Improvement of Methane Production from Corn Stalk for Whole Slurry Anaerobic Co-digestion Under Hydrothermal Wastewater Pretreatment

Corn stalk hydrothermal wastewater(CSHW)was used as a pretreatment for whole-slurry anaerobic co-digestion instead of conventional acid pretreatment.CSHW pretreatment was conducted at 20℃,35℃and 50℃for 3,6 and 9 h,after which all experimental groups were digested at 35℃for 24 days.This pretreatment method efficiently broke the lignocellulose structure of the corn stalk.Different from the volatile fatty acids(VFAs)content,the pH and RS contents were relatively higher than those of the control during the pretreatment process.Furthermore,the highest methane production[185.03 mL•g-1 VS(volatile solid)]was achieved at 55.46%under 35℃in 6 h,which was higher than that of the normal corn stalk anaerobic digestion.The VFAs contents and pH increased compared to CK upon the addition of NaOH to adjust pH,and the RS content also increased slightly due to the degradability of lignocellulose during the whole-slurry anaerobic co-digestion.This work provided a potential method to sustainably treat wastewater and improve fermentation performance.

Biogas Production from Various Typical Organic Wastes Generated in the Region of Cantabria (Spain): Methane Yields and Co-Digestion Tests

Batch trials were carried out to determine the methane potential yields of some typical organic wastes generated in the region of Cantabria (Spain): cocoa shell, cheese whey and sludges from dairy industry. Anaerobic co-digestion trials of these wastes with dairy manure were also investigated in batch at 35℃. Cheese whey obtained similar methane yields than dairy manure, between 17.5 and 19.3 L CH4kg-1 cheese whey compared with 18.0 L CH4kg-1 manure. Methane yields of various sludge samples collected from wastewater treatment facilities of dairy industries were influenced by its origin. Sludge samples from fat separation devices were the most productive in terms of specific methane yields compared with biological sludge from an aerobic reactor. Sludge samples from fat separator reached specific methane productivities of 350 and 388 L CH4kg-1 VS (10.5 and 24.1 L CH4kg-1 sludge), whereas biological sludge yielded 125 L CH4kg-1 VS (12.6 L CH4kg-1 sludge). The methane potential of sludge samples was influenced by solids content. Cocoa shell resulted to be an interesting waste for anaerobic digestion due to its high VS content, yielding 195 L CH4kg-1 cocoa shell. It is a waste that can considerably improve methane yields in anaerobic co-digestion with dairy manure. However, at proportions of 10% cocoa shell, the process was hindered by hydrolysis of particulate matter. Anaerobic digestion at higher temperatures (thermophilic range) could be a better option for this kind of waste. Co-digestion of 5% cocoa shell with 35% dairy sludge and 60% dairy manure resulted in 80.5% higher methane production compared to anaerobic digestion of dairy manure alone.

Study on anaerobic co-digestion with distillery wastewater to improve the dewatering property of the secondary sludge

This paper presents the results obtained for the effluent dewatering properties of anaerobic digestion of secondary sludge （SS） and anaerobic co-digestion of mixture of this sludge with the distillery wastewater （DW） under thermophilic （55±1 ℃）, 5 L of working volume, three parallel lab-scale conditions. Its mixtures were prepared with a DW content of 25%and 50% and the C/N ratios of mixtures are 13.1 and 17.6, respectively. The effluent dewatering properties were evaluated under stable conditions which the biogas yield and the effluent pH were steady. The natural settleability, biogas yield, centrifugal dewatering, centrifugal supernatant turbidity and specific resistance filtration （SRF） were investigated. The results showed that the effluent dewatering properties of anaerobic co-digestion of mixtures between SS and DW were better than that of anaerobic digestion of SS alone. In the anaerobic digestion system with the feed were SS, mixture of SS and a DW content of 25%and 50% in order, the net biogas yield of secondary sludge in ADSA,ADSB and ADSC were 0.42 0.507 and 0.511 m3 biogass/kg.VS.d ; compared with the biogas yield in anaerobic digestion system A （ADSA）, the biogas yield in anaerobic digestion system B （ADSB） and anaerobic digestion system C （ADSC） had been increased by more than 20% respectively; the SRF of three digested sludge are（were） from 6.8×10^13, 1. 1×10^13 to 5.1×10^12 m/Kg, natural settling rates of 12 h are 26, 37 and 56% and that of 24 h are 32%, 45% and 59% respectively; the centrifugal dewatering rate of 3 min at speed of 1000 rpm were 16%, 31% and 51% respectively; the turbidity of centrifugal supernatant were 804, 754 and 678FTU simultaneously.

