Anaerobic Co-digestion Of Swine Manure Research Articles

Kinetic modelling and improvement of methane production from the anaerobic co-digestion of swine manure and cassava bagasse

Anaerobic co-digestion (AcoD) is a promising biotechnological approach for the management of livestock and agro-industrial wastes with the concomitant production of renewable energy. This study investigated methane production during batch AcoD of swine manure (SM) and different amounts of cassava bagasse (CB), using Na2CO3 to adjust initial pH (8.0) and as buffering agent. The highest methane yield of 41,129 ± 1783.6 mL CH4 L−1 (157,04 ± 6,81 mL CH4 g VSinitial−1) was observed with 90.6 g total solids (TS) L−1, in systems containing 16.87 g TS L−1 from cassava bagasse. At this condition and in comparison, with the control (C1), the reactor R4 presented a superior removal of 83.8% for TS, 101.1% for VS, 42.1% for COD, and 161.6% for CODS. Nevertheless, methane production was inhibited at higher CB additions (22.48–33.72 g TS L−1). Methane production kinetics was well explained by including the first order specific growth rate with metabolism as the limiting step for two different substrates (SM and CB) and the linear buffering capacity behavior from CB. This novel proposed model describes the phenomenon of acid inhibition and inactivation of cell biomass caused by the insufficient buffering capacity. The developed model might apply to other similar systems where acid failure could occur, and can be used for a rational scale-up of batch and continuous processes.

Optimization and microbial diversity of anaerobic co-digestion of swine manure with waste kitchen oil at high organic loading rates

Anaerobic co-digestion of swine manure (SM) and waste kitchen oil (WKO) was conducted to evaluate the effect of high organic loading rates (OLRs) on biogas production efficiency and microbial changes. Combinations of different loading rates of SM and WKO, with total OLRs from 2 to 8 g VS (volatile solid)/L/d, were evaluated in a laboratory-scale study. While feeding more than 4 g VSSM/L/d did not result in higher biogas production in both mono- and co-digestion scenarios, the addition of WKO increased the total OLR up to 6 g VS/L/d without significant reduction of system productivity. Biogas yields of M2O1 (2 g VSSM/L/d + 1 g VSWKO/L/d) and M4O2 were 910 ± 35 and 849 ± 85 mL/g VSfed which were 25.2 % and 16.9 % higher than the mono-digestion of M2, respectively. A significant increase of bacterial alpha-diversity (Shannon index) was observed in M2O1, at 233.0 ± 3.6 compared with 218.7 ± 5.1 of M2 (p < 0.05). Less bacterial alpha-diversity and accumulation of volatile fatty acids were observed in M4O1 and M4O2, suggesting their potential instability. When digesters were fed with M2, the introduction of 1.4 g VSWKO/L/d or more did not increase biogas yield and could cause system imbalance. The study suggests the limit of WKO could be increased when higher OLRs of SM were applied but should not be more than 4 g VSSM/L/d, and ratio between SM and WKO should be considered to avoid failure. Some of the system disturbances took up to three months to show.

Anaerobic co-digestion of swine manure and forage at two harvesting ages

ABSTRACT: The co-digestion of swine manure with vegetable waste is an alternative that can increase the production of biogas and methane generated by the isolated digestion of manure. However, recommendations that are based on the best ratio between manure and forage, as well as the age of harvest, are still scarce in the literature. This study was conducted to evaluate inclusions (0, 25, 50, 75 and 100%) of the total solids (TS) of Elephant grass (Pennisetum purpureum Schum) harvested at two ages medium age (MA) at 45 days of growth and advanced age (AA) at 90 days in co-digestion with swine manure, using an entirely randomized design in a 5x2 factorial scheme. Batch digesters were used and biogas production was monitored for 12 weeks. There was influence of forage age (P &lt;0.05) on the degradation of solids and neutral detergent fiber, with higher values for the substrates containing MA forage. The highest CH4 yields were obtained by the substrates containing MA forage in the inclusion of 27.7 and 31.6%, being 253.7 and 222.2 L of CH4 per Kg of total or volatile solids. The age of the forages influenced the onset and persistence of biogas production, being advantageous only in the inclusion of 25% of MA forage. The AA forage inclusion is not recommended for co-digestion with swine manure.

