A start-up of psychrophilic anaerobic sequence batch reactor digesting a 35 % total solids feed of dairy manure and wheat straw.

Zero liquid discharge is currently an objective in livestock manure management to minimize water pollution. This paper reports the start-up phase of a novel psychrophilic (20 °C) dry anaerobic digestion of dairy manure with bedding fed at 35 % total solids and an organic loading rate of 3.0 g total chemical oxygen demand kg(-1) inoculum day(-1) in anaerobic sequence batch reactors. The specific methane (CH4) yield ranged from 165.4 ± 9.8 to 213.9 ± 13.6 NL CH4 kg(-1) volatile solids (VS) with an overall average of 188 ± 17 NL CH4 kg(-1) VS during 11 successive start-up cycles (231 days) and a maximum CH4 production rate of 10.2 ± 0.6 NL CH4 kg(-1) VS day(-1). The inoculum-to-substrate (VS-based) ratio ranged from 4.06 to 4.47. Although methanogenesis proceeded fairly well the hydrolysis seemed to be the rate limiting step. It is possible start up psychrophilic dry anaerobic digestion of cow feces and wheat straw at feed TS of 35 % within 7-10 successive cycles (147-210 days).

High rate psychrophilic anaerobic digestion of undiluted dairy cow feces.

Novel high rate psychrophilic (20°C) anaerobic digestion (PAD) of undiluted cow feces (11.5-13.5% total solids) was demonstrated using sequence batch reactor in long-term operation with successive cycles of 21days treatment cycle length (TCL). At organic loading rates (OLR) 9.0, 10.0, 11.0 and 12.0g TCOD kg(-1) inoculum d(-1) average specific methane yield (SMY) was 154.0±11.7, 152.1±12.2, 126.0±2.8 and 116.0±6.1NL CH4 per kg of VS fed, respectively. Volatile solids removal averaged around 31.7±3.3%, 32.2±1.0%, 27.9±2.2% and 23.4±0.5%, respectively. Substrate-to-inoculum ratio (SIR; wet-mass basis) ranged between 1.17±0.06 and 1.43±0.05. Concentration of volatile fatty acids in the bioreactors during the TCL indicated that hydrolysis was the rate limiting reaction. High rate PAD of undiluted cow feces is possible at OLR (g TCOD kg(-1) inoculum d(-1)) 9.0 and 10.0 with a TCL of 21days; however, OLR of 11.0 and 12.0 are also possible but require longer TCL to maintain the SMY.

High rate psychrophilic anaerobic digestion of high solids (35%) dairy manure in sequence batch reactor.

Zero liquid discharge is increasingly adopted as an objective for waste treatment process. The objective of this study was to increase the feed total solids (TS) and the organic loading rate (OLR) fed to a novel psychrophilic (20°C) dry anaerobic digestion (PDAD). Duplicate laboratory-scale bioreactors were fed cow feces and wheat straw (35% TS in feed) at OLR of 6.0 g TCOD kg(-1) inoculum d(-1) during long-term operation (147 days consisting of 7 successive cycles). An overall average specific methane yield (SMY) of 151.8±7.9 N L CH4 kg(-1) VS fed with an averaged volatile solids removal of 42.4±4.3% were obtained at a volatile solids-based inoculum-to-substrate ratio (ISR) of 2.13±0.2. The operation was stable as indicated by biogas and VFAs profiles and the results were reproducible in successive cycles; a maximum SMY of 163.3±5.7 N L CH4 kg(-1) VS fed was obtained. Hydrolysis was the reaction limiting step. High rate PDAD of 35% TS dairy manure is possible in sequential batch reactor within 21 days treatment cycle length.

Dry anaerobic digestion of high solids content dairy manure at high organic loading rates in psychrophilic sequence batch reactor.

