Manure Storage Research Articles

Biochar from animal manure: A critical assessment on technical feasibility, economic viability, and ecological impact

AbstractAnimal manure has been used to manage soil fertility since the dawn of agriculture. It provides plant nutrients and improves soil fertility. In the last decades, animal husbandry has been significantly expanded globally. Its economics were optimized via the (international) trade of feed, resulting in a surplus of animal manure in areas with intensive livestock farming. Potentially toxic elements (PTEs), pathogenic microorganisms, antibiotic residues, biocides, and other micropollutants in manure threaten animal, human, and environmental health. Hence, manure application in crop fields is increasingly restricted, especially in hotspot regions with intensive livestock activities. Furthermore, ammonia volatilization and greenhouse gas (GHG) emissions during manure storage, field application, and decomposition contribute to air pollution and climate change. Conventional manure management scenarios such as composting and anaerobic digestion partially improve the system but cannot guarantee to eliminate sanitary and contamination risks and only marginally reducing its climate burden. Hence, this review discusses the potential of pyrolysis, the thermochemical conversion under oxygen‐limited conditions as an alternative treatment for animal manure providing energy and biochar. Manure pyrolysis reduces the bioavailability of PTEs, eliminates pathogenic microorganisms and organic micropollutants, and reduces GHG emissions. Pyrolysis also results in the loss of nitrogen, which can be minimized by pretreatment, that is, after removing soluble nitrogen fraction of manure, for example, by digestion and stripping of ammonia–nitrogen or liquid–solid separation. However, conclusions on the effect of manure pyrolysis on crop yield and fertilization efficiencies are hampered by a lack of nutrient mass balances based on livestock unit equivalent comparisons of manure and manure biochar applications. Hence, it is essential to design and conduct experiments in more practically relevant scenarios and depict the observations based on the amount of manure used to produce a certain amount of biochar.

Isolation and application of pH- and salt-resistant Bacillus strains to reduce ammonia emission from pig manure during the storage period.

Ammonia released during the storage period from pig manure causes severe air pollution and odor issues, ultimately leading to nitrogen loss in the manure. In this study, we investigated the application of 13 Bacillus spp. strains isolated from paddy soil and their potential to minimize reactive nitrogen loss during pig manure storage at 28°C and initial moisture content at 76.45%. We selected five strains of Bacillus spp. named H3-1, H4-10, H5-5, H5-9, and Y3-28, capable of reducing ammonia emissions by 23.58%, 24.65%, 25.58%, 25.36%, and 26.82% in pig manure over 60 days compared to control. We further tested their ability on various pH, salinity, and ammonium-nitrogen concentrations for future field applications. Our investigation revealed that certain bacteria could survive and grow at pH 6, 8, and 10; 4, 8, and 10% salinity and up to 8 g l-1 of ammonium-nitrogen concentration. The results from our study show that saline and ammonium-nitrogen tolerant Bacillus strains isolated from soil can potentially reduce ammonia emissions in pig manure, even at high moisture content during their storage period.

Effectiveness of precision feeding in reducing N excretion in dairy cattle

Two periods enrolling 56 (milk yield 36.2 ± 7.91 kg/d) and 58 (milk yield 32.4 ± 4.99 kg/d) grouped-fed dairy cows were performed to evaluate nutrient adjustment and N emissions of a precision feeding strategy. Pens blocked by parity were randomly assigned to a conventional (CONV) or to a precision feeding scheme (PREC) for a 21-d period. The CONV group was offered a total mixed ration (TMR, 6.82 and 6.65 MJ of NEl/kg of DM, in period 1 and 2, respectively, and 165 g of CP/kg of DM in both periods; whereas PREC cows were fed a partial mixed ration (PMR, 6.65 and 6.40 MJ of NEl/kg of DM, 135 and 137 g of CP/kg of DM, in period 1 and 2, respectively) and a concentrate feed supplemented twice daily in the milking parlour, which contained different quantities of soybean meal, corn meal, and wheat middling’s according to estimated nutritional needs of each cow above those supplied by the consumption of PMR. Individual daily nutritional needs and nutrients consumed from the PMR were calculated using a 10-d rolling average of performance data (milk yield and concentration of its components, and BW daily recorded in both periods). A N balance using urine and fecal spot sampling during the last 3 d of the study was performed in period 1, and stored manure gaseous emissions (ammonia, methane, nitrous oxide, and carbon dioxide) were measured for 2 wk in period 2. After 2 wk of adaptation to the diet, 82 cows homogeneously distributed in 4 DIM categories: early DIM (< 81), mid-early DIM (81−150), mid-late DIM (151−220), late DIM (> 220) were used to assess how energy and protein requirements were adjusted using both feeding system. Dairy cows in both feeding systems were energetically overfed, and CONV cows tended to be more CP overfed in mid-late and late DIM cows than PREC fed cows. Total daily N urine excretion, and milk N urea concentration were greater in CONV than in PREC cows. There were no differences in ammonia and nitrous oxide emissions from the manure storage between PREC and CONV cows; however, methane and carbon dioxide emissions from manure increased by 55% and 15%, respectively in PREC fed cows. Precision feeding system based on preceding average daily milk yield and composition can reduce N excretion without affecting short-term milking performance but increasing C gaseous emissions from manure.

