Maximum Biogas Yield Research Articles

Effects of Salt on Anaerobic Digestion of Food Waste with Different Component Characteristics and Fermentation Concentrations

Effects of salt on anaerobic digestion are dosage-dependent. As salt is a widely used condiment in food processing, effects of salt are bound to be considered when food waste is digested. In this study, salt addition effects (0, 2, 4, 6, 9, 12 g∙L−1) on biogas and methane yields and kinetics of biogas production were researched. Meanwhile, component characteristics (food waste featured in carbohydrate, protein and fat, respectively) and fermentation concentrations (5 and 8 gVS∙L−1) were also taken into consideration. Results showed that 2–4 g∙L−1 salt addition was the optimal addition dosage for AD systems as they not only have the maximum biogas and methane yields, but also the maximum vs. removal in most cases. Also, according to the results of a modified Gompertz model, which is used to predict biogas and methane production rates, suitable salt addition can accelerate biogas production, improving the maximum biogas production rate (Rmax). Factorial design (2 × 2) proved that interaction of salt and fermentation concentrations was significant for food waste featured with carbohydrate and with protein (p < 0.05). High salt addition and fermentation concentration can break the AD system when the feeding material was food waste featured with carbohydrate, but for food waste featured with protein, interaction of fermentation concentrations and salt addition can alleviate inhibition degrees.

Performance and Kinetic Model of a Single-Stage Anaerobic Digestion System Operated at Different Successive Operating Stages for the Treatment of Food Waste

A large quantity of food waste (FW) is generated annually across the world and results in environmental pollution and degradation. This study investigated the performance of a 160 L anaerobic biofilm single-stage reactor in treating FW. The reactor was operated at different hydraulic retention times (HRTs) of 124, 62, and 35 days under mesophilic conditions. The maximum biogas and methane yield achieved was 0.934 L/g VSadded and 0.607 L CH4/g VSadded, respectively, at an HRT of 124 days. When HRT decreased to 62 days, the volatile fatty acid (VFA) and ammonia accumulation increased rapidly whereas pH, methane yield, and biogas yield decreased continuously. The decline in biogas production was likely due to shock loading, which resulted in scum accumulation in the reactor. A negative correlation between biogas yield and volatile solid (VS) removal efficiency was also observed, owing to the floating scum carrying and urging the sludge toward the upper portion of the reactor. The highest VS (79%) and chemical oxygen demand (COD) removal efficiency (80%) were achieved at an HRT of 35 days. Three kinetic models—the first-order kinetic model, the modified Gompertz model, and the logistic function model—were used to fit the cumulative biogas production experimental data. The kinetic study showed that the modified Gompertz model had the best fit with the experimental data out of the three models. This study demonstrates that the stability and performance of the anaerobic digestion (AD) process, namely biogas production rate, methane yield, intermediate metabolism, and removal efficiency, were significantly affected by HRTs.

Effect of Zn Addition on the Cd-Containing Anaerobic Fermentation Process: Biodegradation and Microbial Communities.

Anaerobic fermentation is considered as a cost-effective way of biomass waste disposal. However, the compound heavy metals contained in the biomass may induce complex effects on anaerobic fermentation, which limit the utilization of metal-contaminated biowaste. In this study, the impacts of Cd and Zn addition on biogas properties, process stability, substrate biodegradation, enzyme activity, and microbial properties were studied. The results showed that the addition of Cd together with Zn (Cd+Zn) increased the maximum daily and cumulative biogas yields, and brought forward the gas production peak compared with the Cd-added group. Taking the whole fermentation process into account, the promotion effects of adding Zn into the Cd-containing fermentation system on biogas yields were mainly attributable to better process stability, higher average NH4+-N concentration in the later stage of fermentation, reduced COD (p < 0.05), and increased biodegradability of lignocelluloses (p < 0.01), especially cellulose (p < 0.05) and lignin (p < 0.01). Meanwhile, the addition of Zn promoted the coenzyme M activity (p < 0.05), and increased the absolute abundance of Methanothermobacter. The bacteria communities during the fermentation process were responsible for the degradation of lignocelluloses. The results demonstrated that the addition of appropriate Zn into the Cd-containing fermentation system enhanced the efficiency of anaerobic fermentation and utilization of biowaste.

