Accumulated Methane Production Research Articles

Metataxonomic characterization of the microbial present in the anaerobic digestion of turkey litter waste with the addition of two inocula: allochthonous and commercial.

Turkey litter waste is lignocellulosic waste that can be sustainably used as an energy source through anaerobic digestion (AD). The 16S ribosomal RNA technique helps to unravel microbial diversity and predominant metabolic pathways. The assays were performed in 600-mL-glass bottles with 400 mL volume, for 60 days at 37 °C. The study evaluated the physicochemical parameters, the composition of the microbiota, and the functional inference in AD of different concentrations of turkey litter (T) using two inocula: granular inoculum (S) and commercial inoculum (B). The highest accumulated methane production (633 mL CH4·L-1) was observed in the test containing 25.5 g VS·L-1 of turkey litter with the addition of the two inocula (T3BS). In tests without inoculum (T3) and with commercial inoculum (T3B), there was an accumulation of acids and consequent inhibition of methane production 239 mL CH4·L-1 and 389 mL CH4·L-1, respectively. Bacteroidota, Firmicutes, and Actinobacteria were the main phyla identified. The presence of archaea Methanobacterium, Methanocorpusculum, and Methanolinea highlighted the hydrogenotrophic metabolic pathway in T3BS. Functional prediction showed enzymes involved in three metabolic pathways in turkey litter biodigestion: acetotrophic, hydrogenotrophic, and methylotrophic methanogenesis. The predominant hydrogenotrophic pathway can be observed by analyzing the microbiota, archaea involved in this specific pathway, genes involved, and relative acid consumption for T3S and T3BS samples with higher methane production. Molecular tools help to understand the main groups of microorganisms and metabolic pathways involved in turkey litter AD, such as the use of different inocula, allowing the development of strategies for the sustainable disposal of turkey litter.

Impact of Iron Oxide on Anaerobic Digestion of Frass in Biogas and Methanogenic Archaeal Communities' Analysis.

With the increasing prominence of the global energy problem, socioeconomic activities have been seriously affected. Biofuels, as a renewable source of energy, are of great significance in promoting sustainable development. In this study, batch anaerobic digestion (AD) of frass (swine manure after bioconversion by black soldier fly larvae) and co-digestion with corn straw after the addition of iron oxide (Fe3O4) nanoparticles is investigated, as well as the start-up period without inoculation. The biochemical methane potential of pure frass was obtained using blank 1 group and after the addition of various sizes of Fe3O4 nanoparticles for 30 days period, and similarly, the digestion of frass with straw (blank 2) and after the addition of various sizes of Fe3O4 nanoparticles for 61 days period. The results showed that the average gas production was 209.43 mL/gVS, 197.68 mL/gVS, 151.85 mL/gVS, and 238.15 mL/gVS for the blank, ~176 nm, ~164 nm, and ~184 nm, respectively. The average gas production of frass with straw (blank 2) was 261.64 mL/gVS, 259.62 mL/gVS, 241.51 mL/gVS, and 285.98 mL/gVS for blank 2, ~176 nm, ~164 nm, and ~184 nm, respectively. Meanwhile, the accumulated methane production of the ~184 nm group was 2312.98 mL and 10,952.96 mL, respectively, which significantly increased the biogas production compared to the other groups. The methanogenic results of the frass (30 days) indicated that Methanocorpusculum, Methanosarcina, and Methanomassiliicoccus are the important methanogenic species in the AD reactor, while the microbial diversity of the ~184 nm group was optimal, which may be the reason for the high gas production of ~184 nm.

Acyl homoserine lactone-based regulation strategy for improved methane production in anaerobic digestion of agricultural wastes

The acyl homoserine lactone (AHL)-based regulation strategy presents a considerable potential in improving anaerobic digestion (AD) efficiency of complex substrates. However, the reinforcement mechanisms are still unclear. In this study, the effects of different AHL types (C4-HSL, C7-HSL, C12-HSL) and different adding times (0 d, 5 d, 15 d) on AD performance of agricultural wastes (corn straw and cattle manure) were investigated. The results indicated that all types of AHLs exerted positive effects on AD, and the adding time rather than the AHL type was the key factor affecting AD processes. The C12-5d group obtained the highest accumulated methane production (310.7 ± 2.56 mL/g VS), which increased by 47.71% than that of the Control group. The exogenous AHLs facilitated the hydrolysis and acidification of complex substrates and the utilization of released low-molecular-weight organic acids in AD systems. Furthermore, the role of methanogenic archaea was upregulated and the dominance of bacteria was relatively weakened in AD systems, which favored the establishment of their balanced and symbiotic metabolic relationship. The enriched Methanobacterium strengthened the hydrogenotrophic methanogenesis pathway. This study provides new insights into the regulation strategy of AD for agricultural waste treatment based on AHL addition.

