Cumulative Biogas Production Research Articles

Modeling Anaerobic Co-Digestion of Corn Stover Hydrochar and Food Waste for Sustainable Biogas Production

Despite the importance of the biodegradability of lignocellulose biomass, few studies have evaluated the lignocellulose biomass digestion kinetics and modeling of the process. Anaerobic digestion (AD) is a mature energy production technique in which lignocellulose biomass is converted into biogas. However, using different organic waste fractions in AD plants is challenging. In this study, lignocellulose biomass (corn stover hydrochar) obtained from hydrothermal carbonization at a temperature, residential time, and biomass/water ratio of 215 °C, 45 min, and 0.115, respectively, was added to the bioreactor as a substrate inoculated with food waste and cow dung to generate biogas. A state–space AD model containing one algebraic equation and two differential equations was constructed. All the parameters used in the model were dependent on the AD process conditions. An adaptive identifier system was developed to automatically estimate parameter values from input and output data. This made it possible to operate the system under different conditions. Daily cumulative biogas production was predicted using the model, and goodness-of-fit analysis indicated that the predicted biogas production values had accuracies of >90% during both model construction and validation. Future work will focus on the application of modeling predictive control into an AD system that would comprise both models and parameters estimation.

Impact of Fe3O4 Nanoparticles on Methane Production from Anaerobic Digestion and Kinetic Analysis

Anaerobic digestion (AD) is one of the most widely used processes to stabilize waste sewage sludge and produce biogas as renewable energy. This study investigated the effects of Fe3O4 NPs at different concentrations (0,100 and 300 mg/L) on AD. 100mg/L Fe3O4 NPs could increase gas production by 21.9% and reach the highest methane content of 66.75%. In addition, 100 mg/L Fe3O4 kept pH at an appropriate level. Scanning electron microscope (SEM) was used to study the changes in surface morphology in sludge. The dynamics of cumulative biogas production and daily biogas production were studied by using the Logistic model and modified Gompertz model respectively. Other indices also had changed in the whole process, which in the end lead to the variation of biogas production. These results suggested that Fe3O4 NPs could increase microbial activity and relevant enzyme activities, caused changes and transitions between different phases in the system.

A new mechanical cutting pretreatment approach towards the improvement of primary sludge fermentation and anaerobic digestion

Pretreatment technologies for improving the anaerobic digestion of waste activated sludge have been studied extensively; however, studies on the improvement of pretreatment technology for primary sludge (PS) fermentation and anaerobic digestion are scarce. In this study, a novel mechanical cutting pretreatment (MCP) method was proposed to enhance the performance of PS fermentation and anaerobic digestion. PS was disintegrated by MCP, the average particle size of PS reduced from 45.7 µm to 7.0 µm, and soluble COD (SCOD) increased by 1206 mg/L with pretreatment for 8 min. The hydrolysis and acidification of PS was promoted significantly by MCP. Compared with the control group, the production of SCOD and volatile fatty acids (VFAs) in the pretreatment group during sludge fermentation increased by 167% and 115.3%, respectively. The performance of PS anaerobic digestion was remarkably improved by MCP. The maximum cumulative biogas production in the pretreatment group was 3153 mL, which was 6.33 times that in the control group (498.5 mL). Sludge disintegration by mechanical pretreatment resulted in the enrichment of bacteria, especially Firmicutes, in the sludge fermentation system, and the quantity of bacteria in the pretreatment group was 1.95 times that in the control group. However, MCP had little effect on archaea in the anaerobic digestion of PS, and the methanogens in the control and pretreatment reactors were 1.493 × 109 and 1.519 × 109 copies/g, respectively.

