Quantifying ammonia emissions from a cattle feedlot using a dispersion model

Feeding or pen surface application of clinoptilolite with different particle sizes: impact on nitrogen utilization and manure ammonia emissions in feedlot cattle

This study investigated the effects of feeding clinoptilolite (CLN; 2.5% of diet dry matter) with a particle size of either 30- or 400-µm on ruminal fermentation characteristics, measures of nitrogen (N) utilization, and manure ammonia-N (NH3) emissions in feedlot cattle. The impact of directly applying 30- or 400-µm CLN to the pen surface (2,250 kg/ha) on manure NH3-N emissions was also evaluated. Six beef heifers were used in a replicated 3 × 3 Latin square design with 21-d periods. Dietary treatments were 1) finishing ration with no supplement (CON), 2) CON + 30-µm CLN (CLN-30), and 3) CON + 400-µm CL (CLN-400). Intake was measured daily. To evaluate fermentation characteristics, ruminal fluid was collected on day 19. Indwelling pH loggers were used to measure ruminal pH from days 15 to 21. Blood was collected 3-h post-feeding on day 21 for metabolite analysis. Fecal grab and urine spot samples were also collected from days 19 to 21 to measure nutrient digestibility, route of N excretion, and in vitro NH3 emissions. There was no diet effect (P ≥ 0.12) on nutrient intake and apparent total tract digestibility, and ruminal short-chain fatty acid profile and pH. Ruminal NH3 concentration, which was lower (P = 0.04) for CLN-30 than CON heifers, did not differ between CON and CLN-400 heifers. Although there was no diet effect (P = 0.50) on plasma urea-N (PUN) concentration, proportion of urea-N excreted in urine was lower (P = 0.01) for CLN-30 than CON and CLN-400 heifers. Urinary NH3-N excretion, which was greater (P ≤ 0.04) for CLN-400 than CON heifers, did not differ between CLN-30 and CLN-400 heifers. Feeding CLN also increased (P ≤ 0.02) fecal excretion of potassium (K) and iron (Fe) and reduced (P = 0.01) urinary excretion of calcium (Ca). There was a treatment × time interaction (P = 0.01) for NH3 emission rate, which was greatest within the first 36 h of incubation and was lower for manure from CLN-400 compared to CON and CLN-30 heifers and pen surface application treatments. Cumulative NH3 emissions were lower (P < 0.01) for manure from CLN-400 compared to CON and CLN-30 heifers and the pen surface application treatments. Although surface application was ineffective, feeding 400-µm CLN to finishing cattle could result in a beneficial decrease in manure NH3 emissions. However, changes in fecal and urine excretion of minerals like K and Ca, which suggest a decrease in bioavailability, need to be considered when feeding CLN in finishing cattle diets.

Ammonia emissions from a dairy housing and wastewater treatment plant quantified with an inverse dispersion method accounting for deposition loss

Ammonia (NH3) emissions negatively impact air, soil, and water quality, hence human health and biodiversity. Significant emissions, including the largest sources, originate from single or multiple structures, such as livestock facilities and wastewater treatment plants (WWTPs). The inverse dispersion method (IDM) is effective in measuring total emissions from such sources, although depositional loss between the source and point of measurement is often not accounted for. We applied IDM with a deposition correction to determine total emissions from a representative dairy housing and WWTP during several months in autumn and winter in Switzerland. Total emissions were 1.19 ± 0.48 and 2.27 ± 1.53 kg NH3 d-1 for the dairy housing and WWTP, respectively, which compared well with literature values, despite the paucity of WWTP data. A concurrent comparison with an inhouse tracer ratio method at the dairy housing indicated an offset of the IDM emissions by < 20%. Diurnal emission patterns were evident at both sites mostly driven by changes in air temperature with potential lag effects such as following sludge agitation. Modeled deposition corrections to adjust the concentration loss detected at the measurement point with the associated footprint were 22-28% of the total emissions and the cumulative fraction of deposition to emission modeled with distance from the source was between 7% and 12% for the measurement distances (60-150 m). Although estimates of depositional loss were plausible, the approach is still connected with substantial uncertainty, which calls for future validation measurements. Longer measurement periods encompassing more management activities and environmental conditions are required to assess predictor variable importance on emission dynamics. Combined, IDM with deposition correction will allow the determination of emission factors at reduced efforts and costs, thereby supporting the development and assessment of emission reducing methods and expand the data availability for emission inventories.Implications: Ammonia emissions must be measured to determine emission factors and reporting national inventories. Measurements from structures like farms and industrial plants are complex due to the many different emitting surfaces and the building configuration leading to a poor data availability. Micrometeorological methods provide high resolution emission data from the entire structure, but suffer from uncertainties, as the instruments must be placed at a distance from the structure resulting in a greater loss of the emitted ammonia via dry deposition before it reaches the measurement. This study constrains such emission measurements from a dairy housing and wastewater treatment plant by applying a simple correction to account for the deposition loss and compares the results to other methods.

