Cumulative Biogas Research Articles

Optimization of biogas production through selection of appropriate Inoculum-to-Substrate ((I/S) ratio

The impact of Inoculum-to-Substrate (I/S) ratio on the optimization of biogas yield from the co-digestion of FW and MH was investigated in five anaerobic reactors B-1 to B-5 at 37±1oC. Cumulative biogas yield of digester B-3(28.92 L/gVS) with the I/S ratio 1 was higher than that of the other digesters. Simulation study through adoption of Gompertz model (modified) showed a large reduction in latency (λ) by 59.7% with increase in I/S ratio from 0.25 to 1, which indicates that the time taken for methanogenesis to begin was reduced by over 59%. Increase in I/S ratio had positive effects on maximum specific biogas production (Rm) and maximum biogas production potential (A) with reactor B-3 having the largest (Rm) and (A) values of 1.26 L/gVS/day and 29.58 L/gVS respectively. Lower I/S ratios of 0.25 and 0.5 were found to rather decrease biogas production. Biogas yield at I/S ratios 2 and 4 was lower than the yield at ratio 1.Keywords: Optimization, Inoculum-to-Substrate, Biogas, Gompertz modelling, Digester

A comparative study of biogasification of wheat straw, sugarcane bagasse and pressmud

A study to compare biogas production potentials of wheat straw, sugarcane bagasse and pressmud was conducted at pH 8.0, temperature 40 °C and substrate concentration 20 g/L. Raw substrates were thermogravimetrically and Fourier-transform infrared spectroscopically characterised. TGA showed the weight loss of samples attributable to moisture, hemicellulose, cellulose and lignin losses. FTIR analysis indicated functional groups characteristics of hemicellulose, cellulose and lignin. Biogas production was the maximum between 10th and 25th day for all the tests. WS with 10% inoculum showed the highest cumulative biogas production of 370 mL/g followed by the SB (316 mL/g) and PM (211 mL/g) counterparts. The corresponding values with 5% inoculum were 303 mL/g (WS), 244 mL/g (SB) and 152 mL/g (PM). The inoculum volume also positively affected the cumulative biogas production (22.1, 29.5 and 38.8% respectively). The higher volatile fatty acids as observed in case of WS which further facilitated higher biogas production could be due to its maximum volatile solids content (88.9%) and water swelling capacity (7.37). A consistently increasing trend in the methane content (varying between 54 and 61%) in all the tests was observed till the 20th day. The biogas (7.7–21.7 mL/g) and the methane (35–42%) contents showed a decreasing trend thereafter, the lowest being observed during the 35–40-day period.

Impact of hydrothermal pre-treatment on the anaerobic digestion of different solid-liquid ratio sludges and kinetic analysis.

This study is an assessment of hydrothermal pre-treatment (HTP) of different solid–liquid ratio (SLR) sewage sludge for enhancement of biogas production by anaerobic digestion. Anaerobic digestion efficacy was investigated by biochemical methane potential (BMP) tests and kinetic analyses. The results indicated that the solid–liquid ratio (SLR) of sludge could influence the COD solubilization and the concentration of volatile fatty acids (VFAs) after HTP. BMP tests revealed that HTP could improve the final methane yield. For the different solid–liquid ratios (5%, 8%, 10%, 12% and 15%) of sludge after HTP, the methane contents were found to be 64%, 66%, 62%, 61% and 60%, respectively. The optimum solid–liquid ratio was found to be 8%, and its cumulative biogas yield was 425.57 N ml g−1 VS. The modified Gompertz model and Logistic model were used for kinetic study of biogas production. Kinetic study results showed that the experimental data could be fitted with the two models and the modified Gompertz model was better fitted with the experimental data than the Logistic model. These findings proved that choosing an appropriate solid–liquid ratio for HTP could effectively improve the anaerobic digestion process of sewage sludge.