Evaluation of a zeolite/anaerobic buffled reactor hybrid system for treatment of low bio-degradable effluents.

The main objective of this work was to reduce the inhibitory effects of high contents of organics, ammonia, and heavy metals in an anaerobic buffled reactor (ABR), and to prevent the sludge wash-out using zeolites as media. In this work, a pilot scale of ABR with 8 compartments and a working volume of 14.4 L was used, and the last four ABR compartments were filled with a zeolite. The bioreactor was operated at HRTs of 3, 4, and 5 days, zeolite filling ratios of 10, 20, and 30%, and influent chemical oxygen demand (COD) concentrations of 10,000, 20,000, and 30,000 mg/L. The results obtained showed that the maximum removal efficiencies of COD and BOD5 reached 78 and 68%, respectively. The maximum removal was observed at a HRT of 5 days, a 30% medium filling ratio, and a COD of 10,000 mg/L. Increasing the filling ratio in the reactor increased the removal efficiencies of COD and BOD5 but increasing the concentration of the influent COD and decreasing HRT reduced the removal efficiency of the reactor. The initial BOD5/COD ratio was equal to 0.36, which increased by 46% when the medium filling ratio was elevated to 30%. The maximum biogas yield was 0.23 L/g of CODRemoved, and the specific methanogenic activity test verified the toxicity effect of the leachate on the gas-producer organisms. The results of scanning electronic microscopy and EDS showed that the zeolite medium immobilized the microorganisms and a biofilm was formed. Also the zeolite, as a well-known ion exchanger, decreased the concentrations of the major inhibitors (ammonia and heavy metals) and improved the reactor efficiency.

Production of biogas from poultry waste using the biomass of plants from Amaranthaceae family

The experimental results of kinetics of biogas formation for the organic waste utilization are presented for the case where combinations of technological and microbiological methods are used to enhance the process (ultrasonic pre-treatment and coenzyme with a new plant supplement). The plants from Amaranthaceae family are used as plant supplements. The influence of Amaranthus hypochondriacus and Amaranthus retroflexus L. on the process of methanogenesis for poultry wastes is analyzed. Based on the experimental results it is obtained that the maximum daily yield of biogas from substrate including the Amaranthus retroflexus L. and Amaranthus hypochondriacus are 310 ml and 252 ml respectively. For example the maximum daily yield of biogas from substrate without any plant supplements was 211 ml (“pure substrate”). Thus the biogas output rate from poultry waste using the biomass of plants from Amaranthaceae family is 47% higher than standard case. The total biogas yield using the plants supplement from Amaranthaceae family is higher than standard case.

Effect of solid–liquid separation enhanced by low-temperature hydrolysis in methanogenic phase on two-phase anaerobic sludge digestion system

In this study, a mesophilic two-phase anaerobic digestion system was used to treat waste activated sludge at the temperature of 35 ± 1 °C. The internal structure of the anaerobic sequencing batch reactor (methanogenic phase) has been improved by providing a solid–liquid separation plate, and a continuous-flow stirred tank reactor was employed as the acidogenic phase. The results of the study indicate that solid–liquid separation can be achieved in the methanogenic phase, and the low-temperature hydrolysis pretreatment can enhance solid–liquid separation capability. The separation of solids retention time and hydraulic retention time was also achieved in methanogenic phase, and the solids retention time was extended, which effectively improved the anaerobic digestion performance of the system. The organic concentration and total solids concentration in the methanogenic reactor were significantly different in height. The bottom of the reactor formed an area of high solids and low organic precipitation, while the upper part of the reactor formed a clear water area. The suspended solids concentration in the reactor clear water area was maintained at 359 ± 84 to 533 ± 93 mg/L, and the better solid–liquid separation effect was obtained inside the methanogenic phase. The maximum biogas yield was 258 ± 3 mL/g with the maximum volatile solids degradation rates of 59.43% in the system in Stage 3. Considering the efficiency of anaerobic digestion and the operating costs, the operating condition of Stage 4 (the designed hydraulic retention time was 10.67 d, the feed sludge was thermally pretreated, and its volume was 3 L) in this test is the optimal.

