Richard W Todd

Use of Fat and Zeolite to Reduce Ammonia Emissions from Beef Cattle Feedyards

Ammonia emissions from cattle feedyards may comprise 40% or more of nitrogen intakes. Decreasing ammonia emissions would improve the fertilizer value of feedyard manure and decrease potential adverse effects on the environment. Two trials were conducted to evaluate the effects of fat and zeolite on potential ammonia emissions from a feedlot surface. In the first trial corn oil, alum, a urease inhibitor, or potassium zeolite were added to simulated feedlot surfaces in lab-scale chambers and ammonia losses were captured using an acid solution. In trial two, five beef steers were fed one of five finishing diets (0% added fat, 3% added fat, 6% added fat, 3% fat+1% zeolite, or 3% fat+2% zeolite) in a 5 x 5 Latin square. During the last 5 days of each period feces and urine output were collected in stalls to determine nutrient digestion and retention. Feces and urine from each steer were used in the lab-scale flow-through chambers to estimate potential ammonia losses. In trial 1, zeolite and fat additions decreased ammonia losses by 51 to 86%; however the effects were not additive. In trial 2, apparent protein digestion, nitrogen retention, and nitrogen excretion were not affected by dietary fat or zeolite. In vitro ammonia losses were not significantly affected by dietary zeolite; however in vitro ammonia losses were greater (P < 0.05) when steers were fed diets containing no added fat. These results suggest that fat and zeolites can potentially decrease ammonia emissions from beef cattle feedyards.

Knowledge and tools to enhance resilience of beef grazing systems for sustainable animal protein production

Ruminant livestock provides meat and dairy products that sustain health and livelihood for much of the worlds population. Grazing lands that support ruminant livestock provide numerous ecosystem services, including provision of food, water, and genetic resources; climate and water regulation; support of soil formation; nutrient cycling; and cultural services. In the U.S. southern Great Plains, beef production on pastures, rangelands, and hay is a major economic activity. The regions climate is characterized by extremes of heat and cold and extremes of drought and flooding. Grazing lands occupy a large portion of the regions land, significantly affecting carbon, nitrogen, and water budgets. To understand vulnerabilities and enhance resilience of beef production, a multi‐institutional Coordinated Agricultural Project (CAP), the “grazing CAP,” was established. Integrative research and extension spanning biophysical, socioeconomic, and agricultural disciplines address management effects on productivity and environmental footprints of production systems. Knowledge and tools being developed will allow farmers and ranchers to evaluate risks and increase resilience to dynamic conditions. The knowledge and tools developed will also have relevance to grazing lands in semiarid and subhumid regions of the world.

Flux-Gradient Estimates of Ammonia Emissions from Beef Cattle Feedyard Pens

Concentrated animal feeding operations are major sources of ammonia emitted to the atmosphere. There is a considerable literature on ammonia emissions from poultry and swine, but few studies have investigated large, open lot beef cattle feedyards. We used the micrometeorological flux-gradient method to estimate ammonia emissions during six field campaigns in three seasons. Profiles of ammonia, wind speed and air temperature were measured on towers located within feedyard pens. Atmospheric ammonia concentration was measured using either acid gas washing or chemiluminescence. Mean daily ammonia flux in summer averaged 72 µg m-2 s-1, and in winter, 39 µg m-2 s-1. Springtime fluxes were highly variable and averaged 79 µg m-2 s-1; high springtime fluxes were attributed to greater ammonium concentration in manure and high wind speeds. Ammonia-N emisson rate averaged 3930 and 2150 kg d-1 in summer and winter, respectively, which was 45% and 27% of fed N. Assuming that the mean of summer and winter emission rates represented a mean annual emission, ammonia-N loss was 36% of fed N, and an annual emission factor for feedyard pens based on total yearly per head production was 11.0 kg NH3-N head-1 yr-1. Ammonia emissions increased after N in cattle rations was increased from 13.5% to 14.5%. Ammonia emissions estimated using the flux-gradient method were 22 to 36% less than those derived from an inverse dispersion model. Uncertainty in the Schmidt number and possible violation of the assumption of homogeneous flow could have contributed to the lower flux estimates of the flux-gradient method. Optimizing fed N through practices such as phase feeding could help minimize ammonia emissions. Longer term, more continuous monitoring of ammonia emissions is needed to better define annual variability, emission rates and factors, and facilitate development of process models.

