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Manure management systems have a major impact on odor from swine operations. A study was conducted to compare deep-pit manure management systems to flushing barn manure management systems for odor reduction and organic matter degradation. Bioreactors were used to mimic manure management systems in which manure and lagoon effluent were loaded initially, and subsequent manure was added daily at 5% of its storage capacity (1 L). Final manure-to-lagoon effluent ratios were 10:0 (deep-pit manure management system), 7:3 (Korean flushing systems), 5:5 (enhanced flushing systems), and 2:8 (enhanced flushing systems). At the end of the trial, at 4 (2:8), 10 (5:5), or 14 (10:0, 7:3) d, manure and gas concentrations of odorants were measured, including total solids (TS), total N (TN), and total C (TC) of manure. Odor was evaluated using the odor activity values (OAVs), and regression analysis was used to determine the effects of dilution and TS on manure properties and OAVs. Solids in the manure were positively correlated to TN, TC, straight chain fatty acids (SCFAs), branch chain fatty acids (BCFAs), total phenols, and total indoles and positively correlated to OAV for SCFAs, BCFAs, ammonia, total phenols, and total indoles. Reducing TS by 90% reduced BCFA, ammonia, phenols, and indoles by equal amounts in air. Carbon dioxide was the main C source evolved, averaging over 90%, and CH4 increased with dilution quadratically. Overall, reducing solids in manure by dilution had the biggest impact on reducing odor and increasing organic C degradation.

Nutrients excreted from animals affect the nutritive value of manure as a soil amendment as well as the composition of gases emitted from manure storage facilities. There is a dearth of information, however, on how diet type in combination with dietary particle size affects nutrients deposited into manure storage facilities and how this affects manure composition and gas emissions. To fill this knowledge gap, an animal feeding trial was performed to evaluate potential interactive effects between feed particle size and diet composition on manure characteristics and manure-derived gaseous emissions. Forty-eight finishing pigs housed in individual metabolism crates that allowed for daily collection of urine and feces were fed diets differing in fiber content and particle size. Urine and feces were collected and stored in 446-L stainless steel containers for 49 d. There were no interactive effects between diet composition and feed particle size on any manure or gas emission parameter measured. In general, diets higher in fiber content increased manure nitrogen (N), carbon (C), and total volatile fatty acid (VFA) concentrations and increased manure VFA emissions but decreased manure ammonia emissions. Decreasing the particle size of the diet lowered manure N, C, VFAs, phenolics, and indole concentrations and decreased manure emissions of total VFAs. Neither diet composition nor particle size affected manure greenhouse gas emissions.

An experiment was conducted to determine the effect of feeding finishing pigs a corn-soybean (CSBM) diet or a CSBM diet supplemented with 30% dried distillers grains with solubles (DDGS), in combination with or without a growth-promoting ionophore (0 or 30 mg narasin/kg of diet), has on manure composition, microbial ecology, and gas emissions. Two separate groups of 24 gilts (initial BW = 145.1 kg, SD = 7.8 kg) were allotted to individual metabolism crates that allowed for total but separate collection of feces and urine during the 48-d collection period. After each of the twice-daily feedings, feces and urine from each crate was collected and added to its assigned enclosed manure storage tank. Each tank contained an individual fan system that pulled a constant stream of air over the manure surface for 2 wk prior to air (day 52) and manure sampling (day 53). After manure sampling, the manure in the tanks was dumped and the tanks cleaned for the second group of pigs. Except for total manure Ca and P output as a percent of intake and for manure methane product rate and biochemical methane potential (P ≤ 0.08), there were no interactions between diet composition and narasin supplementation. Narasin supplementation resulted in increased manure C (P = 0.05), increased manure DM, C, S, Ca, and phosphorus as a percent of animal intake (P ≤ 0.07), and increased manure volatile solids and foaming capacity (P ≤ 0.09). No effect of narasin supplementation was noted on manure VFA concentrations or any of the gas emission parameters measured (P ≥ 0.29). In contrast, feeding finishing pigs a diet containing DDGS dramatically affected manure composition as indicated by increased concentration of DM, C, ammonia, N, and total and volatile solids (P = 0.01), increased manure DM, N, and C as a percent of animal intake (P = 0.01), increased manure total VFA and phenols (P ≤ 0.05), decreased gas emissions of ammonia and volatile sulfur compounds (VSC; P = 0.01), increased emissions of phenols and indoles (P ≤ 0.06), decreased methane production rate (P = 0.01), and slight differences in microbial ecology (R ≤ 0.47). In conclusion, feeding a diet which contains an elevated level of indigestible fiber (i.e., DDGS) resulted in more fiber in the manure which therefore dramatically affected manure composition, gas emissions, and microbial ecology, while narasin supplementation to the diet did not exhibit a significant effect on any of these parameters in the resultant swine manure.