Effects of rice straw ratio on mesophilic and thermophilic anaerobic co-digestion of swine manure and rice straw mixture

The mesophilic and thermophilic anaerobic co-digestion (Co-AD) of swine manure (SM) and rice straw (RS) mixtures was evaluated in lab-scale continuously stirred tank reactors through long-term semi-continuous experiments to investigate the effects of three RS ratios (25%, 33.3%, and 50%, based on total solids). The experimental results showed that an increase in the RS ratio reduced the biogas and methane production, and methane content in both Co-ADs and the effects of the increased RS ratio on the mesophilic Co-AD (Co-MAD) were slightly lower than those on the thermophilic Co-AD (Co-TAD). The digestate characteristics were also affected by the RS ratio. A reduction analysis demonstrated the higher importance of the RS ratio in the substrate with respect to gas production in Co-MAD compared to Co-TAD. The increase in the RS ratio increased the relative abundance of Clostridium_sensu_strricto_1, and changed the predominant archaea and methanogenesis pathways in both Co-ADs.

Improving two-stage thermophilic-mesophilic anaerobic co-digestion of swine manure and rice straw by digestate recirculation

The anaerobic co-digestion (coAD) of swine manure (SM) and rice straw (RS) is appealing for renewable energy recovery and waste treatment worldwidely. Improving its performance is very important for its application. In this study, long-term semi-continuous experiments were conducted to evaluate the improving effects of digestate recirculation on the performance, energy recovery, and microbial community of two-stage thermophilic-mesophilic coAD of swine manure (SM) and rice straw (RS). The experimental results indicated that the coAD systems of SM and RS (mixing ratio of 3:1) with or without digestate recirculation could not realize phase separation. The reactors of both coAD systems were characterized by pH values ranging from 7.74 to 7.85, methane production as 0.41 ± 0.02 and 0.44 ± 0.03 L/L/d, and stable operation. Notably, digestate recirculation increased total methane production, organic matter removal, and reaction rate of the coAD system by 9.92 ± 5.08, 5.22 ± 1.94, and 9.73–12.60%, respectively. Digestate recirculation improved the performance of the coAD by significantly increasing the abundance of Methanosarcina (from 4.1% to 7.5%–10.7% and 35.7%) and decreasing that of Methanothermobacter (from 94.2% to 87.3%–83.6% and 56.8%). Thus, the main methanogenesis pathway of the coAD system was changed by digestate recirculation and the methane production was effectively improved. Although the energy input of the coAD system increased by 30.26%, digestate recirculation improved the energy balance of the total system by 6.83%.

Effects of mixing ratios on anaerobic co-digestion of swine manure and rice straw: methane production and kinetics

The effects of seven mixing ratios (1:0, 3:1, 2:1, 1:1, 1:2, 1:3, and 0:1, swine manure (SM)/rice straw (RS), based on total solid) on anaerobic co-digestion (co-AD) of SM and RS mixtures were investigated in batch tests. The results showed that the highest methane yield (188.79 mL/g VSadded) was obtained at the ratio of 1:1, which was higher than that of the mono-digestion of RS or SM by 178.77% and 18.94%, respectively. For the remained six ratios, the methane yield increased with the increase of SM proportion. The highest organic matter degradation rates were also observed at the ratio of 1:1. The methane content of biogas and the pH, total alkalinity, and total ammonia nitrogen of the digestate all decreased with the increase of RS proportion and decrease of SM proportion. Additionally, the kinetic results of each anaerobic digestion (AD) step suggested that the co-AD of SM and RS at the ratio of 1:1 significantly improved the reaction rates of the four AD steps. Meanwhile, the methane production time was prolonged and the lag time of methanogenesis was shortened at the ratio of 1:1.

