels which are generally regarded as undesirable for several reasons. Among the various other energy resources available, biogas has emerged as a promising fuel for the future with numerous advantages. This paper throws light upon the progress of biogas technology in India, suggesting how this valuable potent resource can be used for future sustainability. This study can be helpful in implementing biogas technology in many rural areas across India thereby establishing social and economic stability. Biogas is produced by anaerobic digestion of manure, energy crops (mainly maize), wastewater treatment sludge and organic waste. Biogas is a renewable energy source. Sustainability requirements are increasingly important. As a greenhouse gas, methane is 25 times stronger than carbon dioxide, so small leakages of biogas have a strong negative effect on the total greenhouse gas performance of the energy production pathway. This chapter covers an overview from the literature concerning methane emissions from different steps in the biogas production chain with reference to relevant selected articles

H2S Emission and Microbial Community of Chicken Manure and Vegetable Waste in Anaerobic Digestion: A Comparative Study

In order to solve the problem of H2S corrosion in biogas utilization, it is necessary to understand the characteristics and mechanisms of H2S production in chicken manure anaerobic digestion (CMAD) and vegetable waste anaerobic digestion (VWAD). In this study, lab-scale batch tests of CMAD and VWAD were conducted for 67 days at 35 °C. The results showed that sulfide was found to be the major form of sulfur in CMAD (accounting for 90%) and VWAD (70%). The average concentration of H2S was 198 ± 79 ppm in CMAD and 738 ± 210 ppm in VWAD. Moreover, 81% of total H2S was produced at 20 days of methane production in CMAD, but 80% of total H2S was produced in the first day in VWAD because of the rapid production of biogas and fermentation acidification. The sulfide ion equilibrium model could universally and feasibly predict the H2S production in CMAD and VWAD. The abundance of Firmicutes, Bacteroidetes, Proteobacteria and Euryarchaeota accounted for about 95% of the total microbes in both CMAD and VWAD; the influence of the fermentation stage on the microbial community was greater than that of the difference between CM and VW; the abundance of SRB was 0.01~0.07%, while that concerning organosulfur compounds fermentation was 22.8~30.5%. This study indicated that the H2S concentration of CMAD biogas was more than five times that of VWAD because CM is alkalescent but VW is acidic.

Comparative functional microbiome profiling of various animal manures during their anaerobic digestion in biogas production processes

Anaerobic digestion (AD) for bio-methane production continues to be plagued by major problems such as acidification, ammonia inhibition, long reaction periods, and expensive biogas upgrading. In this study, the authors suggest that intrinsic microbial roles during AD have previously been understudied yet they are the basis for discovery of effective and substrate-specific strategies for biogas process improvement. A comparison of the functional microbiome profiling of fresh cow, horse, pig, and chicken manures sourced from seven farms around Gauteng in South Africa was done. Correlation of profiles of the daily and cumulative biogas and bio-methane production determined in an automatic methane potential system (AMPTS), six intermediate AD compounds (propionate, butyrate, formic acid, lactic acid, ethanol, and acetate) observed using a modular Thermo Scientific Vanquish Core high performance liquid chromatography (HPLC) system, and active microbiome observed through Illumina 16S rDNA high-throughput sequencing suggests that cow manure AD went through 2 quick and efficient phases while horse manure showed 3 phases with hydrolysis being the rate limiting step, pig manure showed 4 phases and was dominated with hydrogenotrophic methanogenesis, and chicken manure had 2 phases affected by ammonia inhibition. It was inferred from the findings, that co-digestion of the horse manure within the first 9 days with cow manure, manipulation of Methanococcus hydrogenotrophs from pig manure AD in 2 stage reactor co-digestion systems, introduction of Methanococcus-rich inoculum from a pig manure AD system (between Day 15 & Day 24) as well as trace nutrient supplementation to boost SAOB, are strategies that can improve hydrolysis & methanogenesis in horse manure AD, upgrade biogas quality from various substrates, counter ammonia inhibition in chicken manure AD as well as in other similar substrates respectively.