Anaerobic Digestion Of Dairy Manure Research Articles

Succession of microbial community in anaerobic digestion of dairy manure induced by manure-derived biochar

The present study investigates possible roles of manure-derived biochar (MBC) in anaerobic digestion (AD) of dairy manure. Addition of MBC led to an increase in cumulative methane yield and a decrease in lag phase under all tested conditions (concentration of MBC: 1 and 10 g/L, temperature: 20, 35 and 55°C). For example, the cumulative methane yield in the mesophilic AD with 10 g/L MBC were 24.51% higher than that of the AD without MBC. Additionally, lag phage of mesophilic AD with 10 g/L MBC decreased from 2.08 d to 1.52 d. Microbial community analysis indicated that the addition of MBC to mesophilic and thermophilic AD of dairy manure increased the relative abundance of <i>Ruminofilibacter</i> which related to the hydrolysis. In addition, the addition of MBC to AD potentially stimulated the growth of syntrophic bacteria (e.g., genera Clostridium, Syntrophomonas and Syntrophus) and hydrogenotrophic methanogens (e.g., genera <i>Methanobacterium, Methanolinea</i> and <i>Methanomassiliicoccus</i>). Furthermore, microbial community analysis also suggested that mediate interspecies electron transfer and direct interspecies electron transfer would be accelerated by addition of MBC which showed high electrical conductivity (3230 μS/cm).

Effect of ceftiofur on mesophilic anaerobic digestion of dairy manure and the reduction of the cephalosporin-resistance gene cmy-2

The effect of ceftiofur (CEF), a commonly used antibiotics on dairy farms, on the performance and stability of mesophilic batch anaerobic digestion (AD) of dairy manure was evaluated in terms of methane production, organic matter removal (COD, dCOD, TS, and VS), and synthesis of end-products (VFAs, CO2, and H2). The results indicated that only CEF concentrations of 10 mg/L or higher significantly affected the performance of the AD process, although the overall stability was not compromised. Biochemical analyses suggested that hydrolytic microorganisms were the most affected by the presence of CEF leading to lower COD removal, whereas acetogens were only temporarily slowed down. Methanogens, on the other hand, were not directly affected by any of the CEF concentrations tested (0.2–250 mg/L). Additionally, the presence of CEF was shown to alter the incidence of the cephalosporin-resistance marker, cmy-2, although an overall reduction was achieved in 15-day batch anaerobic digestion trials.

Effect of solid-liquid separation on anaerobic digestion of dairy manure in semi-continuous stirred tank reactors: Process performance and digestate characteristics.

The objective of this study was to investigate the effect of solid-liquid separation on anaerobic digestion of dairy manure in semi-continuous stirred tank reactors. Reactors fed with liquid fraction of dairy manure (screened liquid manure) were kept in water baths at mesophilic (Run 1) and thermophilic (Run 3) temperatures, respectively, while reactors fed with water diluted manure and kept at mesophilic (Run 2) and thermophilic (Run 4) temperatures as control reactors. The performances of reactors were compared in terms of biogas and methane production, and digestate characteristics. The methane yields obtained from screened manure were higher than those from diluted manure at both mesophilic and thermophilic temperatures, while the highest methane yield was 185L/kg VSadded under thermophilic temperature. Solid-liquid separation also had improved the effect on digestate fertilizer characteristics. Among four digestates from reactors, the highest contents of nutrients, N (4.12g/kg) and P (2.36g/kg) were found in Run 3, while the highest content of K (3.42g/kg) was found in Run 1. These results showed the benefits of solid-liquid separation of dairy manure on process performance and digestate characteristics.

Effect of Substrate to Inoculum Ratio and Inoculum Type on Solid State Anaerobic Digestion of Dairy Manure

Effect of Substrate to Inoculum Ratio and Inoculum Type on Solid State Anaerobic Digestion of Dairy Manure

Facilitated methanogenesis involved in anaerobic digestion of dairy manure by soil

