Methanogenic Fermentation Research Articles

Biogas Production based on Thermophilic Methanogenic Fermentation of Chicken Manure

Biogas Production based on Thermophilic Methanogenic Fermentation of Chicken Manure

Winter drainage and film mulching cultivation mitigated CH4 emission by regulating the function and structure of methanogenic archaeal and fermenting bacterial communities in paddy soil

AbstractWinter flooding of harvested rice fields is a typical cropping system in mountainous areas, which emits considerable amounts of CH4. Plastic film mulching cultivation is recognized as an important rice cultivation practice in paddy field for water-saving irrigation. However, the effects of these managements on CH4 emissions in paddy soil and the underlying microbial mechanism are unclear. A field experiment was carried out with the application of winter drainage followed by traditional rice cultivation (WD), winter drainage followed by plastic film mulching cultivation (MC), as well as winter flooding followed by traditional rice cultivation (WF) as control in hilly paddy fields. We investigated the CH4 emissions, functional (CH4 production rate, 13C isotope) and structural (abundance, structure) responses of soil methanogenic archaeal and fermenting bacterial communities during rice season. Shifting the fields from WF into WD and MC substantially mitigated CH4 emissions by 62.3% and 59.2%, respectively, paralleled with the enhancement of soil Eh and the reductions of soil DOC content. Compared with WF, WD and MC both significantly decreased CH4 production rates and the copy numbers of mcrA gene. Moreover, an increasing contribution of hydrogenotrophic methanogenesis (from 30.7% to 50.0%) to total CH4 production was observed during the conversion from WF to MC under an anaerobic incubation, paralleled with the decreased acetate content and increased δ13C values of acetate-methyl and total acetate. The communities of methanogenic archaea and fermenting bacteria strongly responded to the shift from WF to WD, while MC only showed significant effects on the methanogenic archaeal communities. Compared with WF, WD and MC significantly increased the relative abundance of Methanothrix, Methanosarcina and Methanocella, while those of Methanoregula, Massilia and Geobacter were decreased. The co-occurrence networks showed that WD and MC induced the loss of mixed methanogenic fermentation modules, indicating the decrease in functional biodiversity and redundancy of fermenting bacterial and methanogenic archaeal communities.The findings suggest that WD and MC approach mitigate CH4 emission by regulating the function and structure of methanogenic archaeal and fermenting bacterial communities in paddy soil, which represent the effective management strategies considering the water availability and CH4 mitigation in paddy-field agriculture.

Enhancing two-phase anaerobic digestion of mixture of primary and secondary sludge by adding granular activated carbon (GAC): Evaluating acidogenic and methanogenic efficiency

Although the granular activated carbon (GAC) has been proved to enhance conventional single-phase anaerobic digestion (AD), how it impacts on acidogenic and methanogenic fermentation is still unknown. In this study, GAC was introduced to elevate the efficiency of two-phase AD, with mixture of primary and secondary sludge as substrate. Five dosages: 0, 0.1, 0.3, 0.5 and 0.7 g GAC/g TSS (Total Suspended Solids) were investigated to determine influences of GAC. The variations of biogas (hydrogen and methane), volatile fatty acids (VFAs), organics degradation and transformation in extracellular polymeric substances (EPS) and dissolved organic matters (DOM) were analyzed. Modified Gompertz model and first-order reaction equation was applied to analyze the kinetics of biogas yield and VFAs utilization, respectively. Sludge reduction, electrical conductance and pH were also quantified to evaluate the system performance. The results showed that GAC could improve two-phase AD performance by enhancing methane production and organics conversion.

Quantitative water content estimation in landfills through joint inversion of seismic refraction and electrical resistivity data considering surface conduction

The disposal of municipal solid waste (MSW) in landfills is the prevalent method of waste management at the global scale. However, the production of landfill gases due to the methanogenic fermentation of wet MSW is a possible threat to human health and accounts for a substantial contribution to the global greenhouse gas emissions. Accordingly, information regarding water content is critical as it is an important factor triggering methane production in MSW landfills. In this study, we propose a petrophysical joint inversion scheme to quantitatively solve for the water content (WC) in landfills based on seismic refraction as well as electrical resistivity data collected at two different frequencies. In this way, we also take into account the contribution of the surface conductivity to the observed electrical response, which is crucial for a reliable quantification of the WC. Our results reveal a high water content within the MSW unit (WC > 20%) for areas characterized by a strong polarization response (normalized chargeability > 5 Mn mS/m). Such areas can be related to an increased biogeochemical activity as evidenced by the detected methane production. We observe consistent estimates between the water content resolved through the proposed joint inversion scheme and values measured in waste samples with a median percentage error of 17%. Our study demonstrates the possibility to obtain reliable estimates for the WC in MSW landfills through the petrophysical joint inversion of seismic and electrical data when surface conductivity is explicitly considered.