Production and Evaluation of Biogas from Mixed Fruits and Vegetable Wastes Collected from Arba Minch Market

The world is in need of a green, efficient, carbon- neutral energy source to replace fossil fuels. The search for energy alternatives involving locally available and renewable resource is one of the main concerns of governments, scientists, and business people worldwide. Biogas, formed by anaerobic digestion of organic materials makes sustainable, reliable and renewable energy possible. This study involves the construction of a lab scale biogas production plant digester. The production of biogas was carried out by employing the mixed substrates of 13 different fruit and vegetable wastes collected from Arbaminch vegetable market. The materials used as feed were Apple, Mango, Cabbage, Avocado, onion, potato, Tomato, Banana, Lemon, Orange, Carrot, Papaya and cow manure. The total solid, volatile solids, moisture content and ash content of the wastes were examined. The anaerobic digestion of fruit and vegetable wastes mixed with different waste took 35-40 days to produce biogas (for complete digestion). Anaerobic digestion is very sensitive to change in pH and it is important to maintain pH of 6.7-7.4 for healthy system. The process resulted in the production of nutrient rich slurry high C/N ratio. The presented data on the moisture content, total solid, volatile solid and ash content of the wastes shows that tomato had maximum moisture content of 95.02% and lemon had the least with a moisture content of 73.4%. The maximum TS were recorded in Avocado (24.47%). The VS in all wastes used for the study varied from 20% (carrot) to 46.5% (Mango) wastes. The characteristics of these wastes were found to be: TS 14.13% of wet weight, VS 26.71%, TS/VS initial 0.461 and TS/VS final 0.394 which lead to TS/VS lost 0.394. The carbon and nitrogen composition of these mixed wastes was 53.85% and 2.205% respectively. The cumulative biogas production was 105.5 mL/1000g of food waste. This was the most effective as it showed maximum percentage removal of organic matter due to efficient working of the digester. Therefore, the application of biogas technology has economic, environmental, health and social benefits. It ultimately contributes towards sustainable development.

Effects of pre-treatments and co-digestion on biogas production from Okra waste

The effects of pre-treatment and co-digestion on the biogas yield of okra wastes are the focus of this paper. Okra wastes (O) were treated with 5% alkaline (NaOH) (OA), microwave (OMW), and microwave + alkaline. Sheep slurry (S) was co-digested with okra waste in varying proportions [25% (OS25), 50% (OS50), and 100% (S)]. Biomethane potential tests using 500 ml bioreactors were carried out in the batch mode at a hydraulic retention time of 25 days under mesophilic conditions (37 °C). The cumulative biogas yield from the alkaline treated sample (OA) increased by 45.87% when compared to the control (O), and other pre-treated samples were statistically the same with untreated okra waste at the 95% confidence level. Samples co-digested with sheep slurry recorded a low biogas yield. The results of the kinetic studies performed with the measured cumulative biogas yield showed that while the modified Gompertz model presented a better prediction range (0.66%–2.48%), the first-order kinetic model produced a better goodness of fit (<10) and R2 values when compared to the modified Gompertz model. The results of the Artificial neural network (ANN) performed were compared with the earlier used kinetic models, and it was observed that all the performance indicators (R2, RMSE and %prediction difference) from the ANN model best predicted the biomethane yields.

Comparative Study of Biogas Production from Sugarcane Bagasse and Cow Dung

Renewable energy such as the Biogas has recently been receiving attention. This may be connected to numerous advantages including energy security, and sustainability. However, several challenges including amount of gas produce, nature of substrate, high cost of production remains a problem. This research aimed at investigating biogas production from sugarcane bagasse, cow dung and co-digestion of the two substrates. In this research, sugarcane bagasse which is one of the most common wastes cellulosic materials was used as substrate to generate gas and to compare the rate of production with the most common substrate use (cow dung). Sample of sugarcane bagasse and cow dung ware obtain from Katsina metropolis. Samples were initially, processed (dried, and ground to powder) before preparing slurry in a specialize bioreactor that was constructed using a 900g tin. Three different sets of biogas were made including reactor containing co-digestion of bagasse with cow dung, cow dung alone and sugarcane bagasse alone. The gas generated was allowed only one passage via a tube and collected by downward delivery. The result shows that the digester containing co-digestion of sugarcane bagasse and cow dung has the highest cumulative biogas generation of 74.00 cm3, followed by the digester containing cow dung only which produces a total volume of 52.00 cm3, while the digester containing sugarcane bagasse only has a cumulative biogas generation of 39.00 cm3 with a pH range of 4.6 – 6.6. It was found that, agricultural wastes such as groundnut shell, rice straw maize cobs and sugarcane bagasse which naturally have been dumped carelessly as domestic waste especially when co-digested can provide an alternative substrate for efficient biogas production.