Abstract Shaping the microbial community involved in anaerobic digestion (AD) systems to achieve highly efficient methane production is a major challenge. In order to improve the methane recovery from dairy manure, soil, which has the potential of enhancing methane production from biomass, was used in an AD system as an additive. The results showed that the AD process performance and methane production efficiency were significantly improved by soil; an improvement in daily methane production, reduced time to steady state, enhancement of the methane content, and reduction in carbon dioxide content were obtained. The maximum methane production was obtained at a feedstock: soil ratio of 2.5:1 with yellow soil addition, which was 147.7 L/kg volatile solids (VS) and 25.4% higher than that of the control. High-throughput sequencing of the 16S ribosomal RNA gene and synthetic solution with cations equivalent to those of yellow and black soil revealed that soil addition mainly stimulated the growth of bacterial genera Ochrobactrum and Clostridium and archaeal genera Methanosaeta and Methanosarcina. The method of ion extraction was used to extract ions from the soil, and the ions were verified to be a main contributor to methane production improvement. By mimicking the cation components of soil, a synthetic solution was prepared and used in the AD system. The results showed that the cations contained in the ion liquid played a key role in improving methane production. The contribution of VS in the soil to the AD system was studied and found to have no significant effect on the improvement in methane production. It was found that the cations in soil played a key role in enhancing AD efficiency. Therefore, the simplified, low cost, and efficient approach used in this study had good practicability and could be used for treating other various biowastes with high energy recovery, which has the potential of promoting the development of AD technology.

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

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

Investigation of the effect of intermittent minimal mixing intensity on methane production during anaerobic digestion of dairy manure

Mixing plays an important role in maintaining the solids suspended and the fermenting liquid homogeneous throughout the digester, which helps to improve methane production. The pilot-scale digester with working volume of 1 m3 was mixed with a top-driven impeller. Three mixing intensities, 50, 100 and 150 rpm were minimally intermittent mixed once a day for 5 min under mesophilic temperature conditions (35 ± 0.3 °C) with average total solids content of 14.1% and hydraulic retention time of 30 days. The results show that 100 rpm mixing intensity outperformed the other two, indicating that mixing intensity threshold exists and beyond which methane production is negatively affected. However, 50 rpm was regarded as the economical mixing intensity even though dead zones were recorded. Minimally intermittent mixing once a day was enough to maintain anaerobic digestion process and performance efficiency for optimum methane production. Computational fluid dynamics (CFD) results agreed with the experiment, demonstrating that 100 rpm mixing intensity was sufficient to homogenize the digester content. Further, CFD was used to predict the mixing time in the digester.

Effects of Laser Irradiation and Ni Nanoparticles on Biogas Production from Anaerobic Digestion of Slurry

This study investigated the simultaneous effects of nanoparticles (NPs) addition to rumen fluid (archaea source) and laser irradiation of the mixture on biogas production from anaerobic digestion of dairy manure. Where, the previous study reported that the addition of 2 mg L−1 nickel nanoparticles (Ni NPs) significantly (p < 0.05) increased the biogas and methane volumes by 1.74 and 2.01 times compared to the control, respectively. The results indicated that the most efficient irradiation time was 2 h laser with the addition of 2 mg L−1 Ni NPs (p < 0.05), which minimized the lag phase from 4 days to 1 day and the Hydraulic Retention Time (HRT) to attain the peak of biogas production in comparison to the control from 28 days to 16 days. The combination of laser irradiation and nanoparticles addition yielded the highest significant value of the specific biogas and methane production, compared to all treatments (incandescent light, control), which were 679.5 mL biogas g−1 VS and 453.3 mL CH4 g−1 VS. Furthermore, Laser photocatalysis of Ni NPs enhances the photo-reduction/photo-oxidation of CH4 formation pathways. Consequently, this treatment increased the biogas and methane volumes by 1.9 and 2.32 times the biogas and methane volumes resulted from the control, respectively.

Semi-continuous anaerobic co-digestion of dairy manure, meat and bone meal and crude glycerol: Process performance and digestate valorization