Cow manure with bedding is renewable organic biomass available around the year on dairy farms. Developing efficient and cost-effective psychrophilic dry anaerobic digestion (PDAD) processes could contribute to solving farm-related environmental, energy, and manure management problems in cold-climate regions. This study was to increase the organic loading rate (OLR), fed to a novel psychrophilic (20 °C) dry anaerobic digestion of 27% total solid dairy manure (cow feces and wheat straw) in sequence batch reactor (PDAD-SBR), by 133 to 160%. The PDAD-SBR process operated at treatment cycle length of 21 days and OLR of 7.0 and 8.0 g total chemical oxygen demand (TCOD) kg(-1) inoculum day(-1) (5.2 ± 0.1 and 5.8 ± 0.0 g volatile solids (VS) kg(-1) inoculum day(-1)) for four successive cycles (84 days) produced average specific methane yields (SMYs) of 147.1 ± 17.2 and 143.2 ± 11.7 normalized liters (NL) CH4 kg(-1) VS fed, respectively. PDAD of cow feces and wheat straw is possible with VS-based inoculum-to-substrate ratio of 1.45 at OLR of 8.0 g TCOD kg(-1) inoculum day(-1). Hydrolysis was the limiting step reaction. The VS removal averaged around 57.4 ± 0.5 and 60.5 ± 5.7% at OLR 7.0 and 8.0 g TCOD kg(-1) inoculum day(-1), respectively.

Impact of organic loading rate on the performance of psychrophilic dry anaerobic digestion of dairy manure and wheat straw: long-term operation.

Development of efficient processes for valorising animal wastes would be a major advancement in cold-climate regions. This paper reports the results of long term (315 days experiment) of novel psychrophilic (20°C) dry anaerobic digestion (PDAD) of cow feces and wheat straw in laboratory scale sequence batch reactor operated at increasing organic loading rate. The PDAD process fed with a mixture of feces and straw (TS of 27%) over a treatment cycle length of 21 days at organic loading rate (OLR) 4.0, 5.0 and 6.0 g TCOD kg(-1) inoculum d(-1) (of 2.9 ± 0.1, 3.7 ± 0.1, and 4.4 ± 0.1g VS kg(-1) inoculum d(-1), respectively) resulted in average specific methane yield (SMY) of 187.3 ± 18.1, 163.6 ± 39.5, 150.8 ± 32.9 N L CH4 kg(-1)VS fed, respectively. PDAD of cow feces and wheat straw is possible with VS-based inoculum-to-substrate ratio of 1.4 at OLR of 6.0 g TCOD kg(-1) inoculum d(-1). Hydrolysis was the limiting step reaction.

Anaerobic digestibility of beef hooves with swine manure or slaughterhouse sludge.

Anaerobic digestion is an effective method for treating animal by-products, generating at the same time green energy as methane (CH4). However, the methods and mechanisms involved in anaerobic digestion of α-keratin wastes like hair, nails, horns and hooves are still not clear. In this study we investigated the feasibility of anaerobically co-digesting ground beef hooves in the presence of swine manure or slaughterhouse sludge at 25 °C using eight 42-L Plexiglas lab-scale digesters. Our results showed addition of beef hooves statistically significantly increased the rate of CH4 production with swine manure, but only increased it slightly with slaughterhouse sludge. After 90-day digestion, 73% of beef hoof material added to the swine manure-inoculated digesters had been converted into CH4, which was significantly higher than the 45% level achieved in the slaughterhouse sludge inoculated digesters. BODIPY-Fluorescent casein staining detected proteolytic bacteria in all digesters with and without added beef hooves, and their relative abundances corresponded to the rate of methanogenesis of the digesters with the different inocula. Fluorescence in situ hybridization in combination with BODIPY-Fluorescent casein staining identified most proteolytic bacteria as members of genus Alkaliphilus in the subfamily Clostridiaceae 2 of family Clostridiaceae. They thus appear to be the bacteria mainly responsible for digestion of beef hooves.

Psychrophilic dry anaerobic digestion of dairy cow feces: long-term operation.

This paper reports experimental results which demonstrate psychrophilic dry anaerobic digestion of cow feces during long-term operation in sequence batch reactor. Cow feces (13-16% total solids) has been anaerobically digested in 12 successive cycles (252 days) at 21 days treatment cycle length (TCL) and temperature of 20 °C using psychrotrophic anaerobic mixed culture. An average specific methane yield (SMY) of 184.9 ± 24.0, 189.9 ± 27.3, and 222 ± 27.7 (N)L CH4 kg(-1) of VS fed has been achieved at an organic loading rate of 3.0, 4.0, and 5.0 g TCOD kg(-1) inoculum d(-1) and TCL of 21 days, respectively. The corresponding substrate to inoculum ratio (SIR) was 0.39 ± 0.06, 0.48 ± .02, 0.53 ± 0.05, respectively. Average methane production rate of 10 ± 1.4(N)L CH4 kg(-1) VS fed d(-1) has been obtained. The low concentration of volatile fatty acids indicated that hydrolysis was the reaction limiting step.