Co-digestion Of Olive Mill Wastewater and Swine Manure Using Up-Flow Anaerobic Sludge Blanket Reactor for Biogas Production

Swine wastewater (SW) and olive mill wastewater (OMW) are two problematic wastes that have become major causes of health and environmental concerns. The main objective of the current work was to evaluate the efficiency of the co-digestion strategy for treatment of SW and OMW mixtures. Mesophilic batch reac-tors fed with mixtures of SW and OMW showed that the two adapted sludges Gadot and Prigat exhibited the best COD removal capacity and biogas production;therefore both were selected to seed up-flow anaerobic sludge blanket (UASB) continuous reactors. During 170 days of operation, both sludges Gadot and Prigat showed high biodegradation potential. The highest COD removal of 85-95% and biogas production of 0.55 L?g-1 COD were obtained at a mixture consisting of 33% OMW and 67% SW. Under these conditions, an organic load of 28,000 mg?L-1 COD was reduced to 1,500-3,500 mg?L-1. These results strongly suggest that co-digestion technology using UASB reactors is a highly reliable and promising technology for wastewater treatment and biogas production.

Characterization of Digestates from Anaerobic Co-Digestion of Manioc Effluent, Human Urine and Cow Dung

This study focused on the characterization of digestates resulting from anaerobic digestion of manioc effluents from attiéké factories. Two types of digestate were characterized, one consisting of manioc effluent + urine and another composed of manioc effluent + urine + cow dung. As a result, these residues of bio-digestion rich in nutrients (NPK) can be used as agricultural fertilizer. Moreover, the determination of some microorganisms and heavy metals digestates allowed to better appreciate its fertilizing quality. These parameters remained in accordance with the quality standards of a digestate prescribed. These results show that digestates from anaerobic co-digestion of manioc effluents, urine and cow dung can be used without fear as an agricultural biofertilizer.

Biogas Production from the Co-Digestion of Cornstalks with Cow Dung and Poultry Droppings

The Anaerobic digestion of Corn Stalk (CS) with Cow Dung (CD) and Poultry Droppings (PD) was investigated. Batch mono-digestion and Co-digestion experiments were performed with initial total solid loading of 37.5%. The main objective of this work was to investigate the biogas yield at different CS to CD ratios and CS to PD ratios. Results show that the highest Cumulative Gas Yield (CGY) of 6833 mL/g of biomass was achieved in 21 days for CS-CD ratio of 2:1. Similarly high CGY of 6107 mL/g, 6100 mL/g and 5333 mL/g were obtained for CS-PD ratio of 2:1, CS-CD ratio of 1:1 and CS-PD ratio of 1:1 respectively. It is concluded that co-digestion of Cow dung or poultry droppings is beneficial for improving bio-digestibility and Biogas yield from corn stalk. The results of this work provide useful information to improve the efficiency of co-digestion of CS with CD and PD under anaerobic conditions.

Anaerobic Co-digestion Process Efficiency Estimation in Phases as an Alternative for Municipal Waste Treatment

The incorrect disposal of the waste generated in the municipalities contributes to water and soil contamination,resulting in a real concern in order to find an adequate disposal as well as obtain by-products that can be used to reduce CO2 emissions.Anaerobic digestion turns out to be the most efficient treatment,both in environmental and economic terms.The objective of this study is to evaluate the anaerobic co-digestion process in phases as an alternative for the treatment of municipal waste:sludge from water treatment plants and the biodegradable part of Municipal Solid Waste(MSW),for three HRTs(Hydraulic Retention Times).Testing results show up a max elimination of 70.68%in VS(Volatile Solids)and 74.01%in COD(Chemical Oxygen Demand).With these percentages of elimination on average,15.96 L/d of biogas was produced,for each kg of COD eliminated 0.56 m3 of biogas was produced and for each kg of SV 0.85 m3 and methane of 50.10%.