Three experiments were conducted to determine the effect of narasin on growth performance and on GE and nutrient digestibility in nursery, grower, and finishing pigs fed either a corn-soybean meal (CSBM) diet or a CSBM diet supplemented with distillers dried grains with solubles (DDGS), in combination with either 0 or 30 mg narasin/kg of diet. In Exp. 1 (64 gilts, initial BW = 9.0 kg, SD = 1.0 kg) and Exp. 2 (60 gilts. initial BW = 81.1 kg, SD = 6.1 kg), gilts were allotted into individual pens and fed their experimental diets for 24 and 21 d, respectively. On the last 2 d of each experiment, fecal samples were collected to assess apparent total tract digestibility (ATTD) of GE and various nutrients. In Exp. 3, 2 separate groups of 24 gilts (initial BW = 145.1 kg, SD = 7.8 kg) were allotted to individual metabolism crates and fed their experimental diets for 30 d prior to a time-based 6-d total fecal collection period to assess GE and nutrient digestibility. In Exp. 1, there was an interaction between diet type and narasin addition for G:F and for many of the ATTD coefficients measured. When narasin was supplemented to the CSBM diet, ATTD of GE, DM, C, S, phosphorus, NDF, and ADF was either not changed or reduced, while when narasin was supplemented to DDGS diets, these same ATTD parameters were increased (interaction, ≤ 0.05). Even though ADG and ADFI were not affected, G:F was improved in pigs fed the CSBM diet with supplemental narasin, but was reduced in pigs fed the DDGS diet with supplemental narasin (interaction, < 0.05). In Exp. 2, there was an interaction between diet type and narasin supplementation only for ATTD of Ca (interaction, < 0.01), in that narasin supplementation did not change the ATTD of Ca in pigs fed the CSBM diet, while narasin supplementation reduced the ATTD of Ca in pigs fed the DDGS containing diet. In Exp. 3, there was an interaction between diet and narasin only for ATTD of C (interaction, < 0.01) in that narasin supplementation resulted in an increased ATTD of C in pigs fed the CSBM diet, while narasin supplementation to the DDGS containing diet resulted in a reduced ATTD of Ca. In general, the data indicate that narasin interacted with and had its largest effect on pig performance and GE or nutrient digestibility in 9 to 23 kg pigs compared to pigs weighing greater than 80 kg. The data also indicate that the addition of DDGS reduced GE, DM, Ca, and N digestibility, regardless of BW.

Crude protein (CP) is a key nutrient in swine diets supplying essential amino acids, N, and S to animals for growth are fed in excess to maximize growth. Swine diets reduced in CP and supplemented with crystalline amino acids have been shown effective at maintaining animal growth while increasing overall CP use efficiency. A feeding trial study was conducted to determine the effects of reduced dietary CP levels on manure slurry chemical properties and gas emissions. A total of 24 gilts averaging 111 kg BW were fed corn and soybean meal diets formulated with 8.7, 14.8, and 17.6% CP using crystalline amino acid supplementation in the 8.7 and 14.8% CP diets, but only intact protein, soybean meal, in the diet containing 17.6% CP. Diets were fed for 45 d with an average daily feed intake (ADFI) of 2.70 kg across all diets. Animals were fed twice daily with both feces and urine collected during each feeding and added to animal-specific manure storage containers. At the end of the study, manure slurries were monitored for gas emissions and chemical properties. Increasing dietary CP levels increased manure pH, total solids, total N, and total S, including increased levels of ammonia (NH3), volatile fatty acids, and phenolic compounds. Pigs fed lower CP diets had lower emissions of NH3, branched chain fatty acids (BCFA), and phenol compounds which translated into lower emissions in total odor. Emissions of NH3 and odor were reduced by 8.9% and 4.2%, respectively, for each unit percent decline in dietary CP. Hydrogen sulfide was the dominate odorant associated with manure odor emissions. Based on nutrient mass balance, animal retention of dietary N and S increased by 7.0% and 2.4%, respectively, for each unit percent drop in crude protein fed animals, while C retention in the animal declined by 2.1%.