Optimization of methane production from co-digestion of citrus agro-industrial waste in a two-stage system: Investigation of the effects of organic matter concentration and alkalinization

The essential oils in citrus waste poses challenges for the anaerobic digestion application to energy recovery from these wastes due to the potential to inhibit the bioprocess. The two-stage system is a practical alternative to overcome these limitations of anaerobic co-digestion of citrus peel waste and wastewater. This study proposes to overcome drawbacks associated with the use of these substrates in anaerobic digestion by separating the phases, performing parameters optimization of the methanogenic stage. To obtain optimized conditions for the methanogenic stage, the Rotational Central Composite Design (RCCD) and Response Surface Methodology (RSM) were applied, evaluating the effects of diluting the Fermentation Reactor Content (FRC) of the first stage (35.7%–100%) and alkalinization (up to 0.60 g sodium bicarbonate.gCOD−1), in methane production and organic matter removal. Values from 2100.4 to 6320.6 mLCH4.L−1 were obtained in the experimental design assays, with no inhibition identified by the high substrate concentration, nor by the limonene content (1.5–5.0 mg.L−1). Lower dilution of the fermentation reactor content (90%–100%) resulted in higher accumulated methane production, while the variation in the alkalinization did not imply significant effects on this response. The optimized condition for maximum production potential was obtained with 99.3% of fermentation reactor content and 0.58 gNaCHO3.gCOD−1, reaching a production of 6549.7 mLCH4.L−1, with organic matter removal (rCOD) of 87.1%, and 58.6% of reduction in solid waste content. For this condition, acetogenic metabolism predominance was observed, in the conversion of butyric acid and propionic acid into acetic acid. In the analysis of the microbial community of the optimized condition assay, a high relative abundance of hydrolytic and acidogenic bacteria (AUTHM297, Lachnospiraceae, and Hungateiclostridiaceae) was observed, as well as methanogenic archaea related to acetoclastic, hydrogenotrophic, and methylotrophic methanogenesis (Methanoregula, Methanolinea, Methanomassiliicoccus, Candidatus Methanomethylicus, and Methanofolis).

Effect of inoculum composition on the microbial community involved in the anaerobic digestion of sugarcane bagasse

ABSTRACT In anaerobic digestion (AD), the choice of inoculum type seems to be relevant for methane production for complex substrates, such as lignocellulosic material. Previous work demonstrated that the addition of fresh manure and ruminal fluid to anaerobic sludge improved methane productivity and kinetics of AD of crude sugarcane bagasse (CSB). Considering that the improvement of methane production could be a result of a more adapted microbial community, the present study performed the Next Generation Sequencing analysis to identify changes in the microbiome of anaerobic sludge inoculum, resulting from fresh manure and ruminal fluid addition. In comparison with AD performed only with anaerobic sludge inoculum (50:50, U), accumulated methane production was 15% higher with anaerobic sludge plus ruminal fluid inoculum (50:50, UR) and even higher (68%) with anaerobic sludge with fresh bovine manure inoculum (50:50, UFM), reaching the value of 143 NmLCH4.gVS −1. Clostridium species were highly abundant in all inocula, playing an important role during the hydrolysis and fermentation of CSB, and detoxifying potential inhibitors. Microbial composition also revealed the occurrence of Pseudomonas and Anaerobaculum at UFM inoculum that seem to have contributed to the higher methane production rate, mainly due to their hydrolytic and fermentative ability on lignocellulosic substrates. On the other hand, the presence of Alcaligenes might have had a negative effect on methane production due to their ability to perform methane oxidation.

