Maximum Methane Concentration Research Articles

Enhanced biofilm-dependent biogas upgrading from waste activated sludge fermentation liquor in microbial electrolysis cells

This study demonstrated that metal-organic frameworks (MOFs)-derived Fe-NC cathode improved both methane yield and methane content in a microbial electrolysis cell-coupled anaerobic digestion (MEC-AD) system treating waste activated sludge (WAS) fermentation liquor. Results revealed that Fe-NC maintained a meso‑macroporous structure with a large specific surface area of 1381 m2/g and superior electrochemical properties. Its calculated specific capacitance and electron transfer resistance were 5.7 and 0.4 times of the carbon felt (CF) group. The bacterial and archaeal gene loads of Fe-NC biofilm after multiple acclimation cycles were 5.69E+10 and 1.86E+9 copies/cm2 and Proteiniphilum and Methanobacterium were the most enriched syntrophs from stage Ⅰ to stage Ⅱ acclimation. Corresponding maximum methane yield and content achieved were 0.31 m3 CH4/kg COD and 92.8 %, and its CO2-dependent methane production was improved by 107.6 %. Mechanistic investigations showed that Fe-NC biofilm improved enzyme-associated CO2 reduction pathway companying by promoting the intra- and extracellular electron transfer as well as ATP synthesis, therefore favoring methanogenic energetic metabolism. More importantly, an enhanced proton-coupled electron transfer (PCET) process was proposed within Fe-NC biofilm, providing a synergistic advantage over unbalanced conventional sole electron/proton transfer. This work provides an effective strategy to strengthen the waste-to-energy and biogas upgrading technology, potentially bringing economic benefits to wastewater treatment.

The occurrence of coalbed methane in the depocentre of the Upper Silesian Coal Basin in the light of the research from the Orzesze-1 deep exploratory well

The Orzesze-1 exploratory well with a depth of 3708 m (TVD) was drilled in 2019–2020 in the depocentre of the Upper Silesian Coal Basin (USCB). The methane content in the coal seams has been tested to a depth of 2840 m and the sorption capacity of the coal to a depth of 2576 m. These are the deepest measurements in the USCB so far. The vertical distribution of methane content in the borehole shows two depth zones of interest, the first at a depth 883 m to about 1300 m (maximum methane content about 12 m3/t coaldaf) and another in the range of 1500–2840 m, that is, to the maximum measurement depth, so the actual lower boundary depth of this zone is unknown. The maximum methane content here exceeds 18 m3/t coaldaf at a depth of >2800 m. Both zones are separated by an interval of reduced methane content of about 5 m3/t coaldaf at a depth of approximately 1400 m. The gas composition is dominated by methane (∼90%), and the content of carbon dioxide increases to approximately 15% at a depth of >2300 m. The methane-bearing zone at ∼900–1300 m corresponds to the zone of high- and medium-volatile bituminous coal (second coalification jump), while the highest methane content at a depth of >2800 m was determined in anthracite. The methane sorption capacity of the coal seams oscillates between 16 and 40 m3/t coaldaf with a maximum in anthracite at a depth of >2800 m, where the temperature of the rock approaches 100 °C and the deposit pressure exceeds 28 MPa. The highest sorption capacity in anthracite results from its inner structure characterised by the predominance of ordered aromatic lamellas and the dominance of vitrinite macerals (>70%), which contain coal micropores accumulating adsorbed methane. The comparison of the sorption capacity of the tested coal and the measured methane content displays undersaturation of 11–59%, however, due to significant gas content in the deep zone (depth > 1500 m), the drilling area can be considered as a prospect for further exploration and development of coalbed methane (CBM).

Grid study on methane diffusion law in confined space of working face

AbstractThe layout of methane sensors in the working face cannot meet the needs for monitoring methane concentrations within confined spaces, and it is challenging to determine the precise locations for manual inspections. Therefore, the working face is firstly divided into different areas and grids. Then combined with the characteristics of methane emissions and the measured data on site, the boundary conditions of simulation experiments are set up and the research is carried out on the diffusion law of methane in the confined space of the working face under different conditions. The experimental results show that methane emission intensity from coal walls affects its distribution. As emission intensity rises, methane nearer the coal wall decreases, while methane further away increases. Among coal mining points, point 2 shows the widest methane diffusion range. Rising wind speeds decrease methane diffusion from the coal wall, increasing vertical diffusion distance. Methane from the coal wall shifts to the air inlet, while methane from the mining point diffuses increasingly to the downwind side. The location of the maximum methane concentration generated from falling coal and its transportation process is only related to the location of the coal mining point. The key areas for methane monitoring in confined spaces of the working face should be the overlapping locations of the vertical‐3 and vertical‐4 areas and the horizontal‐1 and horizontal‐3 areas. The key areas for manual inspection should be the overlapping locations of the vertical‐2 and vertical‐3 areas and the horizontal‐1 area.