Impacts of molybdate and ferric chloride on biohythane production through two-stage anaerobic digestion of sulfate-rich hydrolyzed tofu processing residue

Biohythane production through one-stage anaerobic digestion of sulfate-rich hydrolyzed tofu processing residue has been hampered by high H2S production. Herein, two-stage anaerobic digestion was investigated with the addition of molybdate (MoO42-; 0.24–3.63 g/L) and ferric chloride (FeCl3; 0.025–5.4 g/L) to the dark fermentation stage (DF) to improve biohythane production. DF supplemented with 1.21 g/L MoO42- increased hydrogen yield by 14.6% over the control (68.39 ml/g-VSfed), while FeCl3 had no effect. Furthermore, the maximum methane yields of methanogenic fermentation were 524.8 and 521.6 ml/g-VSfed with 3.63 g/L MoO42- and 0.6 g/L FeCl3 compared to 466.07 ml/g-VSfed of the control. The maximum yields of biohythane and energy were 796.7 ml/g-VSfed and 21.8 MJ/kg-VSfed with 0.6 g/L FeCl3 when the sulfate removal efficiency was 66.7%, and H2S content was limited at 0.08%. Therefore, adding 0.6 g/L FeCl3 is the most beneficial in improving energy recovery and sulfate removal with low H2S content.

Variimorphobacter saccharofermentans gen. nov., sp. nov., a new member of the family Lachnospiraceae, isolated from a maize-fed biogas fermenter.

Strain MD1T is an anaerobic, Gram-stain-negative bacterium isolated from a lab-scale biogas fermenter fed with maize silage. It has a rod-shaped morphology with peritrichously arranged appendages and forms long chains of cells and coccoid structures. The colonies of MD1T were white, circular, slightly convex and had a smooth rim. The isolate is mesophilic, displaying growth between 25 and 45 °C with an optimum at 40 °C. It grew at pH values of pH 6.7-8.2 (optimum, pH 7.1) and tolerated the addition of up to 1.5% (w/v) NaCl to the medium. The main cellular fatty acids of MD1T are C14:0 DMA and C16:0. Strain MD1T fermented xylose, arabinose, glucose, galactose, cellobiose, maltose, maltodextrin10, lactose starch, and xylan, producing mainly 2-propanol and acetic acid. The genome of the organism has a total length of 4163427 bp with a G+C content of 38.5 mol%. The two closest relatives to MD1T are Mobilitalea sibirica P3M-3T and Anaerotaenia torta FH052T with 96.44 or 95.8 % 16S rRNA gene sequence similarity and POCP values of 46.58 and 50.58%, respectively. As MD1T showed saccharolytic and xylanolytic properties, it may play an important role in the biogas fermentation process. Closely related variants of MD1T were also abundant in microbial communities involved in methanogenic fermentation. Based on morphological, phylogenetic and genomic data, the isolated strain can be considered as representing a novel genus in the family Lachnospiraceae, for which the name Variimorphobacter saccharofermentans gen. nov., sp. nov. (type strain MD1T=DSM 110715T=JCM 39125T) is proposed.

Deeper investigation on methane generation from synthetic wastewater containing oxytetracycline in a scale up acidic anaerobic baffled reactor

Acidic anaerobic digestion attracted much attention and interest due to its significant advantage in wastewater treatment. In the present study, methanogenic fermentation was successfully operated under acidic condition during treating wastewater containing oxytetracycline (OTC) in a scale up anaerobic baffled reactor (ABR). After start-up process, the pH value in the first compartment was 4.60 with high activity of methanogenesis. After stabilization, different OTC loading of 1.0, 3.3 and 5.0 g/m3/d was added in the influent for OTC removal. The resulted showed that OTC addition had little impact on the methane generation with whole COD and OTC removal rate of 95% and 60%, respectively. The microbial analysis, OTC addition could significantly influence the bacteria and archaea communities. To be more specific, Methanosaeta showed the highest relative abundance and tolerance to OTC under acidic condition. The present work supplied deeper insights into methane generation from acidic condition during wastewater containing OTC treatment.