Microbial community structures and antibiotic biodegradation characteristics during anaerobic digestion of chicken manure containing residual enrofloxacin

To explore the interaction between the residual antibiotic in animal manure and biological treatment, the effect of enrofloxacin (ENR) on the anaerobic digestion of chicken manure, and biodegradation rate of ENR was studied under the condition of actual residual ENR content of 0, 8, 16 and 32 mg/kg·TS. The results showed that the addition of ENR increased the total biogas production, especially 8 mg/kg·TS promoted the anaerobic reaction obviously, and the corresponding cumulative biogas production was increased by 15.33%. However, in the presence of 32 mg/kg·TS, the biogas production rate was reduced and the peak period of biogas production was delayed. The results of enzyme activities determination and 16S rRNA sequencing showed that ENR had different effects on archaea and bacteria. The residual ENR could promote hydrolysis reactions in the anaerobic system, but could inhibit acetoclastic methanogens, and the relative abundance of Methanosaeta declined by 7.22‒12.41%. The first-order kinetic model showed that the half-life period of ENR in the anaerobic digestion system was 9.16‒10.83 days, and the biodegradation rate exceeded 80% after the treatment. This study can bring important information for the management of animal manure in the future.

Pre-treatment of lignocellulosic materials by enzymatic mixture to enhance biogas production

Abstract The aim of this study was to evaluate the effect of an enzymatic mixture on the increase of biogas production from lignocellulosic materials as rapeseed straw, maize waste, and wheat straw. For efficient application of the enzymatic mixture, conditions of its use were optimized regarding 50 °C, pH 7 and an enzyme dose of 0.25 % w/v. Biogas potential test confirmed positive effect of the enzymatic mixture on anaerobic digestion of already thermally and alkali pre-treated lignocellulosic materials, as significantly higher biogas production was observed after the enzymatic mixture addition for all monitored substrates. Addition of the enzymatic mixture to the most used substrate at biogas plants — maize silage, had also positive effect on biogas production during the biogas potential test. This fact was not proven during long-term operations of the reactors as the values of total cumulative biogas productions for the whole monitored period from reactors for anaerobic digestion of maize silage with and without addition of enzymatic mixture did not differ significantly.

Experimental and kinetic studies for improvement of biogas production from KOH pretreated wheat straw

The objective of the present work was to investigate the influence of potassium hydroxide (KOH) based pretreatment of wheat straw for biogas production. For this purpose, different concentrations (0.5%,1.0%,2.0% and 4.0%) of potassium hydroxide was used to pre-treat wheat straw at ambient temperature (about 30 ​°C) to improve its biodegradability prior to its application for biogas production. Biogas efficiency of wheat straw with and without pretreatment was estimated. The highest cumulative biogas production (558 ​ml) was obtained with wheat straw pretreated with 2.0% KOH. Further kinetic study of biogas production confirm the shorter lag phase (λ ​= ​0.15) and maximum biogas production (718.32 ​ml) with 2.0% KOH pretreated whet straw. Therefore 2.0% KOH can be used as an effective method of pretreatment to improve the biogas production of wheat straw.

Treatment of fracturing wastewater by anaerobic granular sludge: The short-term effect of salinity and its mechanism

The effects of salinity shock on the anaerobic treatment of fracturing wastewater regarding chemical oxygen demand (COD) removal performance, sludge characteristics and microbial community were investigated. Results showed COD removal efficiency decreased from 76.0% to 69.1%, 65.6%, 33.7% and 21.9% with the increase of salinity from 2.5 g/L to 10, 15, 25 and 45 g/L, respectively. The cumulative biogas production decreased by 13.8%–81.1% when salinity increased to 15–85 g/L. The increase of salinity led to the decline in particle size of granular sludge, and the activity of granular sludge, including SMA, coenzyme F420 and dehydrogenase, was inhibited significantly. Flow cytometry indicated the percentage of damaged cells in granular sludge gradually increased with the increase of salinity. Sequence analysis illustrated that microbial community structure in anaerobic digestion reactor was influenced by the salinity, high salinity reduced the diversity of archaea and decreased the abundance of methanogens, especially Methanosaeta.