ANAEROBIC CO-DIGESTION OF SUGARCANE VINASSE AND ELEPHANT GRASS JUICE FOR BIOMETHAN PRODUCTION

In the present study, biogas production was investigated by co-digesting elephant grass juice (EGJ) and sugarcane vinasse using batch reactor. Some factors that influence biomethane production were observed, including initial pH, inoculum concentration and proportions of each substrate. Two tests were carried out. In Experiment I, the following proportions (%v/v sugarcane vinasse/elephant grass juice) were tested: A - 25/75, B - 50/50, C - 75/25, D - 100/0, E - 0/100. In Experiment II, the effect of adding alkalizer to the condition that showed the highest methane production (in Experiment I) was also evaluated. In the Experiment I, the highest accumulated production was observed for the proportion 1:1 corresponding to 50% of EGJ and 50% of vinasse (370.94 mLCH4/gVS). Experiment II showed the higher values of accumulated methane production of 1,364.1 mLCH4/gVS. Regarding addition of alkalizing, a maximum production of 836.18 mLCH4/gVS was obtained in the experimental condition with 50% EGJ and 50% vinasse, but with the lowest addition of alkalizer tested (0.05 g HCO3/gCOD). In general, the use of elephant grass caused the acidification of the reactors and was unfavorable for biogas production.

Multicomponent nanoparticles as means to improve anaerobic digestion performance

Sufficient quantity of trace metals is essential for a well performing anaerobic digestion (AD) process. Among the essential trace elements in active sites of multiple important enzymes for AD are iron and nickel ions. In the present study, iron and nickel in the form of Fe2O3 and NiO were coated on TiO2 nanoparticles to be used in batch and continuous operation mode. The effect of TiO2, Fe2O3–TiO2, and NiO–TiO2 nanoparticles on each step of AD process was assessed utilizing simple substrates (i.e. cellulose, glucose, acetic acid, and mixture of H2–CO2) as well as complex ones (i.e. municipal biopulp). The hydrolysis rate of cellulose substrate increased with higher dosages of the coated TiO2 with both metals. For instance, the hydrolysis rate was increased up to 54% at Fe2O3–TiO2 and at a concentration of 23.5 mg/L for NiO–TiO2 it was increased up to 58%, while higher dosage suppressed the hydrolytic activity. Experimental results revealed that low dosages of NiO–TiO2 increased the accumulated methane production up to 24% probably by increasing the enzymatic activity of acetoclastic methanogenesis. NiO–TiO2 showed positive effect on batch and continuous AD of biopulp and improved methane yield up to 8%.

Effect of proton pump inhibitor on microbial community, function, and kinetics in anaerobic digestion with ammonia stress

The proton pump is a convincing mechanism for ammonia inhibition in anaerobic digestion, which explained how the ammonia accumulated intercellularly due to diffusion of free ammonia. Proton pump inhibitor (PPI) was dosed for mitigating the accumulation in anaerobic digestion with ammonia stress, with respect to kinetics. Results show PPI inhibited β-oxidation of fatty acids by targeting ATPase in anaerobic digestion with ammonia stress. Alternatively, PPI stimulated syntrophic acetate oxidization. Random forest located key genera as syntrophic consortia. Methane increased 18.72 ± 7.39% with 20 mg/L PPI at the first peak, consistent with microbial results. The deterministic Gompertz kinetics and stochastic Gaussian processes contributed 97.63 ± 8.93% and 2.37 ± 8.93% in accumulated methane production, respectively. Thus, the use of PPI for anaerobic digestion allowed mitigate ammonia inhibition based on the mechanism of proton pump, facilitate intercellularly ammonia accumulation, stimulate syntrophic consortia, and eliminate uncertainty of process failure, which resulted in efficient methane production under ammonia stress.

Identification of the Methanogenesis Inhibition Mechanism Using Comparative Analysis of Mathematical Models.

