Mesophilic Methane Fermentation Research Articles

Pig slurry - A polydisperse substrate necessary for the biogasification of a lignite bed

The in situ transformation of the carbohydrate substances is presented in the context of methane (CH4) formation by methanogens. In situ coal conversion methods have been characterized due to the beneficial effect of unconventional coal mining. The research was carried out on less mature coals, with a lower carbonisation degree of organic matter, because they are more effective in conversion to bioenergy gas, which can be used for all pro-ecological activities. The original concept of experimental research was presented by combining the properties of a polydisperse substrate, which is pig slurry, and used for brown coal biogasification (anaerobic digestion) in two brown coal bed systems. For this purpose, a laboratory monosubstrate reactor for the fermentation of pig slurry in a lignite bed was developed. The mainaim of the research presented in the article is to assess the amount of agricultural biogas produced in the process of mesophilic methane fermentation with the use of a polydisperse substrate using a brown coal bed placed in a fermentor. The partial goals are:- presentation of analogies of techniques and methods of underground coal gasification (UCG) to biogasification of brown coal;- a set of correlation equations for calculating flow resistance coefficients through granular porous structures;- comparison of experimental values of flow resistance with calculations according to various models.The justification of the main goal and partial goals refers to the development of a new technique and method of obtaining biogas, taking into account the Reynolds number and the own model of the gas flow resistance coefficient.The novelty of the article are: developed own model for determining the correlation dependence of the flow resistance coefficient as a function of the Reynolds number, - the results of research that indicate the practical use of pig slurry in a lignite bed for which intensive biogas production takes place at lignite.- minor deposit in relation to lignite - flat fragments of a deposit. The inhibition phenomenon and the dynamics of the process during the production of biogas in the brown coal bed were also observed in the research. An additional advantage of the innovation in the article is the combination of a polydisperse substrate with a porous bed - the simplicity of the research is the production of biogas on a lignite bed, which is a medium for biogas-producing bacteria.It has been shown that:- the developed lignite biogasification system with the participation of a polydisperse substrate in the fermenter (laboratory vessel) ensures the production of biogas in the absence of thermal insulation of the fermenter;- for a lignite deposit, the biogas stream is stable with increasing temperature; while above the temperature of 38 °C–42 °C, the biogas stream is characterized by a downward trend.Comparing the flows of the biogas stream, the following can be observed:- the intensity of biogas production for lignite (smaller bed), there is a greater phase exchange, because the bed layout provides more space for the adhesion of methanogenic microorganisms, - in turn, in the case of lignite (flat fragments of the deposit), there is less phase exchange, i.e. less biogas production.The performed rheological tests of pig slurry proved the foaming properties of the sub-strate at 25 °C and 500 rpm for a kinematic viscosity of 27.5 mPa. Characteristic foaming properties are manifested by the polydisperse system, which is pig slurry.

Mesophilic methane fermentation performance and ammonia inhibition of fish processing wastewater treatment using a self-agitated anaerobic baffled reactor

The performance of the self-agitated anaerobic baffled reactor (SA-ABR) was investigated by increasing the organic loading rates (OLRs) from 0.46 to 9.50 g-COD/L/d. A good performance was achieved by the SA-ABR for the treatment of fish processing wastewater (FPW). The maximum OLR was 6.77 g-COD/L/d and the biogas production rate reached 2.16 L/L-reactor/d with a methane content of 69% at this OLR. The COD, carbohydrate, protein, lipid and VS removal efficiencies were as high as 64, 65, 68, 78 and 79%, respectively. Ammonia inhibition was assumed with inhibition concentrations of 10% (IC10) and 20% (IC20) at 4140 and 5780 mg/L. However, it was found that the reactor could tolerate ammonia at a high concentration range of 4500–6373 mg/L after a long-term continuous experiment. Ammonia inhibition was addressed by diluting the substrate and the sludge in the reactor with tap water.