Intramammary and systemic use of antimicrobials and their association with resistance in generic Escherichia coli recovered from fecal samples from Canadian dairy herds: A cross-sectional study.

Antimicrobial resistance (AMR) in animals, including dairy cattle, is a significant concern for animal and public health worldwide. In this study, we used data collected through the Canadian Dairy Network for Antimicrobial Stewardship and Resistance (CaDNetASR) to: (1) describe the proportions of AMR in fecal E. coli, and (2) investigate the relationship between antimicrobial use (AMU) (intramammary and systemic routes, while accounting for confounding by other variables) and AMR/multidrug resistance (MDR - resistance to ≥ 3 antimicrobial classes) in fecal E. coli from Canadian dairy farms. We hypothesized that an increase of the AMU was associated with an increase in AMR in E. coli isolates. A total of 140 dairy farms across five provinces in Canada were included in the study. Fecal samples from pre-weaned calves, post-weaned heifers, lactating cows, and farm manure storage were cultured, and E. coli isolates were identified using MALDI-TOF MS. The minimum inhibitory concentrations (MIC) to 14 antimicrobials were evaluated using a microbroth dilution methodology. AMU was quantified in Defined Course Dose (DCD - the dose for a standardized complete treatment course on a standard size animal) and converted to a rate indicator - DCD/100 animal-years. Of 1134 fecal samples collected, the proportion of samples positive for E. coli in 2019 and 2020 was 97.1% (544/560) and 94.4% (542/574), respectively. Overall, 24.5% (266/1086) of the E. coli isolates were resistant to at least one antimicrobial. Resistance towards tetracycline was commonly observed (20.7%), whereas resistance to third-generation cephalosporins, fluoroquinolones, and carbapenems was found in 2.2%, 1.4%, and 0.1% of E. coli isolates, respectively. E. coli isolates resistant to two or ≥3 antimicrobial classes (MDR) was 2.7% and 15%, respectively. Two multilevel models were built to explore risk factors associated with AMR with AMU being the main exposure. Systemic AMU was associated with increased E. coli resistance. For an increase in systemic AMU equivalent to its IQR, the odds of resistance to any antimicrobial in the model increased by 18%. Fecal samples from calves had higher odds of being resistant to any antimicrobial when compared to other production ages and farm manure storage. The samples collected in 2020 were less likely to be resistant when compared to samples collected in 2019. Compared to previous studies in dairy cattle in North America, AMR in E. coli was lower.

Dairy manure nutrient recovery reduces greenhouse gas emissions and transportation cost in a modeling study