Impact of sludge recirculation ratios on the performance of anaerobic membrane bioreactor for wastewater treatment

The performance of a lab scale anaerobic membrane bioreactor (AnMBR) was evaluated for wastewater treatment. The efficacy of the system was determined at different operating conditions in terms of fluxes and recirculation ratios (R); 10.28 L/m2 h (R = 1, Phase I), 8.8 L/m2 h (R = 2, Phase II and R = 3, Phase III) and 6 L/m2 h (R = 2, Phase IV and R = 3, Phase V), respectively. In comparison with all the operating conditions tested, optimum efficacy of the system was found at flux of 6 L/m2 h and R of 3 in terms of highest COD removal (96.7%), and maximum biogas yield (0.44 L/g CODremoved). The MLSS and MLVSS concentrations under optimum phase were 6.23 and 4.83 g/L, respectively at OLR of 0.46 kg COD/m3 day. The system also exhibited significant reduction of foulants i.e. extracellular polymeric substances (EPS) and soluble microbial products (SMP) resulting in longer membrane runs in optimized phase.

Вплив низькочастотного електромагнітного поля на динаміку виходу біогазу

Вплив низькочастотного електромагнітного поля на динаміку виходу біогазу

Effect of bamboo hydrochar on anaerobic digestion of fish processing waste for biogas production

The effect of hydrothermal carbonization (HTC) temperature and bamboo hydrochar (BHC) addition on biogas production in anaerobic digestion of fish processing waste (FPW) was studied. HTC temperature (200–280 °C) had significant effects on methane yield and content, but the BHC had little effects. The maximum biogas yield observed with HTC at 200 °C and a BHC adding ratio of 1:2 (dry mass ratio of FPW to BHC) reached 292 L/kg volatile solids (VS), which were 64% higher than the control group with only FPW, with the maximum methane yield of 219 L/kg-VS and highest net methane energy yield of 3410 kJ/kg-VS. The obtained results can be used to design an efficient anaerobic digestion process for treating and effectively utilizing fish processing waste.

Biogas Production Using Slaughterhouse Wastewater Co-digested with Domestic Sludge

The paper investigates producing biogas using Co-digestion of slaughterhouse wastewater (SHW) with primary sludge (PS). Lab experiments were executed at mesophilic condition (35±2°C). Two experiments were performed; the first in a 2000 ml vessel and the second in 600 ml serum bottles, both to mimic batch bioreactors. Among others, acidity (pH), alkalinity (ALK), and volatile fatty acids (VFA) were measured before and after the digestion process. The daily biogas and methane production were also measured. The experiments showed that Co-digestion achieved maximum biogas yield at 499.8 Nml Biogas/g VS fed. The biogas yield for PS and SHW were 411.5 Nml biogas /g VS fed and 433.8 Nml biogas /g VS fed respectively. CH4 yield from the Co-digestion was the highest compared to digest SHW separately. This proves the occurrence of inhibition in methanogenesis activity. The VFA final concentration was higher than the initial concentration for digest SHW.

Effect of substrate ratio on biogas yield for anaerobic co-digestion of fruit vegetable waste &amp; sugarcane bagasse