Analysis of trimethoprim, lincomycin, sulfadoxin and tylosin in swine manure using laser diode thermal desorption-atmospheric pressure chemical ionization-tandem mass spectrometry.

A new extraction method coupled to a high throughput sample analysis technique was developed for the determination of four veterinary antibiotics. The analytes belong to different groups of antibiotics such as chemotherapeutics, sulfonamides, lincosamides and macrolides. Trimethoprim (TMP), sulfadoxin (SFX), lincomycin (LCM) and tylosin (TYL) were extracted from lyophilized manure using a sonication extraction. McIlvaine buffer and methanol (MeOH) were used as extraction buffers, followed by cation-exchange solid phase extraction (SPE) for clean-up. Analysis was performed by laser diode thermal desorption-atmospheric pressure chemical-ionization (LDTD-APCI) tandem mass spectrometry (MS/MS) with selected reaction monitoring (SRM) detection. The LDTD is a high throughput sample introduction method that reduces total analysis time to less than 15s per sample, compared to minutes when using traditional liquid chromatography (LC). Various SPE parameters were optimized after sample extraction: the stationary phase, the extraction solvent composition, the quantity of sample extracted and sample pH. LDTD parameters were also optimized: solvent deposition, carrier gas, laser power and corona discharge. The method limit of detection (MLD) ranged from 2.5 to 8.3 µg kg(-1) while the method limit of quantification (MLQ) ranged from 8.3 to 28µgkg(-1). Calibration curves in the manure matrix showed good linearity (R(2)≥ 0.996) for all analytes and the interday and intraday coefficients of variation were below 14%. Recoveries of analytes from manure ranged from 53% to 69%. The method was successfully applied to real manure samples.

Effects of Adding Corn Dried Distiller Grains with Solubles (DDGS) to the Dairy Cow Diet and Effects of Bedding in Dairy Cow Slurry on Fugitive Methane Emissions.

The specific objectives of this experiment were to investigate the effects of adding 10% or 30% corn dried distillers grains with solubles (DDGS) to the dairy cow diet and the effects of bedding type (wood shavings, straw or peat moss) in dairy slurry on fugitive CH4 emissions. The addition of DDGS10 to the dairy cow diet significantly increased (29%) the daily amount of fat excreted in slurry compared to the control diet. The inclusion of DDGS30 in the diet increased the daily amounts of excreted DM, volatile solids (VS), fat, neutral detergent fiber (NDF), acid detergent fiber (ADF) and hemicellulose by 18%, 18%, 70%, 30%, 15% and 53%, respectively, compared to the control diet. During the storage experiment, daily fugitive CH4 emissions showed a significant increase of 15% (p < 0.05) for the slurry resulting from the corn DDGS30 diet. The addition of wood shavings and straw did not have a significant effect on daily fugitive CH4 emissions relative to the control diet, whereas the addition of peat moss caused a significant increase of 27% (p < 0.05) in fugitive CH4 emissions.

Effect of Corn Dried Distiller Grains with Solubles (DDGS) in Dairy Cow Diets on Manure Bioenergy Production Potential.