The application of cationic polymers to enhance membrane fluxes in anaerobic membrane bioreactors has been proposed by several authors. However, literature shows contradictory results on the influence of those chemicals on the biological activity. In this research, we studied the effect of a cationic polymer on the production of methane from acetate by acetoclastic methanogens. We assessed the effect of polymer concentration on the accumulated methane production (AMP) and the specific methanogenic activity (SMA) in batch tests. Batch tests results showed lower SMA values at higher concentrations of polymer and no effect on the final AMP. Different inhibition models were calibrated and compared to find the best fit and to hypothesize the prevailing inhibition mechanisms. The assessed inhibition models were: competitive (M1a), non-competitive (M2a), un-competitive (M3a), biocide-linear (M4a), and biocide-exponential (M5a). The parameters in the model related to the polymer characteristics were adjusted to fit the experimental data. M2a and M3a were the only models that fitted both experimental SMA and AMP. Although M1a and M4a adequately fitted the experimental SMA, M1a simulations slightly deviated from the experimental AMP, and M4a considerably underpredicted the AMP at concentrations of polymer above 0.23 gCOD L−1. M5a did not adequately fit either experimental SMA and AMP results. We compared models a (M1a to M5a), which consider the inhibition by the concentration of polymer in the bulk liquid, with models b (M1b to M5b) considering the inhibition being caused by the total concentration of polymer in the reactor. Results showed that the difference between a and b models' simulations were negligible for all kinetic models considered (M1, M2, M3, M4, and M5). Therefore, the models that better predicted the experimental data were the non-competitive (M2a and M2b) and un-competitive (M3a and M3b) inhibition models, which are biostatic inhibition models. Consequently, the decreased methanogenic activity caused by polymer additions is presumably a reversible process

Mesophilic Anaerobic Co-digestion of Olive-Mill Waste With Cattle Manure: Effects of Mixture Ratio

The co-digestion of agri-food by-products and livestock manure is a feasible alternative for waste management and the recovery of biogas provides an option to generate renewable energy. A series of batch experiments were carried out in order to investigate the mesophilic anaerobic co-digestion of two-phase olive-mill waste (2POMW) and cattle manure (CM) in different mixtures (2POMW:CM = 50:50; 60:40; 75:25; 85:15). In addition, the biodegradability of the co-substrates was studied in order to analyze the performance of the co-digestion process. The results obtained in this study indicate that 2POMW has a low biodegradability since a high soluble organic matter concentration and a low accumulated methane production were obtained at the end of the corresponding biodegradability test. However, CM is more easily biodegradable in mesophilic anaerobic conditions. The co-digestion of both wastes produced an enhancement of the hydrolytic-acidogenic phase, increasing the organic matter potentially bioavailable as volatile fatty acids (VFAs) and the biogas productivity, as a consequence of the subsequent degradation of VFAs by methanogens. However, an accumulation of VFA, principally propionic acid, was observed in the reactors with higher proportions of 2POMW. The volatile solids (VS) removal increased with the 2POMW percentage of the mixture up to 75% fresh weight. The increase of 2POMW above 75% led to a decrease in total VS removal. Moreover, a decrease in methane production was observed for the 85:15 mixture, as a consequence of the high concentration of propionic acid, which is a known inhibitor of methanogenesis. The maximum cumulative methane production and methane yield were achieved in the 75:25 mixture with values of 18.70 L and 112.40 LCH4/kgVSadded, respectively. Compared with 2POMW, the co-digestion produced an increase of 264-319% in the volume of accumulated methane (L), 293-351% in the methane yield (LCH4/kgVSadded) and 312-342% based on the VS consumed (LCH4/kgVSremoved). These results suggest that the mixture of these agro-industrial by-products could be effective to enhance biogas production and organic matter removal from 2POMW.

Anaerobic co-digestion of industrial landfill leachate and glycerin: methanogenic potential, organic matter removal and process optimization