Effect of Wind Tunnel Air Velocity on VOC Flux Rates from CAFO Manure and Wastewater

Wind tunnels and flux chambers are often used to measure volatile organic compound (VOC) emissions and estimate emission factors from animal feeding operations (AFOs) without regard to air velocity or sweep air flow rates. Laboratory experiments were conducted to evaluate the effect of wind tunnel air velocity on VOC emission rates. VOC emissions were measured on standard solutions of VOCs in water, and on manure and wastewater from beef cattle and dairy AFOs at wind tunnel air velocities between 0.003 and 0.2 m/s corresponding to volumetric air exchange rates of 0.6 to 39 exchanges per minute. Activated-carbon-filtered air was passed through a small rectangular wind tunnel (30.5 cm length, 15.2 cm width, 5.1 cm height). Outlet air was sampled using stainless steel sorbent tubes (Tenax® TA) and analyzed for seven volatile fatty acids (acetic, propionic, isobutyric, butyric, isovaleric, valeric, hexanoic) and four heavier molecular weight (MW) semi-VOCs (phenol, p-cresol, indole and skatole) using gas chromatography/mass spectrometry. VOC emission rates increased linearly with increasing wind velocity. These results show that wind velocity is a major factor affecting VOC emissions from AFOs. Selection of representative air velocity or sweep air flow rate is critical when estimating VOC emission factors using wind tunnels and flux chambers.

Ammonia Concentration and Modeled Emission Rates from a Beef Cattle Feedyard

Ambient NH3 concentrations were measured at a beef cattle CAFO during the spring and summer months of 2007. Concentrations were measured every five minutes, 24-hours per day at a sample intake height of 3.3 m using a chemiluminescence analyzer. On site weather data was collected concurrently. Emission rates were estimated using a backward Lagrangian Stochastic model (WindTrax 2.0.7.8). Mean 24-hr concentrations for spring were 0.498, 0.597 and 0.568 ppm for March, April and May, respectively. Corresponding fluxes for March, April and May were 57.76, 123.10 and 86.34 µg m-2 sec-1, respectively. Summer mean ambient concentrations were 0.684, 0.702 and 0.568 ppm for June, July and August, respectively. Summer fluxes were 85.27, 75.06 and 71.56 µg m-2 sec-1 for June, July and August, respectively.

Inverse-dispersion technique for assessing lagoon gas emissions

Measuring gas emissions from treatment lagoons and storage ponds poses challenging conditions for existing micrometeorological techniques because of non-ideal wind conditions, such as those induced by trees and crops surrounding the lagoons, and lagoons with dimensions too small to establish equilibrated microclimate conditions within the water boundary. This study evaluated the accuracy of the backward Lagrangian stochastic (bLS) inverse-dispersion technique to measure lagoon emissions using a fabricated floating emission source with known emission rates from an irrigation pond that resembled typical treatment lagoon environments. Anemometers were located on the upwind, downwind, side berm parallel to wind or directly above water surface. Path integrated concentrations (PICs) were monitored within the pond and on the downwind berm. The berm surface was deliberately roughened during the summer by placing pine straw bales along the berms to simulate vegetation growth. Generally using an anemometer located on the berm produced the more accurate results than using an anemometer located directly above water surface. The berm location is also the most convenient place for both wind and concentration sensors to be placed in typical lagoon environments. The overall average accuracy of all combinations of the anemometer and the PIC locations for both smooth and rough berm surface conditions was 0.77 ± 0.23 (N = 398). This lagoon study demonstrated that the bLS inverse-dispersion technique can be effectively used to measure lagoon emission with relatively high accuracy and convenience.

Methane Emissions From A New Mexico Dairy Lagoon System

Methane is a greenhouse gas with a global warming potential twenty-five times that of carbon dioxide. Animal production is recognized as a significant source of methane to the atmosphere. Dairies on the southern High Plains of New Mexico and Texas are typically open lot, and major sources of methane are enteric emissions from cattle and wastewater lagoons. Uncovered anaerobic lagoons are identified by the U.S. Environmental Protection Agency as a major source of methane in dairy manure management systems. Our objective was to quantify methane emissions from the wastewater lagoons of a commercial dairy located in eastern New Mexico. Research was conducted during six days in August, 2009 at a 3500-cow open lot dairy with flush alleys. Methane concentration over three interconnected lagoons (total area 1.8 ha) was measured using open path laser spectroscopy. Background methane concentration was measured using a back-flush gas chromatography system with flame ionization located upwind in the direction of prevailing winds. Wind and turbulence data were measured using a three-axis sonic anemometer. Emissions were estimated using an inverse dispersion model. Methane concentration over the lagoons ranged from 3 to 12 ppm, and averaged 5.6 ppm; background methane concentration averaged 1.83 ppm. Methane flux density ranged from 165 to 1184 µg m-2 s-1. Mean daily methane flux density was 402 kg ha-1 d-1. Per capita methane emission rate averaged 0.211 kg head-1 d-1. Uncovered anaerobic lagoons were a significant source of methane emitted from this southern High Plains dairy, and lagoons could be a significant control point for emission reduction.