The main objective of this study was to obtain scientifically sound data on the bioenergy potential of dairy manures from cows fed different levels of corn dried distillers grains with solubles (DDGS). Three diets differing in corn DDGS content were formulated: 0% corn DDGS (DDGS0; control diet), 10% corn DDGS (DDGS10) and 30% corn DDGS (DDGS30). Bioenergy production was determined in psychrophilic (25 ± 1 °C) sequencing batch reactors (SBRs) fed 3 g COD L(-1)·day(-1) during a two-week feeding period followed by a two-week react period. Compared to the control diet, adding DDGS10 and DDGS30 to the dairy cow diet increased the daily amount of fat excreted in slurry by 29% and 70%, respectively. The addition of DDGS30 increased the cows' daily production of fresh feces and slurry by 15% and 11%, respectively. Furthermore, the incorporation of DDGS30 in the diet increased the daily amounts of dry matter (DM), volatile solids (VS), neutral detergent fiber (NDF), acid detergent fiber (ADF) and hemicellulose by 18%, 18%, 30%, 15% and 53%, respectively, compared to the control diet. While the addition of DDGS did not significantly affect the specific CH4 production per kg VS compared to the control diet, DDGS30 increased the per cow daily CH4 production by 14% compared to the control diet.

Potential of Biological Processes to Eliminate Antibiotics in Livestock Manure: An Overview.

Degrading antibiotics discharged in the livestock manure in a well-controlled bioprocess contributes to a more sustainable and environment-friendly livestock breeding. Although most antibiotics remain stable during manure storage, anaerobic digestion can degrade and remove them to various extents depending on the concentration and class of antibiotic, bioreactor operating conditions, type of feedstock and inoculum sources. Generally, antibiotics are degraded during composting > anaerobic digestion > manure storage > soil. Manure matrix variation influences extraction, quantification, and degradation of antibiotics, but it has not been well investigated. Fractioning of manure-laden antibiotics into liquid and solid phases and its effects on their anaerobic degradation and the contribution of abiotic (physical and chemical) versus biotic degradation mechanisms need to be quantified for various manures, antibiotics types, reactor designs and temperature of operations. More research is required to determine the kinetics of antibiotics' metabolites degradation during anaerobic digestion. Further investigations are required to assess the degradation of antibiotics during psychrophilic anaerobic digestion.

A critical review on inhibition of anaerobic digestion process by excess ammonia.

Ammonia plays a vital role in the performance and stability of anaerobic digestion (AD) of N-rich organic-feedstock. Several research works were carried-out to study the effect of ammonia on the efficiency of AD of agro-food, industrial and livestock wastes/wastewater. However, excess ammonia remains a critical hitch in AD process. The mechanism of ammonia-inhibition has also been studied and there is no simple strategy available to mitigate ammonia-toxicity, when it exceeds threshold inhibition-level. For successful operation of AD systems at higher ammonia-level, adequate choice of temperature, control of pH and C/N ratio, and utilization of acclimatized-microflora to higher ammonia concentrations may ensure a stable and undisturbed digestion. This review provides a critical summary of earlier and recent research conducted on ammonia-inhibition during the anaerobic degradation of organic substrates, especially, at high ammonia concentrations. This article emphasizes that more profound knowledge on parameters influencing ammonia-inhibition is needed to apply appropriate control strategies.

Psychrophilic anaerobic digestion of lignocellulosic biomass: a characterization study.

Psychrophilic (20°C) specific methane (CH4) yield from cellulose (C), xylan (X), cellulose/xylan mixture (CX), cow feces (CF), and wheat straw (WS) achieved (Nl CH4 kg(-1)VS) of 338.5 ± 14.3 (C), 310.5 ± 3.4 (X), 305.5 ± 29.6 (CX mixture), and 235.3 ± 22.7 (WS) during 56 days, and 237.6 ± 17.7 (CF) during 70 days. These yields corresponded to COD recovery of 73.3 ± 3.1% (C)=69.1 ± 0.76% (X)=67.3 ± 5.8% (CX mixture)>52.9 ± 2.6% (CF)>46.5 ± 2.7% (WS). Cellulose-fed culture had a lower and statistically different initial CH4 production rate from those calculated for cultures fed X, CX mixture, CF and WS. It seemed that the presence of hemicellulose in complex substrate such as wheat straw and cow feces supported the higher initial CH4 rate compared to cellulose. Biomethanation of the pure and complex lignocellulosic substrates tested is feasible at psychrophilic conditions given that a well-adapted inoculum is used; however, hydrolysis was the rate limiting step.

Nitrous oxide emissions from clayey soils amended with paper sludges and biosolids of separated pig slurry.