Abstract The objective of this study was to investigate the effects of the addition of meat and bone meal (MBM) and crude glycerol (CG) on the anaerobic digestion of dairy manure (DM) with respect to digestion performance and digestate fertilizer value. The anaerobic co-digestion of DM, MBM and CG was conducted in semi-continuous stirred tank reactors at 37 °C with organic loadings between 2.63 and 2.86 g volatile solids (gVS)/L·d. Run 1 was a control reactor, while in Runs 2 and 3, DM was co-digested with MBM at ratios of 3.0:1.0 and 1.0:1.0 (gVSDM:gVSMBM), respectively. In Run 4, DM and MBM were co-digested with CG at a ratio of 1.0:0.7:0.3 (gVSDM:gVSMBM:gVSCG). The results showed that methane yields were increased by 9.1% and 30.2% in Runs 2 and 3, respectively, compared to Run 1, while the highest methane yield (0.39 L/gVSadded·d) was obtained in Run 4. The co-digestion of DM with MBM increased the ammoniacal nitrogen in the digestate by 2.1- to 2.3-fold, while no significant difference was observed for phosphorus. Due to the overabundance of nutrients in soil, the recovery of phosphorus and nitrogen and the recycling of water are the best strategies to sustain anaerobic digestion via an environmentally friendly approach.

Low-cost composited accelerants for anaerobic digestion of dairy manure: Focusing on methane yield, digestate utilization and energy evaluation

To improve the methane yield and digestate utilization of anaerobic digestion (AD), low-cost composited accelerants consisting of urea (0.2–0.5%), bentonite (0.5–0.8%), active carbon (0.6–0.9%), and plant ash (0.01–0.3%) were designed and tested in batch experiments. Total biogas yield (485.7–681.9 mL/g VS) and methane content (63.0–66.6%) were remarkably enhanced in AD systems by adding accelerants compared to those of control group (361.9 mL/g VS, 59.4%). Composited accelerant addition led to the highest methane yield (454.1 mL/g VS), more than double that of control group. The TS, VS, and CODt removal rates (29.7–55.3%, 50.9–63.0%, and 46.8–69.1%) for AD with accelerants were much higher than control group (26.2%, 37.1%, and 39.6%). The improved digestate stability and enhanced fertilizer nutrient content (4.95–5.66%) confirmed that the digestate of AD systems with composited accelerants could safely serve as a potential component of bioorganic fertilizer. These findings open innovative avenues in composited accelerant development and application.

Solid-State Anaerobic Digestion of Dairy Manure from a Sawdust-Bedded Pack Barn: Moisture Responses

Bedded pack manure has long been considered an unsuitable feedstock for conventional anaerobic digestion systems due to its high solids content. However, solid-state anaerobic digestion (SS-AD) provides an opportunity to generate methane from such high-solids feedstocks. This study was conducted to determine the influence of moisture content on the digestion of bedded pack dairy manure using SS-AD. Mixtures of sawdust bedding and dairy manure were prepared with moisture contents (MCs) of 70, 76, and 83% and digested at 37 °C for 85 days. The performance of digesters containing manure at 83% MC was 1.3 to 1.4-fold higher than that of digesters containing 70% MC manure in terms of volatile solids (VS) reduction and biogas production. VS reduction rates were 55 to 75% and cumulative methane yield ranged from 64 to 90 NmL (gVS)−1. These values are lower than those from SS-AD of fresh manure and this is likely due to the partial decomposition of biodegradable materials during the two to three-month period before the manure was removed from the barn. However, in terms of efficient management of farm odors and providing a renewable energy source for heating, SS-AD of bedded pack manure offers a potential alternative to the conventional composting systems currently in use.

Comparative fertilizer properties of digestates from mesophilic and thermophilic anaerobic digestion of dairy manure: focusing on plant growth promoting bacteria (PGPB) and environmental risk

The fertilizer properties of anaerobic digestate depend on the feedstock and operating conditions of digestion. In this study, the comparative fertilizer properties of mesophilic and thermophilic digestates from dairy manure were evaluated for plant nutrient contents, and special attention was paid to plant growth promoting bacteria (PGPB). Two digestates contained similar plant nutrient contents, while the thermophilic digestate contained higher contents of NH4+–N. The quantity of Bacillus and Pseudomonas in the mesophilic digestate was significantly higher than in the thermophilic digestate. Furthermore, Bacillus showed siderophore production and antifungal activity (43.5–75.3%), and Pseudomonas showed siderophore and phytohormone production (4.2–75.2 µg ml−1). One phosphate solubilizing isolate was also detected in the mesophilic digestate. These results indicated that two digestates showed different fertilizer properties with respect to nutrient contents and PGPB, and digestates had the potential to increase the availability of phosphorus and iron in the soil, both to provide phytohormones to plant roots and protect plants from fungal phytopathogens. The contents of indicator bacteria and heavy metals were analyzed to determine their environmental risk, and the results showed a high reduction in indicator bacteria and lower levels of heavy metals than in other feedstocks.