Enhancing methanogenic fermentation of waste activated sludge via isoelectric-point pretreatment: Insights from interfacial thermodynamics, electron transfer and microbial community

The usefulness of waste activated sludge (WAS) as an energy source is limited by the poor generation efficiency of methane from WAS, which is mainly due to the complex nature of sludge and low abundance of functional microbes. In this study, the interfacial thermodynamics, electron transfer and microbial community of sludge were investigated to reveal the enhancing effects of isoelectric-point (pI) pretreatment on the efficiency of methane generation from WAS. Experimentally, after pI pretreatment, the methane production potential, maximum methane production rate and maximum methane proportion in the biogas increased by 122.2%, 154.4% and 17.4%, respectively, indicating that pI pretreatment enhanced the generation efficiency of methane. Analyses of changes in the solid-liquid interfacial non-covalent interaction energy, electron transfer capacity (ETC) and reductive peak potential values of sludge samples with and without pI pretreatment during a 170-day methanogenic fermentation period revealed that pI pretreatment enhanced the self-driven solid-liquid interfacial hydrophobic attractions of sludge, increased the abiotic driving forces of interfacial enzymatic reactions, promoted the electron transfer efficiency and lowered the barrier of the reduction reaction. It was thus hypothesised that these changes would be responsible for increasing methane production, which was confirmed by the correlation analyses between the interfacial free energy (IFE) and ETC versus daily methane production. Moreover, statistical analyses of the differences between the microbial communities of sludge samples with and without pI pretreatment during fermentation demonstrated that pI pretreatment significantly (P < 0.05) improved the relative abundances of the main functional microbes with respect to hydrolysis, acidification and methanation. A further investigation of the relationships of IFE and ETC with the relative abundances of the main genera of methanogens indicated that the hydrophobic attraction of sludge surface and a high ETC are conducive to the enrichment of hydrogenotrophic methanogens (+29.9%). These findings are expected to provide a conceptual framework for developing second-generation pretreatment methods and provide a methodological reference for revealing the details of the ‘black-box’ anaerobic digestion process.

POTENTIAL BAGGASE AND MOLASSES WASTE SUGAR FACTORY FOR MIXED SUBSTRATES WITH COW MANURE IN FERMENTATION PROCESS METHANOGENIC

This study aims to analyze the potential of the sugar mill waste, namely baggase and molasses as a mixture of cow manure as a substrate in a methanogenic fermentation. This study uses 4 treatment that is P0 as controls (100% cow manure), later in other treatment using a mixture of cow manure comparison: baggase: molasses, P1 (50:20:30), P2 (50:30:20) and P3 ( 50: 40; 10). Parameters measured were nitrogen, carbon, ratio C / N and pH value. The analyze used in this research is statistic analysis. The results were obtained P3 which is a mixture of substrate (50:40:10) has an average value of the content of nitrogen, carbon, ratio C / N, and high pH value is compared to the other treatments. Ratio C / N at P3 of 24.47 closest Ratio C / N ideal for methanogenic fermentation which amounted to 25. The pH value of the treatment amounted to 7.05 billion P3 also meet the standards for process fermentation ranging from 6.6 to 7.6.

Controls on carbonate cementation in early syn-rift terrestrial siliciclastics: The Lower Cretaceous of the Bayindulan Sag in Er'lian Basin, China