Improved utilization of CP in swine diets has the potential to lower emissions of gases and odorants from swine production. Two experiments were conducted to determine the effect of dietary CP level and source has on manure composition and gas emissions. In Experiment 1 two groups of 12 gilts averaging 96.13 kg BW were fed three CP levels through the replacement of soybean meal (CSBM) with crystalline AA (8.7% to 17.6% CP) with an ADFI of 2.74 kg/d over a 42 d trial. In Exp 2, two groups of 32 gilts averaging 99.09 kg BW were fed diets containing 17.6% CP as supplied by CSBM, corn gluten meal (CGM), Canola meal (CM), or poultry meal (PM) with an ADFI of 2.73 kg/d over a 42 d trial. In each experiment, feces and urine were collected after each feeding and added to manure storage containers. At the end of each experiment, stored manures were monitored for gas emissions and chemical properties. In Exp. 1, regression analysis was used to determine the effects of CP levels in the diet. CP levels in the diet increased manure pH by 0.15 units, and decreased NH3, VFA, and phenols by 7.4%, 5.4%, and 6.2%, respectively, for each % of CP reduced in the diet. Emissions of NH3, H2S, and odor were reduced by 9.4%, 4.3%, 6.3%, respectively for each % reduction in CP content in the diet. In Exp. 2, ANOVA indicated that CP source had a significant effect on excretion of DM, C, N, S in manure. Animals fed CM diet had significantly higher levels of C, N, and S in manure compared to animals fed CSBM diets. In conclusion, dietary CP levels and the source of CP have a dramatic impact on manure composition and gas emissions.

Dietary fiber is known to reduce ammonia emissions, but little is known about its effect on emissions of major odorants. An experiment was conducted to determine the effect fiber and fiber source has on manure composition and gas emissions. Two groups of 44 gilts averaging 128 kg BW were fed standard corn soybean meal diets that contained 9.6% NDF or 17% NDF with the following fiber sources: beet pulp (BP); dried distillers grain with solubles (DDGS); soybean hulls (SB); and wheat bran (WB). Animals were fed twice daily, and feces and urine were collected after each feeding and added to manure storage containers. At the end of the experiment, stored manures were monitored for gas emissions and chemical properties. Animals on average gained 724 g/d and consumed 2.74 kg feed/d over 42-d trial ANOVA showed that dietary fiber in swine diets significantly increased the animals manure acidity, dry matter (DM), organic N, total N, total C, and volatile fatty acids contents, while the source of the fiber material in the diet significantly impacted the animals manure DM, total N, total C, and total S. Manures of animals fed lower fiber diets had significantly higher ammonia (NH3) and hydrogen sulfide emissions, while manure emissions of NH3 and total phenols was impacted by the fiber source in the animal diet. In conclusion, dietary fiber and the source of fiber have a dramatic impact on manure composition and gas emissions.