Technologies that separate manure or digestate into fractions with different solids and nutrient contents present interesting options to mitigate manure storage emissions (by reducing the quantity of carbon stored anaerobically) and to improve nutrient distribution (by reducing the quantity of water transported with nutrients). In this study, the dairy farm model, DairyCrop-Syst, was used to simulate storage emissions of methane (CH4), nitrous oxide (N2O), and ammonia (NH3), and to simulate nutrient distribution for a case-study farm in Canada. The farm used several types of manure processing, including: anaerobic digestion (AD), solid-liquid separation (SLS), and nutrient recovery (NR). Simulations were done with combinations of the above technologies, i.e., a baseline with only AD that produced a single (unseparated) effluent, compared to AD+SLS, and AD+SLS+NR that produced two separate fractions. With AD+SLS+NR, the processing system isolated a solid fraction with a high concentration of N and P, and a liquid fraction containing less nutrients. Compared to the baseline system, the addition of solid liquid separation and nutrient recovery (i.e. SLS+NR) reduced CH4 emissions from outdoor liquid digestate storage by 87%, with only a small offset from higher N2O and NH3 emissions from storing the solid fraction. The solid fraction was simulated to be transported to fields at least 30 km away from the dairy barns, while the liquid fraction was transported by dragline to fields adjacent to the barn. The advanced nutrient separation system resulted in much lower transport costs for manure nutrients and the ability to transport N and P to greater distances.

Characterizing NH3 emissions from a sheep feedlot and a manure composting facility in North China with the inverse dispersion technique

Ammonia (NH3) emissions from manure storage in animal feedlots and post-farm treatment facilities, such as composting facilities, are the key contributors to the agricultural NH3 budget. Simultaneous quantification of NH3 emissions from these two sectors at the same site can provide information on NH3 emissions along the manure management chain, which will aid in accurately evaluating best management practices for NH3 mitigation. The NH3 emission rates of a large sheep feedlot with a full capacity of ∼30,000 heads, consisting of occupied pens, unoccupied pens (empty), and a neighboring composting facility for sheep manure in North China, were quantified using the multiple-source determination of an inverse dispersion technique in winter season. This was followed by a year-round measurement to track the NH3 emission patterns (diurnal and seasonal) of these two sectors and further quantify the NH3 emissions. The NH3 flux of the occupied pens was 2.07 and 2.64 times that of the empty pens and the composting facility, respectively. After excluding the NH3 emissions from the empty pens, the NH3 emission rates per head in four seasons changed from 11.01 to 22.43 to 8.58–11.13 g head–1 d–1. The NH3 emissions from the feedlot accounted for 25.26% of the feed N intake (or 33.68% of the excreted N), and the NH3 emissions from the manure composting facility accounted for 2.20% of the initial N in sheep manure. This study is novel in filling the data gap for both the NH3 emissions from sheep feedlots and the representative contributions of different manure management sectors.

Effect of sodium hypochlorite on the microbiota and odor of manure effluents

Manure effluents (ME) of livestock enterprises represent a rich nutrient medium for the development of various aerobic microorganisms (MO). During the biodegradation of the organic components of ME, a wide range of odor-forming substances (OFS) and greenhouse gases enter the atmospheric air. The intensity and main directions of ME destruction depend on the composition and amount of microbiota. A solution of sodium hypochlorite can be used to suppress the decomposition of the biogenic components of ME. In the course of our research, it was found that the introduction of 0.005% active chlorine into the liquid fraction of ME (pH ~ 6.8; humidity ~ 99.1%) leads to a decrease in the numbers of putrefactive microbiota, namely: Bacteroides, Clostridium, Escherichia coli, Pseudomonas, Sarcina ventriculi, and Peptostreptococcus anaerobius. The corresponding ammonifiers are actively involved in the biodegradation processes of organic substances to form acetic acid, isovaleric acid, butyric acid, indoles, skatoles, ammonia, hydrogen sulfide, mercaptans and others. The numbers of microbiota not making a significant contribution to the production of OFS (Saccharomyces cerevisiae, Rhodotorula glutinis, Lactobacillus ssp. and others), on the contrary, increased. The numbers of some producers of volatile fatty acids (VFA), namely: Anaerococcus prevotii, Acidaminococcus, Prevotella spp. etc. increased. However, this did not affect the intensity and nature of the ME odor, which can be explained by the formation of non-volatile VFA salts at pH above 7.0. The numbers of Staphylococcus aureus, Staphylococcus epidermidis, Klebsiella sp., Proteus ssp., Alistipes putredinis, Bifidobacterium ssp., Candida tropicalis, and Candida albicans almost did not change when NaOCl was added to ME. As a result of the microbiota transformation, the total emission of gaseous substances, whose main components are the greenhouse gases CO2 and CH4, decreased by more than 17%. The unpleasant odor intensity has significantly decreased. A NaOCl solution can be used to treat ME in manure storage baths. The introduction of the practice of treating ME with this biocide is facilitated by its availability, low cost and safety for the environment.

