Dairy Manure Storage Research Articles

A physics-informed long short-term memory (LSTM) model for estimating ammonia emissions from dairy manure during storage

Manure management on dairy farms impacts how farmers maximize its value as fertilizer, reduce operating costs, and minimize environmental pollution potential. A persistent challenge on many farms is minimizing ammonia losses through volatilization during storage to maintain manure nitrogen content. Knowing the quantities of emitted pollutants is at the core of designing and improving mitigation strategies for livestock operations. Although process-based models have improved the accuracy of estimating ammonia emissions, complex systems such as manure storage still need to be solved because some underlying science still needs work. This study presents a novel physics-informed long short-term memory (PI-LSTM) modeling approach combining traditional process-based with recurrent neural networks to estimate ammonia loss from dairy manure during storage. The method entails inverse modeling to optimize hyperparameters to improve the accuracy of estimating physicochemical properties pertinent to ammonia's transport and surface emissions. The study used open data sets from two on-farm studies on liquid dairy manure storage in Switzerland and Indiana, U.S.A. The root mean square errors were 1.51 g m−2 h−1 for the PI-LSTM model, 3.01 g m−2 h−1 for the base compartmental process-based (Base-CPBM) model, and 2.17 g m−2 h−1 for the hyperparameter-tuned compartmental process-based (HT-CPBM) model. In addition, the PI-LSTM model outperformed the Base-CPBM and the HT-CPBM models by 20 to 80 % during summer and spring, when most annual ammonia emissions occur. The study demonstrated that incorporating physical knowledge into machine learning models improves generalization accuracy. The outcomes of this study provide the scientific basis to improve policymaking decisions and the design of suitable on-farm strategies to minimize manure nutrient losses on dairy farms during storage periods.

Methane Emissions of a Western Dairy Manure Storage Basin and Their Correlation with Hydrogen Sulfide Emissions

Anaerobic decomposition in manure storage contributes to hydrogen sulfide (H2S) and methane (CH4) emissions. Coincident emission measurements were made of these gases from a western free stall dairy manure storage basin over a two-month period (August and September) as manure filled the basin and dried to assess the similarity or differences in the emissions characteristics. Path-integrated CH4 concentrations were measured from sampled air using photoacoustic spectrometric technology. Half-hourly emissions were determined using a backward Lagrangian Stochastic method utilizing on-site turbulence measurements. The median daily CH4 emission for the basin was 3.5 mg CH4 m−2 s−1 (772 g d−1 hd−1). Aging of the manure over the 44 days of this study did not appear to influence the CH4 emissions. A high correlation between the CH4 and H2S emissions during the study period suggested that the production and transport of these two gases from the basin were influenced by the same factors. Emissions did not appear to be influenced by the above-ground environmental conditions (wind speed, turbulent mixing, air temperature, change in barometric pressure, or vapor pressure deficit) but were likely more a function of the bacterial population present and/or available substrate for bacterial decomposition. Similarity in the CH4 to H2S emission ratio during basin manure filling and drying down to that of a slurry storage in a midwestern US dairy suggested that the bacterial species involved in the decomposition of dairy manure slurry is similar regardless of climate.

Effect of Mechanical Solids Separators on Potential Reduction of Methane Emissions From Dairy Manure Storage

Highlights Four mechanical manure separators were evaluated in on-farm studies. Mass balances and biochemical methane potential tests were conducted to measure on-farm separation efficiencies. Separator performance depended on environmental, material, and design factors. Over 70% solids separation and methane emission reduction potentials were achieved. Abstract. The separation efficiencies of four mechanical solid-liquid separation technologies and their effect on the reduction of methane production potential from dairy lagoons were studied using on-farm separator measurements and laboratory biomethane potential tests. The studied technologies included 1-stage sloped dual-screen, 2-stage sloped dual-screen, 1-stage horizontal scraped screen, and 1-stage sloped single-screen separators. The technologies were evaluated across various seasons on four dairies in California. On-farm sampling and measurements of the influent of flushed manure and the mass of the solids separated, as well as in-laboratory measurements of methane (CH4) production potential, were carried out. A mass balance approach was employed to determine the removal efficiencies of total and volatile solids (TS and VS) and nutrients, as well as methane emission reduction potential. The performance of the separators depended on manure characteristics, system design (e.g., screen size and orientation), separator operation and management (e.g., manure flow rate), and manure processing pit type and configuration. Among the four studied separator systems, the 2-stage sloped dual-screen separator showed the highest average TS and VS removal efficiencies, and methane emission potential reduction of 52.5%, 59.7%, and 55.8%, respectively. The 1-stage horizontal scraped screen separator had the lowest TS and VS removal efficiencies, and methane emission reduction potential of 6.3%, 9.3%, and 4.9%, respectively. The results have potential implications for nutrient and greenhouse gas management strategies and/or policies in agriculture. Keywords: Greenhouse gas, Lagoon, Manure management, Separation efficiency, Settling basin, Solid-liquid separation, Sustainable agriculture.

