Average Methane Content Research Articles

Shrimp mariculture may increase aquatic CO2, CH4, and N2O emissions in semi-indoor and indoor ponds.

This study revealed the greenhouse gas (GHG) emission patterns during shrimp mariculture in both semi-indoor and indoor ponds. In the semi-indoor ponds, the average carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) concentrations of pond water varied from 1373.0±721.7 μatm, 4.4±1.3nM, and 14.2±3.5nM, respectively, at the initiation of stocking to 5296.0±1474.7 μatm, 3.8±0.3nM, and 28.1±17.9nM, respectively, in the harvest stage. In the indoor pond, these varied from 562 μatm, 3.5±0.2nM, and 10.7±0.1nM, respectively, at the initiation of stocking to 4728.0 μatm, 18.2±0.7nM, and 94.1±0.6nM, respectively, in the harvest stage. An upward trend in CO₂ and N₂O concentrations was observed in the water of both semi-indoor and indoor ponds as the culture period progressed. The discharged waters exhibited the highest GHG concentrations, potentially acting as emission hotspots if left untreated. The total average CO₂-equivalent (CO₂-eq) fluxes from pond water during the shrimp mariculture period were 49.8±40.7mg CO₂-eqm-2h-1 in the semi-indoor ponds, with 44% of these GHG emissions attributable to shrimp mariculture practices. In the indoor pond, the fluxes were 101.5±52.6mg CO₂-eqm-2h-1, with 86% of the GHG emissions attributable to shrimp mariculture practices. According to these results, shading effects may increase the GHG emissions from aquaculture pond waters.

Monthly and annual oscillation of methane and ozone in eastern India using Sentinel-5P TROPOMI: assessment and validation.

The eastern India has greater Global Warming Potential with increased greenhouse gases emissions due to extensive rice production, coal burning, and rapid urbanization. The present study aimed to assess the monthly and annual dynamics of methane and ozone over the eastern Indian sates from February, 2019 to February, 2024 using Sentinel-5P Tropospheric Monitoring Instrument (TROPOMI). Chhattisgarh recorded the lowest concentration in most of the years. Chhattisgarh experienced the maximum growth in methane content by 3.41% followed by Bihar with 2.44% growth from 2019 to 2023. Although West Bengal recorded the highest average annual methane concentration, the methane growth is the minimum over the state with 1.87%. Periodical oscillation of methane concentration was characterized by the pre-monsoon (March-May) low and post-monsoon (September-November) high. Cloud interference during monsoon months caused data gap. In all the districts except Bihar, ozone concentration increased from 2019 and continued to rise up to 2022 followed by a subsequent decline in 2023. Linear trend of annual mean ozone concentration revealed a non-significant rising trend. Ozone concentration was found to be the minimum during post-monsoon months and the maximum during pre-monsoon months indicating a seasonal oscillation. Atmospheric Infrared Sounder (AIRS) and Ozone Monitoring Instrument (OMI) generated datasets were used to validate the methane and ozone concentration respectively obtained from TROPOMI observations. AIRS and TROPOMI datasets exhibited a good agreement with a correlation coefficient (r) of 0.45 and coefficient of determination (R2) of 0.204. On the other hand, OMI and TROPOMI showed an excellent agreement with an r value of 0.99 and an R2 value of 0.978. The study assessed the spatial and temporal pattern of methane and ozone content in the recent times which helps the planners and policy makers to understand the trends and to develop effective mitigation strategies.

A novel tubular single-chamber microbial electrolysis cell for efficient methane production from industrial potato starch wastewater

The integration of microbial electrolysis cells (MEC) with anaerobic digestion (AD) shows great promise for enhancing methane production from high-COD wastewater. However, an efficient MEC-AD reactor design remains elusive. Here, a novel tubular single-chamber MEC-AD reactor was constructed to treat potato starch wastewater (COD over 20,000 mg/L). The concentric and compact design of the stainless-steel cathode and anode reduced internal resistance, resulting in enhanced methane production. Applying −0.2 V vs. Ag/AgCl to the anode increased methane production by 1.73 times compared to the open circuit and halved hydraulic retention time. Moreover, the reactor achieved an average methane content of 82.57 %, which was 23.89 % higher than the open circuit. The reactor showed a total COD removal of 92.2 %, which was 24 % higher than the open circuit. Additionally, base consumption to maintain pH was reduced to one-sixth of that in conventional AD, preventing volatile fatty acid accumulation. Microbial analysis showed Geobacter (63.4 %) and Methanobacterium (96.8 %) were highly enriched in the anode and cathode biofilms, respectively. The proportion of fermentative bacteria also increased in the MEC-AD system. These results demonstrate the effectiveness of the tubular single-chamber MEC-AD reactor in enhancing methane production from potato starch wastewater, with strong potential for scale-up applications.