The fate and effect of monensin during anaerobic digestion of dairy manure under mesophilic conditions.

There is growing concern about residual antibiotics and feed additives in the manure of treated animals because of the effects of these residues in the environment. Monensin is the most widely used ionophore coccidiostat in the U.S. The objective of this study was to determine the fate and effect of monensin during the anaerobic digestion of dairy manure. Duplicate plug flow field-scale digesters were operated using non-amended dairy manure and dairy manure amended with monensin to 1 and 10 mg/L for 56 days at 30°C at an organic loading rate of 1.4 kg VS/m3-d and 17-day hydraulic retention time. Results showed that monensin was reduced approximately 70% during anaerobic digestion. Methane production from digesters using manure amended with 1 mg/L monensin was comparable to that from digesters operated without added monensin. However, digesters using manure amended with 10 mg/L monensin yielded 75% less methane than digesters using manure without added monensin. These results suggest that anaerobic digestion is an effective treatment for reducing, but not eliminating, monensin in dairy manure. Monensin did not reduce methane production at concentrations expected in dairy manure at recommended dosage rates.

Anaerobic Digestion of Dairy Manure and Rice Straw in Batch Reactor for Biogas Production

Anaerobic Digestion of Dairy Manure and Rice Straw in Batch Reactor for Biogas Production

Effects of dairy manure-derived biochar on psychrophilic, mesophilic and thermophilic anaerobic digestions of dairy manure

Effects of dairy manure-derived biochar (M-BC) on methane production in anaerobic digestion (AD) of dry dairy manure were investigated with three different concentrations of biochar (0, 1 and 10 g/L) and temperatures (psychrophilic, 20 °C; mesophilic, 35 °C; thermophilic, 55 °C). Compared with the AD without any biochar, the cumulative methane and yield in the AD with 10 g/L biochar were increased to 27.65% and 26.47% in psychrophilic, 32.21% and 24.90% in mesophilic and 35.71% and 24.69% in thermophilic digestions. The addition of M-BC shortened the lag phases of AD at all temperatures in the study while it lowered the concentration of total VFAs and propionic acid. It was suggested that the high nutrients and alkalinity potential of M-BC (i.e. 9.1% Ca, 3.6% Mg, 1.3% N, 0.14% P) would play significant roles in enhancing methane production and shortening lag phases from the AD of dairy manure.

Evaluation of Leachate Replacement Effect on Solid State Anaerobic Digestion of Dairy Manure and Sawdust Bedding Mixtures

This experiment was conducted to evaluate the effect of leachate replacement frequency on solid state anaerobic digestion (SSAD) of dairy manure using 22 L volume lab-scale digesters at mesophilic temperature (37°C) in batch mode. Three different leachate replacement strategies (no replacement, once every three days, and once every nine days) were applied and three digesters per each treatment were operated for 45 days. Results showed that leachate replacement test unit every nine days resulted in 1.6 times more methane production (53.8 N․mL g-1․VS) from SSAD compared to test unit every three days (34.0 N․mL g-1․VS). No leachate replacement strategy applied group showed slightly higher methane production (56.3 N․mL g-1․VS) than every nine days replaced one. When added the methane production potential of replaced leachate itself to the methane produced from digester, leachate replacement every nine days resulted in quite similar methane production (56.5 N․mL g-1․VS) to no leachate replacement group. Even though methane production potential of replaced leachate itself added to the methane produced from digester, every three days replacement showed only 34 N․mL methane production per gram of volatile solids. These results suggest that farmers do not need to replace leachate during SSAD of dairy manure and sawdust mixture in order to maximize methane production. If there are any concerns with accumulation of inhibiting substances in the digester, the 9-day cycle leachate replacement is appropriateHighest methane yield was observed in the No replacing and Replacing (every 9 days), while the methane yield of the Replacing (every 3 days) was 1.6 times lower than the highest yield.