Distribution of livestock sectors in Canada: Implications for manureshed management

Canada's livestock production and human populations are concentrated in southern regions. Understanding spatial and temporal distributions of animals and excreted nutrients is key to optimizing manure resources and minimizing impact of livestock. Here, we identify manureshed concerns and opportunities by reconciling nitrogen supply and demand on a regional and national scale. Data based on national statistics and farm surveys were allocated to homogeneous soil polygons (Soil Landscapes of Canada [SLC]) to quantify changes in nutrient distribution and ammonia (NH₃ ) emissions across Canada (1981-2018). Livestock sectors tied to domestic consumption, dairy and poultry, were stable over time and well dispersed. Export driven beef production has moved west since 1981, whereas pig production was prominent in Manitoba, Quebec, and Ontario. Per ha manure N excretion across livestock sectors in 2018 was generally low with 58% and 6% of the SLCs averaging <25 and >100 kg N ha^-1 , respectively. Although only 3% of SLCs had average NH₃ emissions reaching 16-200 kg ha^-1 , most of these were located near cities and emissions spiked in spring when more people might be exposed. The greatest concentrations of nutrients and livestock occurred around the three largest metropolitan areas: Toronto, Montreal-Quebec City, and Vancouver, posing challenges for nutrient recycling and public health. This study shows that as Canadian cities and livestock agriculture grow in southern Canada, so will challenges around food production, human health, and managing nutrients. Livestock and land use strategies are needed to reconcile changing animal sectors and growing populations.

Quantification of methane emitted by ruminants: a review of methods

The contribution of greenhouse gas (GHG) emissions from ruminant production systems varies between countries and between regions within individual countries. The appropriate quantification of GHG emissions, specifically methane (CH4), has raised questions about the correct reporting of GHG inventories and, perhaps more importantly, how best to mitigate CH4 emissions. This review documents existing methods and methodologies to measure and estimate CH4 emissions from ruminant animals and the manure produced therein over various scales and conditions. Measurements of CH4 have frequently been conducted in research settings using classical methodologies developed for bioenergetic purposes, such as gas exchange techniques (respiration chambers, headboxes). While very precise, these techniques are limited to research settings as they are expensive, labor-intensive, and applicable only to a few animals. Head-stalls, such as the GreenFeed system, have been used to measure expired CH4 for individual animals housed alone or in groups in confinement or grazing. This technique requires frequent animal visitation over the diurnal measurement period and an adequate number of collection days. The tracer gas technique can be used to measure CH4 from individual animals housed outdoors, as there is a need to ensure low background concentrations. Micrometeorological techniques (e.g., open-path lasers) can measure CH4 emissions over larger areas and many animals, but limitations exist, including the need to measure over more extended periods. Measurement of CH4 emissions from manure depends on the type of storage, animal housing, CH4 concentration inside and outside the boundaries of the area of interest, and ventilation rate, which is likely the variable that contributes the greatest to measurement uncertainty. For large-scale areas, aircraft, drones, and satellites have been used in association with the tracer flux method, inverse modeling, imagery, and LiDAR (Light Detection and Ranging), but research is lagging in validating these methods. Bottom-up approaches to estimating CH4 emissions rely on empirical or mechanistic modeling to quantify the contribution of individual sources (enteric and manure). In contrast, top-down approaches estimate the amount of CH4 in the atmosphere using spatial and temporal models to account for transportation from an emitter to an observation point. While these two estimation approaches rarely agree, they help identify knowledge gaps and research requirements in practice.

Comparisons of forward-in-time and backward-in-time Lagrangian stochastic dispersion models for micro-scale atmospheric dispersion

Lagrangian stochastic dispersion models are sometimes run in backward mode to estimate air emissions from different types of sources including area sources. The forward-in-time and backward-in-time Lagrangian stochastic (fLS and bLS) dispersion models may not result in the same estimates. The two models were compared under different atmospheric conditions in micro-scale applications. They are equivalent in a steady-state and horizontally homogeneous atmosphere in many features including estimating concentration at a point, using surface receptor, and prerunning the models. Although bLS shows better computational efficiency, it has a larger uncertainty in results due to the use of surface receptors. In a non-steady-state wind field, the two models show opposite transition trends when the wind fields experience a step change. Under sinusoidal-varying winds, the two models show different shapes of the predicated concentration curves. The normalized differences of the mean concentrations mainly increase with the receptor height when the source-receptor distance is fixed. A controlled methane release experiment was conducted to investigate the behaviors of the two models driven by real wind fields. The correlation coefficient between model-predicted concentrations is 0.95. The model-predicted (forward model) and measured concentrations show similar trend with a correlation coefficient of 0.70. The bLS model estimates larger peak concentrations than that fLS model under the same emission rate. The best-fitted results of the fLS and bLS models give recovery ratios of 1.1558 and 0.9675, respectively, which are better than that using a constant 15-min averaged wind (0.7922).Implications: There are large uncertainties and difficulties in quantification of fugitive air emissions from area sources such as landfills, agriculture, and industry sections. Lagrangian stochastic dispersion model is a versatile tool for these applications with the capability of near-field description and good efficiency. Backward models are usually used to estimate emission rates from area sources due to high computing efficiencies. But they may not result in the same estimate as the forward models due to factors involving model realization and input parameters. It is necessary to investigate the discrepancies to select the best model with minimal uncertainty in the results.