Pilot-scale in-situ biomethanation of sewage sludge: Effects of gas recirculation method

The methanation efficiency and operational stability of a 2 m3 pilot-scale in-situ biomethanation reactor were investigated using on-site sewage sludge as the substrate, at a wastewater treatment plant. In parallel, a laboratory-scale study was conducted. Hydrogen conversion efficiencies of 96.7 and 97.5 %, and average methane contents of 84.2 and 83.2 % were obtained, for the laboratory and pilot experiments, respectively. The pilot-scale digester was operated at various conditions for 137 d, of which the last 30 d were stable with a high biomethanation efficiency and an average pH of 8.2. Gas recirculation increased the hydrogen conversion efficiency. When hydrogen injection and gas recirculation were applied separately, a 96 % lower gas recirculation rate was needed to achieve the same hydrogen conversion efficiency, compared to a mixture of hydrogen injection and gas recirculation in the same line. These findings may facilitate the selection of suitable gas recirculation concepts for practical biomethanation applications.

Determination of the biochemical methane potential of swine hydrolyzate

Swine farming generates remains of births and animals that die during the process. Implementing a plan to eliminate these materials by hydrolysis process results in an animal by-product called swine hydrolyzate. The treatment of this by-product through its application in the anaerobic digestion process can also represent its conversion into a resource for energy production. Thus, the present study focuses on this by-product as a potential substrate for anaerobic digestion, evaluating the methane production potential. The results show biogas production with an average methane content of about 70 %. Theoretical biochemical methane potential was 967.95 ± 0.11 mL g VS−1, which represented a bioconversion efficiency of 59.97 ± 3.54 % and 62.26 ± 0.43 %, considering the experimental results of 580.47 ± 34.29 mL g VS−1 and 602.67 ± 4.16 mL g VS−1, respectively. By comparing the experimental biochemical methane potential with the predicted value using the modified Gompertz model, it was possible to conclude that the maximum methane production rate was 73.46 ± 0.36 mL g VS−1 day−1, with a digestion time of 18 days to obtain 90 % of the methane production potential.

Performance of anaerobic baffled reactor (ABR) and multi-staged UASB in anaerobic digestion process for treating leachate from refuse transfer stations under loading shocks

ABSTRACT This study compared an anaerobic baffled reactor (ABR) with a multi-staged UASB (MS-UASB) to investigate the effects of loading shocks on the anaerobic digestion in both reactors. Both reactors were subjected to five hydraulic/organic loading shocks, each lasting 3 days. During the hydraulic shock with the highest organic loading rate (OLR) (OLR of 24 g COD L−1 d−1), MS-UASB and ABR exhibited minimum effluent COD removal efficiency of 90.9 and 73.0%, with average methane concentrations decreasing to 62.4 ± 0.9% and 59.8 ± 3.0%. Under the highest organic shock (OLR of 12 g COD L−1 d−1), the minimum effluent COD removal efficiency of MS-UASB and ABR was 81.5 and 73.4%, with average methane concentrations decreasing to 60.4 ± 1.1% and 58.6 ± 0.8%. After the hydraulic and organic shock phase, the biomass concentration in the MS-UASB reached 159 and 130% of the ABR, respectively. The reason for the improved operational stability of the MS-UASB is due to the presence of the solid/liquid/gas separator, which promotes the formation of granular sludge and reduces biomass washout. In addition, MS-UASB exhibited a higher abundance of the syntrophic bacterium Candidatus cloacamonas, which plays a crucial role in maintaining the stability of anaerobic digestion systems.

Anaerobic dynamic membrane bioreactor for the co-digestion of toilet blackwater and kitchen waste.

