Zifei Liu

The organic composition of diesel particulate matter, diesel fuel and engine oil of a non-road diesel generator.

Diesel-powered equipment is known to emit significant quantities of fine particulate matter to the atmosphere. Numerous organic compounds can be adsorbed onto the surfaces of these inhalable particles, among which polycyclic aromatic hydrocarbons (PAHs) are considered potential occupational carcinogens. Guidelines have been established by various agencies regarding diesel emissions and various control technologies are under development. The purpose of this study is to identify, quantify and compare the organic compounds in diesel particulate matter (DPM) with the diesel fuel and engine oil used in a non-road diesel generator. Approximately 90 organic compounds were quantified (with molecular weight ranging from 120 to 350), which include alkanes, PAHs, alkylated PAHs, alkylbenzenes and alkanoic acids. The low sulfur diesel fuel contains 61% alkanes and 7.1% of PAHs. The identifiable portion of the engine oil contains mainly the alkanoic and benzoic acids. The composition of DPM suggests that they may be originated from unburned diesel fuel, engine oil evaporation and combustion generated products. Compared with diesel fuel, DPM contains fewer fractions of alkanes and more PAH compounds, with the shift toward higher molecular weight ones. The enrichment of compounds with higher molecular weight in DPM may be combustion related (pyrogenic).

Modeling Ammonia Emissions from Broiler Litter at Laboratory Scale

The objectives of this study were to develop a mechanistic emission model to estimate ammonia flux from broiler litter and to evaluate the model at laboratory scale. In the proposed model, the ammonia flux is essentially a function of the litters total ammoniacal nitrogen (TAN) content, moisture content, pH, and temperature, as well as the Freundlich partition coefficient (Kf), mass transfer coefficient (KG), ventilation rate (Q), and emission surface area (A). The Freundlich partition coefficient (Kf) was used as a fitting parameter in the model. A dynamic flow-through chamber system and a wind tunnel were designed to measure ammonia fluxes from broiler litter. The dynamic flow-through chamber experiments evaluated the proposed model with various litter samples under a constant temperature and wind profile. The wind tunnel experiments evaluated the proposed model under various temperatures and wind profiles. Model parameters such as Kf and KG were estimated. The results from the two experiments were consistent with each other. The estimated KG ranged from 1.11 to 27.64 m h-1, and the estimated Kf ranged from 0.56 to 4.48 L kg-1. A regression sub-model was developed to estimate Kf as function of litter pH and temperature, which indicated that Kf increased with increasing litter pH and decreased with increasing temperature. The proposed model was used to estimate the equilibrium gas phase ammonia concentration (Cg,0) in litter, and the model-predicted values were compared with the observed values. The normalized mean error (NME), the normalized mean square error (NMSE), and fractional bias (FB) were calculated to be 25%, 12%, and -0.3%, respectively, for all 94 measurements, and the model was able to reproduce 80% of the variability of the data. Sensitivity analysis of the model showed that ammonia flux is very sensitive to litter pH and to a lesser extent temperature. The relative sensitivity of pH or temperature increases as the pH or temperature increases.

Greenhouse gas emissions from swine operations: evaluation of the Intergovernmental Panel on Climate Change approaches through meta-analysis.

The objective was to provide a systematic review of the literature on greenhouse gas (GHG) emissions from swine operations, with a meta-analysis that integrates results of independent studies. A total of 53 studies that measured GHG emissions from swine operations were included in the analyses. Results showed that the Intergovernmental Panel on Climate Change (IPCC) approaches were effective in estimating the overall CH4 and N2O emission levels from swine operations, but the variation of the measured emissions is not adequately captured. An overestimation by the IPCC approaches for CH4 emissions was observed for swine buildings with pit systems in European studies and the average percentage relative difference (PRD) between the measured and the IPCC values is -21.1%. The observed CH4 emissions from lagoons were lower than the IPCC estimated values and the average PRD is -33.9%. In North American studies the observed N2O emission factors for swine buildings with pit systems were significantly lower than the IPCC default values whereas in European studies they were significantly greater than the IPCC default values. The measured CH4 and N2O emissions were significantly affected by stage of production (P = 0.05 and <0.01, respectively) and geographic regions (P = 0.04 and 0.02, respectively). The IPCC approaches were effective in simulating the effect of temperature on CH4 emissions from outdoor slurry storage facilities whereas they could overestimate CH4 emissions from lagoons at low temperatures. The CH4 emissions from pits inside swine buildings were not significantly affected by average ambient temperatures. A positive relationship between diet CP content and CH4 emissions was confirmed in the meta-analysis. The obtained knowledge can be helpful in efforts to improve estimation of GHG emissions from swine operations.