Abstract The present study investigates the influence of mixture of waste activated sludge (WAS) as inoculum (I) to the ratio of sugarcane bagasse (SB) and fruit-vegetable waste (FVW) as substrate (S) on biogas yield during anaerobic co-digestion. The lignin content of SB is very high, limiting its application for anaerobic digestion; therefore, FVW was used at varied ratio as substrate. Batch studies were conducted under ambient conditions in 500 mL glass bottles for 30 d at five different mixtures ratio of SB: FVW (100:0, 70:30, 50:50, 30:70 and 0:100) at different organic loading rate (OLR) varied from 0.85–2.4 g VS L−1 d−1 and at fixed Inoculum/Substrate (I/S) ratio of 1. Results demonstrate that the maximum biogas yield of 2600 mL d − 1 was observed at substrate (SB: FVW) ratio of 30:70 with I/S ratio ≈ 1.0. An increment of 79, 58 and 56% in biogas generation at 70:30, 50:50 and 30:70 mixture ratio of SB: FVW was observed compared to the mono anaerobic digestion of SB. The experimental data was validated with modified Gompertz equation and first order model and fits well. The kinetic coefficients determined at optimum ratio of 70:30 from Gompertz model were well supported the experimental data.

Characteristics and Anaerobic Digestion of Fruits Wastes from Ubungo-Urafiki Market in Dar Es Salaam

Fruits are susceptible to mechanical damages during their transfer to the markets if they are not packed well in containers. Hence fruits wastes are generated in large quantities and because of their organic nature they decompose, which leads to environmental problems. The objective of this research was to quantify and characterize the fruits wastes generated from the Ubungo Urafiki Market in Ubungo Municipality and to establish the potential treatment of these wastes by anaerobic digestion. The data were collected in the field to establish the characteristics quantity of wastes generated in order to determine the potential degradation of fruit wastes using anaerobic digestion process. The market receives seven main kinds of fruits including pineapples, mangoes, water melons, avocados, oranges; paw paws and ripe bananas, which generate about 4.85 tons of fruit wastes per day. The leading fruits with higher percentage of wastes were water melons and oranges, which generated about 800 kg/day and 797 kg/day, respectively. The results of batch plants experiments showed that the reactor with fruit waste-cattle manure-wood ash mixtures had a maximum biogas yield of 34.2 liters while the reactor with fruit wastes-mixtures had lowest biogas yields of 0.1 liters. The reactor with fruit waste- wood ash mixtures had high volatile solid and total solid removal efficiencies of 8.0% and 14.3%, respectively. For the maximization of biogas production wood ash was recommended in order to raise the pH value of the fruit wastes. The batch reactor used in this study was limiting pH control and therefore activities of methanogenic bacteria. It is recommended to adopt a semi continuous or continuous reactor in order to limit excessive production of organic acids, which are responsible for inhibition of biogas production.

Biofuel Production and Phosphorus Recovery through an Integrated Treatment of Agro-Industrial Waste

The present study aimed to develop an integrated treatment of agro-industrial waste for biofuel (biogas and syngas) production and for phosphorus recovery. In the first step, an anaerobic digestion (AD) process was carried out on two different mixtures of raw agro-industrial residues. Specifically, a mixture of asparagus and tomato wastes (mixture-1) and a mixture of potatoes and kiwifruit residues (mixture-2) were investigated. The results proved that the properties of mixtures notably affect the evolution of the digestion process. Indeed, despite the lower organic load, the maximum biogas yield, of about 0.44 L/gCODremoved, was obtained for mixture-1. For mixture-2, the digestion process was hindered by the accumulation of acidity due to the lack of alkalinity in respect to the amount of volatile fatty acids. In the second step, the digestates from AD were utilized for syngas production using supercritical water gasification (SCWG) at 450 °C and 250 bar. Both the digestates were rapidly converted into syngas, which was mainly composed of H2, CO2, CH4, and CO. The maximum values of global gasification efficiency, equal to 56.5 g/kgCOD, and gas yield, equal to 1.8 mol/kgTS, were detected for mixture-2. The last step of the integrated treatment aimed to recover the phosphorus content, in the form of MgKPO4ˑ6H2O, from the residual liquid fraction of SCWG. The experimental results proved that at pH = 10 and Mg/P = 1 it is possible to obtain almost complete phosphorus removal. Moreover, by using the scanning electronic microscopy, it was demonstrated that the produced precipitate was effectively composed of magnesium potassium phosphate crystals.