Biogas enhancement in the anaerobic digestion of thermo-chemically pretreated sludge by stimulating direct interspecies electron transfer by biochar and graphene

It is necessary to pretreat waste-activated sludge (WAS) to disintegrate the sludge matrix and amend its anaerobic digestion (AD) with carbon-based materials (CMs) to accelerate direct interspecies electron transfer (DIET) in order to realize the maximum biogas potential of abundant and habitat-threatening organic WAS. The AD of WAS pretreated thermo-chemically at 0.5% NaOH (g/g dry sludge) and 125 °C microwave irradiation was amended by biochar doses of 0–40 g/L and graphene doses of 50–1,000 mg/L in the batch operation mode. Hybrid pretreatment of WAS deteriorated dewaterability but solubilized 38% of total chemical oxygen demand (COD). AD amended with 20 g/L biochar and 100 mg/L graphene had the optimum accumulative methane yield of 183.6 and 153.8 mL/gVS, respectively, which correspond to 42.8% and 24.8% increases compared to an unamended control assay with maximum methane content of 70.3% and 71.9%, respectively. The digestate of biochar- and graphene-amended assays resulted in higher TS% and alkalinity, reduced sCOD, VFA, and turbidity, and increased particle size distribution compared to control. Biochar-amended digestate had improved dewaterability, while digestate of graphene-amended assays resulted in worse dewaterability than control. The t-test showed a significant difference between the biochar and graphene amended batch assays, while principal component analysis (PCA) indicated that biogas yield was closely correlated with pH. CM-amended batch assays demonstrated superb fitting with modified Gompertz, logistic, and first-order models with a coefficient of determination above 0.97. Microbial community abundance and diversity were affected by CMs amendment, resulting in increased acetoclastic methanogen growth and transformed methanogenic metabolic pathways. An extended pilot-scale study and techno-economic and life cycle assessments are required to investigate environmental impacts and feasibility.

Integrated microcontroller mq sensors for monitoring biogas: Advancements in methane and hydrogen sulfide detection

Recent technological advances in microcontroller systems enable novel biogas monitoring capabilities. This study investigates microcontroller-based quantification of methane and hydrogen sulfide concentrations in biogas derived from anaerobic digestion. Anaerobic digesters were fed either 100% cow dung substrates or a 50:50 mixture of cow dung with municipal solid waste (MSW). Methane levels were monitored using an MQ-4 sensor, hydrogen sulfide via an MQ-136 sensor, and temperature with a K-type thermocouple, all integrated with an ATmega 2560 microcontroller system. The 100% cow dung digester produced biogas with maximum methane concentrations of 3488 ppm at 21 days, indicating improved methane production compared to the 50:50 mixture of cow dung with MSW. Hydrogen sulfide reached 195 ppm and 192 ppm for the 100% cow dung and mixed digesters. Mesophilic temperature conditions were maintained throughout the digestion process. Real-time quantification of biogas composition demonstrates the capabilities of microcontroller-based anaerobic digester monitoring to provide precise methane and hydrogen sulfide measurements.

Unlocking potential: Exploring the methane production potential in anaerobic co-digestion of cassava wastewater and glycerol

This study aimed at evaluating the feasibility of CH4 production in a mesophilic (30 °C) single-stage anaerobic co-digestion of cassava wastewater (CW) and glycerol in an anaerobic fluidized bed reactor (AFBR) with mixing ratio of 50 % / 50 % CW/Gly on a (chemical oxygen demand)COD basis. Thus, the following strategy was used: increasing the organic loading rate (OLR) (1–20 g COD.L−1.d−1) by increasing the substrate concentration (1–20 g COD.L−1) and applying a hydraulic detention time (HRT) of 24 h. The AFBR presented a maximum methane (CH4) content of 88.38±1.94 % and a CH4 yield (MY) of 293.48±18.37 mL of CH4.mL−1CODrem in the OLR of 1 g COD.L−1.d−1 and the maximum methane production rate (MPR) of 62.09±2.75 mL of CH4.L−1.h−1 in the OLR of 20 g COD.L−1.d−1. The conversion of glycerol and carbohydrates remained above 91±0.54 % and 82±2.79 %, respectively, and the COD conversion was above 80±0.65 %. The main metabolites were HAc, HPr, HBu, EtOH and HVa. The most abundant genera identified in the AFBR were Izemoplasmatales and Enterobacteriaceae for the bacteria domain, and Methanosaeta, Methanobacterium for the archaea domain. The single-stage system is robust and can operate with higher OLR without reducing the efficiency of wastewater treatment and CH4 production.