A model to identify entry points to curb emissions from complex manure management chains

Livestock operations deploy increasingly complex facilities and technologies in manure management to reduce negative environmental impacts and to improve the agronomic value of manures. To capture and quantify processes of degradation, conversion and emission of manure constituents in these complex systems, this study presented a newly developed modular manure management (FarmM3) model. Using this model, we simulated flows and losses of manure organic matter (OM), carbon (C), nitrogen (N), phosphorus (P) and potassium (K) from manure management chains (MMCs) with deep litter, anaerobic lagoon, solid-liquid separation (SLS), anaerobic digestion (AD), and combinations of SLS and AD. The sensitivity of degradation and losses of manure constituents to changes in the configuration and parameters of MMCs was assessed. Results showed the MMCs with deep litter and AD led to higher OM degradation, C losses and greenhouse gas (GHG) emissions due to the substantial amounts of straw added to bedding and the digester. A trade-off between GHG and ammonia emissions was identified in the MMCs with deep litter. Application of SLS could reduce GHG emissions by 40% to 60% due to reduced methane and nitrous oxide emissions from separated liquid fraction storage. A stronger reduction of ammonia emission was observed when applying SLS to digested slurry than to raw slurry. Sensitivity analysis showed that the N loss was most sensitive to N transformation in the MMC with deep litter, and was most affected by the loss coefficients of ammonia during liquid manure storage and application in MMCs with SLS and AD. Losses of P and K from MMCs with SLS were influenced by separation efficiencies from SLS and loss coefficients from solid fraction storage. The impact of model input parameters on GHG emissions highly depended on the selected manure management facilities. This study shows that manure management facilities have a strong influence on the fate of manure constituents. The FarmM3 model can be used to quantify the degradation and losses of different manure constituents in complex MMCs and the effects of manure treatment facilities, and to identify the most important parameters determining these losses.

Preliminary results of the combined production of duckweed Spirodela polyrhiza and common carp (Cyprinus carpio) in an aquaponic system

As a result of population growth, increasin amount of food is needed, and agriculture is under an increasing burden to meet these needs. Traditional agriculture is often attacked due to its environmental impact. We must find alternative, environmentally friendly ways to produce more food. Aquaponics is a closed system in which we can produce both fish and plants at the same time. Duckweed species are small, aquatic, floating plants belonging to angiosperms. It can potentially be an alternative protein source, due to its high protein content, good amino acid supply, and rapid growth. Under suitable conditions, it doubles its weight in 2–4 days, and can reach a yield of 30 t ha-1 year-1in dry matter. It forms a carpet on top of the water and can be found in slow-moving or still waters. Since they are resistant to a wide range of nutrient concentrations, they are also suitable for cleaning wastewater (such as eutrophicated lakes, sewage reservoirs, liquid manure storage). Fish feed is the primary nutrient source for aquaponic systems, which usually contains fishmeal. If duckweed can be used as an alternative for fishmeal in the feed, it could improve the sustainability of the aquaponic and aquaculture systems. In this study, the aim was to develop an optimal harvesting protocol for duckweed Spirodela polyrhiza under aquaponic conditions. In a four weeks experiments, four harvesting protocols were set up, a control where only biomass measurements were made, a 25% group where 25% of the biomass at the time of measurement was harvested, and a 50% and a 75% group where at the time of measurement 50% and 75% of the biomass was harvested. Three replicates were used per treatment. We weighed the biomass every week and removed the amount corresponding to the group. Based on the preliminary results, it can be said that more biomass was obtained in the groups with the 25% harvesting protocol and the control group.

