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1.
Anaerobic co-digestion of cow manure (CM) and waste milk (WM), produced by sick cows during treatment with antibiotics, was evaluated in two-stage process under thermophilic condition (55 °C) to determine the effect of WM addition on hydrogen (H2) and methane (CH4) production potentials, volatile solids (VS) removal, and energy recovery. Six CM to WM VS ratios of 100:0, 90:10, 70:30, 50:50, 30:70, and 10:90 were examined using 1-L batch digesters. The WM VS ratio of 30 % was found to be the minimum limit for significant increases in specific H2 and CH4 yields, and VS removal as compared to digestion of manure alone (P < 0.05). The highest specific H2 and CH4 yields, VS removal and energy yield were 38.2 mL/g VS, 627.6 mL/g VS, 78.4 % and 25,459.8 kJ/kg VS, respectively, in CM:WM 30:70. Lag phases to H2 and CH4 productions were observed in CM–WM mixtures, increased with increasing the amount of WM in the feedstock and were greater than 72 h in CM:WM 50:50 and 30:70. The digestion system failed in CM:WM 10:90. The results suggest that CM:WM 30:70 was optimum, however, due to limited amount of WM usually generated and long lag phase at this ratio which may make the process uneconomical, CM:WM 70:30 is recommended in practice.  相似文献   

2.
Solid state anaerobic digestion, as a safe and environment-friendly technology to dispose municipal solid wastes, can produce methane and reduce the volume of wastes. In order to raise the digestion efficiency, this study investigated the pretreatment of yard waste by thermal or chemical method to break down the complex lignocellulosic structure. The composition and structure of pretreated yard waste were analyzed and characterized. The results showed that the pretreatment decreased the content of cellulose and hemicelluloses in yard waste and in turn improved the hydrolysis and methanogenic processes. The thermal pretreatment sample (P1) had the highest methane yield, by increasing 88 % in comparison with digesting the raw material. The maximum biogas production reached 253 mL/g volatile solids (VS). The largest substrate mass reduction was obtained by the alkaline pretreatment (P5). The VS of the alkaline-treated sample decreased about 60 % in comparison with the raw material.  相似文献   

3.
Anaerobic digestion is a consolidated bioprocess which can be further enhanced by incorporating an upstream pretreatment unit. The olive oil production produces a large amount of solid waste which needs to be properly managed and disposed. Three different pretreatment techniques were evaluated in regard to their impact on the anaerobic biodegradability: manual milling of olive pomace (OP), enzyme maceration, direct enzyme addition, and thermal hydrolysis of two-phase olive mill waste. The Gompertz equation was used to obtain parameters for comparison purposes. A substrate/inoculum ratio 0.5 was found to be the best to be used in anaerobic batch test with olive pomace as substrate. Mechanical pretreatment of OP by milling increases the methane production rate while keeping the maximum methane yield. The enzymatic pretreatment showed different results depending on the chosen pretreatment strategies. After the enzymatic maceration pretreatment, a methane production of 274 ml CH4 g VS added ?1 was achieved, which represents an improvement of 32 and 71 % compared to the blank and control, respectively. The direct enzyme addition pretreatment showed no improvement in both the rate and the maximum methane production. Steam explosion showed no improvement on the anaerobic degradability of two-phase olive mill waste; however, thermal hydrolysis with no rapid depressurization enhanced notoriously both the maximum rate (50 %) and methane yield (70 %).  相似文献   

