Identification, evaluation and quantification of VOCs as biosecure markers of swine carcass degradation

Swine carcasses were composted using passively-aerated composting system designed by the Canadian Food Inspection Agency during the 2004 Avian influenza outbreak in British Columbia. In this system, swine carcasses were fully covered by plastic sheets due to biosecurity concerns and visual inspection of the swine carcasses was impossible. Monitoring volatile organic compounds (VOCs) released from carcasses was a promising approach to assess progress and completion of the carcass degradation. In this study, VOCs were sampled using solid phase microextraction (SPME). Samples were analyzed using multidimensional gas chromatography-mass spectrometry (MDGC-MS) (a) to develop a comprehensive chemical library of volatile organic compounds emitted during carcass composting, (b) to determine if specific compounds could be correlated with various phases of the composting process and therefore be used to determine completion of composting and, (c) to determine the effects of compost operating parameters on the chemical make-up of gaseous emissions.;A completely new quantification method of measuring VOCs was developed with accuracy ranging from 79.04 to 98.53% and method detection limits ranging from 0.01 to 580 ppbv. Eighty five microm CAR/PDMS was shown to extract the highest amount of analytes at one hour sampling time. Dimethyl disulfide, dimethyl trisulfide, and pyrimidine were found to be produced during degradation of swine carcass tissues but not produced from decaying plant (envelope) materials. These compounds could serve as marker compounds of swine carcass degradation process. Laboratory studies showed that marker compounds cannot be detected in the headspace when the respiration rates of carcasses decrease to a level of 3.25 mg CO2-C/g VS*d (stable compost). Field studies showed that when carcass degradation was incomplete, detection of marker compounds was still possible in the eighth week of the process. After eight week composting time, the highest concentrations of marker compounds were detected for the carcass samples with the highest respiration rates (least stabilization). No relation was observed between temperature data and degradation rates of carcasses. A better estimate of carcass degradation was made by measuring concentrations of the marker compounds. The highest concentrations of the compounds were detected from the swine carcasses with the highest respiration rates and lowest decomposition. Dimethyl disulfide, dimethyl trisulfide, and pyrimidine were produced from all compost units under various conditions regardless of the plant material, moisture content, porosity and temperature. These compounds were reliable marker compounds that could be followed to test completion of a swine mortality composting process when the carcasses were fully covered by plant materials and plastic sheets due to biosecurity reasons.;Keywords. Compost, Dimethyl disulfide, Dimethyl trisulfide, GC-MS, Mortality, Pyrimidine, SPME, Swine, VFA, VO

Catheter ablation of drug resistant supraventricular tachycardia in neonates and infants

Background: The aim of this study was to evaluate the indications, results and complicationsof radiofrequency ablation (RFA) and transcatheter cryoablation (TCA) in neonates andinfants with incessant drug-resistant supraventricular tachycardia (SVT).Methods: Out of 225 patients who underwent RFA and TCA at our center between January2010 and February 2012, 5 patients under the age of 1 (4 male, 1 female) were evaluated. Theindication for RFA/TCA was recurrent hemodynamically compromising drug-resistant SVT.Results: Over a 2-year period, 6 ablation procedures were performed in 5 patients. Averagepatient age was 3.3 ± 3.9 months (12 days – 9.5 months); average patient weight was 5.4 ± 2.2 kg (3.5–9 kg). One patient had ventricular septal defect, 1 had corrected transposition of great arteries, ventricular septal defect, right ventricular hypoplasia and pulmonary hypertension, while 3 had only patent foramen ovale. Electrophysiology study showed 1 accessory pathway in each patient (right posteroseptal in 2, left posteroseptal in 2 and left lateral in 1). The pathway was manifest in 1 patient with Wolff-Parkinson-White syndrome (WPW) andconcealed in the rest. Two of the concealed pathways had slow conduction time and decremental properties (the permanent form of junctional reciprocating tachycardia). Two patients underwentTCA and 3 — RFA, with an acute success rate of 100%. In the first week after the procedure, the patient with the complex cardiac anomaly and WPW developed recurrence and under went ablation again. Four of the procedures were carried out using an electroanatomic mapping system besides fluoroscopy. Average procedure time was 167 min (100–234); fluoroscopy time was 8.2 min (0.7–19.7). None of the patients developed major complications. After the average follow-upperiod of 6.5 months (3–18), all patients were symptom-free without medication.Conclusions: RFA and TCA can be performed successfully in neonates and infants within cessant medically refractory SVT