Effect of micro-aerobic conditions based on semipermeable membrane-covered on greenhouse gas emissions and bacterial community during dairy manure storage at industrial scale

This study evaluated the greenhouse gas emissions of solid dairy manure storage with the micro-aerobic group (MA; oxygen concentration <5%) and control group (CK; oxygen concentration <1%), and explained the difference in greenhouse gas emissions by exploring bacterial community succession. The results showed that the MA remained the micro-aerobic conditions, which the maximum and average oxygen concentrations were 4.1% and 1.9%, respectively; while the average oxygen concentrations of the CK without intervention management was 0.5%. Compared with the CK, carbon dioxide and methane emissions in MA were reduced by 78.68% and 99.97%, respectively, and nitrous oxide emission was increased by almost three times with a small absolute loss, but total greenhouse gas emissions decreased by 91.23%. BugBase analysis showed that the relative abundance of aerobic bacteria in CK decreased to 0.73% on day 30, while that in MA increased to 6.56%. Genus MBA03 was significantly different between the two groups (p < 0.05) and was significantly positively correlated with carbon dioxide and methane emissions (p < 0.05). A structural equation model also revealed that the oxygen concentration and MBA03 of the MA had significant direct effects on methane emission rate (p < 0.001). The research results could provide theoretical basis and measures for directional regulation of greenhouse gas emission reduction during dairy manure storage.

Acidification of Residual Manure in Liquid Dairy Manure Storages and Its Effect on Greenhouse Gas Emissions

Liquid manure storages are an important source of greenhouse gases (GHG) on dairy farms. Methane (CH4) and nitrous oxide (N2O) are the predominant GHGs, while ammonia (NH3) is an indirect source of N2O. Addition of acid to manure has shown promising emission reductions, however, cost of acidification may be unfeasible for farmers. Fully cleaning storages has also shown to reduce CH4, due to removal of inoculating effects of residual manure (“inoculum”) on fresh manure (FM). However, complete removal of inoculum is practically impossible on large farms, thus acidifying only the inoculum may reduce GHGs without requiring acidification of all FM. This study aimed to quantify the effect of acidified inoculum on CH4, N2O and NH3 emissions from stored manure and quantify the changes in methanogen abundance and activity. Emissions were measured from six 10.6 m3 storages filled with 20% inoculum (1-yr-old manure) and 80% FM. Inoculum was treated in three ways: untreated (control); previously acidified (1-yr prior); and newly acidified with 70% H2SO4 (1.1 L m-3 manure). The CH4 and N2O emissions were continuously measured from June – November using tunable diode trace gas analyzers coupled with venturi air flow systems. The NH3 emissions were measured at 24-h intervals 3 × weekly using acid traps. The activity and abundance of methanogens were quantified by targeting the Methyl Coenzyme M Reductase A (mcrA) gene and transcript which encodes a subunit of the key enzyme that catalyzes the final step of methanogenesis. Bacterial abundance was quantified by targeting the bacterial 16S rRNA gene. Quantifications were performed using quantitative real-time PCR. CH4 emissions were reduced by 77% using newly acidified inoculum and 38% using previously acidified inoculum, compared to the control with untreated inoculum (36.1 g CH4 m-2). Significant treatment reductions in mcrA gene and transcript abundance suggest that CH4 reductions were caused by disruption of methanogen activity. NH3 and N2O emissions were reduced by 33% and 73% using acidified inoculum and 23% and 50% using previously acidified inoculum, respectively, compared to the control. Results suggest that lower acid rates and acidifying less frequently may still have good treatment effects while minimizing cost.