ABSTRACT The objective of this study was to evaluate the performance of the anaerobic co-digestion of different concentrations of industrial landfill leachate associated with crude residual glycerin, in relation to the methanogenic potential, COD removal, accumulated methane production, the effects of the factors (food/microorganism ratio and percentage of glycerin added to the leachate) and their interactions on kinetic parameters of methane production (CH4) using the modified Gompertz model. Co-digestion tests were carried out in bench scale (400 mL of useful volume) under batch mode at 30 ± 1°C during 30-day incubation of anaerobic sewage sludge as inoculum. The parameters glycerin addition to the leachate (v/v) (0%, 1.5%, 5%, 8.5% and 10%) and F/M ratio (0.3, 0.5, 1, 1.5 and 1.7) were investigated using Central Composite Rotational Design method (CCRD). The results indicated significant effect to the response variables: methanogenic potential, COD removal, accumulated production of CH4 and maximum estimated production of CH4, considering a confidence interval of 95% (p < .05). The ideal mixture of 95.13% of leachate with 4.87% of raw glycerin was obtained by desirability test to F/M of 1.61 gCOD of substrate per gVSS (volatile suspended solids) of sludge. Methanogenic potential was 0.19 LNCH4 gTVSrem −1, and the average removal of COD was 92%, resulting in accumulated production and maximum estimated production of CH4 of 74 and 80 mL, respectively. It was noted that the process of co-digestion of the industrial landfill leachate with the crude residual glycerin is promising, due to is potential of complementing and balancing organic materials, nutrients and other components that influence the biological process. Abbreviations: AN: ammoniacal nitrogen; BMP: biochemical methane potential; CCRD: central composite rotational design; COD: chemical oxygen demand; F/M ratio: food/microorganism ratio; FSS: fixed suspended solids; NTP: normal temperature and pressure; TSS: total suspended solids; TA: total alkalinity; TFS: total fixed solids; TKN: total Kjeldahl nitrogen; TP: total phosphorus; TS: total solids; TVA: total volatile acids; TVS: total volatile solids; VSS: volatile suspended solids; WWTP: wastewater treatment plant

Potential benefits of near critical and supercritical pre-treatment of lignocellulosic biomass towards anaerobic digestion.

Vegetable crop residues, such as sugarcane bagasse (SCB), despite their limited biodegradability, are potential materials for anaerobic processes because of their low cost, high availability, and sugar content. The difficulty of biodegrading this type of material is primarily related to its chemical composition and to the complex interactions between its compounds (cellulose, hemicelluloses, and lignin). Thus, the following supercritical and near critical carbon dioxide (CO2) pre-treatments were evaluated with and without the addition of sodium hydroxide (NaOH): (i) 40°C/70 kgf·cm-2; (ii) 60°C/200 kgf·cm-2; and (iii) 80°C/200 kgf·cm-2, aiming to enhance the anaerobic biodegradability of SCB. The methanogenic production of SCB increased in all cases in which the material was pre-treated, except the case in which NaOH was used together with a high temperature. The condition using CO2 at 60°C/200 kgf·cm-2 was highlighted with a lignin removal of 8.07% and an accumulated methane production of 0.6498 ± 0.014 LN (273.15K, 1.01325 × 105 Pa), 23.4% higher than the value obtained with the untreated material. This condition also showed the highest net energy at the energy balance that was calculated for comparison with the tested conditions. The results showed that pre-treatments with near critical and supercritical fluids have the potential to reduce structural obstacles of lignocellulosic materials and to enhance their anaerobic biodegradability.

Ampelodesmos mauritanicus pyrolysis biochar in anaerobic digestion process: Evaluation of the biogas yield

The integration of different conversion technologies can strongly contribute to the biomass potential exploitation. To this aim, the use of intermediate pyrolysis biochar is analyzed in this paper as an alternative co-substrate in anaerobic digestion. The specie Ampelodesmos mauritanicus has been specifically chosen in this case for its capacity to tolerate, accumulate and, in some cases, degrade organic and inorganic pollutants. The biochar, produced under intermediate pyrolysis conditions at 450 °C, 500 °C and 550 °C, has been here considered for a biomethane potential assessment. The intermediate pyrolysis process improves the herbaceous bioavailability and promotes the microbial activity by reducing the digestion lag phase. Three reactors, namely B450, B500 and B550, have been considered in this study. Acclimatized cow manure from food wastes digestion has been used as inoculum with 5 g of biochar. The reactors have been continuously monitored for 15 days keeping the temperature fixed at 37 °C. Excluding the inoculum contribution, an accumulated methane production of 465–540.4 ml CH4/g-VS has been measured with an LHV evaluated in the range 25.8–26.9 MJ/kg. The modified Gompertz equation has been then used to describe the influence of biochar production temperature on methane conversion. A lag phase of 1.8, 2.2 and 3.8 days respectively for B450, B500 and B550, has been estimated showing an inverse proportionality to the biochar production temperature. The biomass to biogas energy conversion analysis reveals a reduction in the efficiency with the biochar production temperature increase. This fact is attributed to the steep reduction in volatile solids occurring by increasing the pyrolysis process severity. As a whole, the paper present a novel approach to possibly combine phytoremediation and production of renewable energy by using Ampelodesmos mauritanicus.

