Robert T. Burns

Laboratory and In-Situ Reductions of Soluble Phosphorus in Swine Waste Slurries

Laboratory and field experiments were conducted using magnesium chloride (MgCl2) to force the precipitation of struvite (MgNH4PO4·6H2O) and reduce the concentration of soluble phosphorus (SP) in swine waste. In laboratory experiments, reductions of SP of 76% (572 to 135 mg P l−1) were observed in raw swine manure after addition of magnesium chloride (MgCl2) at a rate calculated to provide a 1.6:1 molar ratio of magnesium (Mg) to total phosphorus. Adjusting the pH of the treated manure to pH 9.0 with sodium hydroxide (NaOH) increased SP reduction to 91% (572 to 50 mg P l−1). X-ray diffraction of the precipitate recovered from swine waste slurry treated only with MgCl2 confirmed the presence of struvite. The molar N:P:Mg ratio of the recovered precipitate was 1:1.95:0.24, suggesting that compounds in addition to struvite were formed. In a field experiment conducted in a swine manure holding pond, a 90% reduction in SP concentration was observed in approximately 140 000 l of swine manure slurry treated before land application with 2000 l MgCl2, (64% solution) at ambient slurry temperatures ranging from 5 to 10°C.

Degradation of Estrogens in Dairy Waste Solids: Effects of Acidification and Temperature

Manure–borne estrogens are increasingly recognized as a potential ecological hazard. However, sample–handling nprotocols for these compounds are not clearly delineated in the literature, nor are comparisons between assays for estrogens. nA study was conducted to explore the degradation of estrogen in separated dairy manure waste solids (press cake), using three npopular assay types. Estrogens were measured by enzyme–linked immunosorbent assay (ELISA), gas–chromatography nmass–spectroscopy (GC–MS) and a recombinant yeast estrogen reporter assay. As measured by GC–MS, background estrone nconcentrations were approximately 100 ppb, while 17x01–estradiol concentrations were one–third of the estrone concentration, nand 17x02–estradiol concentrations were below the detection limit (10 ppb). In contrast, background 17x02–estradiol nconcentrations as measured by ELISA were 53 ppb. In press cake samples spiked with 17x02–estradiol, ELISA and GC–MS n17x02–estradiol concentrations from all experiments were well correlated (r 2 = 0.93), although the ELISA values were higher nthan the GC–MS values. The yeast estrogen assay was also highly correlated with GC–MS results (r 2 = 0.94). The rates of ntotal estrogen removal in press cake samples spiked with 500 ppb 17x02–estradiol and incubated over a range of 5–50 n³ nC were ncharacterized by a 1 st –order decay constant (k). The k values increased with temperature and ranged from 0.029 d –1 to 0.12 nd –1 . Rate constants observed in unspiked press cake samples agreed with the values derived from the spiked samples. Over na 7–d period, acidification of samples (pH < 2) and storage at 5 n³ nC reduced 17x02–estradiol losses to 15% and total estrogen nlosses to 17%, whereas unacidified samples lost 90% of 17x02–estradiol and 40% of total estrogen. The results of this study nstrongly suggest the need for acidification and cold storage of environmental samples being tested for estrogens. In this study, nno single assay met all the desirable criteria of speed, sensitivity (<1 ppb), and detection of both 17x02–estradiol and estrone. nTherefore, the use of multiple assays for the detection of environmental estrogens is warranted.

Ammonia emission factors from broiler litter in barns, in storage, and after land application.