Micrometeorological Methods for Measuring Methane Emission Reduction at Beef Cattle Feedlots: Evaluation of 3-Nitrooxypropanol Feed Additive

It is highly desirable to test agricultural emission mitigation strategies in a whole-farm environment to ensure that all aspects of management and production operations are included. However, the large spatial scale of commercial operations makes the dual measurements of control and treatment(s) difficult. We evaluated the application of two micrometeorological methods, a novel concentration ratio method and an inverse dispersion method, where both were used to measure methane (CH) emission reductions in cattle fed the compound 3-nitrooxypropanol compared with cattle fed just the basal diet. In total, there were 1344 cattle used that were located in six pens (∼222 animals per pen). Three adjacent pens to the east and three to the west were designated as the treatment and control blocks, respectively. Underlying the emission reduction method was the assumption of site symmetry between the treatment and control pen blocks in the feedlot. There was, on average, a large CH emission reduction of ∼70% (±18%) due to the additive as found by both micrometeorological methods. Both methods also show a change in the diel distribution (peak emissions after initial morning feeding) and seasonal pattern (a decrease in emission reduction of 7.5 and 26.1% over 90 d). The simplicity of the developed concentration ratio method is expected to have applications for evaluating other mitigation strategies at large commercial scales (e.g., the application of manure additives to pens to reduce odors and ammonia emissions).

Ammonia Emissions Measured Using Two Different GasFinder Open-Path Lasers

The challenges of accurately measuring in situ ammonia (NH3) losses from agricultural systems are well known. Using an open path laser coupled with a backward Lagrangian stochastic dispersion model is a promising approach for quantifying both point- and area-sources; however, this approach requires the open path laser to detect low NH3 concentrations and small concentration differences. In this study, we compared the new GasFinder3 open path laser (Boreal laser Inc., Edmonton, Canada) with the GasFinder2 sensor, the previous version. The study took place at two locations: an outdoor open-air manure compost site, and a field of wheat stubble which was fertilized with urea ammonium nitrate. Results showed the two lasers reported similar concentrations during three days of measurements at the compost site, but differed at the field site, where concentrations were close to the minimum detection limit. The GasFinder3 had a lower standard deviation under all conditions, especially with low wind speed and high relative humidity.

Feeding condensed tannins to mitigate ammonia emissions from beef feedlot cattle fed high-protein finishing diets containing distillers grains

Two experiments were conducted to determine the effects of feeding a condensed tannin extract (CT) on dry matter intake (DMI), growth performance, carcass traits, and NH3-N emissions of beef feedlot cattle fed high-protein barley-based finishing diets. In Exp. 1, 36 crossbred steers (346 ± 4.2 kg) were individually fed 4 diets with 20% corn dried distillers grains (DG) and increasing concentrations of a CT extract from Acacia mearnsii (black wattle) at 0%, 1.2%, 2.4%, and 3.5% of DM (9 steers per diet) for 52 d. The DMI was not affected at 1.2% and 2.4% but tended (P = 0.08, quadratic effect) to decrease at 3.5% CT extract. There was no effect (P ≥ 0.12) of increasing CT extract on ADG, but G:F tended (P = 0.09) to decrease linearly. In Exp. 2, 148 crossbred steers (457 ± 3.8 kg) were allocated to 16 pens with 4 pens per treatment in a completely randomized design and fed for 83 d. The 4 dietary treatments included 0% corn DG (0DG), 20% DG (20DG), 40% DG (40DG), and 40% DG with 2.5% CT extract (40DGCT) and contained 13.3, 15.9, 20.4, and 19.4% CP, respectively. All cattle were weighed, and blood was collected from 5 steers per pen every 3 wk. Ammonia emissions were measured in four 3-wk periods using the integrated horizontal flux technique with passive NH3 samplers from 2 pens of cattle fed 0DG and 20DG (Period 1), 40DG and 40DGCT (Period 2), 0DG and 40DG (Period 3), and 0DG and 40DGCT (Period 4). There was no effect (P ≥ 0.15) of diet on final body weight (621 ± 7.1 kg), DMI (11.9 ± 0.25 kg/d), ADG (1.98 ± 0.07 kg/d), G:F (166 ± 5.4 g/kg), and carcass traits. Plasma urea N (PUN) increased (P < 0.001) from 0DG to 40DG (113 to 170 ± 6.0 mg N/L) and was reduced (P < 0.001) by 40DGCT (146 mg N/L) compared with 40DG and tended (P = 0.09) to be reduced compared with steers fed 20DG (153 mg N/L). Ammonia-N emissions were greater from cattle fed 40DG [113.7 vs. 70.8 ± 4.57 g N/(steer·d), P = 0.003] and tended to be greater from cattle fed 20DG [51.3 vs. 26.3 ± 11.2 g N/(steer·d), P = 0.11] compared with 0DG. Cattle fed 40DGCT tended to have lower NH3-N emissions compared with cattle fed 40DG [72.7 vs. 95.1 ± 9.3 g N/(steer·d), P = 0.09 and 20.5 vs. 26.5 ± 2.64% N intake, P = 0.11]. Feeding 2.5% CT to beef feedlot cattle fed a high-protein diet had no detrimental effect on performance, reduced PUN indicating lower urinary urea N excretion, and lowered NH3-N emissions by 23%.

