Highest Biogas Production Research Articles

High-rate thermophilic bio-methanation of the fine sieved fraction from Dutch municipal raw sewage: Cost-effective potentials for on-site energy recovery

Sieving of Dutch raw sewage over a 350μm screen, produces a cake layer called fine sieved fraction (FSF), an energy-rich material that contains mainly cellulosic fibers originating from toilet paper. The FSF biomethane potential (BMP) was studied under both mesophilic (35°C) and thermophilic (55°C) conditions, whereas the stability of the fed-batch digesters at both 35°C and 55°C was researched by varying the inoculum to substrate ratios (RI/S: 0.5–15). Results clearly showed advantages of thermophilic conditions over mesophilic conditions at all tested RI/S. Stable digestion was even possible at an RI/S of 0.5 at 55°C.Following the results of the batch tests, a compact high loaded thermophilic digester for on-site energy recovery from FSF was proposed. Based on the results of the study, high biogas production rates at high organic loading rates (OLRs) were predicted. In the energy balance calculations, surplus heat production from combined heat and power (CHP) was utilized to dry the digestate sludge before transportation to an incineration plant or for use in pyrolysis or gasification processes. Overall results showed the potential of generating 46% of the required energy for wastewater treatment via high rate FSF digestion and subsequent conversion of the bio-methane into electricity and heat. The net recoverable energy from fine sieving, anaerobic digestion of FSF, dewatering of digestate sludge and drying of dewatered digestate sludge amounted 287MJ/ton FSF and 237kWh electric/ton FSF at 23% TS.

A Comparative Study on Biogas Production between Day and Night at Sime Darby’s Palm Oil Mill

A B S T R A C T Freely emitted biogas at palm oil mills has been regarded as untapped energy source nowadays, despite being recognised as major contributor to the global warming. Up till now, most of palm oil mills are still operating with the conventional anaerobic digestion systems which may not spur biogas industry to life. This study shall explore biogas production between day and night under existing mill operating conditions at KKS Bukit Benut Effluent Treatment Plant (ETP). Biogas produced during day time was 62% as compared to 38% during night time with the total methane emission of 490.3 kg/day. The methane concentration recorded at the digester tank ranged from 58.7 to 68.5%. The correlations between various factors that may influence biogas production were investigated. The finding shows that substrate feeding is the most influencial factor leading to high biogas production during day time.

Improving Biogas Production Performance From Pomegranate Waste, Poultry Manure and Cow Dung Sludge Using Thermophilic Anaerobic Digestion: Effect of Total Solids Adjustment

Context: Biogas is one of the most important sources of renewable energy and is considered as an environmental friendly energy source. One of the most important parameter influencing the production of biogas is total solids (TS). Aims: In this study, the effects of different total amount of solids, which consisted of 5, 10, 15, 20, 25, and 30% treatments, on the biogas production were examined. The solids were obtained at a thermophilic temperature (55°C) from a mixture of pomegranate rind, cow manure, and sludge in 15 days using one-liter glass bottles. Materials and Methods: The influences of TS, volatile solids (VS), pH, and carbon-to-nitrogen ratio on the biogas production volume from optimized TS treatment were also evaluated. In addition, pomegranate peel was pretreated for lignocellulosic destruction. Results: The results showed that the biogas production increased from 0.273 to 0.736 L/day with an increase in TS from 5 to 25%. The 25% treatment had the highest mean biogas production (i.e., 0.736 L/day). Significant difference was observed between the 25% treatment and all other treatments except the 20% treatment. The regression model showed that the VS was the only parameter that had a significant effect on biogas production. This parameter justified about 74.1% of the biogas production accuracy. Conclusion: Anaerobic digestion is an appropriate technology to achieve the organic fraction of solid wastes. Due to higher biogas production, dry anaerobic digestion is of more importance than wet and semi-dry anaerobic digestion.

Enhanced nitrogen distribution and biomethanation of kitchen waste by thermal pre-treatment

The effects of thermal pretreatment (90, 120, 140 and 160 °C) on the morphology (organic and inorganic nitrogen) and distribution properties (in solid phase, liquid phase and gas phase) of nitrogen in kitchen waste (KW) and on anaerobic digestion performance were investigated. The results show that thermal pretreatment could efficiently enhance the solubilisation of organic nitrogen compounds in KW, especially at high temperatures and long heating durations. Approximately 3.0–47.9% of organic nitrogen in KW decreases in total nitrogen content was obtained in the solid phase after thermal pretreatment. Higher biogas production and biodegradability of organics (in terms of the removal rate of soluble chemical oxygen demand, total organic nitrogen, and volatile solids) during subsequent anaerobic digestion were observed compared with the levels for untreated KW. An overall economic analysis indicates that the most profitable pretreatment process was achieved at 90 and 120 °C for treatment time of 30 and 15 min respectively, with a net potential profit (2–8 € ton−1 kW).