4.
Hydrogen and methane production from desugared molasses by a two‐stage thermophilic anaerobic process was investigated in a series of two up‐flow anaerobic sludge blanket (UASB) reactors. The first reactor that was dominated with hydrogen‐producing bacteria of Thermoanaerobacterium thermosaccharolyticum and Thermoanaerobacterium aciditolerans could generate a high hydrogen production rate of 5600 mL H2/day/L, corresponding to a yield of 132 mL H2/g volatile solid (VS). The effluent from the hydrogen reactor was further converted to methane in the second reactor with the optimal production rate of 3380 mL CH4/day/L, corresponding to a yield of 239 mL CH4/g VS. Aceticlastic Methanosarcina mazei was the dominant methanogen in the methanogenesis stage. This work demonstrates that biohydrogen production can be very efficiently coupled with a subsequent step of methane production using desugared molasses. Furthermore, the mixed gas with a volumetric content of 16.5% H2, 38.7% CO2, and 44.8% CH4, containing approximately 15% energy by hydrogen is viable to be bio‐hythane.  相似文献   

5.
Agriculture straw is considered a renewable resource that has the potential to contribute greatly to bioenergy supplies. Chemical pretreatment prior to anaerobic digestion can increase the anaerobic digestibility of agriculture straw. The present study investigated the effects of seven chemical pretreatments on the composition and methane yield of corn straw to assess their effectiveness of digestibility. Four acid reagents (H2SO4, HCl, H2O2, and CH3COOH) at concentrations of 1%, 2%, 3%, and 4% (w/w) and three alkaline reagents (NaOH, Ca(OH)2, and NH3·H2O) at concentrations of 4%, 6%, 8%, and 10% (w/w) were used for the pretreatments. All pretreatments were effective in the biodegradation of the lignocellulosic straw structure. The straw, pretreated with 3% H2O2 and 8% Ca(OH)2, acquired the highest methane yield of 216.7 and 206.6 mL CH4 g VS −1 in the acid and alkaline pretreatments, which are 115.4% and 105.3% greater than the untreated straw. H2O2 and Ca(OH)2 can be considered as the most favorable pretreatment methods for improving the methane yield of straw because of their effectiveness and low cost.  相似文献   

6.
Mesophilic and thermophilic anaerobic digesters (MD and TD, respectively) utilizing Gracilaria and marine sediment as the substrate and inoculum, respectively, were compared by analyzing their performances and microbial community changes. During three successive transfers, the average cumulative methane yields in the MD and TD were 222.6 ± 17.3 mL CH4/g volatile solids (VS) and 246.1 ± 11 mL CH4/g VS, respectively. The higher hydrolysis rate and acidogenesis in the TD resulted in a several fold greater accumulation of volatile fatty acids (acetate, propionate, and butyrate) followed by a larger pH drop with a prolonged recovery than in the MD. However, the operational stability between both digesters remained comparable. Pyrosequencing analyses revealed that the MD had more complex microbial diversity indices and microbial community changes than the TD. Interestingly, Methanomassiliicoccales, the seventh methanogen order was the predominant archaeal order in the MD along with bacterial orders of Clostridiales, Bacteriodales, and Synergistales. Meanwhile, Coprothermobacter and Methanobacteriales dominated the bacterial and archaeal community in the TD, respectively. Although the methane yield is comparable, both MD and TD show a different profile of pH, VFA and the microbial communities.  相似文献   

7.
《Biomass》1990,21(1):43-54
The effect on anaerobic digestion of reducing the lignin content of vine shoots to 1% (w/w), by treatment with sodium chlorite in an acid medium at 80°C, is reported. The yields of methane obtained were 240 ml of CH4 g−1 of VS (volatile solids) fed for untreated vine shoots, and 370 ml of CH4 g−1 of VS fed for treated vine shoots. A mathematical model was used to calculate the kinetic parameters H and μ, and the increased biodegradability of the substrate in which lignin had been removed was confirmed. A study of the mass balances of the process under optimum conditions (temperature = 35°C; loading rate of 1 g litre−1 digester day−1) enabled the percentage of degraded cellulose to be calculated (35·5% for untreated vine shoots, 81·5% for the treated vine shoots), as were the volumes of biogas and methane produced per gram of VS introduced (VS1) and degraded. The blocking effect of lignin on the methanization process was confirmed.  相似文献   