Simultaneous measurements of ammonia volatilisation and deposition at a beef feedlot

The nitrogen (N) excreted at intensive livestock operations is vulnerable to volatilisation, and, subsequently, may form a source of indirect nitrous oxide (N2O) emissions. The present study simultaneously investigated volatilisation and deposition of N at a beef feedlot, semi-continuously over a 129-day period. These data were examined relative to pen manure parameters, management statistics and emission-inventory calculation protocols. Volatilisation measurements were conducted using a single, heated air-sampling inlet, centrally located in a feedlot pen area, with real time concentration analysis via cavity ring-down spectroscopy and backward Lagrangian stochastic (bLS) modelling. Net deposited mineral-N was determined via two transects of soil-deposition traps, with samples collected and re-deployed every 2 weeks. Total volatilised ammonia amounted to 210 tonnes of NH3-N (127 g/animal.day), suggesting that the inventory volatilisation factor probably underestimated volatilisation in this case (inventory, 30% of excreted N; 65 g N volatilised/animal.day; a value of ~60% of excreted N is indicated). Temperature contrast between the manure and air was observed to play a significant role in the rate of emission (R2 = 0.38; 0.46 Kendall’s tau; P &lt; 0.05). Net deposition within 600 m of the pen boundary represented only 1.7% to 3% of volatilised NH4+-N, between 3.6 and 6.7 tonnes N. Beyond this distance, deposition approached background rates (~0.4 kg N/ha.year).

Analytical methods for quantifying greenhouse gas flux in animal production systems

Given increased interest by all stakeholders to better understand the contribution of animal agriculture to climate change, it is important that appropriate methodologies be used when measuring greenhouse gas (GHG) emissions from animal agriculture. Similarly, a fundamental understanding of the differences between methods is necessary to appropriately compare data collected using different approaches and design meaningful experiments. Sources of carbon dioxide, methane, and nitrous oxide emissions in animal production systems includes the animals, feed storage areas, manure deposition and storage areas, and feed and forage production fields. These 3 gases make up the primary GHG emissions from animal feeding operations. Each of the different GHG may be more or less prominent from each emitting source. Similarly, the species dictates the importance of methane emissions from the animals themselves. Measures of GHG flux from animals are often made using respiration chambers, head boxes, tracer gas techniques, or in vitro gas production techniques. In some cases, a combination of techniques are used (i.e., head boxes in combination with tracer gas). The prominent methods for measuring GHG emissions from housing include the use of tracer gas techniques or direct or indirect ventilation measures coupled with concentration measures of gases of interest. Methods for collecting and measuring GHG emissions from manure storage and/or production lots include the use of downwind measures, often using photoacoustic or open path Fourier transform infrared spectroscopy, combined with modeling techniques or the use of static chambers or flux hood methods. Similar methods can be deployed for determining GHG emissions from fields. Each method identified has its own benefits and challenges to use for the stated application. Considerations for use include intended goal, equipment investment and maintenance, frequency and duration of sampling needed to achieve desired representativeness of emissions over time, accuracy and precision of the method, and environmental influences on the method. In the absence of a perfect method for all situations, full knowledge of the advantages and disadvantages of each method is extremely important during the development of the experimental design and interpretation of results. The selection of the suitable technique depends on the animal production system, resource availability, and objective for measurements.

Characterization of Ammonia, Methane, and Nitrous Oxide Emissions from Concentrated Animal Feeding Operations in Northeastern Colorado

Atmospheric emissions from animal husbandry are important to both air quality and climate, but are hard to characterize and quantify as they differ significantly due to management practices and livestock type, and they can vary substantially throughout diurnal and seasonal cycles. Using a new mobile laboratory, ammonia (NH₃), methane (CH₄), nitrous oxide (N₂O), and other trace gas emissions were measured from four concentrated animal feeding operations (CAFOs) in northeastern Colorado. Two dairies, a beef cattle feedlot, and a sheep feedlot were chosen for repeated diurnal and seasonal measurements. A consistent diurnal pattern in the NH₃ to CH₄ enhancement ratio is clearly observed, with midday enhancement ratios approximately four times greater than nighttime values. This diurnal pattern is similar, with slight variations in magnitude, at the four CAFOs and across seasons. The average NH₃ to CH₄ enhancement ratio from all seasons and CAFOs studied is 0.17 (+0.13/-0.08) mol/mol, in agreement with statewide inventory averages and previous literature. Enhancement ratios for NH₃ to N₂O and N₂O to CH₄ are also reported. The enhancement ratios can be used as a source signature to distinguish feedlot emissions from other NH₃ and CH₄ sources, such as fertilizer application and fossil fuel development, and the large diurnal variability is important for refining inventories, models, and emission estimates.