Anaerobic co-digestion using an anaerobic dynamic membrane bioreactor (AnDMBR) can separate the sludge retention time and hydraulic retention time, retaining the biomass for efficient degradation and the use of less expensive large pore-size membrane materials and more sustainable dynamic membranes (DMs). Therefore, anaerobic co-digestion of toilet blackwater (BW) and kitchen waste (KW) using an AnDMBR was hypothesized to increase the potential for co-digestion. Here, the efficiency and stability of AnDMBR in anaerobic co-digestion of toilet BW and KW were investigated. DM morphology and structural characteristics, filtration properties, and composition, as well as membrane contamination and membrane regeneration mechanisms, were investigated. Average daily biogas yields of the reactor in two membrane cycles before and after cleaning were 788.67 and 746.09 ml/g volatile solids, with average methane content of 66.64% and 67.27% and average COD removal efficiencies of 82.03% and 80.96%, respectively. The results showed that the bioreactor obtained good performance and stability. During the stabilization phase of the DM operation, the flux was maintained between 43.65 and 65.15L/m2/h. DM was mainly composed of organic and inorganic elements. Off-line cleaning facilitated DM regulation and regeneration, restoring new Anaerobic morphology and structure. PRACTITIONER POINTS: High efficiency co-digestion of BW and KW was realized in the DMBR system. Average daily biogas yields before and after membrane cleaning were 788.67 and 746.09 ml/g volatile solids. Off-line cleaning facilitated DM regulation and regeneration as well as system stability. The flux was maintained between 43.65 and 65.15L/m2/h during operation.

High-performance internal circulation anaerobic granular sludge reactor for cattle slaughterhouse wastewater treatment and simultaneous biogas production

This research investigates the efficacy of a high-performance pilot-scale Internal Circulation Anaerobic Reactor inoculated with Granular Sludge (ICAGSR) for treating cattle slaughterhouse wastewater while concurrently generating biogas. The primary objective is to assess the efficiency and performance of ICAGSR in terms of organic pollutant removal and biogas production using granular anaerobic sludge. The research methodology entails operating the ICAGSR system under ambient conditions and systematically varying key parameters, including different Hydraulic Retention Times (HRTs) (24, 12, and 8 h) and Organic Loading Rates (OLRs) (3.3, 6.14, and 12.83 kg COD/m³. d). The study focuses on evaluating pollutants’ removal and biogas production rates. Results reveal that the ICAGSR system achieves exceptional removal efficiency for organic pollutants, with Chemical Oxygen Demand (COD) removal exceeding 74%, 67%, and 68% at HRTs of 24, 12, and 8 h, respectively. Furthermore, the system demonstrates stable and sustainable biogas production, maintaining average methane contents of 80%, 76%, and 72% throughout the experimental period. The successful operation of the ICAGSR system underscores its potential as a viable technology for treating cattle slaughterhouse wastewater and generating renewable biogas. In conclusion, this study contributes to wastewater treatment and renewable energy production by providing a comprehensive analysis of the ICAGSR system’s hydrodynamic properties. The research enhances our understanding of the system’s performance optimization under varying conditions, emphasizing the benefits of utilizing ICAGSR reactors with granular sludge as an effective and sustainable approach. Identifying current gaps, future research directions aim to further refine and broaden the application of ICAGSR technology in wastewater treatment and renewable energy initiatives.

Anaerobic Digestion of Maize Husk in Co-Digestion with Goat and Cow Dung for Enhanced Biogas Production

In recent investigations, Anaerobic co-digestion has been superior to traditional anaerobic digestion (AD). The advantages of employing co-substrates for improved bioenergy generation and solids reduction have drawn researchers to investigate the co-digestion technology and understand the impact of multiple substrates on digester performance. This study aimed to generate biogas by co-digestion of maize husk with cow and goat dung as substrates, isolate the bacteria involved in the process, and assess the quantity and makeup of the biogas generated by the substrates. The substrates were fed to mini-digesters fabricated in the laboratory using 1L bottles for 49 days’ retention time. It assessed the production potential of the substrates for biogas yield in mono-digestion and co-digestion. The average biogas yield (cm3) and methane content (%) in the D1, D2, D3, D4, D5, and D6 were 9135 (58%), 8660 (71%), 9820 (69%), 6545 (65%), 5915 (48%) and 1965 (21%) respectively. The highest gas yield was observed in digesters with co-digestion of the substrates (D1 and D2) than the mono-digestion of the GD and CD by 35.2% and 24.4%, respectively, with an improvement in methane content. The process was carried out in a mesophilic condition and a pH range of 6.8-8.2. The study's findings showed that the most frequently isolated and identified bacteria were Klebsiella pneumoniae and Bacillus species, indicating that these species are essential to the microbial activities involved in biogas production. The investigation additionally showed that maize husk in co-digestion with cow dung and goat dung had great potential for generating and producing large quantities of biogas within 49 days’ retention time.