Enhancement of Substrate Decomposition through Potential Hydrolytic Bacteria for Cumulative Biogas Production

Scenarios focus on the practical behavior of anaerobic decomposition systems to enhance biogas production, in addition to assure economic progression and ecological sustainability. The present study has framed to identify the potential hydrolytic bacteria from five different sources since principally the efficacy of hydrolytic bacteria determines the rate of hydrolysis of anaerobic decomposition and thereby biogas production. Among the 40 dominant bacteria isolated from diverse bases, 10 isolates were selected as efficient through preliminary screening. Consequently, the premier enzyme activity obtained from the isolate G5 obtained from goat rumen fluid for cellulase (44.16±1.00 U/ml), protease (260.63±1.35 U/ml) and lipase (33.20 ± 0.81 U/ml). Morphological, biochemical and molecular characterization revealed that G5 is Bacillus sp. DDG5 (KM093856.1). A range of pH (7.0-7.5) and temperature (40oC) was sufficient for the highest activity of hydrolytic enzymes experienced. Biogas production using cow dung showed an improved efficiency of 9.54 % in Bacillus sp. DDG5 treated tank (70.16 ± 1.54 %) in contrast to control (58.13 ± 1.02%) at 30th day. However, this study established that Bacillus sp. DDG5 obtained from goat rumen fluid is the promising hydrolytic bacteria, since it can be applied for proficient hydrolysis of various organic materials to enhance methane production in outlook.
 Int. J. Appl. Sci. Biotechnol. Vol 6(4): 386-396

Effect of sulfuric acid pretreatment on biogas production from Salvinia molesta

The effect of sulfuric acid pretreatment on biogas yield from Salvinia molesta (SM) was studied. The sulfuric acid concentration was varied to be 2, 4, 6% v/v. Pretreatment was carried out under batch system at room temperature and pressure of 1 atm for two days. Then, the digestion was carried out for 30 days under batch system at room temperature and pressure of 1 atm. The pretreatment decreased the lignin content and increased the nitrogen free extract content (non-fiber carbohydrate). The more the sulfuric acid concentration, the more the change of these contents. Furthermore, cumulative biogas yield from pretreated SM using sulfuric acid 2–6% (22.72–24.14 mL/g VS) was higher than that from raw SM (13.28 mL/g VS). For digestion during 30 days, the best pretreatment was 4% because it produced the highest total biogas yield (24.14 mL/g VS) and had very short lag time (0 day). The measured data was simulated using the modified Gompertz and first order kinetic model. The calculation showed that the modified Gompertz model (error 6.141–12.431%) was better than the first order kinetic model (error 7.336–47.606%).

Anaerobic Biogas Production Using Microalgae Chlorella sp. as Biomass Co-digested by Cow Manure and Cow Rumen Fluid as Inoculum.

World’s demand for energy is steadily increasing following population increase, on the other hand reserves for fossil and coal energy are limited. Therefore research for renewable sources of energy is important. Biogas produced from renewable source could be one of the answer for future energy production. Researches regarding biogas production utilizing microalgae biomass such as Chlorella sp. have received much attention. In this study, co-digestion of Chlorella sp. “CD01” isolated from Cideng/Krukut River using cow rumen fluid and cow manure as inoculum were used to enhance biogas production. Our experiment used a simple non-stirred batch anaerobic bioreactor that was carried out for 29 days. Biogas volume, COD value, and microorganism were the parameters in this study. Our result showed that Chlorella sp. “CD01” and rumen fluid alone could not produce biogas. Co-digestion of Chlorella sp. “CD01” substrate and rumen fluid inoculum produced 314.5 mL biogas with yield of 43.23 mL/gTS. Co-digestion of Chlorella sp. “CD01” substrate and manure inoculum produced 1758 mL biogas with yield of 98.96 mL/gTS. The best substrate inoculum ratio (S/X) in this study was 0.33 based on cumulative biogas production. Attempts for isolating anaerobic culture from each reactor had been done using methanogenic selective media. Two methanogens isolates were morphologically characterized.