Carbonate cementation of sandstones at channel bases is commonly interpreted to be a result of solutes generated from surrounding rocks in a burial-diagenetic regime. However, in rapidly buried and under-compacted conglomerates presented in this study, we interpret carbonate cements formed during early-diagenesis (1000–1600 m) to be precipitated directly from Ca- and CO2-rich saline formation water, derived from hypersaline lake water and driven by gravity and compaction. In the Bayindulan Sag of the Er'lian Basin, which is a continental rift basin, the sandstones and conglomerates of the A'ershan Formation (K1ba) were deposited in fan delta front settings during the syn-rift phase. Within these, tightly non-ferroan calcite-cemented conglomerates are present at the bases of distributary channels. In addition, some Fe-dolomite cements are present in sandstones with high present-day porosity, which are located in the upper parts of distributary channels. A petrographic analysis and fluid-inclusion microthermometry study show that the calcite cement predates the Fe-dolomite. Stable isotopic values indicate that both calcite and Fe-dolomite are characterized by enrichment of 13C and depletion of 18O (δ18OV-PDB: −15‰ to −8‰), and the value of δ13C V-PDB in calcite (+1.6‰ to +3.8‰) is less positive than that in Fe-dolomite (+3.1‰ to +8.4‰). Integrated analyses imply that the studied carbonate cements were probably formed within an open diagenetic system and were influenced by multiple diagenetic fluids. During deposition of the A'ershan Formation (K1ba), the lake water was brackish to hypersaline (Sr/Ba>1 and Sr content > 300 ppm). During deposition of the Tenggeer Formation (K1bt), the K1ba progressed rapidly into a deep burial phase (90 m/Ma), diagenetic fluids were controlled by hypersaline lake water, incursion of meteoric water occurred along faults, and methanogenic fermentation. Calcium was probably derived from the saline formation water and the transformation of smectite to illite in associated mudstones, leading to the precipitation of calcite (54–78 °C). In the Saihantala period, the K1ba experienced a slight uplift, the fault activity ceased, and the diagenetic fluids were derived from the saline formation water and were influenced by methanogenic fermentation, and Fe-dolomite began to precipitate. In deeper burial detrital feldspar grains and some calcite cement were probably dissolved by organic acid discharged from mudstones. In conclusion, the early diagenetic characteristics in the continental rift basins were controlled by the composition of the depositional waters and tectonics that controlled the opening and closing the diagenetic system thus influencing fluid composition.

Formate and Hydrogen as Electron Shuttles in Terminal Fermentations in an Oligotrophic Freshwater Lake Sediment.

The energetic situation of terminal fermentations in methanogenesis was analyzed by pool size determinations in sediment cores taken in the oligotrophic Lake Constance, Germany. Distribution profiles of fermentation intermediates and products were measured at three different water depths (2, 10, and 80 m). Methane concentrations were constant below 10 cm of sediment depth. Within the methanogenic zone, concentrations of formate, acetate, propionate, and butyrate varied between 1 and 40 μM, and hydrogen was between 0.5 and 5 Pa. From the distribution profiles of the fermentation intermediates, Gibbs free energy changes for their interconversion were calculated. Pool sizes of formate and hydrogen were energetically nearly equivalent, with -5 ± 5 kJ per mol difference of free energy change (ΔG) for a hypothetical conversion of formate to hydrogen plus CO2 The ΔG values for conversion of fatty acids to methanogenic substrates and their further conversion to methane and CO2 were calculated with hydrogen and with formate as intermediates. Syntrophic propionate oxidation reached energetic equilibrium with formate as the sole electron carrier but was sufficiently exergonic if at least some of the electrons were transferred via hydrogen. The energetic consequences of formate versus hydrogen transfer in secondary and methanogenic fermentations indicate that both carrier systems are probably used simultaneously to optimize the energy yields for the partners involved.IMPORTANCE In the terminal steps of methane formation in freshwater lake sediments, fermenting bacteria cooperate syntrophically with methanogens and homoacetogens at minimum energy increments via interspecies electron transfer. The energy yields of the partner organisms in these cooperations have so far been calculated based mainly on in situ hydrogen partial pressures. In the present study, we also analyzed pools of formate as an alternative electron carrier in sediment cores of an oligotrophic lake. The formate and hydrogen pools appeared to be energetically nearly equivalent and are likely to be used simultaneously for interspecies electron transfer. Calculations of reaction energies of the partners involved suggest that propionate degradation may also proceed through the Smithella pathway, which converts propionate via butyrate and acetate to three acetate residues, thus circumventing one energetically difficult fatty acid oxidation step.

Pretreatment of Corn Stover with Diluted Nitric Acid for the Enhancement of Acidogenic Fermentation

In this study, dilute nitric acid was selected as the catalyst to pretreat corn stover. The effects of nitric acid pretreatments on the efficiency of acidogenic fermentation and the acidogenic characteristic of prehydrolysates were evaluated. The results showed that about 97% hemicelluloses were recovered at the optimal condition (150 °C, 0.6% HNO3, 2 min). Acidogenic fermentation of prehydrolysate B (the highest yield of total sugar) obtained at the optimal condition proved to be more efficient compared with prehydrolysate A (no inhibitor) and prehydrolysate C (the highest yield of inhibitors), the VFAs concentration can reach the highest level, and the distribution of VFAs exhibited butyric acid type fermentation; this was more suitable for subsequent methanogenic fermentation. This research provided an effective and suitable method for accelerating biogas production from corn stover.