Optimization of biogas production from coffee production waste

This study was conducted to investigate the effects of chemical pretreatments on biogas production from coffee waste. After the preparation of a mixture of coffee waste with a TS concentration of 10%w/w, basic and acid pretreatments were conducted in batch mode and their performances were compared with the biogas produced from a mixture without any pretreatment stage. The basic pretreatment demonstrated a very good action on the hydrolysis of the lignin and cellulose, and permitted a biogas production of about 18NL/L with a methane content of almost 80%v/v. Thus, the basic pretreatment has been used to scale-up the process. The coffee refuse was has been carried out in a 45L anaerobic reactor working in continuous mode and in a mesophilic condition (35°C) with a Hydraulic Retention Time (HRT) of about 40days. A high biogas production of 1.14NL/Ld, with a methane percentage of 65%v/v was obtained, thus permitting a process yield of about 83% to be obtained.

Optimal WWTP process selection for treatment of domestic wastewater – A realistic full-scale retrofitting study

Retrofitting existing wastewater treatment plants has become a major challenge in the wastewater engineering area, in particular due to the increasing number of competing technologies and concepts (treatment versus resource problem). In order to support the expert-based approach and provide a rational design for WWTPs, we proposed the use of a mathematical programming based framework to manage the complexity and solve the multi-criteria retrofitting problem. The treatment alternatives were represented in a superstructure – coupled with a database containing information on performance and economics of treatment units. The optimization problem was solved for different objective functions and constraints corresponding to different retrofitting scenarios. The framework was evaluated on two full-scale domestic wastewater treatment plants (265,000 PE and 750,000 PE respectively). To this end, the design space included 9 side-stream treatment technologies and 9 main line technologies resulting in more than 200 retrofitting alternatives. The retrofitting problem resulted in the selection of a high-rate oxic reactor coupled with anammox technology in the main line as the optimal solution, due to the low utility consumption and high biogas production associated with this network. On the other hand, most of the side stream treatment alternatives have similar technical–economic benefits in terms of the whole plant retrofitting cost function. Therefore the selection of the optimal alternative is more based on local conditions and preferences in that case.

Electrical resisitivity to detect zones of biogas accumulation in a landfill

Biogas produced in sanitary landfills consists in a potential source, formed by degradation of organic matter, this gas is constituted by CH 4 , CO 2 and water vapor. Sanitary landfills represent important depository of organic matter with great energetic potential in Brazil, although presently with inexpressive use. Estimates for production or maintenance of productive rates of CH 4 represent one of the main difficulties of technical order to the planning and continuity of collection systems for rational consumption of this resource. Electrical resistivity measurements are routinuously used in profiling oil wells for the determination of levels with accumulations of oil and gas, facing the contrast among fluids and rocks. This paper aims to evaluate eventual relationship among biogas flow quantified in surface drains of a waste cell in landfill, with characteristic patterns of in depth electrical resistivity. The integration of Electrical Resistivity Tomography (ERT) lines allowed for the generation of 3D blocks and a clear distinction among zones of high biogas production, quantified in surface drains, with areas of high resistivity in depth. The results suggest the possibility of use of the method in studies to place drains in areas promising to the collection of biogas for energetic generation in sanitary landfill.

Electrical resisitivity to detect zones of biogas accumulation in a landfill

Biogas produced in sanitary landfills consists in a potential source, formed by degradation of organic matter, this gas is constituted by CH4, CO2 and water vapor. Sanitary landfills represent important depository of organic matter with great energetic potential in Brazil, although presently with inexpressive use. Estimates for production or maintenance of productive rates of CH4 represent one of the main difficulties of technical order to the planning and continuity of collection systems for rational consumption of this resource. Electrical resistivity measurements are routinuously used in profiling oil wells for the determination of levels with accumulations of oil and gas, facing the contrast among fluids and rocks. This paper aims to evaluate eventual relationship among biogas flow quantified in surface drains of a waste cell in landfill, with characteristic patterns of in depth electrical resistivity. The integration of Electrical Resistivity Tomography (ERT) lines allowed for the generation of 3D blocks and a clear distinction among zones of high biogas production, quantified in surface drains, with areas of high resistivity in depth. The results suggest the possibility of use of the method in studies to place drains in areas promising to the collection of biogas for energetic generation in sanitary landfill.