The effect of cow manure and cow rumen fluid on biogas production using Oscillatoria sp. biomass

In order to meet the growing demand for energy and to reduce the dependency on non-renewable energy sources, a renewable alternative energy source is needed. Oscillatoria sp. biomass has the potential to be processed into a renewable energy source because it can be produced continuously in sufficient quantities, environmentally friendly, and does not disrupt agricultural land. This study was conducted to identify the ability of microbes contained in cow manure and rumen fluid to produce biogas from Oscillatoria sp. biomass and optimize the concentration of these microbial sources. Cow manure and rumen fluid were utilized as a source of inoculum and the concentration was further optimized through central composite design (CCD) using a response surface methodological (RSM) approach. The results showed that cow manure had a more significant effect on biogas production compared to cow rumen fluid. In addition, fluctuations in pH values appear to affect biogas production activity. According to the model developed, the amount of optimum biogas produced was estimated can reach around 324 mL with the content of cow manure and rumen fluid are 128.03 mL and 21.97 mL respectively. The results of the validation experiments show that the cumulative biogas production reaches 350.33 mL or 8.12% more than the predicted biogas production from the regression model produced.

Evaluation of the effect of sodium hydroxide solution on biogas yield of anaerobic digestion of poultry waste and the digestate

The effect of adding an alkaline solution, sodium hydroxide (NaOH), in optimizing biogas and methane yield from poultry waste anaerobically was investigated in this work. Two digesters of 50 l capacity each were set up and labeled A and B. Digester A was batched with a mixture of 19 kg of PW and 19 l of water, while digester B has the same mixed volume ratio of poultry waste and water as in digester A but with the addition of 380 ml of 1 M NaOH. Daily gas yield was obtained from the two digesters for a retention period of 30 days; the temperature and pH were also recorded. The peak yield from digester A was recorded on day 23 to be 0.0392 m3, while digester B peak yield of 0.0522 m3 was recorded on day 18. The cumulative biogas yields at the end of the retention period were 0.5511 m3 and 0.6070 m3, respectively, for both digesters. The coefficient of correlation R2 between the gas yields of the two samples is 0.9657. The biogas obtained from the two setups was analyzed with digester B (poultry waste + water + 380 ml of 1 M NaOH) having an appreciable methane yield of 3.03% than digester A.

EFFECT OF FERMENTATION MIXTURE AND PARTICLE SIZE ON BIOGAS PRODUCTION FROM ORGANIC AND AGRICULTURAL WASTES

Six digesters made from transparent plastic with a capacity of 10 l (digestion volume of 7.5 l) were used for producing biogas. Four different organic wastes were used (fresh cattle dung, cotton stalks, water hyacinth and sugar beet). The digesters were experimented under six different fermentation mixtures (A, B, C, D, E and F) and three different particle sizes (5, 10 and 15 mm) .Digesters performance was evaluated through measuring daily gas production, cumulative biogas production, methane production and chemical analysis for biogas slurry such as nitrogen percentage and pH value. The experimental results revealed that the maximum daily biogas production and cumulative biogas values were 8.03 l and 108.3l respectively and also the maximum methane production value was 6.16 l for mixture D and particle size of 5 mm. as the highest nitrogen percentage and pH values were 4.3% and 6.83 for the mixture C and B respectively and particle size of 5 mm.

Co-digestion of food waste and domestic wastewater – effect of copper supplementation on biogas production

This work aims to study the effect of copper supplementation (as CuCl2), at different concentrations (10, 30, and 50 mg/L Cu2+) to enhance the conversion of organics present in a mixture of food waste and domestic wastewater (0.183, v/v) to biogas. The UASB reactor was operated under mesophilic conditions (35±0.1°C) at hydraulic retention time of 10 days in the intermittent feed mode (48 h feed/48 h feedless). Regardless of the Cu2+ concentration supplemented, a higher cumulative biogas yield (260-329 mL CH4/g CODremoved) was obtained compared to the control without supplementation (175 mL CH4/g CODremoved). The microelement supplementation reduced the amount of short chain fatty acids accumulated in the reactor by 35%, stimulating the methane production.