Greenhouse gas emissions from gradually-filled liquid dairy manure storages with different levels of inoculant

Liquid dairy manure storages emit large amounts of methane (CH4), nitrous oxide (N2O) and ammonia (NH3). Gradually filling manure storages is a standard practice, however, most studies have batch filling approaches. Gradual manure filling may emit different GHGs when inoculum is present, as it changes the substrate/microorganism ratio, manure temperature, and distribution of solids. This study compared CH4, N2O and NH3 emissions from gradually-filled and batch-filled 11.9 m3 capacity liquid dairy manure tanks with 0%, 10% or 20% inoculum over 122 day of storage. On average, gradually-filled tanks had 1.8 °C higher manure temperature, which may have contributed to a 12% increase in total CH4 emissions to 6.26 kg m−3 and 28% increase in total NH3 emissions to 328 g m−3. The absence of inoculum reduced CH4 emissions by 25% and 23% compared to the 10% inoculum tanks (6.48 kg m−3) and 20% inoculum tanks (6.31 kg m−3), respectively. Absence of inoculum had no effect on N2O and NH3 emissions. Gradual filling of tanks containing inoculum increased CH4 emissions by 27% to 7.38 kg m−3, while in the absence of inoculum CH4 emissions were reduced by 29% to 4.03 kg m−3. Our results suggest that research using inoculant in batch-filled manure storage systems may underestimate GHG emissions. Future research should further characterize the effects of gradual filling on solids and temperature profiles, and substrate availability linked to production of GHGs.

Greenhouse Gas Mitigation through Dairy Manure Acidification.

Liquid dairy manure storages are sources of methane (CH), nitrous oxide (NO), and ammonia (NH) emissions. Both CH and NO are greenhouse gases (GHGs), whereas NH is an indirect source of NO emissions. Manure acidification is a strategy used to reduce NH emissions from swine manure; however, limited research has expanded this strategy to reducing CH and NO emissions by acidifying dairy manure. This study compared control dairy manure (pH 7.4) with two treatments of acidified manure using 70% sulfuric acid (HSO). These included a medium pH treatment (pH 6.5, 1.4 mL acid L manure) and a low pH treatment (pH 6, 2.4 mL acid L manure). Emissions were measured using replicated mesoscale manure tanks (6.6 m) enclosed by large steady state chambers. Both CH and NO were continuously measured (June-December 2017) using tunable diode laser trace gas analyzers. Ammonia emissions were measured three times weekly for 24 h using acid traps. On a CO equivalent basis, the medium pH treatment reduced total GHG emissions by 85%, whereas the low pH treatment reduced emissions by 88%, relative to untreated (control) manure. Total CH emissions were reduced by 87 and 89% from medium and low pH tanks, respectively. Ammonia emissions were reduced by 41 and 53% from medium and low pH tanks, respectively. Additional research is necessary to make acidification an accessible option for farmers by optimizing acid dosage. More research is need to describe the manure buffering capacity and emission reductions and ultimately find the best approaches for treating farm-scale liquid dairy manure tanks.

Gypsum Bedding Impact on Hydrogen Sulfide Release from Dairy Manure Storages

Abstract. Elevated hydrogen sulfide (H2S) levels have been observed from open-air dairy manure storages that contain gypsum bedding. Gypsum (calcium sulfate), recycled from construction waste and manufacturing defects, provides a cost-effective bedding alternative for dairy cows. Gypsum bedding is reported to control moisture and bacteria in the stalls and can improve soil structure when land-applied. However, gypsum increases H2S production in the anaerobic environment of deep manure storages, which is released in dangerous concentrations when the manure is agitated. This study was undertaken to quantify and compare the H2S concentrations during agitation of manure storages for three dairy stall management categories: farms that use (1) traditional organic bedding, (2) gypsum bedding, and (3) gypsum bedding followed by a treatment added to the manure storage thought to reduce H2S emissions. Three farms used Vital Breakdown (manufactured by Homestead Nutrition, New Holland, Pa.), and one farm used OK-1000 (Pro Ag Solutions, Hawkins, Tex.). Nineteen agitation events at ten farms were monitored during spring and fall hauling seasons. Portable monitoring instruments recorded H2S concentrations around the perimeter of the manure storages prior to and during agitation. Results show that manure storage agitation at farms that use gypsum bedding produced H2S concentrations that were considered immediately dangerous to life and health (above 100 ppm). Increasing gypsum bedding use significantly increased cumulative H2S concentrations (p &amp;lt; 0.0001). Farms that used Vital Breakdown as an amendment significantly reduced cumulative H2S concentrations when compared to farms not using a manure treatment (p &amp;lt; 0.0001). Lower cumulative H2S concentrations at one farm were attributed to the OK-1000 manure treatment. Keywords: Cow, Dairy, Gas, Gypsum, Hydrogen sulfide, Manure, Safety.