Methane emission is an important tool in the evaluation of manure management systems due to the potential impact it has on global climate change. Field procedures used for estimating methane emission rates require expensive equipment, are time consuming, and highly variable between farms. The purpose of this paper is to report a simple laboratory procedure for estimating methane emission from stored manure. The test developed was termed a methane production rate (MPR) assay as it provides a short-term biogas production measurement. The MPR assay incubation time is short (3d), requires no sample preparation in terms of inoculation or dilution of manure, is incubated at room temperature, and the manure is kept stationary. These conditions allow for high throughput of samples and were chosen to replicate the conditions within deep-pit manure storages. In brief, an unaltered aliquot of manure was incubated at room temperature for a three-days to assay the current rate of methane being generated by the manure. The results from this assay predict an average methane emission factor of 12.2 ± 8.1 kg CH4 head(-1) yr(-1) per year, or about 5.5 ± 3.7 kg CH4 per finished animal, both of which compare well to literature values of 5.5 ± 1.1 kg CH4 per finished pig for deep-pit systems (Liu et al., 2013). The average methane flux across all sites and months was estimated to be 22 ± 17 mg CH4 m(-2)-min(-1), which is within literature values for deep-pit systems ranging from 0.24 to 63 mg CH4 m(-2)-min(-1) (Park et al., 2006) and similar to the 15 mg CH4 m(-2)-min(-1) estimated by (Zahn et al., 2001).

Emissions data on air pollutants from large open-lot beef cattle feedlots are limited. This research was conducted to determine emissions of total suspended particulates (TSP) and particulate matter (PM10 and PM2.5) from a commercial beef cattle feedlot in Kansas (USA). Vertical particulate concentration profiles at the feedlot were measured using gravimetric samplers, and micrometeorological parameters were monitored with eddy covariance instrumentation during the nine 4- to 5-day intensive sampling campaigns from May 2010 through September 2011. Emission fluxes were determined from the measured concentration gradients and meteorological parameters using the flux-gradient technique. PM ratios based on calculated emission fluxes were 0.28 for PM2.5/PM10, 0.12 for PM2.5/TSP, and 0.24 for PM10/TSP, indicating that a large fraction of the PM emitted at the studied feedlot was in the coarse range of aerodynamic diameter, >10 μm. Median daily emission factors were 57, 21, and 11 kg 1000-head (hd)−1 d−1 for TSP (n = 20 days), PM10 (n = 19 days), and PM2.5 (n = 11 days), respectively. Cattle pen surface moisture contents of at least 20–30% significantly reduced both TSP and PM10 emissions, but moisture's effect on PM2.5 emissions was not established due to difficulty in measuring PM2.5 concentrations under low-PM conditions.

The objective of this study was to compare the use of thermal combustion (CNS) and inductively coupled plasma (ICP) to measure the total S content in plant-, animal-, and mineral-based feedstuffs, and to provide concentrations of other macro- and micro-minerals contained in these feedstuffs. Forty-five feedstuffs (464 total samples) were obtained from suppliers as well as swine feed and pet food manufacturers throughout the United States. Mineral data from IPC analysis were summarized on a DM basis using sample mean and SD, whereas the comparison of total S content between CNS and ICP was examined by bivariate plot and correspondence correlation. Analyses of a wide range of feedstuffs by CNS and ICP for total S were comparable for all but a few feedstuffs. For potassium iodide and tribasic copper chloride, ICP estimated total S to be lower than when analyzed by CNS (bias = 2.51 +/- 0.15 SE, P < 0.01). In contrast, for defluorinated phosphate and limestone, ICP estimated total S to be greater than when analyzed by CNS (bias = -1.46 +/- 0.51 SE, P < 0.01). All other samples had similar estimates of total S, whether analyzed by CNS or ICP. As expected, S composition varied greatly among feedstuffs. For total S, plant-based feedstuffs generally had lower total S compared with animal-based feedstuffs, whereas minerals supplied in sulfate form had the greatest concentration of total S. In addition to total S, mineral composition data are provided for all feedstuffs as obtained by ICP analysis. Within specific feedstuffs, mineral composition was quite variable, potentially due to low concentrations in the feed-stuff causing high mathematical variation or due to the source of feedstock obtained. In general, analyzed values of P were similar to previous tabular values. These data provide feed formulators a database from which modifications in dietary minerals can be accomplished and from which mineral requirements can be met more precisely to reduce losses of minerals into the environment.