Regression Analysis of Biogas Production from the Co-Digestion of Water Hyacinth and Pig Dung

The aim of this study is to determine the best mix of water hyacinth (WH) to be co-digested with pig dung (PD) in order to maximize biogas production in terms of quantity. 11 mix ratios of WH to PD were evaluated and each experimental run was assessed over a period of 40 days. The data obtained were analyzed using regression analysis and non-linear parameter estimation model. From the results obtained, 3 WH: 7 PD co-digestion mix recorded the highest daily yield of 9.5 L of biogas on the 20th day, starting its gas production on the 3rd day and ending on the 34th day. The results also showed that WH single-substrate digestion produced a cumulative biogas volume of 32.18 L which corresponds to 5.14 L/kg of WH and PD single-substrate digestion produced a cumulative gas volume of 94.47 L corresponding to 15.1 L/kg of PD. 3 WH: 7 PD had the highest cumulative gas volume of 140 L which corresponds to 22.45 L/kg. Similarly, the highest maximum biogas production rate of 9.874057 L/day was observed for the 3 WH: 7 PD co-digestion mix and this was recorded on the 17th day of digestion. From the results obtained the best mix of the PD-aided WH digestion is 3 WH: 7 PD.Keywords— Biogas, Co-digestion, Cumulative, Pig Dung, Water Hyacinth

Kinetic modelling of augmenting biomethane yield from poultry litter by mitigating ammonia

ABSTRACTIn this study, the kinetics of biogas production was studied by performing a series of the laboratory experiment with air stripped poultry litter. Four kilograms of Raw Poultry Litter is mixed with water in the ratio 1:3, respectively, and loaded inside the digesters and the samples are compared with Air stripped Poultry Litter for a retention time of 21 days. The modified Gompertz equation suitably construes the cumulative biogas produced as a function of time. From the kinetics of the system, it is inferred that the biogas production potential (A), maximum biogas production rate , and lag phase period (λ) of Raw Poultry litter is 18.77 (l/kg of VS); 1.08 (l/kg of VS/day); 1.5 days, respectively, comparing with Air stripped Poultry Litter of 22.05 (l/kg of VS); 1.30 (l/kg of VS/day); 1 day, respectively. These results show that biogas production can be enhanced efficiently by means of ammonia removal pre-treatment process.

Iopamidol degradation with ZVI- and ZVA-activated chemical oxidation: Investigation of toxicity, anaerobic inhibition and microbial communities

Treatment of aqueous iopamidol (IOPA, 2 mg/L), an iodinated organic X-ray contrast chemical and micropollutant, with nano-sized zero-valent iron (ZVI) and aluminum (ZVA)-activated hydrogen peroxide (HP) and persulfate (PS) oxidation processes was investigated. Changes in acute toxicity, anaerobic digestion, biogas yield and microbial community were further examined to question the ecotoxicological safety and bioamenability of the proposed treatment systems. For this purpose, two different bioassays were conducted with V. fischeri and P. subcapitata. The cumulative biogas production was monitored in batch anaerobic digestion tests. The microbial community was identified by Illumina MiSeq next generation sequencing (NGS) technology and abundant bacteria and archaea were analysed in the biomass samples taken from anaerobic reactors. The application of activated HP (1.00 mM) and PS (0.50 mM) treatments under acidic conditions (pH 3) resulted in complete IOPA removal. The original IOPA sample caused 5% and 74% inhibitions to V. fischeri and P. subcapitata, respectively. The relative inhibition towards P. subcapitata increased from 74% to 97% and 93% after 5 min HP/ZVI and 120 min PS/ZVA treatments, respectively. No meaningful changes in terms of digestion performance and cumulative biogas production in the presence of untreated and HP/ZVI- or PS/ZVA-treated IOPA samples were evidenced. Moreover, all biomass samples were populated by a bacterial consortium related to different members of Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Hydrogenotrophic (Methanospirillum, Methanobacterium) and acetoclastic (Methanosaeta, Methanosarcina) methanogens were the prevalent members of archaea at genus level. An increase in relative abundance was only identified in Methanobacterium under the phylum namely Euryarchaeota.