Prospects for Production and Consumption of Second Generation Biofuels in Ukraine

Abstract The article analyzes the current state of production of second generation biofuels in the world and evaluates the possibility of launching such production in Ukraine. The work is topical due to the fact that liquid biofuels can replace a certain share of motor fuels consumed in Ukraine, thus contributing to the strengthening of the country’s energy independence. The purpose of the study is to assess feasibility of a project on the production of second generation bioethanol in Ukraine; the task is to carry out a preliminary feasibility study for such a project. The analysis of the study of pure co-substrate fermentation and as a supplement for cattle manure proves that the maximum biogas yield obtained using alcohol stillage in a ratio of 40-80% increased compared to fermentation of pure cattle manure. The use of pure bards compared to the bard and the slurry mixture increases the maximum yield of biogas. It was found that the biogas obtained from the use of alcohol stillage is a high con-sumption of biogas with the methane content of between 70 and 78%.

Synergistic effects of Fe salts and composite additives on anaerobic digestion of dairy manure

Anaerobic digestion (AD) can be accelerated through the addition of effective additives. A batch assay was conducted to determine an optimized organic composite additive (OOCA) consisting of urea, diammonium phosphate (DAP), and citric acid (CA). Fe salts (Fe2(SO4)3, Fe(NO3)3, FeCl3 and FeCl2) were then introduced to explore their synergistic effects with the OOCA during AD. The use of composite additives consisting of Fe salt and the OOCA increased biogas production (505–568 mL/g VS), shortened digestion periods (15–21 days), and promoted total COD removal rates (41.4–69.3%), compared with the control reactor without additives. The maximum biogas yield of 568 mL/g VS was obtained for the treatment receiving composite additive Fe(NO3)3@OOCA. Elemental analysis and fertility tests further demonstrated that the fertility of the digestate was improved considerably by using the composite additives. These results strongly indicated that improved AD performance could be attributed to the synergistic effects of trace element Fe and the OOCA. This finding is expected to have a positive effect on treatment process and open a new avenue for the use of composite Fe salt additives in future biomass energy production.

Comparative evaluation and kinetics of biogas yield from duckweed (&lt;i&gt;Lemna minor&lt;/i&gt;) co-digested with water hyacinth (&lt;i&gt;Eichhornia crassipes&lt;/i&gt;)

Anaerobic co-digestion of duckweed (DW) with water hyacinth (WH) at five DW: WH ratios (1:0, 7:3, 1:1, 3:7 and 0:1 w: w dry basis) was carried out with a view to comparing and evaluating the effect on biogas yield. Fixed quantity of cow dung slurry was added to each treatment as inoculum to seed the digesters before digestion for seventeen weeks in batch type digesters. Biodegradation and maximum biogas yield models based on first-order kinetics were fitted to the experimental biogas yields to describe the cumulative and predict maximum biogas yields, respectively from each treatment. The results indicated that DW was viable for biogas production and more prolific than WH. Co-digestion did not affect (p > 0.05) temperature and pH but affected (p ≤ 0.05) total bacterial count and biogas yield. The high R2 values obtained from the biodegradation model fit showed that the model described the experimental yields satisfactorily. Furthermore, the high R2 values and percentages of predicted maximum yield/observed maximum yield showed that the maximum biogas yield model predicted the maximum yields satisfactorily. The study concluded that co-digestion of DW and WH was best at ratio 7:3 while ratio 1:1 was the best described and predicted by the biodegradation and maximum biogas yield models.

Anaerobic digestion of blood serum water integrated in a valorization process of the bovine blood treatment

The present work aims to analyze the valorization of blood (Category 3 animal by-products). In this study, for the first time, blood serum water, obtained after a sterilization process and a solid/liquid separation unit, has been utilized as energy rich input material for anaerobic digestion. The performance of an up-flow anaerobic filter (UAF) for treating bovine blood serum water under mesophilic conditions was investigated. The reactor was loaded up to an organic loading rate of 2.5 kg m−3 d−1 of total COD, achieving total and soluble COD removal efficiencies of 90% and 92%, respectively. A maximum biogas yield of 0.56 m3 kg−1 of removed total COD was measured.According to the modified Stover-Kincannon kinetic model, maximum removal rate constant, Umax, and saturation value constant, KB, values were estimated as 18.8 g L−1 d−1 and 18.5 g L−1 d−1 for blood serum water, respectively. As the model gave high correlation coefficients (R2 = 97%), it could be used in both designing and predicting the behaviour of the UAF.