There are approximately 2.5 million dairy cows in California. Emission inventories list dairy cows and their manure as the major source of regional air pollutants, but data on their actual emissions remain sparse, particularly for smog-forming volatile organic compounds (VOCs) and greenhouse gases (GHGs). We report measurements of alcohols, volatile fatty acids, phenols, and methane (CH4) emitted from nonlactating (dry) and lactating dairy cows and their manure under controlled conditions. The experiment was conducted in an environmental chamber that simulates commercial concrete-floored freestall cow housing conditions. The fluxes of methanol, ethanol, and CH4 were measured from cows and/or their fresh manure. The average estimated methanol and ethanol emissions were 0.33 and 0.51 g cow(-1) h(-1) from dry cows and manure and 0.7 and 1.27 g cow(-1) h(-1) from lactating cows and manure, respectively. Both alcohols increased over time, coinciding with increasing accumulation of manure on the chamber floor. Volatile fatty acids and phenols were emitted at concentrations close to their detection limit. Average estimated CH4 emissions were predominantly associated with enteric fermentation from cows rather than manure and were 12.35 and 18.23 g cow(-1) h(-1) for dry and lactating cows, respectively. Lactating cows produced considerably more gaseous VOCs and GHGs emissions than dry cows (P < 0.001). Dairy cows and fresh manure have the potential to emit considerable amounts of alcohols and CH4 and research is needed to determine effective mitigation.

Alum [Al(SO4) ·14HO] addition to poultry litter has been shown to reduce ammonia (NH) concentrations in poultry houses; however, its effects on greenhouse gas (GHG; NO, CH, and CO) emissions is unknown. The objectives of this study were to determine the effects of alum additions on (i) in-house NH and GHG concentrations, (ii) NH and GHG emissions, and (iii) litter chemical properties. Two identical broiler houses located in northwest Arkansas were used for this study: one house was a control and the other was treated with alum between each flock of birds. Ventilation rates were coupled with in-house NH and GHG measurements to determine emission rates. Overall, alum additions significantly reduced the daily average in-house NH concentration by 42% (8.9 vs. 15.4 μL L), and the overall NH emission rate was reduced by 47% (7.2 vs. 13.4 kg d house). The average cumulative NH emission for the three flocks was 330 kg house flock for the alum-treated house and 617 kg house flock for the control. Concentrations and emissions of nitrous oxide (NO) and methane (CH) from the alum-treated house were not significantly different than the untreated house. However, carbon dioxide (CO) emissions were significantly higher from the untreated house than the alum-treated house. Alum also significantly increased litter N content and reduced the C/N ratio. These results indicate that the addition of alum to poultry litter is not only an effective management practice for reducing in-house NH concentrations and emissions but also significantly reduces CO emissions from poultry facilities.

An experiment was conducted to investigate the effects of reducing dietary CP and increasing dietary cellulose concentrations on manure DM, C, N, S, VFA, indole, and phenol concentrations. Twenty-two pigs (105 kg initial BW) were fed diets containing either 14.5 or 12.0% CP, in combination with either 2.5 or 8.7% cellulose. Pigs were fed twice daily over the 56-d study, with feed intake averaging 2.74 kg/d. Feces and urine were collected after each feeding and added to the manure storage containers. Manure storage containers were designed to provide a similar unit area per animal as found in industry (7,393 cm2). Before sampling on d 56, the manure was gently stirred to obtain a representative sample for subsequent analyses. An interaction of dietary CP and cellulose was observed for manure acetic acid concentration, in that decreasing CP lowered acetic acid in pigs fed standard levels of cellulose but increased acetic acid in pigs fed greater levels of cellulose (P = 0.03). No other interactions were noted. Decreasing dietary CP reduced manure pH (P = 0.01), NH4 (P = 0.01), isovaleric acid (P = 0.06), phenol (P = 0.05), and 4-ethyl phenol (P = 0.02) concentrations. Increasing dietary cellulose decreased pH (P = 0.01) and NH4 (P = 0.07) concentration but increased manure C (P = 0.03), propionic acid (P = 0.01), butyric acid (P = 0.03), and cresol (P = 0.09) concentrations in the manure. Increasing dietary cellulose also increased manure DM (P = 0.11), N (P = 0.11), and C (P = 0.02) contents as a percentage of nutrient intake. Neither cellulose nor CP level of the diet affected manure S composition or output as a percentage of S intake. Headspace N2O concentration was increased by decreasing dietary CP (P = 0.03) or by increasing dietary cellulose (P = 0.05). Neither dietary CP nor cellulose affected headspace concentration of CH4. This study demonstrates that diets differing in CP and cellulose content can significantly impact manure composition and concentrations of VFA, phenol, and indole, and headspace concentrations of N(2)O, which may thereby affect the environmental impact of livestock production on soil, air, and water.