8.
With increasing concerns of microalgal-biodiesel, algal residues after lipid extraction are raising great attention for energy production. A batch test of 15 days under mesophilic condition was conducted to evaluate the effects of inoculum to substrate ratios (ISRs) on the methane production by anaerobic digestion of Chlorella sp. residue. The stability and progress of the reaction from algal residue to methane were monitored by measuring the pH, volatile fatty acids (VFAs), total ammoniacal nitrogen (TAN), methane volume on a daily basis. The results indicated that the values obtained were 26.6, 191.6, 195.6 and 210.6 ml CH4/g volatile solid (VS) for ISRs of 1:2, 1:1, 2:1 and 3:1. The methane production was significantly decreased as the ISR was lower than 1:1, which was resulting from the poor methanogenesis inhibited by NH4 +-N. It would be of great importance that determination of ISRs might provide useful information on how to initialize a batch digester with algal residue as material.  相似文献   

9.
The effects of crude glycerol on the performance of single-stage anaerobic reactors treating different types of organic waste were examined. A reactor treating the organic fraction of municipal solid waste produced 1400 mL CH4/d before the addition of glycerol and 2094 mL CH4/d after the addition of glycerol. An enhanced methane production rate was also observed when a 1:4 mixture of olive mill wastewater and slaughterhouse wastewater was supplemented with crude glycerol. Specifically, by adding 1% v/v crude glycerol to the feed, the methane production rate increased from 479 mL/d to 1210 mL/d. The extra glycerol-COD added to the feed did not have a negative effect on the reactor performance in either case. Supplementation of the feed with crude glycerol also had a significant positive effect on anaerobic fermentation reactors. Hydrogen yield was 26 mmole H2/g VS added and 15 mmole H2/g VS added in a reactor treating the organic fraction of municipal solid waste and a 1:4 mixture of olive mill and slaughterhouse wastewater. The addition of crude glycerol to the feed enhanced hydrogen yield at 2.9 mmole H2/g glycerol added and 0.7 mmole H2/g glycerol added.  相似文献   

10.
Zhang Q  Tang L  Zhang J  Mao Z  Jiang L 《Bioresource technology》2011,102(4):3958-3965
In this study, the pretreatment of cassava residues by thermal-dilute sulfuric acid (TDSA) hydrolysis was investigated by means of a statistically designed set of experiments. A three-factor central composite design (CCD) was employed to identify the optimum pretreatment condition of cassava residues for methane production. The individual and interactive effects of temperature, H2SO4 concentration and reaction time on increase of methane yield (IMY) were evaluated by applying response surface methodology (RSM). After optimization, the resulting optimum pretreatment condition was 157.84 °C, utilizing 2.99% (w/w TS) H2SO4 for 20.15 min, where the maximum methane yield (248 mL/g VS) was 56.96% higher than the control (158 mL/g VS), which was very close to the predict value 56.53%. These results indicate the model obtained through RSM analysis is suit to predict the optimum pretreatment condition and there is great potential of using TDSA pretreatment of cassava residues to enhance methane yield.  相似文献   

11.
Sugarcane bagasse is a by-product from the sugar and ethanol industry which contains approximately 70 % of its dry mass composed by polysaccharides. To convert these polysaccharides into fuel ethanol it is necessary a pretreatment step to increase the enzymatic digestibility of the recalcitrant raw material. In this work, sugarcane bagasse was pretreated by an alkaline-sulfite chemithermomechanical process for increasing its enzymatic digestibility. Na2SO3 and NaOH ratios were fixed at 2:1, and three increasing chemical loads, varying from 4 to 8 % m/m Na2SO3, were used to prepare the pretreated materials. The increase in the alkaline-sulfite load decreased the lignin content in the pretreated material up to 35.5 % at the highest chemical load. The pretreated samples presented enhanced glucose yields during enzymatic hydrolysis as a function of the pretreatment severity. The maximum glucose yield (64 %) was observed for the samples pretreated with the highest chemical load. The use of 2.5 g l?1 Tween 20 in the hydrolysis step further increased the glucose yield to 75 %. Semi-simultaneous hydrolysis and fermentation of the pretreated materials indicated that the ethanol yield was also enhanced as a function of the pretreatment severity. The maximum ethanol yield was 56 ± 2 % for the sample pretreated with the highest chemical load. For the sample pretreated with the lowest chemical load (2 % m/m NaOH and 4 % m/m Na2SO3), adding Tween 20 during the hydrolysis process increased the ethanol yield from 25 ± 3 to 39.5 ± 1 %.  相似文献   