Anaerobic Digestion for Biogas Production from Municipal Sewage Sludge: A Comparative Study between Fine Mesh Sieved Primary Sludge and Sedimented Primary Sludge

Two different types of primary sewage sludge have been used as feedstock for production of biogas through anaerobic digestion (AD): the one type was sludge from a typical primary clarifier (PC), while the other type of sludge produced by a rotating belt filter, commonly called microsieve (MS). Initially the main physicochemical characteristics of the sludges, such as total solids (TS), volatile solids (VS), VS/TS, pH and carbon to nitrogen ratio (C/N) were determined, for MS: 37.86 ± 0.08%, 83.00 ± 0.41%, 0.83 ± 0.00, 6.67 ± 0.08 and 19.68 ± 0.69, respectively, and for PC: 2.61 ± 0.08%, 78.77 ± 1.91%, 0.79 ± 0.02, 6.61 ± 0.10 and 14.46 ± 1.23, respectively. Then, calculated amounts of the sludges were inserted into airtight vials and were inoculated using anaerobic sludge. The daily biogas production was measured over a period of 30 days. PC sludge maximized the daily biogas production (44.20 mlbiogas/gvsd) 11 days after inoculation, while the MS sludge reach a peak (37.74 mlbiogas/gvsd) 14 days after inoculation. The cumulative biogas production over the 30 days of AD was in the same laver (442.29 mlbiogas/gvs for PC versus 434.73 mlbiogas/gvs for MS). However, PC sludge indicated higher daily biogas production, compared to MS sludge, while the opposite was observed for the period following the peak point. The Volatile Solids Reduction for PC and MS sludges was recorded as 46.06% and 32.39%, respectively.

Co-digestion of spoiled maize silage with cattle manure

In this study, spoiled maize silage (SMS) and cattle manure were co-digested at five different mixtures by the Hohenheim Batch Yield Test unit under mesophilic conditions to explore biogas production possibilities of these wastes together. The mixtures were 100% cattle manure, 100% SMS, 85% cattle manure + 15% SMS, 70% cattle manure + 30% SMS, and 55% cattle manure + 45% SMS. Chemical properties of raw materials and mixtures, including crude fat, dry matter, organic matter, and acid detergent fiber (ADF) contents were determined. As the amount of SMS in the mixtures increased, biogas and methane production increased. The highest cumulative specific biogas and methane production were determined for 100% SMS as 0.62 Nm3 kg-1 organic matter (OM) and 0.31 Nm3 kg-1 OM, respectively, where Nm3 is the volume of biogas under normal conditions. Methane content of the mixture containing SMS (49.99% to 51.87%) was higher than that of cattle manure only (44.01%). Furthermore, the mixtures which had lower ADF content yielded more methane and biogas. In conclusion, the efficiency of biogas and methane production can be increased by applying the co-digestion technique.

Biogas Quantity and Quality from Digestion and Co-Digestion of Food Waste and Cow Dung


 
 
 The aim of this study is to assess the quantity and quality of biogas produced from single substrate digestion of food waste and cow dung as well as co-digestion of food waste and cow dung. Laboratory sized 25 litre plastic biodigesters were used in this study and the digestion processes was carried out for a 30 day retention period. The results revealed that the cumulative biogas production for the single substrate digestion of cow dung was 7,975 ml, the cumulative biogas produced for the single substrate digestion of food waste was 7,742.5 ml while the cumulative volume of biogas produced for the co-digestion of cow dung and food waste was 16,482.5 ml. The results also showed that the total volume of methane produced for the single substrate digestion of cow dung was 955 ml while the total methane produced for the single substrate digestion of the food waste was 765. The total production of methane for the co-digestion of cow dung and food waste was found to be 2,655 ml. This study revealed that though the co-digestion process improved biogas quantity and quality, the percentage methane present in the biogas very low. There would be a need to stimulate the digestion and co-digestion process in order to improve the quality of biogas produced.
 
 

An optimum process for anaerobic digestion of wild tree wastes under alkaline pretreatments in biogas plants

In the present study, a new strategy was developed by integrating mathematical modeling, restrictive goals, and desirability analysis to improve anaerobic digestion of wild tree wastes and clean biogas production. For this purpose, different mixtures (inoculum : terebinth waste : cow manure) and pretreatments (NaOH and urea) were tested based on a combined D-optimal experimental design. The results indicated that biogas production of mixtures with higher cow manure amounts was more purified, with higher terebinth waste had more CO and CO2, and with higher inoculum had more H2S. Further, the addition of NaOH and urea below 1.5% improved the quality of biogas. By overlaying the biogas parameters according to the restriction goals, the best ranges of the inoculum : terebinth waste : cow manure were equaled to 0−10% : 4−22% : 71−97%, and the best concentration ranges of NaOH and urea were 0.19−1.83% and 0−1.2%, respectively. Using these optimum ranges of the input factors, CH4, H2S, CO2, CO, corrected CH4, T90, cumulative biogas production and cumulative methane production were >50.3%, <0.0003%, <9.85%, =0%, >66.21%, >4.89 day, >799.02 mL and >8.49 mL/gVS, respectively. It can be concluded that to improve the biogas plant efficiency in the areas with high tree wastes, a lot of cow manure is needed (> 3 times of tree wastes), and the substrates should be chemically pretreated with NaOH amount less than 1.83% and urea amount less than 1.2%.