We measured NH₃ emissions from litter in broiler houses, during storage, and after land application and conducted a mass balance of N in poultry houses. Four state-of-the-art tunnel-ventilated broiler houses in northwest Arkansas were equipped with NH₃ sensors, anemometers, and data loggers to continuously record NH₃ concentrations and ventilation for 1 yr. Gaseous fluxes of NH₃, N₂O, CH₄, and CO₂ from litter were measured. Nitrogen (N) inputs and outputs were quantified. Ammonia emissions during storage and after land application were measured. Ammonia emissions during the flock averaged approximately 15.2 kg per day-house (equivalent to 28.3 g NH₃per bird marketed). Emissions between flocks equaled 9.09 g NH₃ per bird. Hence, in-house NH₃ emissions were 37.5 g NH₃ per bird, or 14.5 g kg(-1) bird marketed (50-d-old birds). The mass balance study showed N inputs for the year to the four houses totaled 71,340 kg N, with inputs from bedding, chicks, and feed equal to 303, 602, and 70,435 kg, respectively (equivalent to 0.60, 1.19, and 139.56 g N per bird). Nitrogen outputs totaled 70,396 kg N. Annual N output from birds marketed, NH₃ emissions, litter or cake, mortality, and NO₂ emissions was 39,485, 15,571, 14,464, 635, and 241 kg N, respectively (equivalent to 78.2, 30.8, 28.7, 1.3, and 0.5 g N per bird). The percent N recovery for the N mass balance study was 98.8%. Ammonia emissions from stacked litter during a 16-d storage period were 172 g Mg(-1) litter, which is equivalent to 0.18 g NH₃ per bird. Ammonia losses from poultry litter broadcast to pastures were 34 kg N ha (equivalent to 15% of total N applied or 7.91 g NH₃ per bird). When the litter was incorporated into the pasture using a new knifing technique, NH₃ losses were virtually zero. The total NH₃ emission factor for broilers measured in this study, which includes losses in-house, during storage, and after land application, was 45.6 g NH₃ per bird marketed.

Using Biochemical Methane Potential Assays to Aid in Co-substrate Selection for Co-digestion

There has been an increasing interest in manure anaerobic digestion; however, economic constraints are still one of the limits to widespread use of the technology in the United States. Co-digestion of manure with other feedstocks has been noted as a way to increase the economic feasibility of animal feeding operation anaerobic digesters via increased energy production potential. A wide variety of materials have been proposed as co-digestion materials, and additional substrates will continue to receive consideration. Biochemical methane potential assays (BMPs) have been reported to provide a first-cut evaluation of potential substrates. This article provides specific details about the BMP assay process used by the Agricultural Waste Management Laboratory (AWML) at Iowa State University (ISU) on agricultural materials and by-products, including the assay method and utilization of the results. Additionally, BMP results from 31 samples assayed in the ISU AWML as broader anaerobic digestion research or as service to the industry have been included. Results showed that the high solid content and non-homogeneity of agricultural materials and by-products can increase variability in assay results. The method utilized here helped limit the effects by utilizing volatile solids concentrations instead of chemical oxygen demand to initiate the BMP assays and to normalize the results. The coefficient of variation for the assays performed in triplicate ranged from1.6% to 33% in which the majority was less than 15%. For five of the substrate types analyzed (beef manure, dairy manure, cheese when lactate permeate, food processing marinate, and enzyme process by-product), multiple samples were assayed from different sources. The sample standard deviations indicated that methane production potential could be affected by material source and that BMP assays reported here should only be used as an estimate when considering which types of materials to assay.

Effect of Ammonia Soaking Pretreatment and Enzyme Addition on Biochemical Methane Potential of Switchgrass

This article presents the biochemical methane potential (BMP) results from the anaerobic digestion (AD) of switchgrass. Triplicate BMP assays were performed on: untreated switchgrass, aqueous ammonia soaking (AAS) pretreated switchgrass (soaked in 29.5% reagent-grade aqueous ammonia at 5 L kg-1 switchgrass for 5 d), and AAS-pretreated switchgrass plus cellulytic enzymes at 12.5, 25, 62.5, and 125 filter paper units (FPU) enzyme g-1 volatile solids (VS). Biogas production and biogas methane content were measured daily in all treatments for 21 d. Both biogas and corrected methane production varied significantly among treatments, especially during the first 7 d of the BMP period. Total methane production at 21 d was corrected for enzyme degradation, and methane yields ranged from 0.15 to 0.36 m3 CH4 kg-1 VS. We compared the corrected energy yield of biogas from switchgrass to prior reports of the energy yield of ethanol from switchgrass via simultaneous saccharification and fermentation (SSF). The AD of AAS-pretreated switchgrass at the highest enzyme loading rates resulted in a 120% increase in energy extracted as compared to AAS-pretreated switchgrass converted to ethanol via SSF. Overall, the addition of enzymes to AAS-pretreated switchgrass greatly accelerated the rate of methane production over the untreated switchgrass and AAS-pretreated switchgrass without enzymes. However, the process economics are not clear, and additional work is needed to determine whether pretreating switchgrass with aqueous ammonia and/or enzymes before AD is economically advantageous.