Impact of Nano Zero-Valent Iron (NZVI) on Methanogenic Activity, Physiological Traits, and Microbial Community Structure in Anaerobic Digestion

Effects of short-term nano zero-valent iron (NZVI) and zero-valent iron (ZVI) exposure on methanogenic activity of anaerobic sludge, physiological traits, composition of phospholipid fatty acids (PLFA), and microbial community structure were investigated. Results show that accumulated methane production decreased with an increase of NZVI concentration; yet, methane production only changed slightly with the same concentration of ZVI. In the NZVI (100-5000 mg·L-1) sets, dissolved iron (DFe) concentrations were 1.6-7.4 times that of the control value at 5 d, whereas DFe was only slightly above the control in the ZVI set (5000 mg·L-1). The concentration of extracellular polymeric substances and cell viability decreased to 21.1% and 79.7%, respectively, of the control in the 5000 mg·L-1 NZVI treatments. Coenzyme F420 and coenzyme M decreased to 40.2% and 61.1%, respectively, of the control in the 5000 mg·L-1 NZVI treatments, which were significantly increased to 1.3 times that of the control value in the 100 mg·L-1 NZVI and 5000 mg·L-1 ZVI treatments. The order of unsaturation and branch PLFA content was ZVI-5000 (21.18%) > control (19.37%) > NZVI-1000 (16.69%) > NZVI-5000 (15.94%) > NZVI-100 (12.08%). High NZVI concentration (5000 mg·L-1) resulted in an increase of DFe and a decrease of cell membrane fluidity and key coenzyme activity of methanogenesis, which led to the inhibition of methane production. Principle component analysis and redundancy analysis indicated that differences in the microbial community existed among these treatments and that Nakamurella, Bacillus, Trichococcus, and Petrimonas showed tolerance to NZVI.

Mesophilic and Thermophilic Anaerobic Co-Digestion of Food Waste and Straw

The anaerobic co-digestion of food waste and straw is more efficient in avoiding the accumulation of volatile fatty acids and promoting the degradation of lignocellulose in comparison with their individual digestions. The co-digestion of food waste and straw was investigated under mesophilic(35℃) and thermophilic(55℃) condition, respectively. The results indicated that when feeding volatile solid concentration was 3 kg·m-3, the accumulated methane production yield of the mesophilic reactor reached the peak of 272.0 mL·g-1 at a food waste-to-straw ratio of 9:1, while it reached the peak of 402.3 mL·g-1 at a food waste-to-straw ratio of 5:5 for thermophilic reactor. These amounts were significantly higher than those of food waste digestion alone(218.6 mL·g-1 for mesophilic reactor and 322.0 mL·g-1 for thermophilic reactor). Co-digestion promoted the rate of carbon transfer to methane, and further, the rate of the thermophilic reactor was higher than that of the mesophilic reactor. Degradation rate for lignocellulose of thermophilic reactor was 34.7%-45.8%, higher than that of mesophilic reactor, 12.6%-42.2%. It was confirmed by 16S rRNA gene sequences of bacteria and archaea, ITS sequences of fungi based on high-throughput sequencing techniques, which showed the amounts of lignocellulose degrading bacteria and actinomycetes in the thermophilic reactor were both higher than those in the mesophilic reactor.

Anaerobic Digestion of Liquid Fraction Coffee Grounds at Laboratory Scale: Evaluation of the Biogas Yield

Abstract Coffee is one of the most popular beverage in the world. The International Coffee Organization (ICO) in the last 4 years registered an average world consumption higher than 8x106 tons. Over 50% of this mass is discarded after use, becoming a significant waste source known as spent coffee grounds (SCG). SCG usage as a raw material for biogas production emerges with great potential. It is a biomass that does not need pre-treatment, rich in lipids and can be easily separated in bars and restaurants. Lipid concentrations in SCG can reach more than 25% of its dry weight and have a good biogas production behavior, producing over 1 liter of CH4/g-VS. In this paper, the analysis of biogas yield potential of SCG recovery is presented using a laboratory scale batch anaerobic reactor, fed with the liquid fraction obtained by spent coffee filtration. Airtight glass reactors have been realized to guarantee the anaerobic digestion conditions. The reactors, divided into two groups A and B, fed with SGC and cow manure respectively, have been monitored for 22 days at a temperature of 37 °C. The accumulated methane production for a total of 1444 ml of biogas for group A and 1047 ml of methane for Group B was observed. Group A had an output of 296 ml.CH4/g-VS and group B 312 ml.CH4/g-VS. Group A presented fractions of 53.7% of CH4 and 37.80% of CO2. The B group showed 36.7% of CH4 and 27.9% of CO2. In the Group A, the methane production from SGC, reached concentration higher than 50%. This result shows the SCG liquid fraction energy recovery potential using an anaerobic digestion process.