Optimization of the Ex Situ Biomethanation of Hydrogen and Carbon Dioxide in a Novel Meandering Plug Flow Reactor: Start-Up Phase and Flexible Operation.

With the increasing use of renewable energy resources for the power grid, the need for long-term storage technologies, such as power-to-gas systems, is growing. Biomethanation provides the opportunity to store energy in the form of the natural gas-equivalent biomethane. This study investigates a novel plug flow reactor that employs a helical static mixer for the biological methanation of hydrogen and carbon dioxide. In tests, the reactor achieved an average methane production rate of 2.5 LCH4LR∗d (methane production [LCH4] per liter of reactor volume [LR] per day [d]) with a maximum methane content of 94%. It demonstrated good flexibilization properties, as repeated 12 h downtimes did not negatively impact the process. The genera Methanothermobacter and Methanobacterium were predominant during the initial phase, along with volatile organic acid-producing, hydrogenotrophic, and proteolytic bacteria. The average ratio of volatile organic acid to total inorganic carbon increased to 0.52 ± 0.04, while the pH remained stable at an average of pH 8.1 ± 0.25 from day 32 to 98, spanning stable and flexible operation modes. This study contributes to the development of efficient flexible biological methanation systems for sustainable energy storage and management.

Дистанционная оценка качества атмосферного воздуха в населенных пунктах нефтегазовой специализации Ямало-Ненецкого автономного округа

The remote assessment of methane (CH4), nitrogen dioxide (NO2), and sulfur dioxide (SO2) concentrations in the atmosphere of oil-and-gas profile settlements within the Yamalo-Nenets Autonomous Okrug for 2019–2022 was made for the first time. Data analysis from the TROPOMI spectrometer revealed that the highest levels of atmospheric pollution are observed near industrial centers and major cities (Novy Urengoy, Salekhard, Nadym). Increased impurities were identified along gas pipelines (near compressor stations). The highest average values of nitrogen dioxide content were recorded in Novy Urengoy (1,34 mol/m², with contamination peaks occurring in winter months). Excessive concentrations of sulfur dioxide were found in urban-type settlements. The highest average values were recorded in Stary Nadym (20,35 mol/m²). The maximum methane content (1866,2 ppb) was reported in Novy Urengoy. Urban air, in general, has increased methane content. However, focuses of its spread are also observed beyond cities, which may be a consequence of global warming

Forecast of the Maximum Methane Concentration in the Longwall Outlet and in the Ventilation Roadway. Case Study

Abstract The mining process of the coal seam wall is accompanied by the release of methane into the mine atmosphere. This process is highly variable and depends on the methane content in the seam and the methane saturation of the rocks surrounding the seam. This is the specificity of the Polish hard coal mining industry. In the article, prognostic formulas for the maximum methane concentration at the outlet of the longwall ventilation gallery were developed. In the presented article, these formulas were used to predict methane concentration at the longwall outlet and in the ventilation gallery at a distance of up to 10 m in front of the longwall. In order to assess the accuracy of the forecasts, their results were compared with the forecast at the exit of the ventilation roadway. The obtained results are so accurate that it is worth repeating this type of check also using measurements in other longwalls. It will allow to reduce the risk of methane explosion during operation.

Effect of thermal and NaOH pretreatment on water hyacinth to enhance the biogas production.