Wastes from animal production and from the paper industry are often used as amendments to agricultural soils. Although data exist on the impacts of raw animal wastes on NO production, little is known regarding the effects of paper wastes and biosolids from treated animal waste. We measured NO emissions for two consecutive snow-free seasons (mid-May through the end of October) from poorly drained clayey soils under corn ( L.). Soils were amended with raw pig slurry (PS) or biosolids (four PS-derived and two paper sludges) and compared with soils with mineral N fertilizer (CaNHNO) or without N addition (Control). Area-based NO emissions from the mineral N fertilizer (average, 8.2 kg NO-N ha; 4.2% of applied N) were higher ( < 0.001) than emissions from the organic amendments, which ranged from 1.5 to 6.1 kg NO-N ha (-0.4 to 2.5% of applied N). The NO emissions were positively correlated with mean soil NO availability (calculated as "NO exposure"), which was highest with mineral N fertilizer. In plots treated with organic amendments (i.e., biosolids and raw PS), NO exposure was negatively correlated to the C:N ratio of the amendment. This resulted in lower NO emissions from the higher C:N ratio biosolids, especially compared with the low C:N ratio PS. Application of paper sludge or PS-derived biosolids to these fine-textured soils, therefore, reduced NO emissions compared with raw PS and/or mineral N fertilizers ( < 0.01).

Low-temperature anaerobic digestion of swine manure in a plug-flow reactor.

A low-temperature (25 degrees C) anaerobic eight-compartment (PF01 to PF08) cascade reactor simulating a plug-flow reactor (PFR) treating pig manure was monitored for a year. The bioreactor was fed at an average loading rate of 2.4 +/- 0.2 g of total chemical oxygen demand (TCOD) per litre of reactor per day for a theoretical hydraulic retention time (HRT) of 67 +/- 7 d. An average of 79% of TCOD was removed from pig manure (converted into biogas and in sediments), whereas specific methane yields ranging from 397 to 482 NL CH4 kg(-1) VS (148.6 to 171.4 NL CH4 kg(-1) TCOD) were obtained. After 150 d, fluctuating performances of the process were observed, associated with solids accumulation in the upstream compartments, preventing the complete anaerobic digestion of swine manure in the compartments PF01 to PF04. Low-temperature anaerobic PFR represents an interesting alternative for the treatment of pig manure and recovery of green energy. Further investigations regarding a modified design, with better accumulating solids management, are needed to optimize the performance of this low-temperature PFR treating pig manure.

Physico-chemical characteristics and methanogen communities in swine and dairy manure storage tanks: spatio-temporal variations and impact on methanogenic activity.

Greenhouse gas emissions represent a major environmental problem associated with the management of manure from the livestock industry. Methane is the primary GHG emitted during manure outdoor storage. In this paper, the variability of two swine and two dairy manure storage tanks was surveyed, in terms of physico-chemical and microbiological parameters. The impact of the inter-tank and spatio-temporal variations of these parameters on the methanogenic activity of manure was ascertained. A Partial Least Square regression was carried out, which demonstrated that physico-chemical as well as microbiological parameters had a major influence on the methanogenic activity. Among the 19 parameters included in the regression, the concentrations of VFAs had the strongest negative influence on the methane emission rate of manure, resulting from their well-known inhibitory effect. The relative abundance of two amplicons in archaeal fingerprints was found to positively influence the methanogenic activity, suggesting that Methanoculleus spp. and possibly Methanosarcina spp. are major contributors to methanogenesis in storage tanks. This work gave insights into the mechanisms, which drive methanogenesis in swine and dairy manure storage tanks.

Identity and diversity of archaeal communities during anaerobic co-digestion of chicken feathers and other animal wastes.

Digestion of raw feathers in anaerobic digesters inoculated with adapted swine manure, slaughterhouse sludge or dairy manure was investigated using twelve 42-L anaerobic digesters at 25°C. After 120days 74%, 49% and 40% added feathers were converted to methane in swine manure, dairy manure and slaughterhouse sludge anaerobic digesters respectively. 16S rRNA gene clone library analyses identified twenty-one operational taxonomic units containing clone sequences from 5 genera, 5 families and 2 phyla of members of the Archaea from 158 sequenced clones. Fluorescence insitu hybridization revealed that methanogens from the Methanomicrobiales, Methanosarcinales and Methanobacteriales constituted a major fraction (>78%) of these Archaea. A high correlation was seen between the distribution of functional archaeal groups and the NH(3)-N levels of digester mixed liquors. The compositions of archaeal communities fed different substrates were statistically significantly different (P<0.05).