Synergetic disintegration of waste activated sludge: improvement of the anaerobic digestion and hygienization of sludge

The main aim of this study was to investigate the impact of a hybrid disintegration process with the use of alkalization and freezing by dry ice on waste activated sludge (WAS) and on the course of the process of mesophilic methane fermentation. In order to achieve the mentioned goal, various analytical techniques were used for assessment of the sludge disintegration and its influence on the further biogas production. As a result of the investigation, it was found that the chemical-thermal process of destruction of WAS results in an increased concentration of organic compounds in the supernatant (expressed as a change in the value of the soluble chemical oxygen demand – SCOD). The use of disintegrated WAS and feeding of the material into the fermentation digester influences, depending on its proportion by volume, the production of biogas and the biogas yield (higher biogas production by ca. 39% in comparison to blank sample was achieved with the appropriately disintegrated sludge). The hybrid process is simple and easy to implement in the full technical scale and does not influence or change the pH value of the sludge feed into the fermentation chambers (the dry ice neutralizes the high pH of the sludge). Additionally, it was determined that the herein developed process, can improve hygienization of the digested sludge.

Energy Recovery from Rice Straw through Hydrothermal Pretreatment and Subsequent Biomethane Production

Rice straw is an abundant agricultural waste in Asia. Anaerobic digestion (AD) as an environmentally friendly process for bioenergy recovery is expected to solve the environmental issues brought about by open burning of rice straw. In order to test the feasibility and scalability of hydrothermal treatment (HTT) on rice straw for subsequent methane production from pretreated straw, this study attempted two peak HTT temperatures (150 and 210 °C, i.e. HTT150 and HTT210, respectively) for holding 0–30 min to pretreat rice straw which was then used for mesophilic methane fermentation. Thereafter energy balance and energy recovery were analyzed on HTT and subsequent AD of rice straw. Results show that HTT150 exhibited a positive effect on subsequent methane production, achieving the highest methane yield of 134 mL (STP) for per gram of added volatile solid (VSadded) of rice straw after being hydrothermally pretreated at 150 °C for 20 min. The maximum specific methane production rate (μ), around 17–40% higher th...

Different organic loading rates on the biogas production during the anaerobic digestion of rice straw: A pilot study

The aim of this work was to investigate the mesophilic methane fermentation of rice straw at different organic loading rates (OLRs) in a 300m3 bioreactor. It was found that biogas production increased when the OLR was below 2.00kg VSsubstrate/(m3·d). The average volumetric biogas production reached 0.86m3/(m3·d) at an OLR of 2.00kg VSsubstrate/(m3·d). Biogas production rate was 323m3/t dry rice straw over the whole process. The pH, chemical oxygen demand, volatile fatty acid, and NH4+-N concentrations were all in optimal range at different OLRs. High-throughput sequencing analysis indicated that Firmicutes, Fibrobacteres, and Spirochaetes predominated in straw samples. Chloroflexi, Proteobacteria, and Planctomycetes were more abundant in the slurry. The hydrogenotrophic pathway was the main biochemical pathway of methanogenesis in the reactor. This study provides new information regarding the OLR and the differences in the spatial distribution of specific microbiota in a rice straw biogas plant.

Biogas production and microbial community shift through neutral pH control during the anaerobic digestion of pig manure

Laboratory-scale reactors, in which the pH could be auto-adjusted, were employed to investigate the mesophilic methane fermentation with pig manure (7.8% total solids) at pH 6.0, 7.0, and 8.0. Results showed that the performance of anaerobic digestion was strongly dependent on pH value. Biogas production and methane content at neutral pH 7.0 were significantly higher (16,607mL, 51.81%) than those at pH 6.0 (6916mL, 42.9%) and 8.0 (9739mL, 35.6%). Denaturing gradient gel electrophoresis fingerprinting and Shannon’s index indicated that the samples contained highly diverse microbial communities. The major genus at pH 7.0 was Methanocorpusculum, compared with that was Methanosarcina at both pH 6.0 and 8.0. Our research revealed that cultures maintained at pH 7.0 could support increased biogas production, which has significant implications for the scale-up biogas engineering.