Water hyacinth (WH) is used as the substrate for biogas production due to its high lignocellulosic composition and natural abundance. The present study used thermal and chemical (alkali) pretreatment techniques to enhance biogas production from water hyacinth used as a substrate by anaerobic digestion. Thermal pretreatment was done using an autoclave at 121 °C and 15 lb (2 bar) pressure and alkali pretreatment by NaOH at two concentrations (2% and 5% w/v). The inoculum:substrate ratio for biogas production was 2:1, where cow dung was used as inoculum. Results indicated that the pretreatments increased biomass degradability and improved biogas production. Water hyacinth pretreated with 5% NaOH produced the highest amount of biogas (142.61 L/Kg VS) with a maximum methane content of 64.59%. The present study found that alkali pretreatment can modify the chemical structure and enhance WH hydrolysis, leading to enhanced energy production.

Hotspot Detection and Estimation of Methane Emissions from Landfill Final Cover

The main objectives of this study were to identify methane hotspots through spatial distribution tests of the surface methane concentration above a landfill final cover and to investigate the effects of rainfall, atmospheric pressure, ground temperature, and ambient methane concentration on methane emissions. A portable laser methane detector was used to measure the spatial distribution of methane concentrations. The methane concentration distribution showed a distinct spatial variability. The maximum methane concentration reached 3225 ppm, while 73.0% of the methane concentration values were below 10.0 ppm. Several meteorological factors were found to be associated with the variation in methane emissions. Rainfall limited gas transport in the cover, resulting in more significant methane hotspots. Atmospheric pressure was negatively correlated with methane emission. The ambient methane concentration and methane flux had a significant positive linear correlation. Based on a linear correlation equation, the spatial distribution of methane concentrations in the landfill could be converted into a methane emission distribution. The estimated average value for methane emissions in the test area was approximately 4.3 g m−2 d−1. This study provides an experimental basis for locating methane hotspots and assessing methane emissions in landfill final covers, and proposes supplementary means for detecting geomembrane damage in landfill covers.

Study of Methane Emission and Geological Sources in Northeast China Permafrost Area Related to Engineering Construction and Climate Disturbance Based on Ground Monitoring and AIRS

China’s largest high-latitude permafrost distribution zone is in Northeast China. With the intensification of global warming and engineering construction, the carbon stored in permafrost will gradually thaw and be released in the form of methane gas. However, research on the changes in methane concentration and emission sources in this area is still unclear. In this paper, the AIRS (Atmospheric Infrared Sounder) data carried by the Aqua satellite were used to analyze the distribution and change trends in the overall methane concentration in the near-surface troposphere in Northeast China from 2003 to 2022. These data, combined with national meteorological and on-site monitoring data, were used to study the methane emission characteristics and sources in the permafrost area in Northeast China. The results show that the methane concentration in the near-surface troposphere of Northeast China is mainly concentrated in the permafrost area of the Da and Xiao Xing’an Mountains. From 2003 to 2022, the methane concentration in the near-surface troposphere of the permafrost area in Northeast China showed a rapid growth trend, with an average linear trend growth rate of 4.787 ppbv/a. In addition, the methane concentration in the near-surface troposphere of the permafrost area shows a significant bimodal seasonal variation pattern. The first peak appears in summer (June–August), with its maximum value appearing in August, and the second peak appears in winter (December–February), with its maximum value appearing in December. Combined with ground surface methane concentration monitoring, it was found that the maximum annual ground surface methane concentration in degraded permafrost areas occurred in spring, causing the maximum average growth rate in methane concentration, also in spring, in the near-surface troposphere of permafrost areas in Northeast China (with an average value of 6.05 ppbv/a). The growth rate of methane concentration in the southern permafrost degradation zone is higher than that in the northern permafrost stable zone. In addition, with the degradation of permafrost, the geological methane stored deep underground (methane hydrate, coal seam, etc., mainly derived from the accumulation of ancient microbial origin) in the frozen layer will become an important source of near-surface troposphere methane in the permafrost degradation area. Due to the influence of high-permeability channels after permafrost degradation, the release rate of methane gas in spring is faster than predicted, and the growth rate of methane concentration in the near-surface troposphere of permafrost areas can be increased by more than twice. These conclusions can provide a data supplement for the study of the carbon cycle in permafrost areas in Northeast China.