EFFECT OF PITCH ON HEAT TRANSFER CHARACTERISTICS OF HELICAL COILS TO BE USED FOR BIOGAS PRODUCTION

Maintaining temperature and eliminating loss from anaerobic reactor highly improve the production of biogas .To achieve the required temperature inside the reactor supplying hot fluid externally using helical coil heat exchanger is required. Helical coil heat exchangers are widely used in industrial applications because they are more efficient as compared to straight tube type heat exchangers. This paper deals with the effect of pitch variation on the heat transfer characteristics (convective heat transfer coefficient, Nusselt number dean number heat removal rate etc.) of helical coil heat exchangers that can be used for supplying hot fluid to maintain the temperature of the reactor to achieve high biogas production. ANSYS 14.5 was used for the numerical investigation and the present study is done for three different coils of two turns having the same cross section and coil diameter but each coil having a different pitch. Modeling of the study was carried out based on the principles of thermodynamics, fluid mechanics, heat transfer and implementing the necessary boundary conditions. The results indicate that the heat transfer enhances with increasing pitch of the helical coil but with an increased pressure drop.

Eubacteria and archaea communities in seven mesophile anaerobic digester plants in Germany

BackgroundOnly a fraction of the microbial species used for anaerobic digestion in biogas production plants are methanogenic archaea. We have analyzed the taxonomic profiles of eubacteria and archaea, a set of chemical key parameters, and biogas production in samples from nine production plants in seven facilities in Thuringia, Germany, including co-digesters, leach-bed, and sewage sludge treatment plants. Reactors were sampled twice, at a 1-week interval, and three biological replicates were taken in each case.ResultsA complex taxonomic composition was found for both eubacteria and archaea, both of which strongly correlated with digester type. Plant-degrading Firmicutes as well as Bacteroidetes dominated eubacteria profiles in high biogas-producing co-digesters; whereas Bacteroidetes and Spirochaetes were the major phyla in leach-bed and sewage sludge digesters. Methanoculleus was the dominant archaea genus in co-digesters, whereas Methanosarcina and Methanosaeta were the most abundant methanogens in leachate from leach-bed and sewage sludge digesters, respectively.ConclusionsThis is one of the most comprehensive characterizations of the microbial communities of biogas-producing facilities. Bacterial profiles exhibited very low variation within replicates, including those of semi-solid samples; and, in general, low variation in time. However, facility type correlated closely with the bacterial profile: each of the three reactor types exhibited a characteristic eubacteria and archaea profile. Digesters operated with solid feedstock, and high biogas production correlated with abundance of plant degraders (Firmicutes) and biofilm-forming methanogens (Methanoculleus spp.). By contrast, low biogas-producing sewage sludge treatment digesters correlated with high titers of volatile fatty acid-adapted Methanosaeta spp.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0271-6) contains supplementary material, which is available to authorized users.

Energy feasibility study of sludge pretreatments: A review

Abstract Most of the pretreatments to sewage sludge in lab-scale studies show high potentials to be implemented in an anaerobic digester since they produce an increase in the biogas production. However, no energy assessments are usually considered in scientific reports. By making a simple evaluation of energy consumption by pretreatments, it can be stated that unfortunately not all the pretreatment technologies have an energy self-sufficiency to be implemented in a WWTP, requiring many times a continuous energy investment. Generally, pretreatments consuming electricity do not satisfy its energy demands from the biogas production in the same process, although high solubilization or biogas production increases are reached. Just ultrasounds applied in full-scale plants, with commercial technologies such as Sonix or Biosonator, provide an energetically self-sufficient pretreatment. In the case of thermal pretreatments, the potential to be implemented with full energy integration is much higher, since they can recover heat from the biogas engine as well as electrical energy in the same extent as for electric pretreatments. This way, full energy integration can be achieved in thermal hydrolysis plants; such is the case of commercial technologies such as Cambi, Exelys (Veolia) or CTH (Aqualogy). Several theoretical approaches and simulations also state that thermal hydrolysis presents a high potential to be fully integrated in WWTP with a complete energy recovery and self-sufficiency.