Assessment of the biochemical methane potential of in-house and outdoor stored pig and dairy cow manure by evaluating chemical composition and storage conditions

Biogas production is a suitable option for producing energy from dairy and pig manure types. During manure storage, organic matter degradation results in methane emissions decreasing the potential biogas yield. The present research advances the understanding of the biochemical methane potential (BMP) and the chemical characteristics of manure collected year-round from sequential stages of the liquid manure management chain of commercial dairy cow and pig farms. To this end, manure samples from six livestock farms in Germany were analyzed. The results showed that changes in chemical composition during storage led to a 20.5% decrease in the BMP of dairy manure from the barn to outdoor storage. For fattening pig manure samples, there was a 39.5% decrease in the BMP from intermediate to outdoor storage. An analysis of BMP according to manure age showed that pig manure degrades faster than dairy manure; the importance of promptly feeding manure to the biogas plant in order to avoid significant CH4 emission losses and reduction in energy producing capacity was highlighted. The best BMP predictors for dairy manure were the contents of dry matter, volatile solids and lignin, whereas best BMP predictors for pig manure were dry matter and volatile fatty acid (VFA) content. Prediction models performed well for samples from outdoor storages; refinements for predicting BMP of less aged samples presenting lower chemical variability would be necessary.

Hydrochemistry, water quality and health risk assessment of streams in Bismil plain, an important agricultural area in southeast Türkiye

In this study, the water quality of Ambar, Kuruçay, Pamuk and Salat streams, which are the important tributaries of the Tigris River in the Bismil Plain (Diyarbakır, Türkiye) was assessed using 19 physicochemical parameters. Except for a few exceptions, all parameters in the water samples taken from the streams were below the drinking water limit values. Kuruçay Stream had significantly higher TOC, Na+, NO3−, NO2−, Cl− and SO42− levels and lower DO levels than other streams (p < 0.05) due to sewage water discharges, animal manure storage areas near the stream and irrigation return flows. In all streams, Ca–HCO3 was dominant water type. Gibbs diagram indicated that rock weathering is the major factor controlling the hydrochemistry of the streams. According to the results of water quality index (WQI), all sampling stations of Ambar, Pamuk and Salat streams and K1 station of Kuruçay Stream had “good” quality water for drinking purposes, while K2 station of Kuruçay Stream had “poor” quality water. Irrigation indices (permeability index, sodium percentage, magnesium hazard, residual sodium carbonate, Kelley's ratio, sodium adsorption ratio and potential salinity) revealed that all water samples taken from the streams were suitable for irrigation. The water samples from Ambar, Pamuk and Salat streams were in the C2S1 (medium salinity and low alkalinity) category, while the samples from Kuruçay Stream were in the C2S1 and C3S1 (high salinity and low alkalinity) categories. Both hazard quotient and hazard index values of NO3–N, NO2–N and F− for children and adults were found below 1, indicating that adverse health effects are not expected from exposure to these contaminants via water ingestion and dermal contact. The findings of this study showed that the water quality status of Kuruçay Stream is worse as it receives large amounts of irrigation return flows compared to other streams.

Perspectives on peak liquid manure temperature with implications for methane emissions.

Methane emissions from liquid manure storage are currently estimated with a methane conversion factor (MCF) based on manure temperature inputs or air temperatures as a substitute in the 2019 IPCC Tier 2 method. However, differences between peak manure temperature and peak air temperature (Tdiff ) in warm seasons are likely to occur and result in poor estimates of MCF and methane emissions. To address this concern, this study aims to investigate the relationship between the Tdiff and ratio of manure surface area to manure volume (Rs:v ) using a mechanistic model and by analyzing farm-scale measurement studies across Canada. Positive correlations between Tdiff and Rs:v were found using a modeling approach and from farm-scale results (r=0.55, p=0.06). Tdiff ranged from -2.2 to 2.6°C in farm-scale results mainly collected from eastern Canada. We suggest that manure volume and surface area, in addition to removal frequency, could be used to estimate Tdiff and be part of the criteria for improving manure temperature estimates, which could lead to improved estimates of MCF.

Use of reverse osmosis concentrate for mitigating greenhouse gas emissions from pig slurry.