Effect of ammonia inhibition on microbial community dynamic and process functional resilience in mesophilic methane fermentation of chicken manure

BACKGROUND Ammonia nitrogen affects the methane fermentation of chicken manure, both the process resilience and the functional microbial community dynamics. In this study, a mesophilic continuous stirred-tank reactor (CSTR) was investigated with total ammonia nitrogen (TAN) varied from 2000 mg L−1 to 16000 mg L−1. RESULTS 16S-rDNA cloning and TRFLP results revealed that the microbial community shifts significantly responding to TAN. Aceticlastic Methanosarcina acetivorans increased gradually from 17% in the steady stage to 72% in the recovered stage with high resistance compared with aceticlastic Methanosaeta, which almost disappeared at high TAN. In contrast, hydrogenotrophic Methanoculleus increased from 2% in the steady stage to 30% in the inhibited stage and decreased to 13% in the recovered stage. The abundances of the dominant Firmicutes were 74% and 92%, with and without inhibition, and 58% in the recovered stage. Bacteroidetes decreased from 17% in the steady stage to 4% in the inhibited stage and thrived to 31% in the recovered stage. CONCLUSION Process resilience was proven even after serious inhibition. Recoverable shifted archaeal and chaotic shifted bacterial communities with functional stability were observed. This result reveals that TAN has an obvious effect on microbial community shifts and the functional resilience of the process. © 2014 Society of Chemical Industry

The effect of pressure and temperature pretreatment on the biogas output from algal biomass

This paper presents data on methane fermentation of algal biomass containing Chlorella sp. and Scenedesmus sp. The biomass was obtained from closed-culture photobioreactors. Before the process, the algae were subjected to low temperature and pressure pretreatment for 0.0, 0.5, 1.0 and 2.0 h. The prepared biomass was subjected to mesophilic methane fermentation. The amount and composition of the biogas formed in the process were determined. The amount of biogas produced was larger when the biomass was subjected to thermal preprocessing. The proportion of methane in the gas also increased. Extending the heating time beyond 1.0 h did not significantly improve the biogassing effects.

7-4-1 廃食用油を用いた中温メタン発酵における前処理法の開発(7-4 リサイクル2,Session 7 環境対策・リサイクル)

7-4-1 廃食用油を用いた中温メタン発酵における前処理法の開発(7-4 リサイクル2,Session 7 環境対策・リサイクル)

Mesophilic methane fermentation of chicken manure at a wide range of ammonia concentration: Stability, inhibition and recovery

A 12L mesophilic CSTR of chicken manure fermentation was operated for 400 days to evaluate process stability, inhibition occurrence and the recovery behavior suffering TAN concentrations from 2000 mg/L to 16,000 mg/L. A biogas production of 0.35-0.4 L/gVS(in) and a COD conversion of 68% were achieved when TAN concentration was lower than 5000 mg/L. Ammonia inhibition occurred due to the addition of NH4HCO3 to the substrate. The biogas and COD conversion decreased to 0.3 L/gVS(in) and 20% at TAN 10,000 mg/L and was totally suppressed at TAN 16,000 mg/L. Carbohydrate and protein conversion decreased by 33% and 77% after inhibition. After extreme inhibition, the reactor was diluted and washed, reducing TAN and FA to 4000 mg/L and 300 mg/L respectively, and the recovered biogas production was 0.5 L/gVS(in). The extended Monod model manifested the different sensitivities of hydrolysis, acidogenesis and methanogenesis to inhibition. VFA accumulation accompanied an increase in ammonia and exerted a toxic on microorganism.

High-solid mesophilic methane fermentation of food waste with an emphasis on Iron, Cobalt, and Nickel requirements

The effect of trace metals on the mesophilic methane fermentation of high-solid food waste was investigated using both batch and continuous experiments. The continuous experiment was conducted by using a CSTR-type reactor with three run. During the first run, the HRT of the reactor was stepwise decreased from 100days to 30days. From operation day 50, the reactor efficiency deteriorated due to the lack of trace metals. The batch experiment showed that iron, cobalt, and nickel combinations had a significant effect on food waste. According to the results of the batch experiment, a combination of iron, cobalt, and nickel was added into the CSTR reactor by two different methods at run II, and III. Based on experimental results and theoretical calculations, the most suitable values of Fe/COD, Co/COD, and Ni/COD in the substrate were identified as 200, 6.0, and 5.7mg/kg COD, respectively.