Identifying proper agitation interval to prevent floating layers formation of corn stover and improve biogas production in anaerobic digestion

Floating tests were conducted in anaerobic digestion with different OLR of corn stover to investigate formation of floating layers and to find proper agitation interval for preventing floating layer formation. Floating layers were formed in the early stage of no-agitation period. The daily biogas production was decreased by 81.87–87.90% in digesters with no agitation and feeding compared with digesters having agitation. Reduction of biogas production was mainly attributed to poor contact of substrate-microorganisms. Agitation intervals of 10h, 6h, and 2h were found to be proper for eliminating floating layer at OLR of 1.44, 1.78 and 2.11g(TS)L−1d−1, respectively. The proper agitation interval was further validated by anaerobic experiments. It showed that proper agitation interval could not only prevent floating layer formation and achieve high biogas production but also increase energy efficiency of anaerobic digestion. The finding is useful for operating anaerobic digester with corn stover in a cost-effective way.

Modelling the Kinetics of Biogas Production from Mesophilic Anaerobic Co-Digestion of Cow Dung with Plantain Peels

This work investigated the effect of plantain peels as co-substrate in the anaerobic digestion of cow dung for efficient and high biogas production. The biogas experiments were carried out in two different 5 L anaerobic digesters and incubated for 40 days at ambient mesophilic temperatures (28 oC to 34 °C). The results showed that co-digestion of cow dung with plantain peels as co-substrate reduced start-up time for biogas generation and increased biogas yield by 18% as compared to cow dung alone. Peak biogas production was obtained for both digesters at pH of 6.7 and 6.9 as well as temperature of 29 and 30oC, respectively. Modelling study revealed that exponential plot simulated better in both ascending and descending limb than the linear plot the biogas production rates in biogas production from cow dung co-digested with plantain peels and cow dung alone, respectively. Logistic growth model and modified Gompertz plot showed better correlation of cumulative biogas production than exponential rise to maximum plot. These results show that biogas production can be enhanced efficiently through co-digestion process.

Effects of Thermo-chemical Pre-treatment on Bamboo for Biogas Production

The objective of this work was to develop various pre-treatment process, i.e. Ca(OH)2, NaOH, ammonium carbonate, H2SO4, maleic acid and combination of hydrothermal with H2SO4 in a batch anaerobic digestor of bamboo. Biogas efficiency of bamboo with and without pre-treatment was evaluated. The highest biogas production and methane yield were 820 ml/day and 72%, respectively, for hydrothermal + H2SO4 pre-treated bamboo followed by H2SO4, Ca(OH)2, maleic acid and ammonium carbonate. The results indicated that hydrothermal + H2SO4 pre-treatment could be an effective method for improving methane yield with bamboo.

Modelling the Potential Biogas Productivity Range from a MSW Landfill for Its Sustainable Exploitation

A model of biogas generation was modified and applied to the case of a sanitary landfill in Italy. The modifications considered the role of the temperature field normally established within each layer of waste. It must be pointed out the temperature affects the anaerobic biodegradation kinetics. In order to assess the effect of moisture on the waste biodegradation rate, on the bacteria process and then on the methane production, the model was compared with the LandGEM one. Information on the initial water content came from data concerning waste composition. No additional information about the hydrological balance was available. Thus, nine sets of kinetic constants, derived by literature, were adopted for the simulations. Results showed a significant variability of the maximal hourly biogas flows on a yearly basis, with consequences for the collectable amount during the operating period of a hypothetical engine. The approach is a useful tool to assess the lowest and highest biogas productivity in order to analyze the viability of biogas exploitation for energy purposes. This is useful also in countries that must plan for biogas exploitation from old and new landfills, as a consequence of developments in the waste sector.

Improvement of biogas production from orange peel waste by leaching of limonene.

Limonene is present in orange peel wastes and is known as an antimicrobial agent, which impedes biogas production when digesting the peels. In this work, pretreatment of the peels to remove limonene under mild condition was proposed by leaching of limonene using hexane as solvent. The pretreatments were carried out with homogenized or chopped orange peel at 20–40°C with orange peel waste and hexane ratio (w/v) ranging from 1 : 2 to 1 : 12 for 10 to 300 min. The pretreated peels were then digested in batch reactors for 33 days. The highest biogas production was achieved by treating chopped orange peel waste and hexane ratio of 12 : 1 at 20°C for 10 min corresponding to more than threefold increase of biogas production from 0.061 to 0.217 m3 methane/kg VS. The solvent recovery was 90% using vacuum filtration and needs further separation using evaporation. The hexane residue in the peel had a negative impact on biogas production as shown by 28.6% reduction of methane and lower methane production of pretreated orange peel waste in semicontinuous digestion system compared to that of untreated peel.