Ammonia Emission from a Beef Cattle Feedlot and Its Local Dry Deposition and Re-Emission

Ammonia (NH) volatized from livestock manure is affiliated with ecosystem and human health concerns and decreased fertilizer value of manure and can also be an indirect source of greenhouse gas. Beef cattle feedlots, where thousands of cattle are grouped together to enable greater control of feed management and production, are hot spots in the agricultural landscape for NH emissions. Quantifying the feedlot NH emissions is a difficult task, partly due to the reactive nature of NH within and surrounding the feedlot. Our study used a dispersion model coupled to field measurements to derive NH emissions from a feedlot in southern Alberta, Canada. The average feedlot NH emission was 50 μg m s (85 g animal d), which coincides with a low dietary crude protein content. At a location 165 m east of the feedlot, a flux gradient (FG) technique measured an average NH deposition of 12.0 μg m s (west wind) and 5.3 μg m s (east wind). Ammonia FG emission averaged 1 μg m s with east winds, whereas no NH emission was found for west wind. Using soil-captured NH, there was a decrease in deposition with distance from the feedlot (50% over 200 m). Collectively, the results of this study provide insight into the dynamics of NH in the agricultural landscape and illustrate the need for NH mitigation to improve the environmental and economic sustainability of cattle feedlots.

Distillers By-Product Cattle Diets Enhance Reduced Sulfur Gas Fluxes from Feedlot Soils and Manures

Total reduced sulfur (TRS) emissions from animal feeding operations are a concern with increased feeding of high-sulfur distillers by-products. Three feeding trials were conducted to evaluate feeding wet distillers grain plus solubles (WDGS) on TRS fluxes. Fresh manure was collected three times during Feeding Trial 1 from cattle fed 0, 20, 40, and 60% WDGS. Fluxes of TRS from 40 and 60% WDGS manures were 3- to 13-fold greater than the 0 and 20% WDGS manures during the first two periods. In the final period, TRS flux from 60% WDGS was 5- to 22-fold greater than other WDGS manures. During Feeding Trial 2, 0 and 40% WDGS diets on four dates were compared in feedlot-scale pens. On two dates, fluxes from mixed manure and soil near the feed bunk were 3.5-fold greater from 40% WDGS pens. After removing animals, soil TRS flux decreased 82% over 19 d but remained 50% greater in 40% WDGS pens, principally from the wetter pen edges (1.9-fold greater than the drier central mound). During two cycles of cattle production in Feeding Trial 3, TRS soil fluxes were 0.3- to 4-fold greater over six dates for pens feeding WDGS compared with dry-rolled corn diet and principally from wetter pen edges. Soil TRS flux correlated with %WDGS, total N, total P, manure pack temperature, and surface temperature. Consistent results among these three trials indicate that TRS fluxes increase by two- to fivefold when cattle were fed greater levels of WDGS, but specific manure management practices may help control TRS fluxes.

Using airborne technology to quantify and apportion emissions of CH4 and NH3 from feedlots

A novel airborne approach using the latest technology in concentration measurements of methane (CH4) and ammonia (NH3), with quantum cascade laser gas analysers (QCLAs) and high-resolution wind, turbulence and other atmospheric parameters integrated into a low- and slow-flying modern airborne platform, was tested at a 17 000 head feedlot near Charlton, Victoria, Australia, in early 2015. Aircraft flights on 7 days aimed to define the lateral and vertical dimensions of the gas plume above and downwind of the feedlot and the gas concentrations within the plume, allowing emission rates of the target gases to be calculated. The airborne methodology, in the first instance, allowed the emissions to be qualitatively apportioned to individual rows of cattle pens, effluent ponds and manure piles. During each flight, independent measurements of emissions were conducted by ground-based inverse-dispersion and eddy covariance techniques, simultaneously. The aircraft measurements showed good agreement with earlier studies using more traditional approaches and the concurrent ground-based measurements. It is envisaged to use the aircraft technology for determining emissions from large-scale open grazing farms with low cattle densities. Our results suggested that this technique is able to quantify emissions from various sources within a feedlot (pens, manure piles and ponds), as well as the whole feedlot. Furthermore, the airborne technique enables tracing emissions for considerable distances downwind. In the current case, it was possible to detect elevated CH4 to at least 25 km and NH3 at least 7 km downwind of the feedlot.