Unveiling the bioaugmentation mechanism of Clostridium thermopalmarium HK1 enhancing methane production in thermophilic anaerobic digestion of food waste

To enhance methane production and ensure system stability in the thermophilic anaerobic digestion (TAD) of food waste (FW), bioaugmentation is a straightforward and effective strategy. This study investigated the bioaugmentation effect of Clostridium thermopalmarium HK1 on the TAD of FW. The results showed that the cumulative methane production (CMP) and the average methane content after bioaugmentation increased by 23.67% and 22.69%, respectively. Moreover, the addition of C. thermopalmarium HK1 contributed to alleviating ammonia inhibition and promoting volatile fatty acids (VFAs) conversion, thus maintaining the system stability. The dominant hydrolytic bacteria and hydrogenotrophic methanogens were enriched in the early stage after bioaugmentation. The genus Clostridium was positively correlated with methane content. Metagenomic analysis further suggested that methane metabolism was strengthened, and the relative abundances of genes encoding the key functional enzymes associated with hydrogenotrophic and acetoclastic methanogenic pathways were enhanced. Therefore, bioaugmentation with C. thermopalmarium HK1 had great potential for improving the efficiency of the TAD of FW.

Is Biomethane Production from Common Reed Biomass Influenced by the Hydraulic Parameters of Treatment Wetlands?

Treatment wetlands (TWs) are Nature-Based Solutions which have been increasingly used worldwide for wastewater (WW) treatment as they are able to remove mineral and organic pollutants through both physical and biochemical processes. Besides the reusable effluent, the TWs produce, as their main output, plant biomass that needs to be harvested and disposed of at least once a year with significant management costs and causing the TW to be temporarily out of service. This study aims (i) to evaluate the potential of TWs’ biomass for local energy production and (ii) to understand the effects of TWs’ hydraulic conductivity (Ks) on the biomass biomethane yield. Specifically, this was addressed by determining the Biochemical Methane Potential of common reed (CR) (Phragmites australis) samples collected at three harvest times from the 10-year-old horizontal subsurface treatment wetland (HSTW) used as a secondary WW treatment system for the IKEA® store situated in Catania (Eastern Sicily, Italy). Furthermore, the falling-head test was conducted to assess the hydraulic conductivity (Ks) variation in the hydraulic conductivity (Ks) of the HSTW, in order to understand its influence on the CR biomethane production. The average methane content values were 130.57 Nm3CH4/tVS (±24.29), 212.70 Nm3CH4/tVS (±50.62) and 72.83 Nm3CH4/tVS (±23.19) in August, September, October 2022, respectively. Ks was correlated with both dry matter (R2 = 0.58) and fiber content (R2 = 0.74) and, consequently, affected the biomethane yield, which increased as the Ks increased (R2 = 0.30 in August; R2 = 0.57 in September). In the framework of a circular economy, the results showed the successful possibility of integrating bioenergy production into TWs. The research could contribute (i) to encouraging plant operators to reuse biomass from TWs for local energy production and (ii) to help plant operators to understand Ks effects on the biomass biomethane yield in order to increase the sustainability of the system and to reduce the maintenance costs.

Highly sensitive mid-infrared methane remote sensor using a deep neural network filter.

A novel mid-infrared methane remote sensor integrated on a movable platform based on a 3.291-µm interband cascade laser (ICL) and wavelength modulation spectroscopy (WMS) is proposed. A transmitting-receiving coaxial, visualized optical layout is employed to minimize laser energy loss. Using a hollow retro-reflector remotely deployed as a cooperative target, the atmospheric average methane concentration over a 100-meter optical range is measured with high sensitivity. A deep neural network (DNN) filter is used for second harmonic (2f) signal denoising to compensate for the performance shortcomings of conventional filtering. Allan deviation analysis indicated that after applying the DNN filter, the limit of detection (LOD) of methane was 86.62 ppb with an average time of 1 s, decreasing to 12.03 ppb with an average time of 229 s, which is a significant promotion compared to similar work reported. The high sensitivity and stability of the proposed sensor are shown through a 24-hour continuous monitoring experiment of atmospheric methane conducted outdoors, providing a new solution for high-sensitivity remote sensing of atmospheric methane.