Stability Evaluation of Simulated Plant and Animal Composts Utilizing Respiration Rates and VOC Emissions

Composting livestock carcasses is an economically and biologically safe method to convert carcasses into odorless, humus like material useful as a soil amendment. One of the key factors to determine the quality of the end product is stability. In this study, mortality composting is simulated using a laboratory set-up operating under aerobic and anaerobic conditions. 85 µm Carboxen/PDMS SPME fiber coating and 10 minutes sampling time are used to sample headspace of decaying plant (corn silage) and animal (shredded whole pig body) tissues. Compounds are separated and identified on a multidimensional gas chromatography-mass spectrometry-olfactometry (MDGC-MS-O) system. Sulfur containing compounds (methyl mercaptan, carbondisulfide, dimethyl disulfide, dimethyl trisulfide, 1,4-dimethyl tetra sulfide) and 1-H-indole and 3-methyl-1H-indole are found as indicators of decaying animal tissue. Peak area counts of these compounds show a decrease after eight week composting time. This trend in VOC emissions can be explained by decrease in the microbial activity and stabilization of the composts. These results are also supported with respirometric measurements. The measured respiration rates of aerobically composted animal tissues during 60 days are half of the respiration rates of fresh animal tissues. Also, a significant difference is observed in VOC emissions from plant and animal materials composted under aerobic and anaerobic conditions. The number of detected compounds during anaerobic decomposition is twice as much as the ones detected under aerobic decomposition. It can be concluded that monitoring VOC emissions can be a useful tool to estimate aeration status and completion of real life mortality composts

Qualitative Characterization of Volatile Compound Emissions during Biological Decomposition of Plant Materials using SPME-GC-MS

Composting is an alternative method of animal mortality disposal suitable for on-farm emergency containment of infectious diseases. Mortality composting can produce a complex variety of gases and some of them are known to be odorous. To date, relatively little is known about the makeup and temporal trends of organic gases and odors produced and emitted during composting processes. In this research, utilizing gas characterization for monitoring of the composting process was investigated. Emissions of volatile organic compounds (VOCs) and odors produced during composting of three carcass cover materials (corn stalks, oat straw and corn silage) were qualitatively studied at a laboratory scale set-up. Headspace samples were analyzed with multidimensional gas chromatography - mass spectrometry – olfactometry (MDGC-MS-O). Headspaces of decaying plant materials were tested using 85 µm Carboxen/polydimethylsiloxane (CAR/PDMS) SPME fiber. Aerobic and anaerobic conditions representing extremes of composting conditions were simulated to determine if composition of the gaseous byproducts can be used to evaluate aeration effectiveness. Volatile fatty acids (acetic, propanoic, isobutyic, butyric, isovaleric, valeric, hexanoic and heptanoic) were found as indicators of anaerobic decomposition of corn stalks and oat straw. The chemical makeup of gas and odor emissions was observed to decrease with compost age and was different for aerobic and anaerobic conditions. Chemical makeup and temporal trends in specific VOCs can be useful in non-invasive and indirect determination of the aeration status and completion of the composting process inside the biosecurity containment

Performance Evaluation of a Passively-Aerated Plastic-Wrapped Composting System Designed for Emergency Disposal of Swine Mortalities

Monitoring of a passively-aerated plastic-wrapped mortality composting system designed for emergency disposal of diseased swine highlighted the importance of the physical characteristics of materials used to envelop the carcasses. Inadequate moisture was a problem when using envelope materials such as ground cornstalks or straw having low density and high air-filled porosity. High O2 concentrations throughout these materials, and significantly higher moisture levels in the top layers than in the materials surrounding the carcasses, suggested significant air movement and transport of carcass moisture away from the carcasses, resulting in carcass desiccation and incomplete decay. Although internal temperatures and moisture levels in test units constructed with corn silage were much more favorable than in those constructed with cornstalks or straw, less carcass decomposition occurred. Settling and compaction, resulting in high bulk density and low air-filled porosity, caused low O2 concentrations that appeared to impair carcass decay in the silage test units

Pathogen Inactivation Potential and Carcass Degradation in a Bio-secure Emergency Livestock Mortality Composting System