Nutrient Variability Following Dairy Manure Storage Agitation

Abstract. The nutrient profile in stored manure can be highly variable due to the solids building up at the bottom of the storage over time as unagitated manure is removed. This variability can lead to under- or over-application of nutrients potentially reducing crop yields or increasing nutrient losses, respectively. Agitation of stored manure is a common practice to re-suspend solids providing a more uniform nutrient consistency for application. This study explores the solids and nutrient variability in stored dairy manure after agitation and the relationship between the number of samples and the quality of the nutrient content estimate. A total of 16 dairy facilities across Wisconsin were sampled in the study. Samples were taken during agitation and analyzed for total solids (TS), total Kjeldahl nitrogen (TKN), total ammonia nitrogen (TAN), total phosphorus (TP), total potassium (TK), and microminerals. Overall, TKN, TAN, and TP contents were more uniform than TS. The mean concentrations (wet basis) from the 16 farms range from 2.45% to 15.28% for TS, 0.17% to 0.53% for TKN, 0.01% to 0.33 for TAN, 0.02 to 0.06 for TP, and 0.11% to 0.31% for TK. This range is mostly attributed to the between-farms variability in manure nutrient content. In addition, 54% of the total variation in the TS content was attributable to within-farm sample variability. These results show that TS was variable on farms whereas TKN, TAN, and TP were variable between farms. A random resampling analysis showed that three samples generate a mean between 20% to 30% of the true experimental mean for TKN and TAN whereas nine samples are required to be in this range for TP. Results show that the improvement achieved by adding more samples than 11 is less than 10%. Keywords: Dairy manure, Manure agitation, Nutrients, Nutrient variability, Sample size.

Iron Oxide to Mitigate Hydrogen Sulfide Gas Release from Gypsum-Bedded Dairy Manure Storages

Abstract. To mitigate noxious hydrogen sulfide (H2S) gas release that has been observed from gypsum-laden dairy manure, three additives were studied in sequential investigations. Three trials with specific aims were conducted using experimental vessels containing 15 kg of dairy manure each. Trial 1 investigated two additives: iron oxide (specifically, iron oxide-hydroxide, FeOOH) and a proprietary gypsum-lime based product (DriMatt). Trial 2 investigated effective ratios of gypsum to iron oxide and a modified DriMatt additive, and trial 3 evaluated iron oxide at the most effective ratio. Manure agitation events were monitored in the first two trials, while gas releases were continuously monitored in trial 3 during and between agitations. Hydrogen sulfide concentrations were captured using electrochemical sensors or a Fourier transfer infrared (FTIR) gas analyzer assembly over an incubation period of two months for the first two trials and over 40 days for the third trial. Additionally, nutrient analyses were performed for each trial. Extremely high concentrations of H2S were observed during most manure agitation events (500 to 8000 ppm), while minimum releases (&amp;lt;10 ppm) were found when samples were static. Means of maximum concentrations of H2S were compared among treatments in each trial. Statistical tests showed that adding iron oxide to gypsum-laden manure reduced H2S production by an average of 94% compared to treatments without iron oxide. With a 1:1 molar ratio of iron oxide to gypsum, the level of H2S released was diminished to as low as the control manure (without gypsum). Therefore, iron oxide is a promising additive to mitigate H2S production in gypsum-laden dairy manure during agitation events. Keywords: Additive, Dairy, Gas, Gypsum bedding, Hydrogen sulfide, Iron oxide, Manure, Safety, Storage.

Effect of Dairy Manure Storage Conditions on the Survival of E. coli O157:H7 and Listeria.