The Survival of Cefazolin Resistant Bacteria in Thermophilic Co-digestion of Dairy Manure and Waste Milk

Recent studies have suggested that there may be a link between the use of in-feed antibiotics and the prevalence of antibiotic-resistant bacteria in human infections. It is believed that anaerobic digestion is a potent method to reduce the antibiotic resistant bacteria present in waste from concentrated animal feeding operations. Cefazolin is a β-1actam antibiotic that is frequently used to treat the cows with mastitis in the Obihiro University herd. Disposal of untreated milk containing cefazolin residues promotes the occurrence of cefazolin resistant bacteria in the vicinity of farm, thus the objective of this study was to investigate the survival of antibiotic resistant bacteria in co-digestion of dairy manure and waste milk obtained from cows treated for mastitis with cefazolin under thermophilic conditions （55 ~C）. Cow manure, digested slurry and waste milk （cefazolin residue concentration 2.17 mg/L） were used as the materials in order to have three digester contents; 100% slurry, 50% slurry ＋ 50% manure and 50% slurry ＋ 45% manure ＋ 5% waste milk. The experiment was carried out using batch digesters （1 L） with active volume of 800 mL at 55 ℃ for 20 days to determine the survival of cefazolin resistant bacteria and to observe the digester performance by determining the bio gas and methane yield using gas chromatpgrapby. Dilution plate method was used to determine the population densities of total and cefazolin resistant bacteria at 0, 10th and 20th day of digestion. Total and cefazolin resistant bacterial counts were reduced with time by several orders until 10th day of digestion and those were almost similar at day 20th. Highest daily biogas and methane yield were observed in the digester contained slurry, manure and waste milk during early digestion period （until 5th day）. The results suggest that thermophilic co-digestion of dairy manure and waste milk would be a suitable technology for reducing antibiotic （cefazolin） resistant bacteria while obtaining better digester performance.

Bioelectricity from Anaerobic Co-Digestion of Organic Solid Wastes and Sewage Sludge Using Microbial Fuel Cells (MFCs)

Recently microbial fuel cells (MFCs) have been considered as an alternative power generation technique by utilizing organic wastes. In this study, an experiment was carried out to generate bioelectricity from co-digestion of organic waste (kitchen waste) and sewage sludge as a waste management option using microbial fuel cell (MFC) in anaerobic process. A total of five samples with different sludge-waste ratio were used with zinc (Zn) and cupper (Cu) as cell electrodes for the test. The trends of voltage generation were different for each sample in cells such as 350 mV, 263 mV, 416 mV maximum voltage were measured from sample I, II and III respectively. It was observed that the MFC with sewage sludge showed the higher values (around 960 mV) of voltages with time whereas 918 mV obtained with organic waste. Precisely comparing cases with varying the organic waste and sewage sludge ratio helps to find the best bioelectricity generation option. Using MFCs can be appeared as the solution of electricity scarcity along the world as an efficient and eco-friendly manner as well as organic solid waste and sewage sludge management.

Effect of goethite on anaerobic co-digestion process of corn straw and algae biomass

1 Introduction Recently the demand for fossil fuel has grown significantly with the rapid development of the Chinese economy.Renewable energy was developed to replace traditional fossil fuels,which would decrease the

Anaerobic Co-Digestion of Fish Processing Waste with Cow Manure and Waste of Market (Rests of Fruits and Vegetables): A Lab Scale Batch Test

The aim of this work was to use fish processing waste (FW) as main substrate for anaerobic digestion. To enhance the biogas production of FW, co-digestion was done with two other substrates: cow dung (CD) and waste of market (MW). Batch test was carried out in an 1 L glass digester in a temperature controlled chamber at 38°C. The following mixtures were carried out: FW with CD respectively at different ratios 100:0% (A), 80:20% (B) and 60:40% (C);FW with MW at the following ratio 80:20% (D);FW with CD and MW respectively at these ratios 80:10:10% (F) and 60:20:20% (G). The biogas produced was measured using a milligas counter® and the volume of gas was recorded. The gas composition was determined using gas chromatography. With a pH stable for raw substrates and mixtures, TS and VS (%TS) contents for FW were respectively 31.01% and 91.55%. Between 3 to 13 days of experimentation, the highest flow rate was observed. The percentage of methane was more important for mixtures B and D, 61% and 59% respectively. pH and VOA/TIC were stable at the end of the batch test for all mixtures, meaning that the organic matter was already well digested. The highest values of Volatile Solid Removal (VSR) were found for mixtures C, D, F and G. Therefore, the promising mixtures for next experimentations in large scale are B and D.