Biorefining of rice straw by sequential fermentation and anaerobic digestion for bioethanol and/or biomethane production: Comparison of structural properties and energy output

Three routes; namely R1 representing direct anaerobic digestion (AD), R2 representing enzymatic hydrolysis followed by fermentation, distillation, then AD, and R3 representing AD of fermentation broth without distillation; of alkali pretreated rice straw were investigated. Results showed that sequential fermentation and AD effectively enhanced fibers degradation with significant changes in the composition. Fermentation through R2 resulted in ethanol yield of 87.4 g kg−1 dry straw. Maximum biogas yields of 286.9, 233.3 and 372.4 L kg−1 VS were recorded by AD for R1, R2 and R3 after reaching the steady state at 36, 24 and 33 days, respectively. However, biogas produced through R3 showed the highest significant biomethane content (79.3%) which represented 15 and 8% higher than that of R1 and R2, respectively. Therefore, the highest bioenergy output and energy conversion efficiency of 10.58 GJ ton−1 and 75.6%, respectively, were obtained through R3 demonstrating the positive effect of fermentation prior to AD.

Nanoparticles augmentation on biogas yield from microalgal biomass anaerobic digestion

This study evaluates the influence of metal and metal-oxide nanoparticles (NPs) on biogas production from green microalgae Enteromorpha. The concentration of metallic NPs (Ni, Co) was 1 mg/L and oxides NPs (Fe3O4, MgO) was 10 mg/L. An anaerobic digestion was carried out batch-wise with working volume, operating temperature, mixing rate and hydraulic retention time as 500 ml, 37 °C, 150 rpm and 170 h, respectively. The measurements of chemical oxygen demand (COD), volatile fatty acids (VFAs), reducing sugar and biogas production were observed to monitor effectivity of nanoparticles. The results showed that NPs has moderate positive influence in biogas production until 60 h of retention time but significantly improve afterward. The maximum total biogas yield of 624 ml was achieved by Fe3O4 NPs whereas highest biohydrogen, 51.42% (v/v) was achieved by Ni NPs. The cumulative increase in biogas production for Fe3O4, Ni, Co and MgO NPs was 28%, 26%, 9% and 8%, respectively. A modified Gompertz and Logistic function model were used to determine kinetic constants of the reaction. The logistic model has the better predicting ability for microalgae anaerobic digestion.

The organic waste fractions ratio optimization in the anaerobic co-digestion process for the increase of biogas yield

Biogas obtained by anaerobic digestion process from various organic fractions of waste is increasingly used as a renewable energy sources for the generation of electricity and heat. The quantity of biogas produced by anaerobic digestion depends on many factors: types and characteristics of organic waste, elemental composition of waste, C/N ratio, pH value, inhibitors, retention time, content of nutrients, etc. In addition to the selection of parameters that influence the process of anaerobic digestion, biogas yield can also be influenced by choosing the optimal combination and ratio of organic fractions of waste. In this paper, an analysis of the influential parameters in the process of anaerobic digestion was per-formed on biogas yields and an overview of the essential characteristics of waste (elementary composition, C/N ratio, lignin content, etc.) for different fractions of organic waste (organic municipal waste, various types of waste of animal origin, as well as agricultural waste). In order to choose the optimal mixing ratio of different fractions of organic waste for maximum biogas yield, a mathematical model has been developed using the multi-criteria optimization method. The boundary conditions set for the multi-criteria optimization was the C/N ratio in the range of 20 to 30 and the minimum content of the lignin in the substrate. The application of the developed model was carried out on the case study of the city of Nis, and the optimal mix of different types of organic waste was determined, as well as the optimal amount of each waste fraction and biogas yield.