The effect storage had on the microbial biomass in two soils (Trevino and Fargo) was compared to the effect storage had on each soil’s capacity to degrade metsulfuron-methyl. Soils were collected from the field and used fresh (

The effect of water application (e.g., through rainfall or sprinkler system) on emissions of greenhouse gases (GHGs), such as nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2), from pen surfaces of open-lot beef cattle feedlots was evaluated under controlled laboratory conditions. Soil/manure samples were collected from several randomly selected pens from two beef cattle feedlots in Kansas and were used as simulated pen surfaces. Three treatments (i.e., dry and loose, moist and loose, and moist and compacted pen surface conditions) were considered, simulating surface conditions in the field after a typical rainfall event or water application with a sprinkler system. Soil/manure and water were mixed within glass containers and analyzed for GHG emission using a photo-acoustic infrared multi-gas analyzer; emission rates were calculated from measured concentrations. GHG emissions from the dry soil/manure samples were low, with mean values of 0.02, 0.00, and 45 mg m−2 h−1 for N2O, CH4, and CO2, respectively, compared to moist soil/manure samples. Water application on the dry manure samples resulted in large peaks of GHG fluxes, with peak values of 99.2, 28.6, and 15,443 mg m−2 h−1 for N2O, CH4, and CO2, respectively. The effect of water application (e.g., through rainfall or sprinkler system) on emissions of greenhouse gases (GHGs), such as nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2), from pen surfaces of open-lot beef cattle feedlots was evaluated under controlled laboratory conditions. Soil/manure samples were collected from several randomly selected pens from two beef cattle feedlots in Kansas and were used as simulated pen surfaces. Three treatments (i.e., dry and loose, moist and loose, and moist and compacted pen surface conditions) were considered, simulating surface conditions in the field after a typical rainfall event or water application with a sprinkler system. Soil/manure and water were mixed within glass containers and analyzed for GHG emission using a photo-acoustic infrared multi-gas analyzer; emission rates were calculated from measured concentrations. GHG emissions from the dry soil/manure samples were low, with mean values of 0.02, 0.00, and 45 mg m−2 h−1 for N2O, CH4, and CO2, respectively, compared to moist soil/manure samples. Water application on the dry manure samples resulted in large peaks of GHG fluxes, with peak values of 99.2, 28.6, and 15,443 mg m−2 h−1 for N2O, CH4, and CO2, respectively.