Anaerobic mono and co-digestion of agro-industrial waste and municipal sewage sludge: Biogas production potential, kinetic modelling, and digestate characteristics

Lignocellulosic substrates, including wastes generated from agro-industrial activities, are bio-residues evaluated to put an end to the energy needs and sustainable waste disposal problems that the world is trying to deal with today. However, the slow rate of hydrolysis of such lignocellulosic wastes limits the biogas production efficiency with the mono-anaerobic digestion (AD) process. Therefore, anaerobic co-digestion (AnCoD) of such wastes with secondary raw materials rich in microorganisms and various nutrients, such as sewage sludge, is an economical and useful method for both enhancing biogas production and disposal of more waste. In this study, AD and AnCoD processes for biogas and methane production were investigated on okra waste (OW) and municipal sewage sludge (MSS) by using cattle manure as inoculation, which constitutes only 8% of the total working volume. Five different substrate mixing ratios (100%OW, 75%OW-25%MSS, 50%OW-50%MSS, 25%OW-75%MSS, and 100MSS%) were prepared to observe the effect of C/N ratio, maximum biogas production potential, methane content, and organic matter removal efficiency on AD and AnCoD processes. All bioreactors were operated in a batch process with 8% TS in mesophilic temperature for 25 days. The amount of biogas produced in the 100%OW experimental set for the AD process was 44% more than 100%MSS. However, the AnCoD process was more efficient than AD, and biogas and methane production increased by up to 66% and 112%, respectively, compared to the mono-substrate experimental set. The highest biogas production value was 1060 mL (375 mL/gVSremoved) with 60% methane content in the bioreactor consisting of 25%OW-75%MSS. As a result of AD and AnCoD process, soluble carbohydrate, protein and COD removal for all bioreactors were between 62% and 79%, 28%-68% and 54%-70%, respectively. The FT-IR peaks seen in digestates were consistent with the presence of functional groups formed as a result of AnCoD. Monod, Cone, Transference function, and Logistic function kinetic models were used for the estimation of cumulative biogas production efficiency. In addition, the energy potential of the methane produced as a result of the AD and AnCoD processes and the financial gain that can be obtained from its direct sale were evaluated.

Organic Solid Waste in Vessel Composting System

Low-level microbial activity due to the production of organic acids is a recognized problem during the initial phase of food waste composting. Increasing such activity levels by adjusting the pH values during the initial composting phase is the primary objective to be investigated. In this study, sodium acetate (NaoAc) was introduced as an amendment to an in-vessel composting system. NaoAc was added when the pH of the compost mixture reached a low level (pH < 5), the addition increased pH to 5.8. This had a positive effect on the degradation of organic materials i.e. the formation of methane gas compared to the results without NaoAc addition.
 The results also proved that anaerobic-aerobic in-vessel composting could reduce the large amounts of wastes by 33% -30%.
 However the addition of NaoAc had no significant influence on temperature profile, bulk density, electric conductivity (EC), moisture contents, Nitrogen, phosphorus, potassium (NPK) and heavy metals )Cu, Cd, Ni, Pb) during the composting process, in fact heavy metals and (NPK) were below the maximum permissible levels of the Japanese organic farming and the USDA and US Compost Council standards .
 To assess the performance of the composting process, two small-scale digesters were used with fixed temperature. Maximum methane content of 68±1% and 75±1% by volume of the generated biogas was achieved in the run without and with NaoAc respectively.
 The germination index was which proved that the stabilized compost obtained in this research is of the “mature" kind and it is satisfactory for agricultural use according to the organic farming recommended by the Japanese Ministry of Agriculture, Forestry and Fisheries, and USDA and US Compost Council standards.

Methane anomaly in soil gas above an abandoned oil & gas exploration borehole in NE Czechia

In the 1950s–1960s, 71 coal and gas exploration wells were drilled in the area of interest in the Western Carpathian Flysch Belt (WCFB) in the NE Czech Republic. Some wells were abandoned while others were used for gas production and storage in the Třanovice underground gas storage (UGS). A monitoring campaign was carried out in place of an earlier abandoned exploration well Žu-108 aiming at proving or ruling out a geochemical relationship of the soil gas and the stored gas in the UGS. The measurements were carried out each month from June 2018 to October 2019 and included amount of methane (CH4), total petroleum gases (CH4 to C4H10), carbon dioxide (CO2) and oxygen (O2) in soil gas in a grid of up to 41 probes. The results show a methane gas peak occurrence with 10 m diameter around the well-top with maximum methane content of 57%vol, while the natural background value of methane content outside the plume is < 500 ppm. The position of the methane peak is associated with significant O2 drop down to 0.25%vol and is surrounded by up to 8.34%vol CO2 halo produced most probably by methanotrophic archea-bacteria. The natural background CO2 values are ca. 0.80%vol. CH4 flux to the atmosphere from the topsoil directly above the well-top of Žu-108 well was measured using the accumulation chamber and range from 2126 to 26 197 g d−1 m−2. The flux increased during drops in atmospheric pressure and ground water level in situ. In contrast, low methane flux was registered after strong rainfalls and when the soil was covered by ice and snow which acted as seal. Based on chemical composition and isotopic signature of methane, the gas is of oil-associated type and methane is thermogenic, similar to that of the original (i.e. pre-UGS) Žukov gas field as well as other small accumulations in the WCFB on the territory of the Czech Republic. It statistically differs from imported mixture of Siberian and Norwegian gas stored in the Třanovice UGS. Based on it, the possible natural gas leakage from the UGS to the Žu-108 is in this case ruled out.