Improved mesophilic anaerobic digestion of swine wastewater by ammonia stripping with microwave irradiation

ABSTRACT Ammonia (NH3) stripping by microwave irradiation was used to increase the efficiency of anaerobic digestion. The effects of final temperature (FT) (80 ≤ FT ≤ 100°C) and microwave irradiation time (MIT) (2.5 ≤ MIT ≤ 5.5 min) of NH3 stripping, and hydraulic retention time (HRT) (7 ≤ HRT ≤ 20 d) in anaerobic digester were quantified. NH3 concentration decreased from 2794 to 140 mg/L within 5.5 min at FT = 100°C. The highest cumulative biogas production (>1800 mL/L) and efficiency of volatile solid removal (> 68%) were achieved at FT = 100°C and MIT = 5.5 min. The removal efficiency of volatile solid in digesters fed with untreated swine wastewater (control) and swine wastewater treated by NH3 stripping decreased as HRT decreased. The highest relative improvement of properties compared to the control occurred at 10 or 15 d HRT. Increases in biogas production compared to the control increased with the NH3 stripping as HRT was reduced to 10 d (243% higher at 10 d). The methane content of the produced biogas was 64–69% for control and 68–75% with NH3 stripping in the range of 10–20 d HRT. NH3 stripping using microwave irradiation is an effective pretreatment to improve the anaerobic digestion of swine wastewater.

Biogas and Volatile Fatty Acid Production During Anaerobic Digestion of Straw, Cellulose, and Hemicellulose with Analysis of Microbial Communities and Functions.

The anaerobic digestion efficiency and methane production of strawwas limited by its complex composition and structure. In this study, rice straw (RS), cellulose, and hemicellulose were used as raw materials to study biogas production performance and changes in the volatile fatty acids (VFAs). Further, microbial communities and genetic functions were analyzed separately for each material. The biogas production potential of RS, cellulose, and hemicellulose was different, with cumulative biogas production of 283.75, 412.50, and 620.64mL/(g·VS), respectively. The methane content of the biogas produced from cellulose and hemicellulose was approximately 10% higher than that produced from RS after the methane content stabilized. The accumulation of VFAs occurred in the early stage of anaerobic digestion in all materials, and the cumulative amount of VFAs in both cellulose and hemicellulose was relatively higher than that in RS, and the accumulation time was 12 and 14days longer, respectively. When anaerobic digestion progressed to a stable stage, Clostridium was the dominant bacterial genus in all three anaerobic digestion systems, and the abundance of Ruminofilibacter was higher during anaerobic digestion of RS. Genetically, anaerobic digestion of all raw materials proceeded mainly via aceticlastic methanogenesis, with similar functional components. The different performance of anaerobic digestion of RS, cellulose, and hemicellulose mainly comes from the difference of composition of raw materials. Increasing the accessibility of cellulose and hemicellulose in RS feedstock by pretreatment is an effective way to improve the efficiency of anaerobic digestion. Since the similar microbial community structure will be acclimated during anaerobic digestion, there is no need to adjust the initial inoculum when the accessibility of cellulose and hemicellulose changes.