12.
In this study, an effective pretreatment of dilute NaOH-soaked chestnut shell (CNS) with glycerol–HClO4–water (88.8:1.2:10, w/w/w) media at 130 °C for 30 min was successfully demonstrated. Results revealed that the combination pretreatment removed 66.0 % of lignin and 73.7 % of hemicellulose in untreated CNS. The changes in the structural features (crystallinity, morphology, and porosity) of the solid residue of CNS were characterized with Fourier transform infrared spectroscopy, fluorescent microscope, scanning electron microscopy, and X-ray diffraction. Biotransformation of glycerol–HClO4–water pretreated–NaOH-soaked CNS (50 g/L) with a cocktail of enzymes for 72 h, the reducing sugars and glucose were 39.7 and 33.4 g/L, respectively. Moreover, the recovered hydrolyzates containing 20 g/L glucose had no inhibitory effects on the ethanol-fermenting microorganism, and the ethanol production was 0.45 g/g glucose within 48 h. In conclusion, this combination pretreatment shows promise as pretreatment solvent for wheat straw, although the in-depth exploration of this subject is needed.  相似文献   

13.
Operation of waste cells as landfill bioreactors with leachate recirculation is known to accelerate waste degradation and landfill gas generation. However, waste degradation rates in landfill bioreactors decrease with time, with the accumulation of difficult to degrade materials, such as lignin-rich waste. Although, potential exists to modify the leachate quality to promote further degradation of such waste, very little information is available in literature. The objective of this study was to determine the viability of augmenting leachate with enzymes to increase the rate of degradation of lignin-rich waste materials. Among the enzymes evaluated MnP enzyme showed the best performance in terms of methane yield and substrate (lignin) utilization. Methane production of 200 mL CH4/g VS was observed for the MnP amended reactor as compared to 5.7 mL CH4/g VS for the control reactor. The lignin reduction in the MnP amended reactor and control reactor was 68.4% and 6.2%, respectively.  相似文献   

14.
The literature concerning methane (CH4) emissions from temperate and boreal lakes is extensive, but emissions from tropical and subtropical lakes have been less documented. In particular, methane emissions from Mexican lakes, which are often polluted by anthropogenic carbon and nutrient inputs, have not been reported previously. In this work, methane emissions from six Mexican lakes were measured, covering a broad range of organic inputs, trophic states, and climatic conditions. Methane emissions ranged from 5 to 5,000 mg CH4 m?2 day?1. Water samples from several depths in each lake were analyzed for correlation between water quality indicators and methane emissions. Trophic state and water quality indexes were most strongly correlated with methane fluxes. The global methane flux from Mexican freshwater lakes was estimated to be approximately 1.3 Tg CH4 year?1, which is about 20% of methane and 4.4% of total national greenhouse gas emissions. Data for untreated wastewater releases to the environment gave an emission factor of 0.19 kg CH4 kg?1 of Biochemical Oxygen Demand, which is superior to that previously estimated by the IPCC for lake discharges. Thus, the large volume of untreated wastewater in Mexico implies higher methane emission than previously estimated.  相似文献   