Particulate Matter Concentrations and Emissions of a High-Rise Layer House in Iowa

Particulate matter (PM) associated with animal feeding operations is a concern for the occupants and the surrounding community. Baseline measurements of PM concentration and emission rate are the first step toward assessing the magnitude of concentrations and emissions and evaluating effectiveness of dust control strategies. This study presents the results of PM measurements at a high-rise layer house (approx. 250,000 hens) in central Iowa using tapered element oscillating microbalance (TEOM) equipment. Daily average concentrations of PM10 and PM2.5 over a 17-month measurement period were 393 (257 SD) and 44 (36 SD) g m -3 , respectively. Daily average PM10 and PM2.5 emission rates during the same monitoring period were, respectively, 26.1 (15.8 SD) and 3.6 ( 3.7 SD) mg bird -1 d -1 , or 8.16 (4.94) and 1.13 (1.16) g AU -1 d -1 (AU = animal unit = 500 kg body weight). PM emission rate was positively related to ventilation rate

BUILDING EMISSIONS UNCERTAINTY ESTIMATES

Analysis of the propagation of measurement error into a computed quantity such as building aerial emissions provides insight into which measurements are most critical and which would have the most impact on the computed quantity if improved. An analysis of different instrument measurements, sampling periods, and sites together comprise an objective means of determining optimal sampling strategies for measurements used to compute aerial emissions from livestock facilities. This article describes the uncertainty analysis for a measurement system used in emissions research, and how it can lead to improvements in measurement system design and implementation to obtain estimates of uncertainty in emissions. The system analyzed was used in a broiler house emission monitoring project that was part of the U.S. EPA Air Consent Agreement. The project required U.S. EPA category I Quality Assurance Project Plan (QAPP) Data Quality Objectives (DQO), which were developed from this uncertainty analysis. Results of the uncertainty analysis suggest that the combined standard uncertainty in ammonia emission from broiler houses in the study was typically less than 6%; it increased with uncertainty in ventilation rate, but decreased as ventilation rate and number of fans running increased. The combined standard uncertainty was quantified for normal measurement conditions (Case 1) and for conditions in which the instrumentation was at the calibration threshold (Case 2). A key conclusion was that, for the measurement system employed in this project, uncertainty in the measurements associated with ventilation rate are the major contributors to emissions rate uncertainty (ranging from 78% to 98.9% of combined standard emission uncertainty).

Ammonia Emissions from Broiler Houses in the Southeastern United States

Continuous monitoring of ammonia (NH3) emissions from two mechanically ventilated commercial broiler houses located in the southeastern United States was performed during a one-year period over 2005-2006 as a joint effort between Iowa State University and the University of Kentucky. Ammonia concentrations were measured using Innova 1412 photoacoustic NH3 monitors. Ventilation rates in each house were measured continuously by monitoring the building static pressure and operational status of all ventilation fans in conjunction with individual performance curves developed and verified in situ using a Fan Assessment Numeration System (FANS) unit. Expressed in various units, NH3 emissions from the two broiler houses over the one-year production period were of the following values: a) 35.4 g per bird marketed (77.9 lb per 1,000 birds marketed), including both grow-out (50-54 d per flock) and downtime (12-25 d between flocks) emissions; b) annual (365-d) emission of 4.63 Mg (5.1 US tons) per house, including both grow-outs and downtime; c) maximum grow-out daily emission of 30.6 kg/d-house (67.4 lb/d-house) for one house and 35.5 kg/d-house (78.2 lb/d-house) for the other; d) mean grow-out daily emission of 14.0 ± 9.1 ( S.D.) kg/d-house; e) mean downtime daily emission of 8.8 ± 8.3 kg/d-house. Flocks on new bedding had a lower emission rate of 12.4 ± 9.4 kg/d-house, as compared to 14.5 ± 8.9 kg/d-house for flocks on built-up litter. The NH3 emission factor of 35.4 g/bird marketed from this study is substantially lower than that cited by US EPA of 100 g/yr-bird (the US EPA yr-bird unit is equivalent to bird marketed).