Effect of Agitation on Anaerobic Co-Digestion of Swine Manure and Food Waste

The synergism of food waste associated with swine manure can provide an increase in biogas production, besides promoting greater stability in the anaerobic co-digestion process. To verify this effect, co-digestion tests were performed in two reactors, one with agitation, and the other without agitation. In both systems, gasometers were used to measure biogas production in an experiment lasting two hydraulic retention times (HRT). On each feeding day, the temperatures of the ambient and of the effluent taken from the reactors were measured, and samples of the food waste and effluent were collected to perform analysis of pH, total solids (TS), volatile solids (VS), fixed solids (FS), volatile acidity (AV), and total alkalinity (TA). In addition, the chemical oxygen demand (COD) was determined every five days, and gas composition was determined at the beginning of the second HRT. As important results, in both reactors a decrease in pH was verified due to the weakening of the buffer effect of the medium. This was due to the low alkalinity found in the food waste, causing an increase in acidity in the contents of the reactors. The volume of biogas produced was higher in the reactor with agitation, which meant an increased efficiency of the process. Finally, a low methane content was verified through chromatographic analyses, indicating a reduction in the activity of the microorganisms present in the medium. Thus, it is concluded that agitation linked to anaerobic co-digestion of swine manure with food waste exerted a positive effect on biogas production.

Optimization and Microbial Diversity of Anaerobic Co-Digestion of Swine Manure with Waste Kitchen Oil

Optimization and Microbial Diversity of Anaerobic Co-Digestion of Swine Manure with Waste Kitchen Oil

Enhanced lactic acid production from the anaerobic co-digestion of swine manure with apple or potato waste via ratio adjustment

The valorization of organic waste into lactic acid (LA) via co-digestion has attracted tremendous research interests in recent years. This study investigated the feasibility of intensifying the LA accumulation from anaerobic digestion (AD) of swine manure (SM) by adding apple waste (AW) or potato waste (PW). Results indicated that AW or PW obviously enhanced the accumulation of LA, and when the optimal mixing ratio of AW or PW to SM of 75:25, the maximum concentrations of LA were 27.61 and 8.91 g COD/L, which were around 3.53- and 1.14-folds of that of the mono-digestion of SM, respectively. Meanwhile, the co-digestion of SM and AW showed significantly higher LA production than that of SM and PW (p < 0.05). High reducing sugar content of AW contributed to LA accumulation in AD process. In addition, AW increased the relative abundance of Lactobacillus and Clostridium, thus benefited the production of LA.

Hygienization and microbial metabolic adaptation during anaerobic co-digestion of swine manure and corn stover

This study assessed the effect of different swine manure (SM)/corn stover (CS) mixtures based on total solids (TS) content with respect to hygienization, microbial community dynamics and methane yields on batch anaerobic co-digestion performance. Different ratios of SM and CS with TS content between 0.69 and 6% digested at 75 d revealed SM had the greatest methane yield at 403.9 mL g−1 volatile solids added (VS) and 86.31% VS reduction. BIOLOG AN microplates and lignocellulolytic enzyme assays proved to be rapid tools for characterizing microbial community metabolism as noted by the different carbon source utilization patterns between TS loadings. Hygienization of fecal indicator bacteria groups was achieved with some (E. coli) but not all groups (Clostridia spp.). The results showed that colorimetric biochemical assays and culture-based techniques can rapidly assess microbial community dynamics during co-digestion, and that TS- in the form of lignocellulosic biomass- influences microbial metabolic activities.

Anaerobic co-digestion of swine manure and chicken feathers: Effects of manure maturation and microbial pretreatment of feathers on methane production