15.
This work examines the methane production potential for the anaerobic co-digestion of swine manure (SM) with winery wastewater (WW). Batch and semi-continuous experiments were carried out under mesophilic conditions. Batch experiments revealed that the highest specific methane yield was 348 mL CH4 g−1 COD added, obtained at 85.4% of WW and 0.7 g COD g−1 VS. Specific methane yield from SM alone was 27 mL CH4 g−1 COD added d−1. Furthermore, specific methane yields were 49, 87 and 107 mL CH4 g−1 COD added d−1 for the reactors co-digesting mixtures with 10% WW, 25% WW and 40% WW, respectively. Co-digestion with 40% WW improved the removal efficiencies up to 52% (TCOD), 132% (SCOD) and 61% (VSS) compared to SM alone. These results suggest that methane can be produced very efficiently by the co-digestion of swine manure with winery wastewater.  相似文献   

16.
Acetone–butanol–ethanol (ABE) production from corncob was achieved using an integrated process combining wet disk milling (WDM) pretreatment with enzymatic hydrolysis and fermentation by Clostridium acetobutylicum SE-1. Sugar yields of 71.3 % for glucose and 39.1 % for xylose from pretreated corncob were observed after enzymatic hydrolysis. The relationship between sugar yields and particle size of the pretreated corncob was investigated, suggesting a smaller particle size benefits enzymatic hydrolysis with the WDM pretreatment approach. Analysis of the correlation between parameters representing particle size and efficiency of enzymatic hydrolysis predicted that frequency 90 % is the best parameter representing particle size for the indication of the readiness of the material for enzymatic hydrolysis. ABE production from corncob was carried out with both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes using C. acetobutylicum SE-1. Interestingly, when considering the time for fermentation as the time for ABE production, a comparable rate of sugar consumption and ABE production in the SHF process (0.55 g/l·h sugar consumption and 0.20 g/l·h ABE production) could be observed when glucose (0.50 g/l·h sugar consumption and 0.17 g/l·h ABE production) or a mixture of glucose and xylose (0.68 g/l·h sugar consumption and 0.22 g/l·h ABE production) mimicking the corncob hydrolysate was used as the substrate for fermentation. This result suggested that the WDM is a suitable pretreatment method for ABE production from corncob owing to the mild conditions. A higher ABE production rate could be observed with the SSF process (0.15 g/l·h) comparing with SHF process (0.12 g/l·h) when combining the time for saccharification and fermentation and consider it as the time for ABE production. This is possibly a result of low sustained sugar level during fermentation. These investigations lead to the suggestion that this new WDM pretreatment method has the potentials to be exploited for efficient ABE production from corncob.  相似文献   

17.
The enhancement of enzyme complex produced by Penicillium echinulatum grown in several culture media components (bagasse sugarcane pretreated by various methods, soybean meal, wheat bran, sucrose, and yeast extract) was studied to increment FPase, xylanase, pectinase, and β-glucosidase enzyme activities. The present results indicated that culture media composed with 10 g/L of the various bagasse pretreatment methods did not have any substantial influence with respect to the FPase, xylanase, and β-glucosidase attained maximum values of, respectively, 2.68 FPU/mL, 2.04, and 115.4 IU/mL. On the other hand, proposed culture media to enhance β-glucosidase production composed of 10 g/L steam-exploded bagasse supplemented with soybean flour 5.0 g/L, yeast extract 1.0 g/L, and sucrose 10.0 g/L attained, respectively, 3.19 FPU/mL and 3.06 IU/mL while xylanase was maintained at the same level. The proteomes obtained from the optimized culture media for enhanced FPase, xylanase, pectinase, and β-glucosidase production were analyzed using mass spectrometry and a panel of GH enzyme activities against 16 different substrates. Culture medium designed to enhance β-glucosidase activity achieved higher enzymatic activities values (13 measured activities), compared to the culture media for FPase/pectinase (9 measured activities) and xylanase (7 measured activities), when tested against the 16 substrates. Mass spectrometry analyses of secretome showed a consistent result and the greatest number of spectral counts of Cazy family enzymes was found in designed β-glucosidase culture medium, followed by FPase/pectinase and xylanase. Most of the Cazy identified protein was cellobiohydrolase (GH6 and GH7), endoglucanase (GH5), and endo-1,4-β-xylanase (GH10). Enzymatic hydrolysis of hydrothermally pretreated sugarcane bagasse performed with β-glucosidase enhanced cocktail achieved 51.4 % glucose yield with 10 % w/v insoluble solids at enzyme load of 15 FPU/g material. Collectively the results demonstrated that it was possible to rationally modulate the GH activity of the enzymatic complex secreted by P. echinulatum using adjustment of the culture medium composition. The proposed strategy may contribute to increase enzymatic hydrolysis of lignocellulosic materials.  相似文献   