Dairy manure is regularly applied to crop fields as a solid or liquid to improve the soil nutrient status. However, pathogens may survive during manure storage and enter the environment during application. In this study, three storage practices were evaluated to understand the survival patterns of O157:H7 and spp. in dairy manure using a culture-based approach. To replicate common farm manure storage techniques, solid manure was stacked as piles with periodic turning or as static piles without turning, whereas liquid manure (feces, urine, and water) was stored as a slurry in small tanks to simulate lagoon conditions. The and levels in the manure samples were determined for 29 wk. Results showed that there was an initial reduction in bacteria levels in the first month; however, both and managed to survive in the solid manure piles for the full study period. In slurry samples, was not detected after 14 wk, but survived until the end of the experiment at relatively lower levels than in the solid manure piles. Ambient weather and pile size were identified as the main reasons for bacteria survival during the course of the experiment. The outcome of this study is important in terms of understanding pathogen survival in manure piles and slurries prior to their application to crop fields.

Year-round methane emissions from liquid dairy manure in a cold climate reveal hysteretic pattern

Liquid dairy manure storage is favourable for methane (CH4) production and a significant source of this greenhouse gas. Manure storage in cold climates faces large temperature variations over the course of a year, and added on-farm complexities in manure loading require year-round measurements which are currently lacking. The objectives of this study were to 1) quantify CH4 emissions from farm-scale liquid dairy manure storage in a cold climate, 2) investigate the effect of manure temperature on CH4 emissions, and 3) compare measured CH4 emissions with values derived from the USEPA temperature model. Methane fluxes were measured from Aug 2010 to early Nov 2011 on a commercial farm in Ontario, Canada, using a micrometeorological mass balance method which relied on 3 towers with air intakes at 4 heights placed around the storage tank. Manure temperature and volatile solid content (VS) were also measured. Monthly CH4 emissions scaled by VS decreased from 43.8 g CH4 kg−1 VS in Sep 2010 to 5.3 g CH4 kg−1 VS in Jan 2011, and were correlated with temperature (r2 = 0.94). Manure temperature increased starting in Feb 2011, but the increase in CH4 emissions was delayed to Jul 2011. Hence, the response of CH4 emissions to temperature showed a hysteretic pattern where emissions in the warming branch after the winter (Apr-Jun) were significantly lower than emissions in the cooling branch after the summer (Sep-Nov) despite similar temperatures. The temperature model predicted emissions during the cooling phase well, but overpredicted emissions during the warming phase, indicating other limiting factors for microbial CH4 production. Thus, the annual predicted CH4 emissions were about 2.3× larger than the measured values. The newly observed hysteresis effect should be considered when predicting CH4 emissions from stored manure.

Estrogens: Properties, behaviors, and fate in dairy manure-amended soils

In 2012 there were 63% fewer dairies in the United States than there were in 1997 as a result of conglomeration of the dairy industry into concentrated animal feeding operations at the expense of smaller farms. Today, 60% of all milk produced in the United States comes from 5% of the nation’s dairies (operations with ≥ 500 cows). Concentrated animal feeding operations are touted as economically efficient agricultural business models, hailed for their increased milk yields. Yet, with an average daily manure production of over 27 000 kg for a 500-head dairy farm, manure storage and disposal are serious management and environmental concerns. A common economical mode of manure disposal is application to nearby agricultural fields. However, a major concern with land application of dairy manure is the fate of manure-borne hormones, compounds considered chemicals of emerging concern, and the potential threat these hormones pose to humans and the environment. The fate of these chemicals in the soil environment is complicated by multiple edaphic variables including pH, mineralogy, organic matter, microbial activity, and redox status. Estrogens are sorbed by soil organic matter and transformed to nonbioactive, highly soluble conjugated forms or to metabolites that exhibit yet additional properties distinct from their parent compounds. However, deconjugation frequently occurs, regenerating endocrine-disrupting free estrogen compounds. It is challenging to fully understand the behavior and predict the fate of estrogenic compounds from dairy manure in soils because of variable and complex interactions with soil factors, as well as possible interactions among the different chemicals of emerging concern. This review focuses on the behavior of naturally occurring estrogen hormones present in dairy manure in the soil environment. Heightened understanding of the fate of these compounds in soil will enhance our ability to reduce their potential risks.

Do volatile solids from bedding materials increase greenhouse gas emissions for stored dairy manure?

Current approaches for estimating greenhouse gas (GHG) emissions from manure storages do not consider contributions due to bedding materials. Compared with sand, wood-based bedding has the potentia...

Operator Exposure to Hydrogen Sulfide from Dairy Manure Storages Containing Gypsum Bedding.