ENERGY USE ANALYSIS OF MAJOR MILKING CENTER COMPONENTS AT A DAIRY EXPERIMENT STATION

Fourteen years of accumulated electrical energy use data related to milking operations at the 160-cow University nof Tennessee Dairy Experiment Station in Lewisburg, Tennessee were analyzed to quantify relative effects of nproduction -related factors on energy use within the milking center. Energy use was measured for vacuum pumps, refrigeration ncompressors, water heaters, and an air compressor. These energy use figures were then related to the recorded production nparameters: number of cows milked, the amount of milk sold, percent butterfat of the milk, the total pounds of fat corrected nmilk, and high and low dry bulb temperature by means of multiple regression. Analyses were made on a monthly and yearly nbasis. Total dairy energy use could not be computed due to numerous non-dairy load components in the Experiment Station nthat could not be subtracted. It followed logically that number of cows milked, milk production, and weather conditions nrepresented by dry bulb temperature were found to be the major factors affecting energy use. However, no parameter, or ncombination of parameters, explained in a statistical sense more than 74% of the variability in the recorded energy use by nthe equipment studied. Quantity, and not quality, of milk produced was the most significant factor affecting energy use, with nthe number of cows milked and outside temperatures playing lesser roles. Regression results showing that cow numbers was nnot a factor related to energy use for milk cooling or vacuum pump operation, lead to some questions about the validity of nkWh/cow/yr as an energy use indicator. nFor the 14 years of data available, average EUIs for the vacuum pumps for milking (1.10 kWh/cwt) and the refrigeration ncompressors for milk cooling (1.02 kWh/cwt) were near the upper range of published reference values (0.4 to 1.19 kWh/cwt nand 0.8 to 1.10 kWh/cwt, respectively), while average EUI for water heaters (0.65 kWh/cwt) were well below the published nrange (0.95 to 1.40 kWh/cwt). The former two results confirm the validity of the published EUIs that were based only on a nfew year’s data. Interestingly, the results also indicate a general consistency in the year to year operation of similarly sized ndairy operations. The lower EUI for the water heater was due to the use of a preheater and also the every-other-day milk ncollection at the dairy.

Evaluation of Ultrasonic Pretreatment on Anaerobic Digestion of Different Animal Manures

This article addresses the effect of ultrasonication as a pretreatment to anaerobic digestion of four types of animal manure, including swine slurry, beef feedlot manure, dairy manure slurry, and separated dairy manure effluent. The effect of ultrasonication on soluble chemical oxygen demand (SCOD) and biochemical methane potential (BMP) were determined, and the energy efficiency of ultrasonic pretreatment was evaluated. Ultrasonic pretreatment was applied at two amplitudes (80 and 160 µmpp) and at two time settings (15 and 30 s) to each of the four manure types. The SCOD of each manure sample was determined before and after ultrasonic pretreatment. In addition, BMP trials were run on each waste with and without ultrasonic pretreatment. As part of the BMP, biogas production was measured and analyzed for methane content and cumulative methane production. Ultrasonic pretreatment of swine slurry, beef feedlot manure, dairy manure slurry, and separated dairy manure effluent increased the average SCOD up to 23%, 92%, 59%, and 33%, respectively, and the average methane yield up to 56%, 43%, 62%, and 20%, respectively. Increasing the ultrasonic amplitude and treatment time resulted in an increase in manure SCOD and methane production; the greatest methane production was obtained using the ultrasonic pretreatment at the highest power and longest treatment time. The observed greatest methane production from swine slurry, beef feedlot manure, dairy manure slurry, and separated dairy manure effluent were 394, 230, 226, and 340 mL CH4 g-1 VS, respectively. In contrast, the greatest energy efficiency was obtained with the lowest ultrasonic amplitude combined with the shortest treatment time.