18.
The biochemical methane potential (BMP) test for thickened sludge was evaluated at three different inoculum/substrate (I:S) ratios. The cumulative methane yield was 51.4 mL CH4/g VSadded at an I:S ratio of 1:1, 76.3 mL CH4/g VSadded at an I:S ratio of 1:3, and 21.9 mL CH4/g VSadded at an I:S ratio of 1:8. The greatest ultimate methane yield and methane production rate constant were achieved at an I:S ratio of 1:3, whereas the least was obtained at an I:S ratio of 1:8. The maximum methane production rate constant was 0.38/day and the minimum methane production rate constant was 0.0016/day. For the case of a lower I:S ratio, the biomass activity may be affected due to the low substrate concentration. On the other hand, for the case of higher I:S ratios, anaerobic digestion of thickened sludge was inhibited by higher concentrations of volatile fatty acids and lower pH.  相似文献   

19.
This study evaluated the potential use of elephant grass biomass, a highly productive species, for cellulase and xylanase production by the cellulolytic mutant Penicillium echinulatum 9A02S1 in submerged cultivation, using untreated biomass, biomass pretreated with different concentrations of NaOH, H2SO4 or NH4OH, or biomass pretreated with H2O at 121 °C. For filter paper activity, all cultivation carried out with pretreated elephant grass under the evaluated conditions showed superior activity when compared with the control (untreated elephant grass). The activities of endoglucanases and β-glucosidases were higher in the cultivation prepared from pretreated samples than the control made with cellulose (Celuflok®). Without pretreatment, elephant grass can be used for xylanase production, enabling similar activities to those obtained in the cultivation with cellulose, reducing the enzyme production cost. These results indicate that the pretreatment of elephant grass, especially when pretreated with H2SO4, may be used as a partial or total replacement for cellulose to cellulase production, and untreated elephant grass may be used for xylanase production.  相似文献   

20.
The presented study aimed at investigating the residual feed intake (RFI) of Sahiwal calves, nutrient utilisation as affected by RFI and its relationship with methane (CH4) emissions and some blood metabolites. Eighteen male Sahiwal calves (10–18 months of age; mean body weight 133 kg) were fed ad libitum with a total mixed ration. After calculating RFI for individual calves (?0.40 to +0.34 kg DM/d), they were divided into three groups with low, medium and high RFI, respectively. Dry matter intake (DMI) was higher (p < 0.05) in Group High RFI, whereas digestibility of all nutrients except crude protein and ether extract was significantly higher in Group Low RFI. Nitrogen balance was also significantly higher in Group Low RFI (20.2 g/d) than in Group High RFI (17.0 g/d). Average daily gain and feed conversion ratio were similar among the groups. With exception of glucose, concentrations of all measured blood metabolites were higher in Group High RFI (p < 0.05). Compared with Group High RFI, the CH4 emission of Group Low RFI was significantly lower (on the basis g/d and g/kg DMI by 11% and 19%, respectively). Furthermore, the CH4 emission [g/d] was significantly correlated with RFI (r = 0.77). Because higher feed efficiency and less CH4 production were observed in Group Low RFI, it was concluded that RFI can be used as a measure of feed efficiency, which has a potential to select Sahiwal calves for lowered CH4 emissions.  相似文献   

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