An emergency swine mortality composting study at Iowa State University was conducted to evaluate the performance of six on-farm carbon source or “envelope” materials (corn silage, oat straw, cornstalks, wood shavings, soybean straw, and alfalfa hay) when used in a plastic-wrapped passively-ventilated emergency composting system that was first employed for emergency disposal of poultry in British Columbia in 2004. With the exception of tub grinding to reduce the particle size of long and fibrous materials, they were used “as is,” in their normal state — as would likely be the case during an emergency — without benefit of mixing or preconditioning to optimize C:N ratios or moisture content. Moisture content fell into two distinct groups: wood, soy, and alfalfa products had initial moisture content of \u3c 20%; while the other materials ranged from 55-62%. After 8 weeks moisture ranged from 11-18% and 27-35% respectively for the two groups. Minimum O 2 concentrations occurred during the first 2 weeks of composting, and ranged from 9-16% in relatively fine-grained wood and silage materials, to 17-20% in the others. Daily temperatures in material surrounding the carcasses also were highest during the first two weeks. Mean temperature ranges during the initial 30 days of composting were 47-57 °C for the moist group, and 35-43 °C for the dry group. Total soft-tissue degradation ranged from 77-78% for silage, wood shavings, and alfalfa hay, and from 85-88% for the other three materials. The highest degradation occurred in two materials having high initial moisture, and high mean 30-day temperatures, while the lowest degradation occurred in two materials having low 30-day mean temperatures and low initial moisture. The temperature/moisture correlation was not consistent, however, as soy straw — exhibiting both low mean temperature and low initial moisture — had high carcass degradation, and silage — having high temperature and high moisture — was in the group producing lower degradation. Remains recovered from all test units after 8 weeks appeared to be desiccated, suggesting that carcass decomposition was terminated by low moisture. This is consistent with the low final moisture levels, and indicates that moisture coming from the carcasses plays a significant role in sustaining decomposition. It also suggests that airflow rates through the matrix may have been excessive and that measures need to be taken to reduce airflow and prevent excessive moisture loss. Success rates meeting USEPA Class A or B criteria for pathogen reduction were much higher for the moist materials than for dry ones, indicating that procedures for emergency composting of carcasses resulting from disease should include pre-moistening of carcass surfaces and envelope materials, and to taking measures to control excessive airflow through the composting matrix that can result in premature drying of envelope materials

Performance of a Bio-secure Emergency Composting System for Disposal of Swine Carcasses

A plastic-wrapped passively-ventilated composting system used by the Canadian Food Inspection Agency for bio-secure emergency disposal of poultry mortalities during an avian influenza outbreak in 2004, was adapted and field tested to determine its feasibility for emergency disposal of infectious swine carcasses. System performance was evaluated during triple-replicated 8-week long trials, and 10-day long lab-scale studies were carried out to supplement the field results. Treatment variables included season (warm or cool), type of envelope material (cornstalks, oat straw, corn silage, wood shavings, alfalfa hay, and soybean straw), and initial moisture content of the envelope materials (low\u3c 20% w.b; moderate 40-65%). Performance variables included: final moisture content and leachate production; ability to sustain desirable internal O2 concentrations; % carcass (soft tissue) decomposition; and ability to attain and sustain pathogen-killing temperatures. Despite release of significant amounts of water from carcasses, and being wrapped in plastic sheeting, little leachate accumulation was observed and the moisture content of envelope materials was generally lower at the end of the trail than at the beginning. All materials, except corn silage, were able to maintain internal O2 concentrations of 10% or higher when air was supplied through flexible 10 cm diameter ducts spaced at 2m intervals. O2 concentrations in corn silage often dropped below 10% even though aeration ducts were spaced at 0.5m intervals. Corn silage demonstrated superior pathogen killing potential. Average daily temperatures in the carcass layer of silage test units during the first 30 days of composting (T30) exceeded 50 oC, and USEPA Class B criteria for pathogen reduction were achieved at 90% of monitored locations. T30 values for cornstalks, soybean straw, and alfalfa hay are about 40 oC, and Class B criteria were achieved in only 45-57% of monitored locations in the carcass layer. Wood shavings and oat straw had the worst temperature performance with T30 values of only about 30 oC, and a Class B success rate of about 35%. Mean soft tissue decomposition in the field was lowest in corn silage (72%), and highest in cornstalks and soybean straw (87% and 85% respectively)

Air sampling methods for VOCs related to field-scale biosecure swine mortality composting