Non-interference measurement of CH4, N2O and NH3 emissions from cattle

A technique combining open-path Fourier transform infrared spectroscopy with an inverse-dispersion model was used to quantify methane (CH4), nitrous oxide (N2O) and ammonia (NH3) emissions from an isolated cattle pen in south-eastern Australia. Twenty-eight Angus steers (1-year old, initial average liveweight 404 kg) were fed a 60% grain diet and kept in a pen (20 × 20 m) for 41 days. Gas concentrations were measured downwind of the pen using an open-path Fourier transform infrared spectroscopy with a path length of 100 m, having a detection sensitivity of 2, 0.3 and 0.4 ppb for CH4, N2O and NH3, respectively. Daily emission rates were 232, 14 and 192 g/cattle.day for CH4, N2O and NH3, respectively. The measured CH4 emissions were in agreement with predictions based on Australian National Inventory recommendations, however, measured N2O and NH3 emissions were much higher than the predicted values. Extrapolation of our measurements would mean that CH4 and N2O emissions from beef feedlot cattle contribute 3.1% and 5.9% of the Australian agricultural CH4 and N2O emissions, respectively.

Large-chamber methane and nitrous oxide measurements are comparable to the backward lagrangian stochastic method

Measurement of individual emission sources (e.g., animals or pen manure) within intensive livestock enterprises is necessary to test emission calculation protocols and to identify targets for decreased emissions. In this study, a vented, fabric-covered large chamber (4.5 × 4.5 m, 1.5 m high; encompassing greater spatial variability than a smaller chamber) in combination with on-line analysis (nitrous oxide [NO] and methane [CH] via Fourier Transform Infrared Spectroscopy; 1 analysis min) was tested as a means to isolate and measure emissions from beef feedlot pen manure sources. An exponential model relating chamber concentrations to ambient gas concentrations, air exchange (e.g., due to poor sealing with the surface; model linear when ≈ 0 m s), and chamber dimensions allowed data to be fitted with high confidence. Alternating manure source emission measurements using the large-chamber and the backward Lagrangian stochastic (bLS) technique (5-mo period; bLS validated via tracer gas release, recovery 94-104%) produced comparable NO and CH emission values (no significant difference at < 0.05). Greater precision of individual measurements was achieved via the large chamber than for the bLS (mean ± standard error of variance components: bLS half-hour measurements, 99.5 ± 325 μg CH s and 9.26 ± 20.6 μg NO s; large-chamber measurements, 99.6 ± 64.2 μg CH s and 8.18 ± 0.3 μg NO s). The large-chamber design is suitable for measurement of emissions from manure on pen surfaces, isolating these emissions from surrounding emission sources, including enteric emissions.

Arrhenius equation for modeling feedyard ammonia emissions using temperature and diet crude protein

Temperature controls many processes of NH volatilization. For example, urea hydrolysis is an enzymatically catalyzed reaction described by the Arrhenius equation. Diet crude protein (CP) controls NH emission by affecting N excretion. Our objectives were to use the Arrhenius equation to model NH emissions from beef cattle () feedyards and test predictions against observed emissions. Per capita NH emission rate (PCER), air temperature (), and CP were measured for 2 yr at two Texas Panhandle feedyards. Data were fitted to analogs of the Arrhenius equation: PCER = () and PCER = (,CP). The models were applied at a third feedyard to predict NH emissions and compare predicted to measured emissions. Predicted mean NH emissions were within -9 and 2% of observed emissions for the () and (T,CP) models, respectively. Annual emission factors calculated from models underestimated annual NH emission by 11% [() model] or overestimated emission by 8% [(,CP) model]. When from a regional weather station and three classes of CP drove the models, the () model overpredicted annual NH emission of the low CP class by 14% and underpredicted emissions of the optimum and high CP classes by 1 and 39%, respectively. The (,CP) model underpredicted NH emissions by 15, 4, and 23% for low, optimum, and high CP classes, respectively. Ammonia emission was successfully modeled using only, but including CP improved predictions. The empirical () and (,CP) models can successfully model NH emissions in the Texas Panhandle. Researchers are encouraged to test the models in other regions where high-quality NH emissions data are available.

Ammonia emissions and performance of backgrounding and finishing beef feedlot cattle fed barley-based diets varying in dietary crude protein concentration and rumen degradability