Phylogenetic Analysis of Anaerobic Co-Digestion of Animal Manure and Corn Stover Reveals Linkages between Bacterial Communities and Digestion Performance

Over 3 million tons of manures are produced annually in the United States and pose environmental and health risks if not remediated. Anaerobic digestion is an effective method in treating organic wastes to reduce environmental impacts and produce methane as an alternative energy. Previous studies suggested that optimization of feed composition, hydraulic retention time, and other operational conditions can greatly improve total solids removal and increase methane productivity. These environmental factors improve functionality by altering the microbial community structure but explicit details of how the bacterial community shifts are poorly understood. Our investigations were conducted to investigate the relationship between environmental factors, microbial community structure and bioreactor efficiency by using metagenomic analysis of the microbial communities. Our results indicated that the bioreactor with the greatest methane production, digestion efficiency and reduced levels of E. coli/Shigella had a distinctive community structure at the genus level with unique and abundant uncultivated strains of Bacteroidetes. Moreover the same bioreactor was enriched in Aminomonas paucivorans and Clostridia populations that can utilize secondary metabolites produced during cellulose/hemicellulose degradation to generate hydrogen and acetate. Hence specific digestion conditions that enrich for these populations may provide a route to the optimization of co-digestion systems and control the variability in reactor performance.

Effect of Variation in Co-Digestion Ratios of Matooke, Cassava and Sweet Potato Peels on Hydraulic Retention Time, Methane Yield and Its Kinetics

This paper presents the results of batch anaerobic co-digestion of matooke, cassava, and sweet potato peels and vines. These agricultural wastes and others form the biggest portion of household wastes in developing countries. However, they have remained an unexploited resource amidst the ever increasing needs of clean energy and waste disposal challenges. Efforts to use them individually as biogas substrates have been associated with process acidification failure resulting from their fast hydrolysis. The aim of this work was to exploit agricultural wastes is co-digestion among themselves and assess their effect on methane yield and its kinetics, pH and hydraulic retention time (HRT). Sixteen ratios of Matooke peels (MP), cassava peels (CP) and sweet potato peels (SP) were assessed in duplicate. Methane yield and its kinetics, pH and HRT demonstrated dependence on the proportion of substrates in the mixture. Depending on the ratio mixture, HRT increased to 15 days compared to less than 5 days for single substrates, hydrolysis rate constant (k) reduced to a range of 0.1 - 0.3 d-1 compared to single substrates whose k-values were above 0.5 d-1, pH was maintained in the range of 6.38 - 6.43 and CH4 yield increased by 15% - 200%. Ratios 2:1:0, 2:0:1, 0:1:2, 1:1:1 and 1:1:4 were consistent all through in terms of model fitting, having a positive synergetic effect on HRT, hydrolysis rate constant, lag phase and methane yield. However, more research is needed in maintaining the pH near the neutral for process stability assurance if household wastes are to be used as standalone substrates for biogas production without being co-substrates with livestock manure.

Bioenergy Production from Anaerobic Co-Digestion of Sewage Sludge and Abattoir Wastes

Energy is the pillar of human economic development. Several energy sources, renewable and non-renewable, have been exploited to assure and sustain the need for sustainable development. However, depletion of non-renewable energy sources forced researchers to search for alternative cost effective and environmental friendly energy sources. Thus, conversion of waste materials into energy has obtained considerable attention. In line with this, the aim of this study is to investigate the improvement of bio-energy production through anaerobic digestion of mixture of wastes from sewage sludge and abattoir sources. The abattoir waste is functioned as a co-substrate. Laboratory scale batch anaerobic co-digestion of the waste is carried out under mesophilic condition for 20 days. Sewage Sludge (SS) alone, and different mix ratios of SS to Abattoir Waste (AW) were analyzed for bioenergy production. Besides, the nutrient values and reduction in volume of the sewage after digestion were determined. The results show that methane productions of 33.8%, 48.3% and 56.9% were obtained for SS alone and for SS:AW mix ratios of 4:1 and 3:2, respectively. The nutrient values of the slurry increased as mix ratio decreased due to the increase in the amount of AW. The obtained results indicate that bio-energy production can be improved through co-digestion of SS using AW as a co-substrate;thus warranting further investigation for the practical application in the energy production.