Methanogenic fermentation of lignite with carbon-bearing additives, inferred from stable carbon and hydrogen isotopes

Lignite from the Konin area (Poland) was used as a substrate for incubation experiments to evaluate its potential for simulation of biogenic methane production. Lignite was incubated with a bacterial inoculum enriched from lake sediments, mineral media, and various supplemental components for microbial life. Additives, such as acetate, methanol, glucose, nutrient broth, and yeast extract, can significantly increase methane production. At the same time, biodegradation of these additional carbon sources leads to overestimation of methane yield. In this paper, selected geochemical properties (total organic carbon content; stable isotopic composition of carbon δ13C) were analyzed in order to evaluate changes in the organic matter of fermented lignite. Stable isotope analysis of carbon and hydrogen was applied in order to identify sources of methane and carbon dioxide formation. TOC decreased in range from 1.4 to 9.6% in lignite after fermentation. The δ13C value of lignite used in the experiments (−25.2‰) decreased after incubation to values in range from −27.1 to −26.2‰. Methane yield per g of TOC (lignite + organic carbon in nutrients) ranged from 0.47 to 2.60mM/g. Glucose, acetate, and methanol significantly increased biogas production. Nutrient broth and yeast extract were not a source of organic carbon for methane formation, but their presence enhanced biogas production. Values of δ13C(CH4) and δ2H(CH4) across incubation conditions ranged from −70.2 to −24.2‰ and from −396.6 to −290.5‰, respectively. Values of δ13C(CO2) ranged from –55.2 to 45.0‰. The high level of variation of δ13C(CH4) and δ13C(CO2) suggests mixing of gases from different carbon sources during incubation, but can also be caused by mixing of metabolic modes by the microbial community. Understanding the δ2H(CH4) variation is even more difficult than the δ13C(CH4) and δ13C(CO2), since many substrates often contain exchangeable hydrogen (e.g. in water, lignite, and elements of nutrients). The combined values of δ13C(CH4) and δ13C(CO2) suggests that the dominant methanogenesis pathway in our experiments may be acetate fermentation. In biodegraded lignite, high relative concentrations of p-cresol (one of the most abundant in the sample) and n-(2-acetylphenyl)formamide were identified. These compounds are most probably lignin decomposition products, or, in the case of the latter, bacterial by-products or remnants. Organic compounds with low molecular weights, n-alkanes, and biomolecules including ferruginol, sugiol, and 6,7-dehydroferruginol, as well as amyrins and tocopherols, were preferentially degraded. The potential for methane production from lignite spiked with carbon-bearing additives is at least one magnitude lower than that from agricultural wastes. The lignite utilization as the single substrate for methanogenic fermentation is economically unprofitable. Mixing of lignite with the external substrate as biomass may be an alternative for consideration and future research.

Use of Acetate, Propionate, and Butyrate for Reduction of Nitrate and Sulfate and Methanogenesis in Microcosms and Bioreactors Simulating an Oil Reservoir.

Acetate, propionate, and butyrate (volatile fatty acids [VFA]) occur in oil field waters and are frequently used for microbial growth of oil field consortia. We determined the kinetics of use of these VFA components (3 mM each) by an anaerobic oil field consortium in microcosms containing 2 mM sulfate and 0, 4, 6, 8, or 13 mM nitrate. Nitrate was reduced first, with a preference for acetate and propionate. Sulfate reduction then proceeded with propionate (but not butyrate) as the electron donor, whereas the fermentation of butyrate (but not propionate) was associated with methanogenesis. Microbial community analyses indicated that Paracoccus and Thauera (Paracoccus-Thauera), Desulfobulbus, and Syntrophomonas-Methanobacterium were the dominant taxa whose members catalyzed these three processes. Most-probable-number assays showed the presence of up to 107/ml of propionate-oxidizing sulfate-reducing bacteria (SRB) in waters from the Medicine Hat Glauconitic C field. Bioreactors with the same concentrations of sulfate and VFA responded similarly to increasing concentrations of injected nitrate as observed in the microcosms: sulfide formation was prevented by adding approximately 80% of the nitrate dose needed to completely oxidize VFA to CO2 in both. Thus, this work has demonstrated that simple time-dependent observations of the use of acetate, propionate, and butyrate for nitrate reduction, sulfate reduction, and methanogenesis in microcosms are a good proxy for these processes in bioreactors, monitoring of which is more complex.IMPORTANCE Oil field volatile fatty acids acetate, propionate, and butyrate were specifically used for nitrate reduction, sulfate reduction, and methanogenic fermentation. Time-dependent analyses of microcosms served as a good proxy for these processes in a bioreactor, mimicking a sulfide-producing (souring) oil reservoir: 80% of the nitrate dose required to oxidize volatile fatty acids to CO2 was needed to prevent souring in both. Our data also suggest that propionate is a good substrate to enumerate oil field SRB.