Biogas Production from Arthrospira platensis Biomass

Biogas production by fermentation is a relatively low-cost and simple method for the transformation of a substrate into an energy carrier with a wide range of possible applications. The aim of this study was to determine the potential of Arthrospira platensis biomass as a source of bioenergy produced during anaerobic digestion (AD). The studies were carried out on a fractional-technical scale. Biogas yield and composition were analyzed as a function of the amount of biomass subjected to anaerobic digestion, the substrate dosing frequency in the digester and the use of biomass pre-hydrolysis in the mixing compartment. The energy efficiency of the process was also compared for each sample. In addition, a biomass conversion power index was developed and determined. It was found that A. platensis biomass had significant energy potential, and the amount of biogas obtained and its calorific value changed depending on the applied treatments. The maximum cumulative biogas production was 505 L kg−1 volatile solids (VS), while the maximum average methane (CH4) content was 67.32%. A two-fold increase in the organic loading rate from 1 g VS·L−1 volatile solids (VS) to 2 g VS·L−1 had a positive effect on methane concentration. The highest energy efficiency of the AD process was obtained for 2 g VS·L−1, with a single feedstock input into the digester, in a single-stage process (2/s/-), while the highest conversion power ratio was for a feedstock of 1 g VS·L−1, under the same process conditions (1/s/-). Moreover, the energy efficiency of the microalgae fermentation process obtained in the study is higher compared to conventional substrates used in biogas plants. This energy analysis can support the selection of cogeneration power engines in a biogas plant and help to determine the potential output of the biogas plant, especially with varying energy and heat demand.

Dissolved Methane Transport in the Tatar Strait and the Deepest Basin of the Japan (East) Sea from Its Possible Sources

Dissolved methane coming from its various sources is an important component of seawater. Finding these probable sources allows for the determination of potential oil and/or gas deposit areas. From an ecological point of view, methane transport studies can reveal probable pollution areas on the one hand and biological communities, being the lower part of the food chain commercial species, on the other hand. Moreover, the methane transport mechanism can help to obtain a better understanding of the contribution of the World’s oceans to global greenhouse gas emissions. Our research combines gas geochemistry and oceanography. In comparing the research results of both branches, we show the mechanism of methane transport. The features of the dissolved methane on oceanographic sections in the southern part of the Tatar Strait are discussed. The CH4 intake from the bottom sediment and the transport of dissolved methane by the currents in the Tatar Strait are shown. The absolute maximum concentration of CH4 (155.6 nM/L) was observed on the western Sakhalin Island shelf at the near-bottom layer at a depth of 65 m. The local maximum, 84.4 nM/L, was found north of the absolute maximum in the jet current under the seasonal pycnocline. A comparison of the simulated surface seawater origin and dissolved methane in the 4 m depth distribution shows methane transport with the currents in the Tatar Strait. Another studied section is along 134° E in the Japan Basin of the Japan (East) Sea. Here, the East Korean Warm Current close to the Yamato Rise slope and a quasi-stationary mesoscale anticyclonic eddy centered at 41° N intersect. The local maximum methane concentration of 8.2 nM/L is also observed under the seasonal pycnocline. In a mesoscale anticyclonic eddy at 134° E in the deep part of the Japan Basin, a local methane maximum of 5.2 nM/L is detected under the seasonal pycnocline as well.