Due to the high global warming potential (GWP) in a short time scale (GWP100 = 28 vs. GWP20 = 86), mitigating CH4 emissions could have an early impact on reducing current global warming effects. The manure storage tank emits a significant amount of CH4, which can diminish the environmental benefit resulting from the anaerobic digestion of manure that can generate renewable energy. In the present study, we added the reverse osmosis concentrate (ROC) rich in salt to the pig slurry (PS) storage tank to reduce CH4 emissions. Simultaneously, pure NaCl was tested at the same concentration to compare and verify the performance of ROC addition. During 40 days of storage, 1.83 kg CH4/ton PS was emitted, which was reduced by 7-75% by the addition of ROC at 1-9 g Na+/L. This decrease was found to be more intensive than that found upon adding pure sodium, which was caused by the presence of sulfate rich in ROC, resulting in synergistic inhibition. The results of the microbial community and activity test showed that sodium directly inhibited methanogenic activity rather than acidogenic activity. In the subsequent biogas production from the stored PS, more CH4 was obtained by ROC addition due to the preservation of organic matter during storage. Overall, 51.2 kg CO2 eq./ton PS was emitted during the storage, while 8 kg CO2 eq./ton PS was reduced by biogas production in the case of control, resulting in a total of 43.2 kg CO2 eq./ton PS. This amount of greenhouse gas emissions was reduced by ROC addition at 5 g Na+/L by 22 and 65 kg CO2 eq./ton PS, considering GWP100 and GWP20 of CH4, respectively, where most of the reduction was achieved during the storage process. To the best of our knowledge, this was the first report using salty waste to reduce GHG emissions in a proper place, e.g., a manure storage tank.

Effects of cornstalk and sawdust coverings on greenhouse gas emissions during sheep manure storage

Manure covered by organic materials during the storage has shown that it can effectively reduce emissions of greenhouse gases, but few studies have focused on the bacterial communities in manure or the coverage and mechanism responsible for reducing gas emissions. Therefore, this study investigated the impacts and mechanisms of cornstalk and sawdust coverings on greenhouse gas emissions during sheep manure storage. Sheep manure covered by organic material reduced nitrous oxide (N2O) emissions (42.27%–42.55%) relative to uncovered control through physical adsorption and biological transformation of Acinetobacter, Corynebacterium, Brachybacterium, Dietzia and Brevibacterium. Sheep manure covered by organic materials also increased methane (CH4) emissions (16.31%–43.07%) by increasing anaerobic zones of coverage. Overall, coverings reduced carbon dioxide equivalent (CO2eq) by 29.87%–33.60%. Coverings had less effect on the bacterial diversity and community of sheep manure, and the number of bacteria shared by sheep manure and the covering material increased with storage progress, indicating that these bacteria were transferred to the covering materials with gas emissions and moisture volatilization. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) images showed that functional group intensities of the covering materials increased and the fibrous structures became more disordered during the storage period. In general, it was safe to use organic materials as coverages during sheep manure storage, which was conducive to reducing greenhouse gas emissions.

Quantifying ammonia lost to the atmosphere during manure storage on a dairy farm as influenced by management and meteorological parameters

Storing manure provides opportunities for dairy farms to maximize using the manure value as a fertilizer, reduce handling costs, and minimize its potential to pollute the environment. However, it also presents the potential to lose the nitrogen in manure to the atmosphere through volatilization as ammonia. Knowing the quantities of nitrogen lost is critical to inform the decision-making process related to developing mitigation strategies. This study aimed to quantify ammonia lost at the farm scale level from manure stored in a clay pit at a dairy farm during two storage periods. The ammonia concentrations, manure temperature, and local meteorological factors were measured and used to calculate the ammonia flux. Further, the crusting on stored manure surface was characterized and related to ammonia loss. The ammonia flux ranged from 0.26 ± 0.01 g m−2 d−1 to 1.30 ± 0.05 g m−2 d−1, averaging 0.57 ± 0.02 g m−2 d−1. Of the local meteorological factors, the wind speed influenced ammonia loss the most, but the ammonia flux patterns were related more closely to the manure temperature than other meteorological factors. The crusting of the manure suppressed the ammonia loss. However, manure agitation before land application accounted for about 25% of the nitrogen loss. The ammonia lost during storage accounted for about 5% of the total nitrogen in the manure going into storage. The outcome of this work contributes knowledge that farmers, practitioners, and policymakers can use to design and improve the guidelines to formulate effective farm manure management and mitigation practices and regulatory programs to minimize ammonia loss from dairy farms using manure scrapers and clay storage pits as part of their manure management system.