Dairy manure storages containing gypsum-based bedding have been linked anecdotally with injury and death due to presumed dangerous levels of gases released. Recycled gypsum products are used as a cost-effective bedding alternative to improve animal welfare and provide agronomic benefits to manure recycled back to the land. Sulfur contained in gypsum (calcium sulfate) can contribute to hydrogen sulfide (H2S) gas formation under the anaerobic storage conditions typical of dairy manure slurry. Disturbance of stored manure during agitation releases a burst of volatile gases. On-farm monitoring was conducted to document conditions during manure storage agitation relative to gas concentration and operator safety. One objective was to document operator exposure to H2S levels; therefore, each operator wore a personal gas monitor while performing tasks associated with manure storage agitation. Data from three dairy bedding management categories on ten farms were compared: (1) traditional organic bedding, (2) gypsum bedding, and (3) gypsum bedding plus a manure additive thought to reduce H2S formation and/or release. Portable meters placed around the perimeter of dairy manure storages recorded H2S concentrations prior to and during 19 agitation events. Results show that farms using gypsum bedding produced higher H2S concentrations during manure storage agitation than farms using traditional bedding. In most cases, gypsum-containing manure storages produced H2S levels above recognized safe thresholds for both livestock and humans. Farm operators were most at risk during activities in close proximity to the manure storage during agitation, and conditions 10 m away from the storage were above the 20 ppm H2S threshold on some farms using gypsum bedding. Although H2S concentrations rose to dangerous levels, only two of 18 operators were exposed to >50 ppm H2S during the first 60 min of manure storage agitation. Operators who are aware of the risk of high H2S concentrations near gypsum-laden manure storages can reduce their exposure risk by working upwind and away from the H2S plume within a closed tractor cab.

Coupling Dairy Manure Storage with Injection to Improve Nitrogen Management: Whole‐Farm Simulation Using the Integrated Farm System Model

Core Ideas Manure storage and injection strategies were simulated using the Integrated Farming Systems Model. Strategies were verified using field data. We compared manure storage in environmental and economic model outputs. Introducing 6 mo of storage on a PA dairy farm decreased whole‐farm NUE without manure injection. Manure injection and 6 mo of storage gave the best combination of profit and environmental outcome. Application of livestock manure to farm soils represents a priority nutrient management concern in the Chesapeake Bay watershed. Historically, strong emphasis has been placed on adding manure storage to dairy operations, with the recognition that manure application methods can be improved. The Integrated Farm System Model was used to simulate manure management on a typical Pennsylvania dairy farm (100 milking cows, 80 ha). Converting the operation from daily haul to 6 mo of storage with broadcast application did not substantially change nitrogen (N) losses to the environment. However, switching to manure injection conserved ammonium N and improved manure N use efficiency by crops, even though it increased N leaching by 27% with 6‐mo storage and 13% with 12‐mo storage. Increasing manure storage from 6 to 12 mo with manure injection reduced nitrate N leaching by 38%, due to better timing of manure application to crop growth, but lowered annual net returns. Overall, manure injection and 6 mo of storage resulted in the best combination of profit and environmental outcome.

Greenhouse Gas Emissions from Stored Dairy Slurry from Multiple Farms.

A significant need exists to improve our understanding of the extent of greenhouse gas emissions from the storage of livestock manure to both improve the reliability of inventory assessments and the impact of beneficial management practice adoption. Factors affecting the extent and variability of greenhouse gas emissions from stored dairy manure were investigated. Emissions from six slurries stored in clean concrete tanks under identical "warm-season" conditions were monitored consecutively over 173 d (18°C average air temperature). Methane (CH) emissions varied considerably among the manures from 6.3 to 25.9 g m d and accounted for ∼96% of the total CO equivalent greenhouse gas emissions. The duration of the lag period, when methane emissions were near baseline levels, varied from 30 to 90 d from the beginning of storage. As a result, CH emissions were poorly correlated with air temperature prior to the time of peak emissions (i.e., the initial 48 to 108 d of storage) but improved afterward. The air temperature following the time of the peak CH flux and the length of the active methanogenesis period (i.e., when the daily CH emissions ≥ 7.6 g m d) were highly correlated with CH emissions ( = 0.98, < 0.01). Methane conversion factors (MCFs) ranged from 0.08 to 0.52 for the different manures. The MCFs generated from existing CH emission models were correlated ( = 0.68, = 0.02) to MCFs calculated for the active methanogenesis period for manure containing wood bedding. A temperature component was added that improved the accuracy ( = 0.82, < 0.01). This demonstrated that an improved understanding of lag period dynamics will enhance stored dairy manure greenhouse gas emission inventory calculations.