Effect of initial pH and substrate to inoculum ratio on the production of methane and hydrogen from food waste

“Anaerobic co-digestion of food waste, cow dung, and sludge solution is experimented by varying the pH to produce hydrogen and methane as a source of renewable energy. The substrate to inoculum ratio (v/v) of 1:1(S1), 1:2(S2), 1:3(S3), 1:4(S4) and 1:5(S5) are investigated in separate fermentative and methanogenic reactors. A maximum hydrogen and methane concentration of 19.73% and 64.81% respectively are obtained in S3. The methane concentration of 53.67%, 64.81% and 59.64% is observed at the pH variation of 6.5, 7, and 7.5 respectively. The obtained result shows the substrate to inoculum ratio of 1:3 to be the optimal combination for the highest methane and hydrogen production during the anaerobic co-digestion process”.

The advantages of co-digestion of vegetable oil industry by-products and sewage sludge: Biogas production potential, kinetic analysis and digestate valorisation.

The production of edible vegetable oils generates considerable amounts of energy-rich waste, which is usually not utilised fully. Besides, inefficient management of such wastes can have a negative impact on the environment. On the other hand, this waste can also serve as a raw material for the production of high value-added products, such is biogas. The mono-digestion of seven different by-products and wastes from the vegetable oil industry was investigated in this study: Pumpkin seeds press cake (PSPC), grape seeds press cake (GSPC), olive mill pomace (OMP), coconut oil cake (CC), filtration additive (FA), spent bleaching earth (SBE) and sludge from a vegetable oil industry (SOI) wastewater treatment plant. In addition, co-digestion of these substrates was performed with municipal sewage sludge (SS). Besides inoculum, rumen fluid was added to the reactors to enhance biogas production. The biogas production potential of the tested substrates was monitored by measuring various parameters. A kinetic analysis was later carried out and a growth test was performed on the digestates to evaluate their potential for agricultural use. The highest biogas yields in the mono-digestion test were obtained with the substrates with the highest fat content: 1402, 1288, 830 and 750mL of biogas/gVS for SOI, FA, PSPC and CC substrate, respectively. Co-digestion of SS with by-products of vegetable oil industry such as FA, SBE, CC, SOI and PSPC increased the biogas yields by 94.9%, 74.1%, 30.8%, 27.4% and 23.6% compared to SS mono-digestion. Furthermore, the data for mono-digestion of PSPC, GSPC, and FA, and co-digestion of SS with these substrates, CC and SBE, have not been found in the literature to date. The maximum methane content ranged from 61 to 74vol%, while the chemical oxygen demand removal efficiency ranged from 42 to 78%. Relatively high fatty acids contents and ammonium concentrations were measured in the reactors. Kinetic analysis showed the best fit to the experimental data for the Cone kinetic model (R2>0.98). The First order kinetic model, Monod, and the modified Gompertz model also exhibited high R2 values. The digestates obtained from co-digestion proved to be excellent in the cress seeds growth test at digestate concentrations of 5-10wt%, while higher concentrations had a toxic effect.

Experimental and simulation analysis of biogas production from beverage wastewater sludge for electricity generation

This study assessed the biogas and methane production potential of wastewater sludge generated from the beverage industry. The optimization of the biogas production potential of a single fed-batch anaerobic digester was operated at different temperatures (25, 35, and 45 ℃), pH (5.5, 6.5, 7.5, 8.5, and 9.5), and organic feeding ratio (1:3, 1:4, 1:5, and 1:6) with a hydraulic retention time of 30 days. The methane and biogas productivity of beverage wastewater sludge in terms of volatile solid (VS) and volume was determined. The maximum production of biogas (15.4 m3/g VS, 9.3 m3) and methane content (6.3 m3/g VS, 3.8 m3) were obtained in terms of VS and volume at 8.5, 35 ℃, 1:3 of optimal pH, temperature, and organic loading ratio, respectively. Furthermore, the maximum methane content (7.4 m3/g VS, 4.4 m3) and biogas production potential (17.9 m3/g VS, 10.8 m3) were achieved per day at room temperature. The total biogas and methane at 35 ℃ (30 days) are 44.3 and 10.8 m3/g VS, respectively, while at 25 ℃ (48 days) increased to 67.3 and 16.1 m3/g VS, respectively. Furthermore, the electricity-generating potential of biogas produced at room temperature (22.1 kWh at 24 days) and optimum temperature (18.9 kWh) at 40 days was estimated. The model simulated optimal HRT (25 days) in terms of biogas and methane production at optimum temperature was in good agreement with the experimental results. Thus, we can conclude that the beverage industrial wastewater sludge has a huge potential for biogas production and electrification.