Microbiological and Technological Insights on Anaerobic Digestion of Animal Manure: A Review

Anaerobic digestion of animal manure results in the production of renewable energy (biogas) and nutrient-rich biofertilizer. A further benefit of the technology is decreased greenhouse gas emissions that otherwise occur during manure storage. Since animal manure makes anaerobic digestion cost-efficient and further advance the technology for higher methane yields, it is of utmost importance to find strategies to improve bottlenecks such as the degradation of lignocellulose, e.g., in cattle manure, or to circumvent microbial inhibition by ammonia caused by the degradation of nitrogen compounds in, e.g., chicken, duck, or swine manure. This review summarizes the characteristics of different animal manures and provides insight into the underlying microbial mechanisms causing challenging problems with the anaerobic digestion process. A particular focus is put upon the retention time and organic loading rate in high-ammonia processes, which should be designed and optimized to support the microorganisms that tolerate high ammonia conditions, such as the syntrophic acetate oxidizing bacteria and the hydrogenotrophic methanogens. Furthermore, operating managements used to stabilize and increase the methane yield of animal manure, including supporting materials, the addition of trace elements, or the incorporation of ammonia removal technologies, are summarized. The review is finalized with a discussion of the research needed to outline conceivable operational methods for the anaerobic digestion process of animal manure to circumvent process instability and improve the process performance.

Antimicrobial use and its association with the isolation of and antimicrobial resistance in Campylobacter spp. recovered from fecal samples from Canadian dairy herds: A cross-sectional study

Campylobacteriosis is one of the most common zoonotic diseases in North America. As opposed to humans, animal infections caused by Campylobacter spp. are often asymptomatic. In this study, data collected through the Canadian Dairy Network for Antimicrobial Stewardship surveillance system were used to determine the proportion of Campylobacter spp. and antimicrobial resistant isolates recovered from dairy cattle herds. Additionally, the association of antimicrobial use (AMU) with fecal carriage and antimicrobial resistance (AMR) of Campylobacter spp. were investigated. Pooled fecal samples from 5 animals from each production phase (pre-weaned calves, post-weaned heifers, lactating cows), and a manure storage sample were collected from 140 dairy herds across Canada. Samples were cultured using selective media, and Campylobacter isolates were speciated using matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Antimicrobial susceptibilities were determined using the minimum inhibitory concentration test, and interpretation was made according to the Clinical and Laboratory Standards Institute. Two multilevel logistic regression models were used to investigate the association between the AMU with the isolation and antimicrobial resistance in Campylobacter spp. Of 560 samples, 63.8% were positive for Campylobacter spp., and 96% of the participating farms had at least one sample source (i.e., calves, heifers, lactating cows, or manure storage) positive for Campylobacter spp. Overall, 54.3% of the Campylobacter spp. isolates were resistant to at least one antimicrobial. Resistance to tetracycline was observed in 49.7% of the Campylobacter spp. isolates, followed by ciprofloxacin (19.9%) and nalidixic acid (19.3%). The proportion of multi-drug resistant (≥3 antimicrobial classes) Campylobacter spp. isolates was low (0.3%); however, 15.6% were resistant to two different classes of antimicrobials. Samples collected from lactating cows, heifers, and manure storage were more likely to be positive for Campylobacter spp. compared to calves. Total AMU was associated with a decreased probability of recovering Campylobacter spp. In addition, AMR to either tetracycline or ciprofloxacin had an interaction with antimicrobial use. The probability of resistance to tetracycline increased for each unit increase in the total AMU (Defined Course Dose/100 animal-years), while the probability of resistance to ciprofloxacin decreased. Campylobacter coli isolates were more likely to be resistant to ciprofloxacin and tetracycline when compared to C. jejuni. Our study demonstrated that Campylobacter spp. is widespread among Canadian dairy farms, and a higher proportion of resistance to tetracycline was identified. The total AMU was associated with increased resistance to tetracycline in Campylobacter spp. isolates; however, for ciprofloxacin the AMU was associated with decreased resistance.

Knowledge and Practices of Cypriot Bovine Farmers towards Effective and Safe Manure Management.