Optimization of process parameters for anaerobic fermentation of corn stalk based on least squares support vector machine

In order to improve the yield and efficiency of biogas produced from anaerobic fermentation of corn stalk, least squares support vector machine (LS-SVM) was used to optimize the pretreatment process parameters. Weight of corn stalk, ultrasonic duration time, alkali pretreatment (2% NaOH) time, and single/dual-frequency ultrasound were selected as the experimental factors of orthogonal experimental design (OED). A new modeling method combining LS-SVM and OED was proposed to establish the predictive model between cumulative biogas production (CBP) and pretreatment process parameters. The effect of experimental factors on CBP was analyzed by two-dimensional (2D) and three-dimensional (3D) contour maps of the predictive model. The optimum parameters for process pretreatment were as follows: weight of corn stalk 53 g, dual-frequency ultrasound, ultrasonic duration time 33 min, alkali pretreatment time 56 h. The CBP of the optimal conditions obtained was 22.69 L and was 14.13% higher than that of optimal conditions for OED.

Multicriteria Decision Model and Thermal Pretreatment of Hotel Food Waste for Robust Output to Biogas: Case Study from City of Jaipur, India.

The anaerobic batch test (45 days at 37°C) was performed to describe the effect of thermal pretreatment at moderate temperatures (60, 80, and 100°C) over durations of 10 and 20 minutes on the enhancement of biogas production using hotel food waste from city of Jaipur, India. The results showed that the total cumulative biogas production with thermal pretreatment (100°C, 10 minutes) was 41% higher than the control. Also, this alternative gets first rank using multicriteria decision making model, VIKOR. This outcome was obtained due to the enhancement of degradation of organic compounds such as protein and volatile solids that occurred in the linear trend. Modified Gompertz and Logistic models were used to study the effect of different pretreatment parameters on lag time and biogas yield. Scanning electron microscopy and Fourier transform infrared spectroscopy were also employed to investigate the effect of thermal pretreatment on the physiochemical properties of food waste.

Isolation of bacteria capable of hydrogen production in dark fermentation and intensification of anaerobic granular sludge activity

In the anaerobic biological treatment of pulp and papermaking wastewater, the gradual deposition of CaCO3 eventually leads to the inhibition of the activity of anaerobic granular sludge. In this study, a hydrogen production bacterial Raoultella DW01 was isolated from domesticated anaerobic granular sludge. The fermentation conditions were designed using central composite design, and the optimum conditions obtained by response surface analysis encompassed an initial pH 5.77, 4.13 g/L l-glutamic acid and an inoculation amount of 15%. The H2 production yield represented a 29.5% increase over the unoptimized conditions. Finally, the effect of adding DW01 on the biogas production in anaerobic granular sludge with different sludge ages was investigated. The cumulative biogas yield and the max biogas production rate increased by 27.8% and 53.5% after adding DW01 to a sludge with an age of 335 days compared with the on-intensified sludge. This paper provides a way to alleviate the CaCO3 deposition by intensifying the activity of H2 and acid-producing bacteria via improving the activity of granular sludge.

Adding benefits to phytoremediation of sugar mill effluent by growing water hyacinth (Eichhornia crassipes): Evaluation of biomass for biogas production

In this experiment, we assessed the phytoremediation potential of water hyacinth (Eichhornia crassipes) for pollutants removal from sugar mill effluent amended at different concentrations and further biogas production from its grown biomass co-digested with cow dung in a laboratory scale anaerobic digester. The results showed that the maximum values of kinetic growth rate (2.56gg-1d-1), total chlorophyll content (4.10±0.10mg/gfwt.) and fresh plant biomass (393.87±4.67g/Kg) of E. crassipes were achieved in 75% concentration of sugar mill effluent after 60 days of phytoremediation experiments. Also, the enrichment factor (Ef) and bioaccumulation factor (Bf) of heavy metals were greater than or equal to 1 in the roots and leaves of E. crassipes which indicated efficient elimination of these metals from the sugar mill effluent. Significant values of cumulative biogas production (5195 ml) and predicted by modified Gompertz kinetic model (5238.71 ml) were found after 15 days of anaerobic digestion at 40°C with maximum reduction of COD (83.11%) of the substrate slurry. The plot of log(COD) vs. t (HRT) suggested good fitness of first order kinetic equation (R2= 0.9746) for reduction of co-substrate COD. The different kinetic parameters of COD reduction for biogas production viz., a, xc and k were noted as 6096.12, 7.73 and 0.26, with R2 value of 0.99, respectively. The findings of this study concluded that E. crassipes can be used for the phytoremediation of heavy metals and other pollutants most efficiently in 75% concentration of the sugar mill effluent. Additionally, the biomass of E. crassipes grown during phytoremediation can be used for enhanced biogas production.