Monitoring specific volatile organic compounds (VOCs) as markers of biosecure carcass degradation is a promising method to test progress and completion of the composting process. The objective of this study was to test the feasibility of using existing aeration ducts in composting units as practical sampling locations. The secondary objective was to test the feasibility of using marker VOC concentrations in aeration ducts to elucidate information about airflow patterns inside composting units. Marker VOC concentrations were significantly higher in the upper aeration duct and this duct can typically be used to collect air samples instead of placing special air sampling probes inside the composting units. Occasionally, the airflow direction inside composting units can change. Marker VOC concentrations can be used to decide the airflow direction inside the composting units. In this study, higher VOC concentrations were measured from the upper aeration duct, and this duct was shown to be an outlet

Performance of a plastic-wrapped composting system for biosecure emergency disposal of disease-related swine mortalities

A passively-ventilated plastic-wrapped composting system initially developed for biosecure disposal of poultry mortalities caused by avian influenza was adapted and tested to assess its potential as an emergency disposal option for disease-related swine mortalities. Fresh air was supplied through perforated plastic tubing routed through the base of the compost pile. The combined air inlet and top vent area is ⩽∼1% of the gas exchange surface of a conventional uncovered windrow. Parameters evaluated included: (1) spatial and temporal variations in matrix moisture content (m.c.), leachate production, and matrix O2 concentrations; (2) extent of soft tissue decomposition; and (3) internal temperature and the success rate in achieving USEPA time/temperature (T) criteria for pathogen reduction. Six envelope materials (wood shavings, corn silage, ground cornstalks, ground oat straw, ground soybean straw, or ground alfalfa hay) and two initial m.c.’s (15–30% w.b. for materials stored indoors, and 45–65% w.b. to simulate materials exposed to precipitation) were tested to determine their effect on performance parameters (1–3). Results of triple-replicated field trials showed that the composting system did not accumulate moisture despite the 150 kg carcass water load (65% of 225 kg total carcass mass) released during decomposition. Mean compost m.c. in the carcass layer declined by ∼7 percentage points during 8-week trials, and a leachate accumulation was rare. Matrix O2 concentrations for all materials other than silage were ⩾10% using the equivalent of 2 m inlet/vent spacing. In silage O2 dropped below 5% in some cases even when 0.5 m inlet/vent spacing was used. Eight week soft tissue decomposition ranged from 87% in cornstalks to 72% in silage. Success rates for achievement of USEPA Class B time/temperature criteria ranged from 91% for silage to 33–57% for other materials. Companion laboratory biodegradation studies suggest that Class B success rates can be improved by slightly increasing envelope material m.c. Moistening initially dry (15% m.c.) envelope materials to 35% m.c. nearly doubled their heat production potential, boosting it to levels ⩾silage. The ‘contradictory’ silage test results showing high temperatures paired with slow soft tissue degradation are likely due to this material’s high density, low gas permeability and low water vapor loss. While slow decomposition typically suggests low microbial activity and heat production, it does not rule out high internal temperatures if the heat produced is conserved. Occasional short-term odor releases during the first 2 weeks of composting were associated with top-to-bottom gas flow which is contrary to the typical bottom-to-top flow typically observed in conventional compost piles. In cases where biosecurity concerns are paramount, results of this study show the plastic-wrapped passively-ventilated composting method to have good potential for above-ground swine mortality disposal

Field scale evaluation of volatile organic compound production inside biosecure swine mortality composts

Emergency mortality composting associated with a disease outbreak has special requirements to reduce the risks of pathogen survival and disease transmission. The most important requirements are to cover mortalities with biosecure barriers and avoid turning compost piles until the pathogens are inactivated. Temperature is the most commonly used parameter for assessing success of a biosecure composting process, but a decline in compost core temperature does not necessarily signify completion of the degradation process. In this study, gas concentrations of volatile organic compounds (VOCs) produced inside biosecure swine mortality composting units filled with six different cover/plant materials were monitored to test the state and completion of the process. Among the 55 compounds identified, dimethyl disulfide, dimethyl trisulfide, and pyrimidine were found to be marker compounds of the process. Temperature at the end of eight weeks was not found as an indicator of swine carcass degradation. However, gas concentrations of the marker compounds at the end of eight weeks were found to be related to carcass degradation. The highest gas concentrations of the marker compounds were measured for the test units with the lowest degradation (highest respiration rates). Dimethyl disulfide was found to be the most robust marker compound as it was detected from all composting units in the eighth week of the trial. Concentration of dimethyl disulfide decreased from a range of 290–4340 ppmv to 6–160 ppbv. Dimethyl trisulfide concentrations decreased to a range of below detection limit to 430 ppbv while pyrimidine concentrations decreased to a range of below detection limit to 13 ppbv