Digested Slurry Recirculation in Thermophilic Wet Anaerobic Digestion of Dairy Manure without Water Dilution

Digested Slurry Recirculation in Thermophilic Wet Anaerobic Digestion of Dairy Manure without Water Dilution

Recycling separated liquid-effluent to dilute feedstock in anaerobic digestion of dairy manure

The major concern of recycling anaerobic digestion (AD) effluent in the digester centers on accumulation of total ammonia nitrogen (TAN) and salinity, both of which can potentially inhibit methane production. In the current study, 30%, 50%, and 80% of separated-liquid AD effluent, were recycled in a series of batch AD experiments. The inhibitions to specific methane potential (SMP) caused by TAN and salinity were evaluated. Recycling up to 80% of un-treated effluent resulted in the best SMP averaging 0.265 ± 0.005 m3 [CH4] Kg−1 [volatile solids], which averaged 10% more compared to recycling 80% treated effluent and 5% more compared to no recycling (the control). After acclimation, up to 6.39 g N L−1 increase in TAN resulted in SMP averaging 0.112 ± 0.002 m3 [CH4] Kg−1 [volatile solids] and up to 12 parts per thousand increase in salinity resulted in SMP averaging 0.163 ± 0.005 m3 [CH4] Kg−1 [volatile solids]. A mass balance for a hypothetical 5000 cows dairy farm showed effluent recycle of up to 66% for maintaining 8% solids in anaerobic digester. Moreover, in the proposed system, the effluent going off-farm was on w/w basis 64% less water, 66% less solids, and 52% less nitrogen compared to the effluent produced with no recycle facility.

Field Nitrogen Losses Induced by Application Timing of Digestate from Dairy Manure Biogas Production.

Anaerobic digestion of dairy manure has environmental benefits, but the impact of effluent (i.e., digestate [DG]) application on environmental nitrogen (N) losses from soils has not been well quantified. Our objective was to evaluate how field application of DG affected nitrous oxide (NO) emissions and nitrate (NO) leaching compared with raw dairy manure (RM) in spring versus fall applications. We measured N losses year-round for 2.5 yr in silage corn on tile-drained clay soil in Alfred, Ontario, Canada. Treatments were: digestate applied in spring (DS) and fall (DF), raw dairy manure applied in spring (RS) and fall (RF), urea applied in spring, and a control. Overall, the source of N had no effect on annual NO emissions (overall average DG and RM, 4.9 kg NO-N ha yr), but more NO leached from DS than RS treatments (8.8 and 4.8 kg NO-N ha yr on average, respectively). Estimated indirect NO emissions from leached NO-N were small (<0.2 kg NO-N ha yr). Timing of application did not affect annual NO emissions but did shift emissions to the non-growing season for fall applications (65% on average) and to the growing season for spring applications (60% on average). Overall environmental N losses (NO-N + NO-N) from DG were similar to RM when applied at the same time. For the conditions of our study, downstream emissions from anaerobic digestion (i.e., emissions induced by applied digestate) do not present an adverse trade-off to the environmental benefits incurred during the biogas production phase.

Comparative evaluation of biogas production from dairy manure and co-digestion with maize silage by CSTR and new anaerobic hybrid reactor.

This study aimed to investigate potential methane production through anaerobic digestion of dairy manure and co-digestion with maize silage. Two different anaerobic reactor configurations (single-stage continuously stirred tank reactor [CSTR] and hybrid anaerobic digester) were used and biogas production performances for each reactor were compared. The HR was planned to enable phase separation in order to improve process stability and biogas production under higher total solids loadings (≥4%). The systems were tested under six different organic loading rates increased steadily from 1.1 to 5.4 g VS/L.d. The CSTR exhibited lower system stability and biomass conversion efficiency than the HR. The specific biogas production of the hybrid system was between 440 and 320 mL/gVS with 81-65% volatile solids (VS) destruction. The hybrid system provided 116% increase in specific biogas production and VS destruction improved by more than 14%. When MS was co-digested together with dairy manure, specific biogas production rates increased about 1.2-fold. Co-digestion was more beneficial than mono-material digestion. The hybrid system allowed for generating methane enriched biogas (>75% methane) by enabling phase separation in the reactor. It was observed that acidogenic conditions prevailed in the first two compartments and the following two segments as methanogenic conditions were observed. The pH of the acidogenic part ranged between 4.7 and 5.5 and the methanogenic part was between 6.8 and 7.2.