Minimum Requirements for Trace Metals (Iron, Nickel, Cobalt, and Zinc) in Thermophilic and Mesophilic Methane Fermentation from Glucose

The minimum requirements for four essential trace metals were examined in both thermophilic and mesophilic methane fermentation of glucose. The minimum requirement here was defined as the amount that supports the effluent soluble chemical oxygen demand (COD) of 1000 mg/ L or less for the duration of several times the hydraulic retention time (HRT). For this purpose, completely mixed reactors were run semi-continuously at 5 days HRT, with 10 g/L substrate COD. The minimum requirements determined as milligrams per gram COD removed were 0.45, 0.049, 0.054, and 0.24 in the thermophilic system and 0.20, 0.0063, 0.017, and 0.049 in the mesophilic system for iron, nickel, cobalt, and zinc, respectively. The thermophilic system required larger amounts (2.2 to 7.8 times) of the trace metals than the mesophilic system, indicating greater assimilation by biomass and/or less bioavailability under thermophilic conditions. The results can give quantitative information on trace metal nutrition for successful methane fermentation.

Comparison of organic matter degradation and microbial community during thermophilic composting of two different types of anaerobic sludge

Changes in organic matter degradation and microbial communities during thermophilic composting were compared using two different types of anaerobic sludge, one from mesophilic methane fermentation, containing a high concentration of proteins (S-sludge), and the other from thermophilic methane fermentation, containing high concentrations of lipids and fibers (K-sludge). The difference in the organic matter degradation rate corresponded to the difference in the organic matter constituents; the CO2 evolution rate was greater in the composting of S-sludge than of K-sludge; moreover, the NH3 evolution resulting from the protein degradation was especially higher in the composting of S-sludge. Then the differences in the microbial communities that contributed to each composting were determined by the PCR-DGGE method. Ureibacillus sp., which is known as a degrader with high organic matter degradation activity, was observed during the composting of S-sludge, whereas Thermobifida fusca, which is a well known thermophilic actinomycete that produces enzymes for lignocellulose degradation, were observed during the composting of K-sludge.

低タンパク質飼料にリンゴジュース粕を添加した飼料給与が豚排せつ物の中温メタン発酵におけるバイオガスの発生量と消化液の性状に及ぼす影響

栄養的制御による窒素排せつ量の低減がメタン発酵におけるバイオガス発生量と消化液の性状に及ぼす影響を明らかにするため，アミノ酸添加低タンパク質飼料（低CP, CP : 11.6％）にリンゴジュース粕を添加した飼料を給与した肥育豚から排せつされたふん尿を用いて，中温メタン発酵処理を行った。低CP飼料にリンゴジュース粕を10％添加した試験飼料を豚に給与すると，標準CP飼料（CP : 15.3％）に比較して，投入液の全窒素濃度は13％，消化液の濃度は9％低下した。同様に投入液のアンモニア性窒素濃度は34％，消化液の濃度は26％低減した。低CPリンゴジュース粕飼料の給与により，標準CP飼料給与に比べて，メタン発酵によるバイオガス発生量が1.3倍に増加し，また，メタン発酵ガス中の硫化水素の濃度が1/5と大きく低下した。以上のことから，メタン発酵処理において，低CPリンゴジュース粕飼料の給与により，標準CP飼料に比べて，発生メタンガス回収効率で約30％向上し，脱硫コストが約70％低減する可能性が示唆された。

高濃度牛ふん尿の中温メタン発酵特性

高濃度搾乳牛ふん尿の中温 (35℃) メタン発酵特性を解明することを目的として, 完全混合反応槽を用いた室内連続実験を行った。メタン発酵槽の水理学的滞留時間 (HRT) を30日, 15日, 7.5日および投入TS濃度を約10%に維持して実験を行ったところ, CODCr, 分解率は45～25%, 投入VSあたりのバイオガス生成量は0.32～0.18m3/kg-VS, メタンガス生成量は0.20～0.11m3-CH4/kg-VSまで変化し, いずれもHRTの短縮に伴って減少した。また有機物の分解を擬似一次反応で解析し, 速度定数と難分解性割合が求められた。