Ammonia and hydrogen sulfide emissions from swine production facilities in North America: A meta-analysis

Literature on NH3 and H2S emissions from swine production facilities in North America was reviewed, and a meta-analysis was conducted on measured emissions data from swine houses and manure storage facilities as well as concentration data in the vicinity of swine production facilities. Results from more than 80 studies were compiled with results from the 11 swine sites in the National Air Emissions Monitoring Study (NAEMS). Data across studies were analyzed statistically using the MIXED procedures of SAS. The median emission rates from swine houses across various production stages and manure handling systems were 2.78 and 0.09 kg/yr per pig for NH3 and H2S, respectively. The median emission rates from swine storage facilities were 2.08 and 0.20 kg/yr per pig for NH3 and H2S, respectively. The size of swine farm that may trigger the need to report NH3 emissions under the Emergency Planning and Community Right-to-Know Act (EPCRA) is 3,410 pigs on the basis of the median NH3 emission rate (4.86 kg/yr per pig), but the threshold can be as low as 992 pigs on the basis of the 90th-percentile emission rates (16.71 kg/yr per pig). Swine hoop houses had significantly higher NH3 emission rate (14.80 kg/yr per pig) than other manure-handling systems (P < 0.01), whereas deep-pit houses had the highest H2S emission rate (16.03 kg/yr per pig, P = 0.03). Farrowing houses had the highest H2S emission rate (2.50 kg/yr per pig), followed by gestation houses, and finishing houses had the lowest H2S emission rate (P < 0.01). Regression models for NH3 and H2S emission rates were developed for finishing houses with deep pits, recharge pits, and lagoons. The NH3 emission rates increased with increasing air temperature, but effects of air temperature on H2S emission rates were not significant. The recharge interval of manure pits significantly affected H2S but not NH3 emission rates. The H2S emission rates were also influenced by the size of the operation. Although NH3 and H2S concentrations at the edge of swine houses or lagoons were often higher than corresponding acute or intermediate minimum risk levels (MRL), they decreased quickly to less than corresponding chronic or intermediate MRL as distances from emission sources increased. At the distances 30 to 1,185 m from emission sources, the average ambient concentrations for NH3 and H2S were 46 ± 46 µg/m(3) and 4.3 ± 8.6 µg/m(3) respectively.

A Review of Emission Models of Ammonia Released from Broiler Houses

Over the last ten years, animal feeding operations (AFOs) have expanded greatly. As a component of animal waste, immeasurable ammonia is released. In both Europe and the United States, the largest source of ammonia emissions is animal production. With increasingly stringent federal and state air pollution regulations and the emerging pressure to regulate agricultural enterprises, ammonia emissions from animal production have become an increasing concern to regulators, producers, and environmental groups in the United States. However, efforts to regulate these emissions have been confounded by a lack of information. One of the technical challenges is the need for modeling the process of ammonia emissions from animal feeding operations. Broiler houses are one aspect of agriculture that is of particular interest to regulators and environmental groups. In recent publications, various models have been proposed to estimate ammonia emissions from broiler houses. These models are diversified in their structures and applications. It appears that a comprehensive review of theses available models would be of benefit to research in this field. This paper summarizes the scientific basis of ammonia emissions from broiler litter and the major factors that may influence ammonia emissions. The theoretical principles and the structures of the models are generalized. These models improved understanding of the physical and chemical processes of ammonia release, and can be useful to improve the accuracy and simplicity in estimating ammonia emissions from broiler houses. The current technical challenges and future direction of developments are discussed.