Increased energy production from sucrose by controlled hydrogen-producing fermentation followed by methanogenic fermentation

ABSTRACTTo improve the low energy production efficiency of fermentative hydrogen production (FHP) and fermentative methane production (FMP), the two types of fermentation were effectively combined in this study. Using sucrose as feedstock, both successive fermentative production of hydrogen followed by methane (SFPHM) and successive fermentative production of methane followed by hydrogen (SFPMH) were performed to improve the energy production efficiency of the overall anaerobic process. The results showed that the energy conversion efficiency of SFPHM was 79.85% whereas that of SFPMH was only 43.12%. Therefore, SFPHM can significantly improve the energy production efficiency of traditional anaerobic biological treatment.

Metabolic Network Modeling of Microbial Interactions in Natural and Engineered Environmental Systems.

We review approaches to characterize metabolic interactions within microbial communities using Stoichiometric Metabolic Network (SMN) models for applications in environmental and industrial biotechnology. SMN models are computational tools used to evaluate the metabolic engineering potential of various organisms. They have successfully been applied to design and optimize the microbial production of antibiotics, alcohols and amino acids by single strains. To date however, such models have been rarely applied to analyze and control the metabolism of more complex microbial communities. This is largely attributed to the diversity of microbial community functions, metabolisms, and interactions. Here, we firstly review different types of microbial interaction and describe their relevance for natural and engineered environmental processes. Next, we provide a general description of the essential methods of the SMN modeling workflow including the steps of network reconstruction, simulation through Flux Balance Analysis (FBA), experimental data gathering, and model calibration. Then we broadly describe and compare four approaches to model microbial interactions using metabolic networks, i.e., (i) lumped networks, (ii) compartment per guild networks, (iii) bi-level optimization simulations, and (iv) dynamic-SMN methods. These approaches can be used to integrate and analyze diverse microbial physiology, ecology and molecular community data. All of them (except the lumped approach) are suitable for incorporating species abundance data but so far they have been used only to model simple communities of two to eight different species. Interactions based on substrate exchange and competition can be directly modeled using the above approaches. However, interactions based on metabolic feedbacks, such as product inhibition and synthropy require extensions to current models, incorporating gene regulation and compounding accumulation mechanisms. SMN models of microbial interactions can be used to analyze complex “omics” data and to infer and optimize metabolic processes. Thereby, SMN models are suitable to capitalize on advances in high-throughput molecular and metabolic data generation. SMN models are starting to be applied to describe microbial interactions during wastewater treatment, in-situ bioremediation, microalgae blooms methanogenic fermentation, and bioplastic production. Despite their current challenges, we envisage that SMN models have future potential for the design and development of novel growth media, biochemical pathways and synthetic microbial associations.

Evaluation of the biological methane potential of various feedstock for the production of biogas to supply agricultural tractors

This work is divided into three parts. The first one presents results of biological methane potential of agriculture raw materials available in Poland. In the second part the simple mathematical model of methanogenic fermentation is proposed. The data for this model were obtained from experimental digestion process of chosen mixtures. Last part includes the results of research of exhaust emissions generated by dual dual-fuel engine of agricultural tractor powered by mixture of model biogas (60% and 70% of methane) and diesel oil. The obtained results revealed that there was a significant difference in chemical composition and yield of biogas between considered feedstock types. The highest biogas and methane production was obtained for mixtures in ratio of 6:4 for swine manure/maize silage and whey/grass silage. Due to agriculture conditions in Poland and obtain results, the maize silage and swine manure were chosen to development of mathematical model of fermentation process. It showed a satisfactory match to the experimental results.Results of emission tests on dual-fuel tractor engine supplied with biogas and diesel oil showed the higher concentrations of hydrocarbons and carbon oxide and lower concentrations of particulate matter in exhaust gases. Level of emission of particular components depends on the biogas composition.