OPTIMIZATION OF THERMOPHILIC ANAEROBIC DIGESTION OF WINERY BIO-WASTE BY MICRO-NUTRIENTS AUGMENTATION

Thermophilic anaerobic digestion is a suitable technology to treat agricultural waste because of its higher biogas production, hygienisation effect and solids removal efficiency. Although these benefits, poor effluent quality and instability are encountered in some cases. The anaerobic co-digestion of winery waste and waste activated sludge at 55°C, operating at 23 days HRT and with an organic loading rate of 3.2 kg COD/m 3 d, was characterized by accumulation of volatile fatty acids, pH fall and reduction of biogas production, while mesophilic process was steady at long term. The study evaluated the effect of trace elements (iron, cobalt and nickel) augmentation in the thermophilic reactor at different concentration of micro-nutrients. The addition improved the process stability: pH became constant and average volatile fatty acids concentration was below 1,000 mg COD/L. The biogas production increased from 0.38 to 0.45 m 3 /kg COD, corresponding to 90% of COD removal, while mesophilic reactor removed the 78% of total COD. Digestate had interesting characteristics as fertilizer in fact the higher solids removal (28%) allowed to concentrate the phosphorus in the particulate fraction and nitrogen was transformed into more available form for plants growth.

Performance of up flow anaerobic sludge fixed film bioreactor for the treatment of high organic load and biogas production of cheese whey wastewater

Among various wastewater treatment technologies, biological wastewater treatment appears to be the most promising method. A pilot scale of hybrid anaerobic bioreactor was fabricated and used for the whey wastewater treatment. The top and bottom of the hybrid bioreactor known as up flow anaerobic sludge fixed film (UASFF); was a combination of up flow anaerobic sludge blanket (UASB) and up flow anaerobic fixed film reactor (UAFF), respectively. The effects of operating parameters such as temperature and hydraulic retention time (HRT) on chemical oxygen demand (COD) removal and biogas production in the hybrid bioreactor were investigated. Treatability of the samples at various HRTs of 12, 24, 36 and 48 hours was evaluated in the fabricated bioreactor. The desired conditions for COD removal such as HRT of 48 hours and operation temperature of 40 ?C were obtained. The maximum COD removal and biogas production were 80% and 2.40 (L/d), respectively. Kinetic models of Riccati, Monod and Verhalst were also evaluated for the living microorganisms in the treatment process. Among the above models, Riccati model was the best growth model fitted with the experimental data with R2 of about 0.99.

Investigation of the Performance and Kinetics of Anaerobic Digestion at 45°C

The objective of this study was to evaluate the performance of anaerobic digestion (AD) within the intermediate zone, specifically at 45°C. Single-stage batch anaerobic digestion system was developed in the lab and performance was monitored for more than 2 years. The AD system was able to achieve high biogas production with about 62% - 67% methane content. The digester exhibited high acetate accumulation, but sufficient buffering capacity was observed as the pH, alkalinity and volatile fatty acids-to-alkalinity ratio were within recommended values. The system achieved 36.5% reduction of total solids (TS) and 47.8% reduction of volatile solids (VS), which exceeded the required VS destruction efficiency for Class A biosolids. The pathogen counts were less than 1000 MPN/g total solids in the effluent, which also satisfied Class A biosolids requirements. The accumulation of acetate was presumably due to the high temperature which contributed to high hydrolysis rate. Consequently, it produced large amount of toxic salts that combined with the acetate, making them not readily available to be consumed by methanogens. The slower degradation of acetate was observed by the kinetic parameters. Accumulation of acetate contributed to 52% to 71% reduction in acetate degradation process, but was not completely inhibitory. The methanogens existing in the system were mostly thermo-tolerant acetate-utilizing methanogens, and specifically from Methanosarcinaceae species.

Effect of enzymatic pretreatment on anaerobic co-digestion of sugar beet pulp silage and vinasse

Results of sugar beet pulp silage (SBPS) and vinasse (mixed in weight ratios of 3:1, 1:1 and 1:3, respectively) co-fermentation, obtained in this study, provide evidence that addition of too high amount of vinasse into the SBPS decreases biogas yields. The highest biogas productivity (598.1mL/g VS) was achieved at the SBPS–vinasse ratio of 3:1 (w/w). Biogas yields from separately fermented SBPS and vinasse were by 13% and 28.6% lower, respectively. It was found that enzymatic pretreatment of SBPS before methane fermentation that caused partial degradation of component polysaccharides, considerably increased biogas production. The highest biogas yield (765.5mL/g VS) was obtained from enzymatic digests of SBPS–vinasse (3:1) blend (27.9% more than from fermentation of the counterpart blend, which was not treated with enzymes). The simulation of potential biogas production from all the aforementioned mixtures using the Gompertz equation showed fair fit to the experimental results.