Field evaluation of particulate matter measurements using tapered element oscillating microbalance in a layer house

The tapered element oscillating microbalance (TEOM) is one type of continuous ambient particulate matter (PM) monitor. Adsorption and desorption of moisture and semivolatile species may cause positive or negative artifacts in TEOM PM mass measurement. The objective of this field study was to investigate possible uncertainties associated with TEOM measurements in the poultry operation environment. For comparisons of TEOM with filter-based gravimetric method, four instruments (TEOM-PM10, low-volume PM10 sampler, TEOM-PM2.5, and PM2.5 speciation sampler) were collocated and tested inside a poultry house for PM2.5 and PM10 (PM with aerodynamic equivalent diameter ≤2.5 and ≤10 μm, respectively) measurements. Fifteen sets of 24-hr PM10 concentrations and 13 sets of 24-hr PM2.5 measurements were obtained. Results indicate that compared with filter-based gravimetric method, TEOM gave significantly lower values of both PM10 and PM2.5 mass concentrations. For PM10, the average ratio of TEOM to the gravimetric method was 0.936. For PM2.5, the average ratio of TEOM to the gravimetric method was 0.738. Particulate matter in the poultry houses possibly contains semivolatile compounds and moisture due to high levels of relative humidity (RH) and gas pollutants. The internal heating mechanism of the TEOM may cause losses in mass through volatilization. To investigate the effects of TEOM settings on concentration measurements, the heaters of two identical TEOMs were set at 50 °C, 30 °C, or no heating at all. They were collocated and tested for total suspended particle (TSP), PM10, and PM2.5 measurements in layer house for 6 weeks. For all TSP, PM10, and PM2.5 measurements, the internal TEOM temperature setting had a significant effect (P < 0.05). Significantly higher PM mass concentrations were measured at lower temperature settings. The effects of environmental (i.e., temperature, RH, NH3 and CO2 concentrations) and instrumental (i.e., filter loading and noise) parameters on PM measurements were also assessed using regression analysis. Implications Because of its potential health and environmental effects, particulate matter (PM) emissions from animal feeding operations (AFOs) have been a great concern to the public and to the regulatory agencies. The tapered element oscillating microbalance (TEOM) PM monitor has been was adapted for continuous PM measurements in some AFO air quality studies. This study investigated possible uncertainties associated with TEOM measurements in an egg production environment. It was discovered that there was a significant bias in TEOM measurements of PM10 as compared with federal reference method. Internal temperature settings of a TEOM have significant impact on its PM measurement.

Gas Emissions from Dairy Cows Fed Typical Diets of Midwest, South, and West Regions of the United States

Gas emissions were determined for dairy cows fed three diets formulated to represent feed ingredients typical of the Midwest, South, or West regions of the United States. Dairy cows were housed and monitored in 12 environmentally controlled rooms (4 cows diet). Two experiments were performed, representing two lactation stages (initial days in milk were 115 ± 39 d in Stage 1 and 216 ± 48 d in Stage 2). The results demonstrated that the combination of different dietary ingredients resulted in different gas emissions while maintaining similar dry matter intake (DMI) and milk yield (MY). Diet effect on ammonia (NH) emissions was more prominent in Stage 1. During Stage 1, cows fed the Midwest diet had the highest daily NH emission, corresponding to the highest crude protein (CP) concentration among the three regions. The differences in NH emissions (39.0%) were much larger than the percent difference in CP concentrations between diets (6.8%). Differences in N intake, N excretion, or milk urea N alone may not serve as a strong indicator of the potential to reduce NH emissions. Lower emissions of methane (CH) per unit DMI or per unit MY were observed for cows offered the South diet during Stage 1 as compared with that from cows offered the Midwest or West diets. No diet effect was observed for hydrogen sulfide (HS) emission per unit S intake, nor for nitrous oxide (NO) emission. The measured NH and CH emissions were comparable, but the NO emissions were much higher than those reported for tie-stall dairy barns in the literature.

Farm-Scale Evaluation of Ozonation for Mitigating Ammonia Concentrations in Broiler Houses

Abstract This study evaluated the effectiveness of in-house ozonation within the public health standard limit (0.1 parts per million [ppm]) for mitigating ammonia (NH3) concentrations inside commercial broiler houses. The project was conducted in four identical tunnel-ventilated houses. Two houses served as treatment and the other two served as control units. The experiment was replicated in five consecutive flocks. Except for ozonation treatment, all other operational parameters including feed, broiler strain, age and number of broilers, and ventilation system were the same among four houses. NH3 and carbon dioxide (CO2) concentrations in the treatment and control houses were measured for a minimum of 48 hr/week throughout the five flocks of 8 or 9 weeks each. The gas measurements were conducted using portable multigas units (PMUs). House temperatures were recorded with data loggers in each flock. Comparison of temperatures and CO2 concentrations among houses indicated no significant differences in ventilation rates among treatment and control houses in any of the five flocks. As a result, comparisons of NH3 concentrations inside houses were used to evaluate the effectiveness of house ozonation for NH3 emission mitigation. Statistical test of mean NH3 concentrations for each flock separated by house indicated that the house-to-house variation was significantly smaller than the flock-to-flock variation. There was a substantial variation in NH3 concentrations across different flocks, but no house had consistently higher or lower mean NH3 concentrations than any other. Evaluations for differences in mean NH3 from week to week, between treatment groups, and differences in week-to-week variations between treatment groups suggested that ozone effect was not uniform for each week and the effect was not statistically significant for any week. Tests of overall ozone treatment effect and treatment-week interaction indicated there was no difference in mean NH3 between the control and ozone treatment groups (P = 0.25), nor was the week effect different for control and treatment groups (P = 0.46). The results of this field evaluation indicate that there was no statistical evidence to suggest that the ozone treatment has any effect on average NH3 concentrations in these chicken houses.