Estimating air methane and total hydrocarbon concentrations in Alberta, Canada using machine learning

Fugitive emission sources are significant contributors to methane emissions, and time series data on reported emissions from such sources remain underutilized. The Alberta Energy Regulator (AER) has been collecting air quality data since 1986, including methane and total hydrocarbons concentration data. However, this data has not been thoroughly analyzed to forecast air quality trends. Our analysis of the data shows that average methane concentrations measured at most Alberta airshed stations exceed the global average, and the data exhibits increasing and decreasing trends depending on the station. We compared the predictive performance of three machine learning methods: Long Short-Term Memory (LSTM) recurrent neural network, Fully-Connected Neural Network (FC-NN), and Autoregressive Integrated Moving Average (ARIMA), using the AER methane concentration data. Our results indicate that the LSTM neural network model outperforms the other two methods. Also, our findings suggest that the AER methane concentration data can be effectively analyzed and utilized to forecast air quality trends in the region.

Anaerobic Digestion of Olive Mill Wastewater and Process Derivatives—Biomethane Potential, Operation of a Continuous Fixed Bed Digester, and Germination Index

Olive mill wastewater (OMW) management is an economic and environmental challenge for olive oil-producing countries. The recovery of components with high added value, such as antioxidants, is a highly researched approach that could help refinance performant wastewater treatment systems. Anaerobic (co-)digestion is a suitable process to valorize the energetic and nutritional content of OMW and OMW-derived waste streams from resource recovery processes. Issues of process stability, operation, and yields discourage industrial application. Deepening the understanding of biomethane potential, continuous anaerobic digester operational parameters, and co-substrates is key to large-scale implementation. The biomethane potential of different OMW-derived samples and organic solid market waste as co-substrate was 106–350 NL methane per kg volatile solids (VS). The highest yields were obtained with the co-substrate and depolyphenolized OMW mixed with retentate from an ultrafiltration pretreatment. Over 150 days, an anaerobic fixed-bed 300 L digester was operated with different OMW-derived substrates, including OMW with selectively reduced polyphenol concentrations. Different combinations of organic loading rate and hydraulic retention time were set. The biogas yields ranged from 0.97 to 0.99 L of biogas per g of volatile solids (VS) eliminated, with an average methane content in the produced biogas of 64%. Potential inhibition of the process due to high polyphenol concentrations or over-acidification through volatile fatty acids was avoided in the continuous process through process and substrate manipulation. High concentrations of potassium and low concentrations of nitrogen and phosphate end up in the digestate. Sulfate reduction results in high H2S concentrations in the biogas. The digestate was tested for phytotoxic properties via the germination index. Diluted digestate samples improved germination by up to 50%.

Post-breeding waste from Zophobas morio for biogas and energy generation via anaerobic methane fermentation

Zophobas morio is one of the most widely bred insect species in commercial farms around the world, however Z. morio post-breeding waste has never been tested for its biogas and biomethane potential. The unseparated waste (M) was sieved to separate it into fractions of feces (F) and remaining wheat bran (W) in order to investigate whether isolated feces can have higher biomethane potential. Mesophilic (37 °C ± 1 °C) anaerobic digestion was performed in glass bioreactors (2 l total volume) for 24 days. The substrate loading was 8 g of the air-dried sample and the inoculum-to-substrate total mass was 125:1. The physicochemical parameters of the wastes and sludges after fermentation were investigated. The biogas potential of the feces was only approximately 3% higher than other tested materials and reached 650 ml of biogas · g−1VS. The average methane concentration was 52% (vol.). The calculation of theoretical electric and heat energy recovery in a co-generation system reached (per 1 Mg of waste VS) 1.3–1.4 MWh and 1.4–1.5 MWh, respectively. Post-breeding waste from Z. morio can be successfully used for energy recovery in the form of biogas.

Carbon Felt Composite Electrode Plates Promote Methanogenesis through Microbial Electrolytic Cells

Bioelectrochemical systems are widely used in waste utilization processes. Among them, anaerobic digestion (AD) and microbial electrolytic cell coupling (MEC) are cost-effective and efficient waste-to-energy technologies. In this study, the proposal was made that a carbon felt composite electrode plate be applied to an AD-MEC reactor. The control experiment was conducted using an AD reactor (without the external power supply). The result shows that the carbon felt composite electrode plate increased the biogas production of the AD-MEC reactor by 15.4%, and the average methane content increased by 9.49% compared to the control AD reactor. The total methane production of the AD-MEC reactor and control reactor was 302.51 and 407.79 mL, respectively. The total methane production of the AD-MEC reactor was 34.8% higher than the control group. In addition, the authors found that Methanosarcina and Methanosaeta activities in the AD-MEC reactor were significantly increased. The carbon felt composite electrode plate applied in AD-MEC may have promoted the methanogenic microorganisms’ interspecific acetic acid transport process and increased biogas production and methane content.