Anaerobic co-digestion of thermo-alkaline pretreated microalgae and sewage sludge: Methane potential and microbial community

To improve methane production from sewage sludge(SS),co-digestion of SS and microalgae(MA)was studied and the application of thermo-alkaline pretreatment to MA was evaluated.The results showed that thermo-alkaline pretreatment at 90℃ for 120 min on MA was the optimum pretreatment condition.Furthermore,when the volatile solids(VS)ratio of SS and MA was 1:2,the methane yield reached maximum(368.94 mL/g VS).Fourier transform infrared(FT-IR)and thermogravimetric analysis confirmed the synergetic effects of thermoalkaline pretreated MA on its co-digestion with SS.The analyses of microbial community indicated that Methanobacterium and Methanosarcina were the dominant methanogens during the co-digestion process.However,the relative abundance of Methanosarcina in thermoalkaline pretreated groups was higher compared to unpretreated groups.The microbial community structure might be affected by thermo-alkaline pretreatment rather than by the MA dosage in the co-digestion.

Co-digestion of food waste and hydrothermal liquid digestate:Promotion effect of self-generated hydrochars

Hydrothermal treatment(HTT)can efficiently valorize the digestate after anaerobic digestion.However,the disposal of the HTT liquid is challenging.This paper proposes a method to recover energy through the anaerobic co-digestion of food waste and HTT liquid fraction.The effect of HTT liquid recirculation on anaerobic co-digestion performance was investigated.This study focused on the self-generated hydrochars that remained in the HTT supernatant after centrifugation.The effect of the self-generated hydrochars on the methane(CH_(4))yield and microbial communities were discussed.After adding HTT liquids treated at 140 and 180
C,the maximum CH4 production increased to 309.36 and 331.61 mL per g COD,respectively.The HTT liquid exhibited a pH buffering effect and kept a favorable pH for the anaerobic co-digestion.In addition,the self-generated hydrochars with higher carbon content and large oxygen-containing functional groups remained in HTT liquid.They increased the electron transferring rate of the anaerobic co-digestion.The increased relative abundance of Methanosarcina,Syntrophomonadaceae,and Synergistota was observed with adding HTT liquid.The results of the principal component analysis indicate that the electron transferring rate constant had positive correlationships with the relative abundance of Methanosarcina,Syntrophomonadaceae,and Synergistota.This study can provide a good reference for the disposal of the HTT liquid and a novel insight regarding the mechanism for the anaerobic co-digestion.

Effects of mixture ratio on anaerobic co-digestion with fruit and vegetable waste and food waste of China

The biochemical methane potentials for typical fruit and vegetable waste （FVW） and food waste （FW） from a northern China city were investigated, which were 0.30, 0.56 m3 CH4/kgVS （volatile solids） with biodegradabilities of 59.3% and 83.6%, respectively. Individual anaerobic digestion testes of FVW and FW were conducted at the organic loading rate （OLR） of 3 kg VS/（m3-day） using a lab-scale continuous stirred-tank reactor at 35°C. FVW could be digested stably with the biogas production rate of 2.17 ma/（m3-day） and methane production yield of 0.42 m3 CH4/kg VS. However, anaerobic digestion process for FW was failed due to acids accumulation. The effects of FVW： FW ratio on co-digestion stability and performance were further investigated at the same OLR. At FVW and FW mixing ratios of 2：1 and 1：1, the performance and operation of the digester were maintained stable, with no accumulation of volatile fatty acids （VFA） and ammonia. Changing the feed to a higher FW content in a ratio of FVW to FW 1：2, resulted in an increase in VFAs concentration to 1100-1200 rag/L, and the methanogenesis was slightly inhibited. At the optimum mixture ratio 1：1 for co-digestion of FVW with FW, the methane production yield was 0.49 m3 CH4/kg VS, and the volatile solids and soluble chemical oxygen demand （sCOD） removal efficiencies were 74.9% and 96.1%, respectively.