Effect of amino acid formulation and supplementation on air emissions from tom turkeys

Air emissions were determined for turkeys fed four diets in a 2×2 factorial design to determine the effects of diets with 100% or 110% of NRC-recommended amino acid (AA) formulation when the diets contained either two (lysine and methionine) or three (lysine, methionine, and threonine) supplemental AA. Hybrid tom turkeys were raised and monitored in 12 rooms (3 reps per diet; 20 toms per room at hatch, culled to 16 toms per room at 21 days, and then 12 toms per room at 28 days of age). Air emissions were measured throughout the 140-day study. Data were analyzed statistically using the Mixed model procedure of SAS. The 100% NRC diets contained less N compared to the 110% NRC diets. Diets containing three supplemental AA had less N content compared to diets containing two supplemental AA. Cumulative feed intake (55.7 kg bird-1) and bird weight (BW; 19.8 kg bird-1) were not affected by diet. Feeding the 100% NRC diets resulted in 9% less cumulative N intakes and 12% less cumulative NH3 emissions as compared with feeding the 110% NRC diets. Formulation with three supplemental AA did not affect N intake but resulted in 25% less cumulative NH3 emissions, as compared with formulation with two supplemental AA, because it significantly reduced the NH3 emission rate (ER) on a per kg N consumption basis (88 vs. 109 g d-1 kg-1 N consumed) . The toms fed the 100% NRC diets generated lower ER of NH3 (1.5 vs. 1.8 g d-1 bird-1), H2S (3.4 vs. 4.4 mg d-1 bird-1), and non-methane total hydrocarbons (NMTHC; 0.08 vs. 0.10 g d-1 bird-1) than the 110% NRC diets (p < 0.05). Results of stepwise regression analysis confirmed the positive influence of N/S intake, room air RH, ventilation rate, and room air temperature on ER of NH3 and H2S. The study demonstrated the potential of reducing NH3 and H2S emissions from turkeys through diet modification of AA while maintaining acceptable production performance. No diet effect was observed on greenhouse gas emissions (N2O and CH4).

Particle Size Distribution of Particulate Matter Emitted from a Layer Operation in Southeast U.S.

This paper reports a field study on characterizing particle size distribution (PSD) of particulate matter (PM) emitted from a commercial layer operation in Southeast U.S. across three seasons from October of 2008 to April of 2009. Six low-volume (1m3/hr) total suspended particulate (TSP) samplers were used to collect PM samples in two high-rise layer houses. Laser diffraction particle size analyzer (LS13 320) was applied to measure PSD of PM samples collected by the TSP samplers. Results of the study indicate that TSP concentrations across the three seasons ranged from 888 to 5333 µg/m3. TSP concentration was affected by season, animal activity, floor and equivalent air flow rate factor. It was observed that TSP concentration in winter was higher than that in spring; concentration on the second floor was higher than that on the first floor; the more active the animals were, the higher the TSP concentration; the more the fans on, the lower the concentration. Compared with PM concentration, PSD (characterized by the mass medium diameter, MMD, & geometric standard deviation, GSD) was much less affected by season, animal activity, floor and equivalent flow rate factor. The MMD was affected by floor and equivalent flow rate factor, but the degree of affection was within the range of one standard deviation. Overall MMDs of PM samples collected in fall, winter and spring were 15.80±1.05µm, 17.13±0.81µm and 18.44±1.44µm, respectively. The difference of MMD among three seasons was within the range of one standard deviation. GSD was relatively constant and not affected by those factors. The overall GSD was 2.65±0.08.