The effect of harvest time, dry matter content and mechanical pretreatments on anaerobic digestion and enzymatic hydrolysis of miscanthus

Miscanthus x giganteus was harvested as both green and mature biomass and the dry matter content of the driest harvest was artificially decreased by adding water in two subsamples, giving a total of five dry matter contents. All five biomass types were mechanically pretreated by roller-milling, extrusion or grinding and accumulated methane production and enzymatically-accessible sugars were measured. Accumulated methane production was studied using sigmoid curves that allowed comparison among the treatments of the rate of the methane production and ultimate methane yield.The green biomass gave the highest methane yield and highest levels of enzymatically-accessible cellulose. The driest biomass gave the best effect from extrusion but with the highest energy consumption, whereas roller-milling was most efficient on wet biomass. The addition of water to the last harvest improved the effect of roller-milling and equalled extrusion of the samples in efficiency.

Effect of Methanogenesis of Residue from Thermal Pre-treatment Sludge by Anaerobic Fermentative Hydrogen Production

The municipal sludge of Wastewater treatment plants generate a mass of municipal sludge is becoming an extremely environment issue. Effective utilization of the sludge to generate benefits concern many scholars. This research worked systematically to study the condition of gas production of sludge by thermal pre-treatment and compared a large differance among the maximum cumulative methane production in the sludge of high temperature thermal treatment. The inoculum via 75°C thermal pretreatment for 10min mixed sludge substrates by different temperature pre-treatment for 30min. The optimum methane production was obtained from 160°C, and the 120°C was worse in the methane produciton. The max accumulated hydrogen and methane production were 3.57mL and 235.97mL respectively of 160°C; the max accumulated methane production was 193.24mL of 120°C. Compared the metabolic process of anaerobic fermentation of methane, the degradation of organic matter in the sludge substrate by 160°C for heat treatment was better than that of 120°C.

Iron-Oxide-Promoted Anaerobic Process of the Aquatic Plant of Curly Leaf Pondweed

The technique of producing methane with lignocellulosic biomass as feedstock has been used worldwide. In the current study, three types of iron oxides, including goethite, hematite, and magnetite, were used to improve methane production from the aquatic plant curly leaf pondweed. In comparison to the control, hydrolysis efficiency of the aquatic plant in reactors with iron oxides was increased from 31.4 ± 0.1% to a higher level, which varied between 49.1 ± 4.6 and 74.1 ± 4.1%, and the accumulated methane production and formation rates were increased significantly. For all reactors with iron oxides, the accumulated methane production increased with increasing dosages. When the dosages of iron oxide were 0.5 and 1.0% (calculated on the basis of the iron contents), reactors with magnetite showed higher promotion effects. However, when the dosage was increased further to 2.0%, no significant difference was found between the reactors with iron oxides.

Codigestão de água residual de suinocultura e vinhaça sob diferentes condições térmicas

The current research aimed to perform the process of anaerobic co-digestion of vinasse, originated from the production of hydrous ethanol, and from the residues of swine raising processes using tubular biodigesters under different temperature conditions, evaluating the removal efficiency of solids, COD removal and biogas production. For this, it was used two reactors, one of which was thermally controlled while the other remained at room temperature. Three hydraulic retention times were determined with 13 days each, performing daily analysis on the reactor effluent. The TVS removal efficiencies were 29.9% for the thermally controlled reactor and 25.4% for the room temperature reactor, for the COD removal efficiency, it was verified mean values of 69.0% in the Reactor 1 and 68.4% in the Reactor 2. The temperature control caused accumulated methane production to the Reactor 1,330% higher than the reactor kept in environmental conditions.