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.

Production of biogas from the industrial hemp variety, Tiborszállási

The suitability of industrial hemp as an alternative substrate for biogas production was evaluated. The influence of the growing stage and fertilization regimen on biogas and methane production was determined. The effectiveness of a common NPK fertilization strategy was compared with the application of biogas plant (BGP) byproducts (liquid and solid phase of the digestate). Hemp biomass was harvested four times during the growth cycle (five leaf pairs, flower formation, beginning of flowering, seed maturity). The samples of hemp biomass from the tested combinations (vegetation period × fertilization strategy) were subjected to anaerobic digestion in laboratory batch reactors for 60 days, and the amount and composition of the released biogas were determined. The yield of biomass and dry matter content increased with the age of plants reaching up to 12.0 t/ha and 32%, respectively. The highest methane production was observed for hemp in the first sampling (309-316 L CH4/kg of organic dry matter, ODM); the lowest production came from hemp at full maturity (289-302 L CH4/kg ODM). Due to a significant growth of hemp biomass during the vegetation period, methane hectare yield (MHY) grew from 142-175 m3/ha for the first growing stage to 2780-3230 m3/ha for the final stage. The average methane content reached approximately 60%. There was no observed significant difference in biogas production between the different modes of fertilization; thus, BGP byproducts were an effective alternative source of nutrients for hemp planting.

Application of a Full-Scale Horizontal Anaerobic Digester for the Co-Digestion of Pig Manure, Food Waste, Excretion, and Thickened Sewage Sludge

Many laboratory- and pilot-scale studies on anaerobic co-digestion have been conducted in Republic of Korea; however, studies on full-scale demonstration facilities are lacking. This study aimed to present a successful case of a large-scale anaerobic co-digestion facility in Republic of Korea for biogas generation from four organic wastes (pig manure, food waste, excretion, and thickened sewage sludge) using a horizontal anaerobic digester. A preliminary biochemical methane potential test was performed for the individual and mixed organic waste to design a treatment facility for 320 m3/day of organic waste generated in Seosan City. Subsequently, a horizontal anaerobic digester with a 35 day-retention time (based on 320 m3/day input) was constructed. Each organic waste was placed in an anaerobic reactor after pretreatment. The input was gradually increased after the first seeding, and the operation continued for 158 days. Total and volatile solids made up 4.1% and 3.3%, respectively. Throughout the operating period, the digester temperature was maintained at 35–40 °C for mesophilic digestion, and the pH was maintained at 7–8. The average organic matter removal efficiency (volatile solids basis) was 64% and the methane gas production rates were 0.35, 0.6, 0.26, 0.28, and 0.39 Nm3CH4/kg vs. for pig manure, food waste, excretion, thickened sewage sludge, and mixed waste, respectively, resulting in an average methane content of the biogas 68.8%.

Data driven analysis of atmospheric methane concentrations as function of geographic, land cover type and season

Over the last decade we have witnessed a rapid, so far unexplained, increase in the emission of methane to the atmosphere and this increase could lead to an acceleration of the ongoing climate changes. The increase is likely to originate from agriculture, but oil and gas production as well as wetlands are also under suspicion. The best way to quantify the emission of methane and other greenhouse gasses to our atmosphere is by using space based remote sensing. Here, we analyse 3 years of measurements of the column-averaged dry-air mole fraction of methane from the Tropospheric Monitoring Instrument on Sentinel-5P obtained with two different retrieval methods in order to evaluate the dependency on geographic, land cover type and season. The land cover types were obtained from the Moderate Resolution Imaging Spectroradiometer aboard the Terra and Aqua satellites and from the World Cover data product using observations from the Copernicus Sentinel-1 and Sentinel-2 missions. The analysis reveals that while the highest methane concentrations are generally found over croplands, the lowest are generally found over shrublands, which is in agreement with expectations. It is more surprising that the analysis also reveals lower than average methane concentrations over wetlands as wetlands are generally thought to be a major source of methane emission. Until this discrepancy is resolved the methane concentration over wetlands from the Tropospheric Monitoring Instrument on Sentinel-5P should be handled with caution. It is also found that the annual methane cycle, as seen in the measured methane concentrations, for croplands, shrublands and savannas is delayed in Africa compared to Asia.