Manures and feathers are abundant wastes from the meat supply chain. Although manures are used in anaerobic digestions to produce methane, feathers recalcitrance might be challenging. Methane production was assessed during mesophilic anaerobic co-digestion (Co-AD) of swine manures with untreated/pretreated feathers. Diluted fresh (DF; 1:2) or matured (DM; 1:1) manures were used both as Co-AD inoculums and main substrates. Co-substrates were feathers (FF) and feather hydrolysates produced through microbial degradation (FH); in Controls, total solids (TS) were adjusted with sterilized manure. In DF experiments, 5.6% TS (27.7% from co-substrate) and 6.8% TS (40.4% from co-substrate) yielded similar methane production [0.48 L CH4/g volatile solids (VSinitial)]. With FF, methane production showed a two-step decomposition pattern. At 6.8% TS, FH reduced yields (43%), possibly through ammonia inhibition. In DM experiments, at 4.60% TS (12.1% from co-substrate) and 5.15% TS (21.3% from co-substrate), methane production was superior with FH (0.16–0.19 L CH4/g VSinitial); FF decreased yields (15–25%), suggesting delayed biodegradation. Modified Gompertz model fitted best to kinetic data. FF and Controls displayed similar methane yields, and FH affected production in a concentration-dependent manner. Microbial pretreatment could increase methane production by improving feathers biodegradability. FH represents a nitrogen-rich substrate for Co-AD with nitrogen-deficient biomasses.

Long-Term Mesophilic Anaerobic Co-Digestion of Swine Manure with Corn Stover and Microbial Community Analysis.

Long-term anaerobic co-digestion of swine manure (SM) and corn stover (CS) was conducted using semi-continuously loaded digesters under mesophilic conditions. A preliminary test was first conducted to test the effects of loading rates, and results indicated the 3 g-VS L−1 d−1 was the optimal loading rate. Based on the preliminary results, a verification replicated test was conducted with 3 g-VS L−1 d−1 loading rate and different SM/CS ratios (1:1, 2:1 and 1:2). Results showed that a SM/CS ratio of 2/1 was optimal, based on maximum observed methane-VSdes generation and carbon conversion efficiency (72.56 ± 3.40 mL g−1 and 40.59%, respectively). Amplicon sequencing analysis suggested that microbial diversity was increased with CS loading. Amino-acid-degrading bacteria were abundant in the treatment groups. Archaea Methanoculleus could enhance biogas and methane productions.

Anaerobic co-digestion of swine manure with sweet potato or cassava in different C/N ratios

ABSTRACT: Anaerobic co-digestion (AcoD) of waste is a method of increasing methane (CH4) yield and improving biofertilizer quality. This study aimed to evaluate the best AcoD conditions for swine manure (SM) with sweet potato (SP) or cassava (C) in different amounts in semi-continuous biodigesters. Initially, using batch biodigesters, an AcoD test of the SM with SP or C was performed, adopting carbon/nitrogen (C/N) ratios of 10/1, 13/1, 17/1, and 22/1. Based on the results, a C/N ratio of 10/1 was chosen, which was the proportion that resulted in the highest reduction of volatile solids (VS) and specific biogas production. From these results, the experiment was carried out in semi-continuous biodigesters, consisting of three treatments (control (SM), SP 10/1, and C 10/1) with five replicates and a hydraulic retention time (HRT) of 30 days. Total solid (TS) and volatile solid (VS) reductions, biogas and CH4 yields, alkalinity, and volatile acidity were measured. The control treatment differed from the others and resulted in decreased biogas yield (752 LN.kgVSadded -1), CH4 (449 LN.kgVSadded -1), and CH4 content (59.7%). The AcoD treatments (SP and C) did not differ significantly for biogas yield (respectively, 901 and 883 LN.kgVSadded -1) and CH4 (respectively, 590 and 547 LN.kgVSadded -1); however, they differed in CH4 content (65.5% and 61.9% respectively). The treatments showed general reduction averages of 76.1% and 85.9% for TS and VS, respectively, with no statistical difference found between them. The AcoD of the SM with SP or C increased the production and quality of the biogas, increasing the concentration of CH4 therein.