Crossbred beef steers (n = 312) were used in an experiment with a completely randomized design during the growing (235 ± 1.6 kg initial BW) and finishing (363 ± 2.7 kg) phase to determine the effects of dietary CP concentration and rumen degradability on NH3-N emissions, growth performance, and carcass traits. Diets were barley based and consisted of 55% silage and 45% concentrate in the backgrounding phase and 9% silage and 91% concentrate in the finishing phase. For each phase, there were 4 dietary treatments (6 pens of 13 cattle per diet): the basal diet with no protein supplementation (12% CP backgrounding and 12.6% CP finishing) or supplemented (14% CP) with urea (UREA), urea and canola meal (UREA+CM), or urea, corn gluten meal, and xylose-treated soybean meal (UREA+CGM+xSBM). Feed intake and BW of cattle were measured at 3-wk intervals. One pen of steers fed the 12 or 12.6% CP and 1 pen fed 1 of the 14% CP diets were housed in 2 isolated pens to quantify NH3-N emissions using the integrated horizontal flux technique with passive NH3 samplers. In the backgrounding phase final BW, ADG, and G:F were less (P < 0.05) in cattle fed the 12% CP and UREA compared with the UREA+CM and UREA+CGM+xSBM diets. Nitrogen-use efficiency of cattle fed UREA+CM and UREA+CGM+xSBM was equal to that of cattle fed 12% CP and averaged 19.8%. In the finishing phase, there was no effect (P > 0.10) of CP supplementation on BW, DMI, ADG, G:F, N-use efficiency, and carcass traits. The NH3-N emissions from December to February during the backgrounding phase ranged from 4.3 to 25.6 g N/(steer•d) and 3.8 to 16.3% of N intake and from April to July during the finishing phase ranged from 9.7 to 76.4 g N/(steer•d) and 4.4 to 26.7% of N intake. Differences in NH3-N emissions between the pens of cattle fed the backgrounding diets with 12 and 14% CP were not detected. For cattle fed the 12.6 and 14% CP finishing diets, NH3-N emissions tended (P ≤ 0.16) to be less for 2 of the 5 periods and averaged 14.4 and 28.1 g N/(steer•d) and 7.7 and 12.7% of N intake, respectively. The NH3-N emitted as a % of N intake averaged 42% less for cattle fed 12.6% compared with 14% CP. Feeding the barley-based concentrate diet to finishing cattle with 12.6% compared with 14% CP diets reduced NH3-N emissions with no effect on performance. Feeding the barley-based forage diet to backgrounding cattle with 12% CP, however, reduced performance compared with growing cattle fed supplementary degradable and undegradable true protein.

Farm practices as they affect NH3 emissions from beef cattle

Sheppard, S. C. and Bittman, S. 2012. Farm practices as they affect NH 3 emissions from beef cattle. Can. J. Anim. Sci. 92: 525–543. Beef cattle farms in Canada are very diverse, both in size and management. Because the total biomass of beef cattle in Canada is larger than any other livestock sector, beef also has the potential for the largest environmental impact. In this study we estimate NH3 emissions associated with beef cattle production across Canada using data on farm practices obtained from a detailed survey answered by 1380 beef farmers in 11 Ecoregions. The farms were various combinations of cow/calf, backgrounding and finishing operations. The proportion of animals on pasture varied markedly among Ecoregions, especially for cows and calves, and this markedly affected the estimated NH3 emissions. The crop components of feed also varied among Ecoregions, but the resulting crude protein concentrations were quite consistent for both backgrounding and finishing cattle. Manure was stored longer in the west than in the east, and fall spreading of manure was notably more common in the west, especially when spread on tilled land. The estimated NH3 emissions per animal were relatively consistent across Ecoregions for confinement production, but because the proportion of animals on pasture varied with Ecoregion, so did the overall estimated NH3 emissions per animal. Temperature is a key factor causing Ecoregion differences, although husbandry and manure management practices are also important. Hypothetical best management practices had little ability to reduce overall emission estimates, and could not be implemented without detailed cost/benefit analysis.

Dairy farm methane emissions using a dispersion model

There is a need to know whole-farm methane (CH(4)) emissions since confined animal facilities such as beef cattle feedlots and dairy farms are emission "hot spots" in the landscape. However, measurements of whole-farm CH(4) emissions can differ between farms because of differences in contributing sources such as manure handling, number of lactating and nonlactating cows, and diet. Such differences may limit the usefulness of whole-farm emissions for national inventories and mitigation purposes unless the variance between farms is taken into account or a large number of farms can be examined. Our study describes the application of a dispersion model used in conjunction with field measurements of CH(4) concentration and stability of the air to calculate whole-farm emissions of CH(4) from three dairy farms in Alberta, Canada, during three sequential campaigns conducted in November 2004 and May and July 2005. The dairy farms ranged in herd size from 208 to 351 cows (102 to 196 lactating cows) and had different manure handling operations. The results indicate that the average CH(4) emission per cow (mixture of lactating and nonlactating) from the three dairy farms was 336 g d(-1), which was reduced to 271 g d(-1) when the emission (estimated) from the manure storage was removed. Further separation of source strength yielded an average CH(4) (enteric) emission of 363 g d(-1) for a lactating cow. The estimated CH(4) emission intensities were approximately 15 g CH(4) kg(-1) dry matter intake and 16.7 L CH(4) L(-1) of milk produced. The approach of understanding the farm-to-farm differences in CH(4) emissions as affected by diet, animal type, and manure management is essential when utilizing whole-farm emission measurements for mitigation and inventory applications.

Daily, monthly, seasonal, and annual ammonia emissions from Southern High Plains cattle feedyards

Ammonia emitted from beef cattle feedyards adds excess reactive N to the environment, contributes to degraded air quality as a precursor to secondary particulate matter, and represents a significant loss of N from beef cattle feedyards. We used open path laser spectroscopy and an inverse dispersion model to quantify daily, monthly, seasonal, and annual NH emissions during 2 yr from two commercial cattle feedyards in the Panhandle High Plains of Texas. Annual patterns of NH fluxes correlated with air temperature, with the greatest fluxes (>100 kg ha d) during the summer and the lowest fluxes (<15 kg ha d) during the winter. Mean monthly per capita emission rate (PCER) of NH-N at one feedyard ranged from 31 g NH-N head d (January) to 207 g NH-N head d (October), when increased dietary crude protein from wet distillers grains elevated emissions. Ammonia N emissions at the other feedyard ranged from 36 g NH-N head d (January) to 121 g NH-N head d (September). Monthly fractional NH-N loss ranged from a low of 19 to 24% to a high of 80 to 85% of fed N at the two feedyards. Seasonal PCER at the two feedyards averaged 60 to 71 g NH-N head d during winter and 103 to 158 g NH-N head d during summer. Annually, PCER was 115 and 80 g NH-N head d at the two feedyards, which represented 59 and 52% of N fed to the cattle. Detailed studies are needed to determine the effect of management and environmental variables such as diet, temperature, precipitation, and manure water content on NH emissions.