Emission of greenhouse gases, including nitrous oxide (N2O), from open beef cattle feedlots is becoming an environmental concern; however, research measuring emission rates of N2O from open beef cattle feedlots has been limited. This study was conducted to quantify N2O emission fluxes as affected by pen surface conditions, in a commercial beef cattle feedlot in the state of Kansas, USA, from July 2010 through September 2011. The measurement period represented typical feedlot conditions, with air temperatures ranging from -24 to 39°C. Static flux chambers were used to collect gas samples from pen surfaces at 0, 15, and 30 minutes. Gas samples were analyzed with a gas chromatograph and from the measured concentrations, fluxes were calculated. Median emission flux from the moist/muddy surface condition was 2.03 mg m−2 hour−1, which was about 20 times larger than the N2O fluxes from the other pen surface conditions. In addition, N2O peaks from the moist/muddy pen surface condition were six times larger than emission peaks previously reported for agricultural soils. Emission of greenhouse gases, including nitrous oxide (N2O), from open beef cattle feedlots is becoming an environmental concern; however, research measuring emission rates of N2O from open beef cattle feedlots has been limited. This study was conducted to quantify N2O emission fluxes as affected by pen surface conditions, in a commercial beef cattle feedlot in the state of Kansas, USA, from July 2010 through September 2011. The measurement period represented typical feedlot conditions, with air temperatures ranging from -24 to 39°C. Static flux chambers were used to collect gas samples from pen surfaces at 0, 15, and 30 minutes. Gas samples were analyzed with a gas chromatograph and from the measured concentrations, fluxes were calculated. Median emission flux from the moist/muddy surface condition was 2.03 mg m−2 hour−1, which was about 20 times larger than the N2O fluxes from the other pen surface conditions. In addition, N2O peaks from the moist/muddy pen surface condition were six times larger than emission peaks previously reported for agricultural soils.

Foam accumulation on the manure slurry at deep pit swine facilities has been linked to flash fire incidents, making it a serious safety concern for pork producers. In order to investigate this phenomenon, samples of swine manure were collected from over 50 swine production facilities in Iowa with varying levels of foam accumulation over a seven month period. These samples were tested for a number of physical and chemical parameters including temperature, pH, total solids, volatile solids, volatile fatty acid concentration, biochemical methane potential, and methane production rate. After establishing these parameters, a “foaming capacity and stability” test was performed where samples were placed in clear PVC tubes with air diffusers at the bottom to simulate biogas production. The amount of foam produced at a set aeration rate was recorded as a measure of foaming capacity, and foam stability was assessed by measuring the height of foam remaining at certain time intervals after aeration had ceased. The results of this test indicated that samples collected from foaming barns showed a greater capacity to produce and stabilize foam. In addition, statistical analysis indicated that manures with foam produced methane at significantly greater rates than non-foaming manures (0.154 ± 0.010 and 0.052 ± 0.003 L CH4./L slurry*day respectively, average ± standard error), and consequently had significantly greater fluxes of methane moving through the manure volume. On the other hand, the biochemical methane production assay suggested that manure from foaming pits had less potential to generate methane (112 ± 9 mL CH 4 /g VS) than non-foaming pits (129 ± 9 mL CH 4 /g VS), and the VFA analysis showed significantly lower concentrations in foaming pits (4472, 3486, and 1439 I¼g/g for the surface level and descending depths of the pit, respectively) as compared to non-foaming pits (9385,8931, and 6938 I¼g/g for the same sample depths). When taken together, these assays suggest enhanced anaerobic digestion efficiency from foaming barns, as well as the possible accumulation of a surfactant at the manure-air interface of foaming deep pits. Overall, this work supports a three-phase system conceptualization of foam production in swine manure deep pits, and that the control of one or more of these phases will be required for mitigation.

Emission of greenhouse gases, including nitrous oxide (N2O), from open beef cattle feedlots is becoming a concern. Research measuring emission rates of N2O from open beef cattle feedlots, however, has been limited. This study was conducted to quantify the N2O emission rate from pen surfaces in a commercial beef cattle feedlot in Kansas. Static flux chambers with a diameter of 30 cm were used to measure the flux from the pen surface as affected by pen surface conditions (i.e., moist/muddy, dry and loose, dry and compacted, and flooded) on 10 sampling days from July to November 2010. Air samples were collected from the chambers’ headspace at 0, 15, and 30 min using syringes and analyzed with a gas chromatograph. From the N2O concentrations, N2O emission fluxes were calculated. For each pen surface condition, N2O emission flux varied considerably with sampling day. Emission flux also varied with pen surface condition, with the moist/muddy surface having the largest median emission flux (7.18 mg m-2 h-1), followed by the dry and compacted, dry and loose, and flooded surfaces with median emission fluxes of 0.18, 0.17, and 0.09 mg m-2 h-1, respectively. This study quantified N2O emission rates from pen surfaces in a cattle feedlot; further work is investigating factors that influence emission rates.