Enhancement of biogas potential of primary sludge by co-digestion with cow manure and brewery sludge

Anaerobic digestion(AD)has long been used to treat different types of organic wastes especially in the developed world.However,organic wastes are still more often considered as a waste instead of a resource in the developing world,which contributes to environmental pollution arising from their disposal.This study has been conducted at Bugolobi Sewage Treatment Plant(BSTP),where two organic wastes,cow manure and brewery sludge were co-digested with primary sludge in different proportions.This study was done in lab-scale reactors at mesophilic temperature and sludge retention time of 20 d.The main objective was to evaluate the biodegradability of primary sludge generated at BSTP,Kampala,Uganda and enhance its ability of biogas production.When the brewery sludge was added to primary STP sludge at all proportions,the biogas production rate increased by a factor of 3.This was significantly(p<0.001)higher than observed gas yield(337±18)mL/(L·d))in the control treatment containing(only STP sludge).Co-digesting STP sludge with cow manure did not show different results compared to the control treatment.In conclusion,Bugolobi STP sludge is poorly anaerobically degradable with low biogas production but co-digestion with brewery sludge enhanced the biogas production rate,while co-digestion with cow manure was not beneficial.

Methanogenic community dynamics in anaerobic co-digestion of fruit and vegetable waste and food waste

A lab-scale continuously-stirred tank reactor （CSTR）, used for anaerobic co-digestion of fruit and vegetable waste （FVW） and food waste （FW） at different mixture ratios, was operated for 178 days at the organic loading rate of 3 kg VS （volatile solids）/（m3.day）. The dynamics of the Archaeal community and the correlations between environmental variables and methanogenic community structure were analyzed by polymerase chain reactions - denaturing gradient gel electrophoresis （PCR-DGGE） and redundancy analysis （RDA）, respectively. PCR-DGGE results demonstrated that the mixture ratio of FVW to FW altered the community composition of Archaea. As the FVW]FW ratio increased, Methanoculleus, Methanosaeta and Methanosarcina became the predominant methanogens in the community. Redundancy analysis results indicated that the shift of the methanogenic community was significantly correlated with the composition of acidogenic products and methane production yield. Different mixture ratios of substrates led to different compositions of intermediate metabolites, which may affect the methanogenic community. These results suggested that the analysis of microbial communities could be used to diagnose anaerobic processes.

Effects of cow manure ratios on methane production and microbial community evolution in anaerobic co-digestion with different crop wastes

The present study investigated the effects of cow manure ratios mixed with maize stover,rice straw,and wheat stalk at 3,2,1(total solid based,TS-based),respectively,on methane production and microbial community structure during the anaerobic co-digestion process.Results showed cow manure co-digested with maize stover,wheat stalk,and rice straw at ratios of 2,1,and 3 had the highest cumulative methane yields(272.99,153.22167.73 mL/g volatile solid(VS),respectively)and better stability(e.g.pH,volatile fatty acids(VFAs)and their component).The main microbe evolution had a similar trend which was Petrimonas and Methanosaeta in the early digestion process(Days 0-7)and then evolved into Longilinea,Ruminofilibacter,and Methanosarcina with the progress of digestion,but the relative abundance of these microbes in each reactor was different.It was worth noting that Caldicoprobacter in cow manure to maize stover ratio of 2,and to rice straw ratio of three reactors had a relatively higher proportion than reactor of cow manure to wheat stalk ratio of 1,and Hydrogenophaga was the specific bacterium in cow manure to wheat stalk ratio of 1 reactor.In addition,Petrimonas showed positive relationship with VFAs and Longilinea was the opposite.Methanosaeta and Methanobacterium contributed the most during the peak period of methane production in cow manure and maize stover co-digested reactor,and showed positive relationship with acetic acid.However,Methanosarcina and Methanospirillum made a great contribution during the peak period of methane production in cow manure co-digested with wheat stalk and rice straw reactors.These findings could provide further information on the application of cow manure co-digested with crop wastes.