Origin of carbonate cements with implications for petroleum reservoir in Eocene sandstones, northern Dongying depression, Bohai Bay basin, China

The Eocene Es4s interval is an important petroleum reservoir of sublacustrine fan dominated at the depths of 2500–4000 m in Dongying depression, Bohai Bay basin. Based on core observation, three types of carbonate-cemented beds have been identified and commonly contain ferroan calcite and ankerite predominantly and less calcite and dolomite. Precipitation temperatures range from 34.6 to 72.8℃ for calcite and dolomite cements, and from 110 to 153℃ for ferroan calcite and ankerite cements. The high δ13CPDB values (−0.65 to +5.59‰) for calcite and dolomite suggest that dissolved inorganic carbon, derived from methanogenic fermentation of organic matter in adjacent mudstones. The low δ13CPDB values (+1.04 to +3.29‰) for ferroan calcite and ankerite probably indicate a mixture of carbon derived from decarboxylation of organic acid as well as from the dissolution of early formed carbonate cements. High plug porosity is mainly developed at the central section of sandstones vertically and the porosity decreases sharply toward the top and base of the sandstones due to extensively carbonate-cemented beds. The carbonate-cemented beds varies from 0.02 to 0.5 m in thickness and might extend from tens to hundreds meters laterally. It could be served as fluid-flow barriers and seals for petroleum, and result in reservoir deterioration and significant heterogeneity.

ANAEROBIC DIGESTION IN SANITIZATION OF PIG SLURRY AND BIOMASS IN AGRICULTURAL BIOGAS PLANT

Pig slurry is one of the production manure, which should be managed properly because of environmental threats it can cause. Pig slurry contains a wide range of microorganisms, most of which are opportunistic or obligatory pathogens for people and animals. Spreading it on fields without control can cause microbial contaminations of water and soil. Use of pig slurry as substrate in anaerobic digestion can be an effective way of sanitization. In this work role of methanogenic fermentation in pig slurry sanitization was laboratory examined. Study materials were biological samples: 1 sample of raw slurry and 3 samples of fermented biomass from different stages of fermentation. Total number of coliforms was determined by MPN (most probable number) method, and presence of enterococci was verified in each sample. Study have shown that anaerobic digestion reduced total number of coliforms from initial amount of 7.0 x 106 [MPN/ml] in raw slurry to 3.7 x 104 [MPN/ml]. Total reduction was 99.47%. Moreover, after first fermentation, enterococci in the sample were undetectable. Results of this study proved anaerobic fermentation to be an affective way to neutralize microbial threat, that is pig slurry.

Diversity and variability of methanogens during the shift from mesophilic to thermohilic conditions while biogas production.

Anaerobic digestion (AD) is the most popular path of organic waste disposal. It is often used in wastewater treatment plants for excessive sludge removal. Methanogenic fermentation had usually been performed under mesophilic conditions, but in the past few years the thermophilic processes have become more popular due to economics and sludge sanitation. Methanogens, the group of microorganisms responsible for methane production, are thought to be sensitive to temperature change and it has already been proven that the communities performing methanogenesis under mesophilic and thermophilic conditions differ. But in most cases the research performed on methanogen diversity and changeability was undertaken in two separate anaerobic chambers for meso- and thermophilic conditions. It is also known that there is a group of microorganisms performing AD which are insensitive to temperature. Also the linkage between digester performance and its microbial content and community changeability is still not fully understood. That is why in this experiment we analyzed the bacterial community performing methanogenesis in a pilot scale anaerobic chamber during the shift from mesophilic to thermophilic conditions to point at the group of temperature tolerant microorganisms and their performance. The research was performed with PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis). It occurred that the community biodiversity decreased together with a temperature increase. The changes were coherent for both the total bacteria community and methanogens. These bacterial shifts were also convergent with biogas production-it decreased in the beginning of the thermophilic phase with the bacterial biodiversity decrease and increased when the community seemed to be restored. DGGE results suggest that among a wide variety of microorganisms involved in AD there is a GC-rich group relatively insensitive towards temperature change, able to adapt quickly to shifts in temperature and perform AD effectively. The studies of this microbial group could be a step forward in developing more efficient anaerobic digestion technology.