Review: Ammonia emissions from dairy farms and beef feedlots

Hristov, A. N., Hanigan, M., Cole, A., Todd, R., McAllister T. A., Ndegwa, P. and Rotz, A. 2011. Review: Ammonia emissions from dairy farms and beef feedlots. Can. J. Anim. Sci. 91: 1–35. Ammonia emitted from animal feeding operations is an environmental and human health hazard, contributing to eutrophication of surface waters and nitrate contamination of ground waters, soil acidity, and fine particulate matter formation. It may also contribute to global warming through nitrous oxide formation. Along with these societal concerns, ammonia emission is a net loss of manure fertilizer value to the producer. A significant portion of cattle manure nitrogen, primarily from urinary urea, is converted to ammonium and eventually lost to the atmosphere as ammonia. Determining ammonia emissions from cattle operations is complicated by the multifaceted nature of the factors regulating ammonia volatilization, such as manure management, ambient temperature, wind speed, and manure composition and pH. Approaches to quantify ammonia emissions include micrometeorological methods, mass balance accounting and enclosures. Each method has its advantages, disadvantages and appropriate application. It is also of interest to determine the ammonia emitting potential of manure (AEP) independent of environmental factors. The ratio of nitrogen to non-volatile minerals (phosphorus, potassium, ash) or nitrogen isotopes ratio in manure has been suggested as a useful indicator of AEP. Existing data on ammonia emission factors and flux rates are extremely variable. For dairy farms, emission factors from 0.82 to 250 g ammonia per cow per day have been reported, with an average of 59 g per cow per day (n=31). Ammonia flux rates for dairy farms averaged 1.03 g m−2 h−1 (n=24). Ammonia losses are significantly greater from beef feedlots, where emission factors average 119 g per animal per day (n=9) with values as high as 280 g per animal per day. Ammonia flux rate for beef feedlots averaged 0.174 g m−2 h−1 (n=12). Using nitrogen mass balance approaches, daily ammonia nitrogen losses of 25 to 50% of the nitrogen excreted in manure have been estimated for dairy cows and feedlot cattle. Practices to mitigate ammonia emissions include reducing excreted N (particularly urinary N), acidifying ammonia sources, or binding ammonium to a substrate. Reducing crude protein concentration in cattle diets and ruminal protein degradability are powerful tools for reducing N excretion, AEP, and whole-farm ammonia emissions. Reducing dietary protein can also benefit the producer by reducing feed cost. These interventions, however, have to be balanced with the risk of lost production. Manure treatment techniques that reduce volatile N species (e.g., urease inhibition, pH reduction, nitrification-denitrification) are also effective for mitigating ammonia emissions. Another option for reducing ammonia emissions is capture and treatment of released ammonia. Examples in the latter category include biofilters, permeable and impermeable covers, and manure incorporation into the soil for crop or pasture production. Process-level simulation of ammonia formation and emission provides a useful tool for estimating emissions over a wide range of production practices and evaluating the potential benefits of mitigation strategies. Reducing ammonia emissions from dairy and beef cattle operations is critical to achieving environmentally sustainable animal production that will benefit producers and society at large.

Coarse particulate matter emissions from cattle feedlots in Australia

Open cattle feedlots are a source of air pollutants that include particular matter (PM). Over 24 h, exposure to ambient concentrations of 50 microg m(-3) of the coarse-sized fraction PM (aerodynamic diameter <10 microm [PM(10)]) is recognized as a health concern for humans. The objective of our study was to document PM(10) concentration and emissions at two cattle feedlots in Australia over several days in summer. Two automated samplers were used to monitor the background and in-feedlot PM(10) concentrations. At the in-feedlot location, the PM(10) emission was calculated using a dispersion model. Our measurements revealed that the 24-h PM(10) concentrations on some of the days approached or exceeded the health criteria threshold of 50 microg m(-3) used in Australia. A key factor responsible for the generation of PM(10) was the increased activity of cattle in the evening that coincided with peak concentrations of PM(10) (maximum, 792 microg m(-3)) between 1930 and 2000 h. Rain coincided with a severe decline in PM(10) concentration and emission. A dispersion model used in our study estimated the emission of PM(10) between 31 and 60 g animal(-1) d(-1). These data contribute to needed information on PM(10) associated with livestock to develop results-based environmental policy.