Methanoculleus spp. as a biomarker of methanogenic activity in swine manure storage tanks.

Greenhouse gas emissions represent a major problem associated with manure management in the livestock industry. A prerequisite to mitigate methane emissions occurring during manure storage is a clearer understanding of how the microbial consortia involved in methanogenesis function. Here, we have examined manure stored in outdoor tanks from two different farms, at different locations and depths. Physico-chemical and microbiological characterization of these samples indicated differences between each tank, as well as differences within each tank dependent on the depth of sampling. The dynamics of both the bacterial and archaeal communities within these samples were monitored over a 150-day period of anaerobic incubation to identify and track emerging microorganisms, which may be temporally important in the methanogenesis process. Analyses based on DNA fingerprinting of microbial communities identified trends common among all samples as well as trends specific to certain samples. All archaeal communities became enriched with Methanoculleus spp. over time, indicating that the hydrogenotrophic pathway of methanogenesis predominated. Although the emerging species differed in samples obtained from shallow depths compared to deep samples, the temporal enrichment of Methanoculleus suggests that this genus may represent a relevant indicator of methanogenic activity in swine manure storage tanks.

Anaerobic digestion of chicken feather with swine manure or slaughterhouse sludge for biogas production.

Biogas production from anaerobic digestion of chicken feathers with swine manure or slaughterhouse sludge was assessed in two separate experiments. Ground feathers without any pre-treatment were added to 42-L digesters inoculated with swine manure or slaughterhouse sludge, representing 37% and 23% of total solids, respectively and incubated at 25°C in batch mode. Compared to the control without feather addition, total CH(4) production increased by 130% (P<0.001) and 110% (P=0.09) in the swine manure and the slaughterhouse sludge digesters, respectively. Mixed liquor NH(4)N concentration increased (P<0.001) from 4.8 and 3.1g/L at the beginning of the digestion to 6.9 and 3.5 g/L at the end of digestion in the swine manure and the slaughterhouse sludge digesters, respectively. The fraction of proteolytic microorganisms increased (P<0.001) during the digestion from 12.5% to 14.5% and 11.3% to 13.0% in the swine manure and the slaughterhouse sludge digesters with feather addition, respectively, but decreased in the controls. These results are reflective of feather digestion. Feather addition did not affect CH(4) yields of the swine manure digesters (P=0.082) and the slaughterhouse sludge digesters (P=0.21), indicating that feathers can be digested together with swine manure or slaughterhouse sludge without negatively affecting the digestion of swine manure and slaughterhouse sludge.

In situ identification of keratin-hydrolyzing organisms in swine manure inoculated anaerobic digesters.

Feathers, a poultry byproduct, are composed of > 90% keratin which is resistant to degradation during anaerobic digestion. In this study, four 42-L anaerobic digesters inoculated with adapted swine manure were used to investigate feather digestion. Ground feathers were added into two anaerobic digesters for biogas production, whereas another two without feathers were used as negative control. Feather degradation and enhanced methane production were recorded. Keratin-hydrolyzing organisms (KHOs) were visualized in the feather bag fluids after boron-dipyrromethene (BODIPY) fluorescence casein staining. Their abundances correlated (R(2)  = 0.96) to feather digestion rates. A 16S rRNA clone library was constructed for the bacterial populations attached to the feather particles. Ninety-three clones (> 1300 bp) were retrieved and 57 (61%) belonged to class Clostridia in the phylum Firmicutes, while 34 (37%) belonged to class Bacteroidia in the phylum Bacteroidetes. Four oligonucleotide FISH probes were designed for the major Clostridia clusters and used with other FISH probes to identify the KHOs. Probe FIMs1029 hybridized with most (> 80%) of the KHOs. Its targeted sequence perfectly matches that possessed by 10 Clostridia 16S rRNA gene clones belonging to a previously uncharacterized new genus closely related to Alkaliphilus in the subfamily Clostridiaceae 2 of family Clostridiaceae.