The seasonal effects of manure management and feeding strategies on hydrogen sulphide emissions from stored dairy manure

The influence of temperature and storage time on hydrogen sulphide (H2S) emissions from two different dairy manures was investigated over four seasons in 2012. Two separate experiments were conducted using dairy manure; (1) water baths at 0, 5, 10, 15, 20, 25 and 30 °C that were incubated for 15 h, and (2) 28-day batch experiment under room temperature. The headspace H2S concentration increased exponentially after 15 °C and reached a maximum of 3.1 mg/L at 30 °C. After the 4th day of storage, dairy manure emitted an average of 3.6 mg/L of H2S. However, a small decrease was observed on the 28th day, with a concentration of 2.8 mg/L. Under natural conditions, dairy manure emitted significantly lower H2S values during winter than during spring, summer and autumn when manure is widely used as fertiliser. Furthermore, regardless of the incubation temperature and storage time, manure from cows fed with concentrate-based feed emitted much higher H2S (6.5 times) than from cows fed with forage-based feed. These results indicated that the emissions of H2S from dairy manure could be managed by feeding cows minimal concentrate feed and by handling manure at cooler temperatures or lengthening the retention time.

Effect of increasing levels of corn silage in an alfalfa-based dairy cow diet and of manure management practices on manure fugitive methane emissions

The main objective of this study was to assess the effect of dairy cow diets and manure storage management practices on manure fugitive CH4 emission in order to precisely establish the carbon footprint of Canadian milk products. The specific objectives of this study were to investigate the effect of incorporating 50 and 100% corn silage (CS) as starch sources in dairy cow diets and the effect of complete removal of residual sludge in the manure storage tank and of storage emptying frequency on manure fugitive CH4 emissions. Alfalfa silage based diets were formulated as follows: 0% corn silage (0% CS, considered as the control diet); 50% corn silage (50% CS); and 100% corn silage (100% CS). Canadian summer manure storage conditions were simulated in laboratory-scale storage structures located in a controlled-environment chamber operated at 20±1°C. The incorporation of 50 and 100% CS in dairy diets was associated with significant increases of 39 and 79%, respectively, in fugitive CH4 emissions expressed in Lday−1cow−1 from manure storage with residual sludge over a 120-day storage period. The complete removal of residual sludge in the manure storage tank resulted in fugitive methane emission reductions exceeding 97.0% irrespective of the diet composition. Emptying of the manure storage tank 2 times and 4 times over the summer period reduced fugitive CH4 emissions on average by 40 and 80%, respectively. The complete removal of the manure storage residual sludge and the increase in manure storage tank emptying frequency over the summer can be adopted as low-cost best management practices (BMPs) for substantially reducing the fugitive CH4 emissions from manure storages.

New York Dairy Manure Management Greenhouse Gas Emissions and Mitigation Costs (1992-2022).

Livestock manure can be a significant source of greenhouse gases (GHG) including methane (CH) and nitrous oxide (NO). However, GHG emissions are strongly affected by the type of waste management system (WMS) used. For example, CH emissions increase substantially under anaerobic conditions that occur in many WMSs. There is a need for improved estimates at regional and national scales of the effect of WMSs on GHG emissions and identification of opportunities and associated costs to mitigate these emissions. As New York State is the fourth largest dairy producer in the country, our objectives were to quantify (i) the changes in WMS and associated GHG emissions over time, (ii) a methane conversion factor (MCF) derived from existing data from three covered manure storage units in New York, and (iii) the benefit and cost of installing covers and flares to destroy CH from existing storage units. We found that GHG emissions from changing manure management increased from 0.7 Tg carbon dioxide equivalents per year (COe yr) in 1992 to 1.6 Tg COe yr in 2012. We derived an MCF of 0.61 based on data from dairy manure storage units with covers that captured and flared CH in 2010 and used this MCF to project GHG reductions for a statewide mitigation scenario in year 2022. This scenario, covering and flaring CH from 662 manure storage units, mitigates 1.8 Tg COe annually or 62% of manure GHG (CH and NO) at an estimated cost of $224 million ($0.005 L milk or $13 Mg COe).