Manure from bovine farms is commonly used as an organic fertiliser. However, if not properly managed, it can spread significant biological and chemical hazards, threatening both human and animal health. The effectiveness of risk control hugely relies on farmers' knowledge regarding safe manure management and on the application of suitable management practices. This study aims to evaluate the knowledge and practices of Cypriot bovine farmers towards safer manure management, from its generation to its final use, in line with the One Health approach. Factors affecting farmers' knowledge and applied practices are also investigated through a questionnaire survey. The questionnaire was developed and sent to all eligible bovine farmers in Cyprus (n = 353), and 30% (n = 105) of them returned the completed questionnaire. Results revealed there are some gaps in farmers' knowledge. The use of manure for fertilising crops dominated. Only half of the farmers stored manure in appropriate facilities, with 28.5% of them using a dedicated area with cement floors and 21.5% utilising leakproof tanks. The majority (65.7%) stored manure for more than three months before its use as a fertiliser in a dried form. In multiple regression analysis, education level and farming purpose were significant determinants of farmer knowledge. In conclusion, Cypriot farmers' knowledge must be reinforced to ensure proper manure management. The results highlight the importance of providing relevant training to farmers. Although the current practices partially decrease manure pathogens, interventions to promote the use of more effective treatment methods, such as biogas transformation and composting, would be beneficial.

Nitrogen transformation processes catalyzed by manure microbiomes in earthen pit and concrete storages on commercial dairy farms

Storing manure is an essential aspect of nutrient management on dairy farms. It presents the opportunity to use manure efficiently as a fertilizer in crop and pasture production. Typically, the manure storages are constructed as earthen, concrete, or steel-based structures. However, storing manure can potentially emit aerial pollutants to the atmosphere, including nitrogen and greenhouse gases, through microbial and physicochemical processes. We have characterized the composition of the microbiome in two manure storage structures, a clay-lined earthen pit and an aboveground concrete storage tank, on commercial dairy farms, to discern the nitrogen transformation processes, and thereby, inform the development of mitigation practices to preserve the value of manure. First, we analyzed the 16S rRNA-V4 amplicons generated from manure samples collected from several locations and depths (0.3, 1.2, and 2.1–2.75 m below the surface) of the storages, identifying a set of Amplicon Sequence Variant (ASVs) and quantifying their abundances. Then, we inferred the respective metabolic capabilities. These results showed that the manure microbiome composition was more complex and exhibited more location-to-location variation in the earthen pit than in the concrete tank. Further, the inlet and a location with hard surface crust in the earthen pit had unique consortia. The microbiomes in both storages had the potential to generate ammonia but lacked the organisms for oxidizing it to gaseous compounds. However, the microbial conversion of nitrate to gaseous N2, NO, and N2O via denitrification and to stable ammonia via dissimilatory nitrite reduction seemed possible; minor quantities of nitrate was present in manure, potentially originating from oxidative processes occurring on the barn floor. The nitrate-transformation linked ASVs were more prevalent at the near-surface locations and all depths of the inlet. Anammox bacteria and archaeal or bacterial autotrophic nitrifiers were not detected in either storage. Hydrogenotrophic Methanocorpusculum species were the primary methanogens or methane producers, exhibiting higher abundance in the earthen pit. These findings suggested that microbial activities were not the main drivers for nitrogen loss from manure storage, and commonly reported losses are associated with the physicochemical processes. Finally, the microbiomes of stored manure had the potential to emit greenhouse gases such as NO, N2O, and methane.

Effects of atmospheric and manure surface conditions on H2 S emissions from an in-ground finisher hog manure slurry tank.

Hydrogen sulfide (H2 S) emitted by livestock operations can be detrimental to human health. The storage of hog manure is a significant agricultural source of H2 S emissions. H2 S emissions from a ground-level Midwestern hog finisher manure tank were measured for 8-20 days each quarter over a 15-month period. After excluding 4 days with outlier emissions the mean daily emission was 1.89g H2 S m-2 day-1 . Mean daily emission was 1.39g H2 S m-2 day-1 when the slurry surface was liquid and 3.00g H2 S m-2 day-1 when crusted. Emissions however were not significantly different whether the surface was liquid or crusted when differences in temperature were considered. Diurnal variation in emissions was not correlated with air temperature, water vapor saturation deficit, or wind speed when the manure surface was crusted but was positively correlated with these variables when the surface was not crusted. Daily H2 S emissions were modeled according to two-film theory incorporating resistance approach with limited success. Additional emissions measurements with greater documentation of the manure liquid composition and crust characteristics are needed to assess the component transport resistances in the emissions model.