Enhancement of high solid anaerobic co-digestion of swine manure with rice straw pretreated by microwave and alkaline

This study was to evaluate the effect of pretreated rice straw on high solid anaerobic co-digestion with swine manure, focusing on biogas production and kinetics. The rice straw pretreated by microwave, alkaline and alkaline-microwave was co-digested with swine manure under high solid state, and the effect was evaluated in bath reactors. The results indicated that, high solid anaerobic co-digestion of swine manure with rice straw pretreated by alkaline and alkaline-microwave could increase biogas yields by around 25%, with biogas productivities improved by 2.85–5.88% for per unit of total solid (TS). The biogas yields and productivities with rice straw pretreated by alkaline and alkaline-microwave could reach 355–357 L kg−1 TS-loaded and 679–699 L kg−1 TS-reduced, and their co-digestion process fitted the two-stage first order model accurately, discerned from the smaller average relative differences of 5.74% and 6.09% in contrast to 11.56% and 13.81% by using the single-stage first order model.

Effects of Corn Stover Pretreated with NaOH and CaO on Anaerobic Co-Digestion of Swine Manure and Corn Stover

In this study, effects of pretreatment of corn stover (CS) with sodium hydroxide (NaOH) combined with calcium oxide (CaO) on anaerobic co-digestion of swine manure and CS for biogas production were investigated. Different pretreated-CSs were prepared by adding different doses of NaOH and CaO to CS: Treat-CSA (0.10 g NaOH/g CS), Treat-CSB ((0.075 g NaOH + 0.05 g CaO)/g CS), Treat-CSC ((0.05 g NaOH + 0.05 g CaO)/g CS), and Treat-CSD ((0.025 g NaOH + 0.1 g CaO)/g CS). Lignin removal rate, biomass recovery, reduced sugar, methane yield, DT80 (digestion time when biogas achieved 80% of the total biogas), composition of residues, and cost-efficiency were measured to characterize CS after pretreatment and to evaluate the performance of co-digestors fed with swine manure and differently-pretreated CS. The results showed that Treat-CSB showed an excellent lignin removal efficiency and biomass recovery, resulting in the highest methane yield in its co-digestion with swine manure. Since the net benefit of Treat-CSB was calculated to be the highest (i.e., $1.89/ton total solids), therefore, we believe the co-digestion of Treat-CSB and swine manure for biogas production be an effective valorization option for the wastes.

Sanitary effectiveness and biogas yield by anaerobic co-digestion of swine carcasses and manure

ABSTRACTThe present study evaluated anaerobic co-digestion of swine manure and swine carcasses for biogas yield and inactivation/behaviour of pathogens purpose. Biochemical Methane Production tests were performed with samples containing ratios of 3, 7.5 and 15 kgcarcass m−3manure. For pathogens inactivation experiments known amounts of model microrganisms (sensitive and resistant) were artificially inoculated in anaerobic reactors at 24°C and 37°C. The addition of carcass resulted in an increase until 119% of biogas yield compared to swine manure mono-digestion. Salmonella enterica, Escherichia coli and PCV2 were reduced >3log10 (24°C or 37°C) during 30 days. At 37°C, MS2 and PhiX-174 were reduced 3log10 and 1.8log10, respectively. At 24°C, MS2 reduced 1.5 log10 and PhiX-174 did not present any decay over 30 days. Considering the most resistant biomarkers pathogens, as bacteriophage, we recommend the swine carcasses pre-treatment, such as high temperatures, for sanitary security.

Anaerobic co-digestion of swine manure and crude glycerol derived from animal fat—Effect of hydraulic retention time

Crude glycerol (CG), an abundant by-product of bio-diesel production, has been identified as a suitable co-substrate for improving the biogas production of livestock manure through anaerobic digestion (AD). In this study, the potential of utilizing CG generated from the esterification of animal fats for biogas production was studied in both batch and continuous AD experiments, with emphasis on the importance of the hydraulic retention time (HRT). Batch experiments showed that the limiting step in the methane production rate during CG mono-digestion was the 1,3-propanediol uptake. Additionally, biochemical methane potential tests indicated that the addition of 1% w/w CG to swine manure-AD is more efficient in terms of percent of theoretical amount of methane obtained than the addition of 3% w/w. However, in continuous experiments, co-digestion of manure with 3% w/w CG did not exhibit any sign of inhibition within the HRTs tested (17–22 days). Moreover, a 222% increase of biogas productivity was observed with 3% CG supplementation at an HRT of 17 days, in contrast to a 146% increase at an HRT of 22 days. Based on this, and on the similar efficiency of soluble COD removal among the processes (ca. 93%), it was shown that it is possible to reduce the HRT without affecting negatively the efficiency of conversion of manure. Moreover, it was shown that CG from 2 nd generation biodiesel based on animal fat, is a suitable feedstock for boosting the methane production of manure-based biogas plants.