Enhanced biogas production in dilute acid-thermal pretreatment and cattle dung biochar mediated biomethanation of water hyacinth

The effect of dilute acid-thermal pretreatment and cattle dung biochar (BC) addition on anaerobic co-digestion (AcoD) of water hyacinth (WH) with waste activated sludge (WAS) was investigated in this study under mesophilic condition. The dilute acid-thermal pretreatment (2% H2SO4 w/v followed by 121 °C, 60 min) hydrolyzed 38.1% (lignin), 56.8% (cellulose) and 86.7% (hemicellulose) of lignocellulosic fraction and increased the soluble chemical oxygen demand (sCOD) and volatile fatty acids (VFA) concentration by 4.91-folds and 2.20-folds, respectively. The cumulative biogas production in pretreated and biochar amended digesters was 73.4–98.7% higher than the control digester. Methane content in biogas improved by 9.33 – 19.8% in BC supplemented assays over control. The highest methane yield of 235 mL and VS removal (77.4%) were observed for pretreated, and biochar (1% dose) amended digester. The morphological and structural transformations in non-pretreated and dilute acid-thermal pretreated WH biomass were studied by Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) analysis. SEM results shows the porous and rougher structure with flake-like structures owing to harsh pre-treatment conditions. FTIR analysis revealed significant changes in polymer composition and strong lignification of WH biomass. Thus, the dilute acid-low thermal pretreatment of lignocellulosic feedstock and cattle dung biochar amendments in digester are promising methods for effective biomethanation.

Effects of Exogenous Biochar Addition on High Solid Anaerobic Fermentation of Livestock Manure for Environmental Pollution Control

In order to explore the effects of adding biochar on biogas production by high solid concentration anaerobic fermentation of livestock and poultry manure and agricultural safety, this study used pig manure, cow manure and chicken manure as fermentation raw materials, and carried out experiments on biogas production by mesophilic temperature anaerobic fermentation with high solid concentration. The changes of cumulative biogas production, biogas production rate, methane (CH4) content, volatile fatty acid (VFA) and hydrogen sulfide (H2S) content in three kinds of livestock manure with or without biochar were analyzed. The results showed that the addition of biochar had different effects on anaerobic fermentation of livestock and poultry manure with high solid concentration, increased the content of CH4 and decreased the content of H2S. the addition of biochar provided enough granular surface to absorb a large number of inoculated microorganisms, which shortened the start-up time, increased the biogas production rate of high-solid anaerobic fermentation of livestock and poultry manure, and advanced the peak period of biogas production; reduced the content of VFA, reduced the inhibition of methanogens, so the methane content increased. The addition of biochar had the most obvious effect on anaerobic fermentation of cow manure and chicken manure with high solid content.

혐기성 공동소화 공정에서 커피찌꺼기 산 발효액이 바이오가스 생산에 미치는 영향

The spent coffee grounds (SCG) were acidogenic fermented and it used as a co-feedstock in the anaerobic co-digestion process. After mixing sewage sludge and acidogenic fermented SCG in a ratio of 7:3 (SF2), the effect on biogas production was observed. The cumulative biogas production during 30-day digestion time was determined 705.28 mL for SF1 (only sewage sludge) and 1891.98 mL for SF2, indicating that SF2 produced about 2.68 fold more cumulative biogas. The methane content in produced biogas was determined 62-65% and 70-73% for SF1 and SF2, respectively. Moreover, the specific biogas production was found to be 0.35 ± 0.11 mL/kg·TS and 0.43 ± 0.13 mL/kg·VS for SF1 and 0.64 ± 0.15 mL/kg·TS and 0.81 ± 0.16 mL/kg·VS for SF2. In addition, the calculated energy production was 2.76 kWh for SF1 and 5.82 kWh for SF2, indicating about 2.1 fold higher energy production than that of SF1. Finally, the co-digestion performance index was 1.69 for SF2, so it was confirmed that the synergistic effect for biogas production was high when anaerobic co-digestion using FSCG as a co-feedstock.

Effect of Autoclave Pretreatment on Biogas Production through Anaerobic Digestion of Green Algae

Anaerobic Digestion (AD) is one of the most widely used methods in the field of sustainable bioenergy production from various feedstock. One such feedstock is algae waste which has become an increasingly serious environmental problem. AD of algal biomass is hindered by the presence of resistant cell walls; hence a pretreatment step is usually required to decompose the cell wall structure. This study uses green algae (Enteromorpha) and anaerobic sludge as raw materials to explore the impact of autoclave (AC) pretreatment on biogas production. AC pretreatment was performed at 120 °C and 80 °C. The cumulative biogas production of the 120 °C AC pretreatment, 80 °C AC pretreatment and control group were 600 mL, 450 mL and 400 mL, respectively. The results showed that AC pretreatment improved the biodegradability of biomass as 120 °C AC pretreatment group achieved higher degradation rate of cells (95.99 %). The energy evaluation showed that the net energy ratio of the 120 °C AC pretreatment group was 1.07, indicating high overall energy gain via AD process. The experimental data is further modeled by using Modified Gompertz Model (MGM) and Logistic Function Model (LFM). To check the applicability of better model for this AD process, an Akaike Information Criteria (AIC) test was performed. AIC showed that the MGM is basically consistent with the experimental data and more reliable for prediction modeling of Enteromorpha AD.