生ごみの高温メタン発酵における負荷とアンモニア阻害の影響

Although the methane fermentation process requires less energy and the collected gas may be used as a fuel, the reaction speed is slow. It leads to the large size reactor and high cost. Therefore, to investigate the practicability and efficiency of the Methane Fermentation as the waste disposal system from the perspective of energy production, advancement of load and reduction of discharge, the thermophilic methane fermentation tests were carried out at the temperature of 55°C changing the loading rate from 2.28 kg-VS/m3/d to 9.90 kg-VS/m3/d continuously. The fermentation could be stable under the following condition, HRT: over 10 days, loading rate: under 9.29 kg-VS/m3/d, moisture percentage: over 90%, Nitrogen content: under 0.0020 kg-N/kg. In case of that the nitrogen concentration in the treated waste is higher, the dilution water is necessary to control the concentration of nitrogen. In the thermophilic methane fermentation, two times more additional water is necessary compared with the mesophilic methane fermentation. The obtained net energy was two times greater by the thermophilic methane fermentation than by the mesophilic methane fermentation in the condition that the additional water for the waste was unnecessary. On the other side, there was no great difference between thermophilic and mesophilic methane fermentation in the condition that the additional water was necessary.

Effect of Heat Pretreatment on Mesophilic Methane Fermentation of Food Refuse in Municipal Solid Waste

The heat pretreatment conditions of food refuse such as leftover food collected from restaurants were examined to improve the gas production efficiency in the mesophilic methane fermentation. In the bench-scale continuous experiment of the mesophilic methane fermentation at the VS loading rate of 2.5kg-VS/m3/day and the HRT of 29 days, the VS removal was improved and the gas production per influent VS increased by 19% with the heat pretreatment. The methane content of produced gas was 68% and there was no difference from that obtained from the control test using non-heat-treated waste.The methane yield per removed VS and the efficiency of carbon conversion to methane were also improved significantly with the heat pretreatment. The measured gas production yield and methane content with the heat pretreatment were notably greater than the theoretically calculated value estimated by the approximate molecular formula and the stoichiometric equation reported to agree well with the experimental results in thermophilic methane fermentation on organic matters in municipal solid waste. The trial calculation results of the energy balance showed that the amount of power generation and available thermal energy can be increased even after compensating the heat required for the pretreatment of waste.

豆腐製造排水のメタン発酵特性と微生物菌群解析

The characteristics of methane fermentation for treating bean-curd (tofu)-processing wastewater (BCW) containing waste bean curd frying oil were determined. To facilitate the dispersion and degradation of the oil in the wastewater, lipase and two emulsifiers were adopted. Lipase pretreatment accelerated methane fermentation. Three anaerobic digester series were continuously supplied with BCW and operated under the following conditions: Run 1, without lipase pretreatment, thermophilic methane fermentation (55°C); Run 2, with lipase pretreatment, thermophilic methane fermentation; Run 3, with lipase pretreatment, mesophilic methane fermentation (35°C). Triglycerides and long-chain fatty acids (LCFAs) were completely eliminated by lipase pretreatment in the digester (Runs 2 and 3). The calculation of mass balance demonstrated that 70% of the supplied CODCr in BCW was eliminated in Run 2, and that 60% of the supplied CODCr was converted to methane. However, only 30-40% of the supplied CODCr was converted to methane in Run 3 or 1. The analysis of the microbial community structure in the sludge of the three digesters showed that the sulfate-reducing activity in Run 2 was lower and sulfate-reducing population was also smaller than those in Runs 1 and 3. Lipase pretreatment and thermophilic methane fermentation conditions promote the prevalence of LCFA utilizing hydrogen-producing acetogenic bacteria in the sludge of Run 2.

Effect of Plastic Media on Mesophilic Methane Fermentation of Separated Dairy Manure Slurry at high solids concentration

Effect of Plastic Media on Mesophilic Methane Fermentation of Separated Dairy Manure Slurry at high solids concentration

Mesophilic methane fermentation of low-solids dairy-cattle waste

Methane fermentation of low-solids dairy waste was studied in horizontal, unagitated, isothermally maintained, tubular fermenters. The methane fermentation characteristics at temperatures of 20, 30 and 40°C and hydraulic retention times (HRTs) of 1, 2, 4, 6, 8 and 10 days are reported. Methane production per fermenter volume was greatest at a 1 day HRT; production of 0·22, 0·31 and 0·32 m 3 of methane/m 3 fermenter volume/day occurred at 20, 30 and 40°C, respectively. Maximum methane production per unit of substrate fed, however, occurred at longer HRTs. Maximum methane production was: 0·55 m 3 at 20°C and an 8 day HRT; 0·55 m 3 at 30°C and an 8 day HRT; 0·82 m 3 at 40°C and an 8 day HRT (all per kg volatile solids fed).