Process performance and methane production optimizing of anaerobic co-digestion of swine manure and corn straw

During anaerobic digestion (AD) process, process parameters e.g., VFA, pH, COD removal … and kinetic parameters e.g., hydrolysis rate, lag phase and methane production potential… are the important indicator for illustrating AD process performance, however, the AD process performance based on these parameters remains poorly understood. To estimate process performance focusing on initial pH and substrate composition, the effects of initial pH and swine manure to corn straw ratio on biogas production and these parameters and linkages of these parameters were analyzed. Also, the methane production was optimized. The results revealed that the maximum methane yield and methane production rate were obtained with initial pH 7.5 and SM/CS ratio of 70:30. Kinetic parameters are coupled with process parameters, especially for COD removal rate, VS degradation rate, VFA and pH. Hydrolysis constant positively correlated with pH, COD removal rate and VS degradation rate, then impacted methane production and lag phase. Meanwhile, lag phase and the maximum methane production rate were directly determined by VFA and COD removal rate. The optimum initial pH and SM/CS ratio were 7.15 and 0.62, respectively, with a predicted maximum methane content of 55.12%. Thinking these findings together, they provide a scientific theory for estimating AD performance.

Produção de biogás por dejetos de ruminantes e monogástricos co-digeridos com manipueira

Objetivou-se avaliar o uso de manipueira na co-digestão anaeróbia com dejetos de animais monogástricos e ruminantes, por meio de parâmetros de monitoramento do processo e da produção de biogás. Foram utilizados oito biodigestores semicontínuos com volume útil de 7,8 L de substrato em fermentação operados com tempo de retenção hidráulica de 30 dias. Realizou-se análises de pH, nitrogênio amoniacal, alcalinidade parcial (AP), sólidos totais (ST), sólidos voláteis (SV), e rendimento do biogás (m3 kg SVadicionados-1). Os valores de pH e concentrações de AP apresentaram-se na faixa ideal para a ocorrência do processo de digestão, de 6,0 a 8,0 e acima de 1.200 mg·L-1, respectivamente. Durante o processo não houve risco de falência por concentrações de nitrogênio amoniacal. As produções médias de biogás acumuladas semanais foram de 0,00676, 0,1167, 0,01515 e 0,01856 m3, respectivamente para substratos formados por dejetos de bovinos de leite, ovinos, aves e/ou suínos codigeridos com manipueira. Os rendimentos para os respectivos substratos foram 0,122, 0,275, 0,535 e 0,843 m3 kg SVadicionados-1. Maiores produções de biogás são obtidas na co-digestão anaeróbia de dejetos de suínos com 10 % (volume/volume) de manipueira.

Prokaryote community dynamics in anaerobic co-digestion of swine manure, rice straw and industrial clay residuals.

The aim of this study was to analyze the effect of the addition of rice straw and clay residuals on the prokaryote methane-producing community structure in a semi-continuously stirred tank reactor fed with swine manure. Molecular techniques, including terminal restriction fragment length polymorphism and a comparative nucleotide sequence analyses of the prokaryotic 16S rRNA genes, were performed. The results showed a positive effect of clay addition on methane yield during the co-digestion of swine manure and rice straw. At the digestion of swine manure, the bacterial phylum Firmicutes and the archaeal family Methanosarcinaceae, particularly Methanosarcina species, were predominant. During the co-digestion of swine manure and rice straw the microbial community changed, and with the addition of clay residual, the phylum Bacteroidetes predominated. The new nutritional conditions resulted in a shift in the archaeal family Methanosarcinaceae community as acetoclastic Methanosaeta species became dominant.