Anaerobic Co-digestion of Organic Fraction of Municipal Solid waste and Septage for Sustainable Waste Treatment: A Case Study from Goa, India

India generates 0.15 million metric tons (MT) of solid waste per day out of which more than 80% is organic fraction. Apart from this, 38% of the households use septic tanks where proper disposal of faecal sludge is also need of the hour. Anaerobic co-digestion (ACD) of two different substrates has positive potential towards solving this problem. In the present study, ACD of organic fraction of municipal solid waste (OFMSW) and septage solids (SS) was studied at three different levels, i.e., lab-scale, pilot-scale (1 m3), and full scale- capacity (325 m3). A loading rate of 1.5 kg VS/m3 was selected. The bio-methanation potential (BMP) assay showed a maximum biogas generation, i.e., 120±20.6 mL/gmVS with 68% maximum methane concentration at a 5:1 OFMSW and SS ratio. Cumulative biogas production after 30 days was 1.6 L/gmVS. The ultimate biogas production in the pilot-scale plant was 1000±100.5 L/day with 71% methane. The plant was also efficient in removing 87% of COD and 61% of VS. The full-scale anaerobic digester was set up at Mormugao Municpal Council, Goa India wherein the objective was to co-digest OFMSW and SS. This digester showed a similar removal pattern like earlier studies i.e., 94% and 45% COD and VS removal, respectively. The average methane content of the biogas was 68%. Full-scale operation of the anaerobic digester did not show any operational problems at the chosen co-digestion conditions.

Enhancing biogas production of anaerobic co-digestion of industrial waste and municipal sewage sludge with mechanical, chemical, thermal, and hybrid pretreatment

This study presents the effect of mechanical, chemical, thermal, and hybrid pretreatment on anaerobic digestion of fruit-juice industrial waste (FW) co-digested with municipal sewage sludge (MSS). The pretreatment of the substrates with ultrasonication, microwave, weak alkali-acid caused an increase in cumulative biogas production of approximately 20.9, 14.9, 8.1, and 5.2%, respectively. Beside this, thermal and strong acid-alkali pretreatment reduced biogas production. The highest cumulative biogas and methane yield was increased with hybrid pretreatment which contains ultrasonication (US) and alkali (AL) pretreatment by 36% and 49%, respectively. Also, compared to untreated mixture, the soluble COD, carbohydrate, and protein removal efficiencies were increased from 42.6% to 65.6%, 65.1% to 86.6%, and 17.3% to 62.4%, respectively for US-AL pretreatment. The kinetic parameters of cumulative biogas production for the selected reactors were further estimated with Monod, Cone, and Transference Function models.

Effects of Pretreatment and Ratio of Solid Sago Waste to Rumen on Biogas Production through Solid-State Anaerobic Digestion

Solid sago waste is a potential source of producing renewable energy in the form of biogas. This study investigated the effects of solid sago waste particle size, biological pretreatment using a microbial consortium of lignocelluloses, pretreatment with NaOH, and the ratio between solid sago waste and cow rumen based on the biogas production rate. Several variations of these conditions were used to achieve this. The anaerobic digestion process was conducted over two months at 30.42 °C ± 0.05 °C, and the biogas production rate was measured every two days. The 1:1 ratio showed better results compared to the 2:1, because it allows the bacteria to achieve metabolic balance. The highest cumulative biogas production (27.91 mL/g TS) was generated when the sago waste underwent milling (±1 mm), pretreatment with 4% NaOH g/g TS, and treatment with microbial consortium 5% v/v at a 1:1 ratio of solid sago waste to the rumen.