Donald W. Wright

Multidimensional Gas Chromatography—Olfactometry for the Identification and Prioritization of Malodors from Confined Animal Feeding Operations

Odor profiling efforts were directed at applying to high-density livestock operations some of the lessons learned in resolving past, highly diverse, odor-focused investigations in the consumer product industry. Solid-phase microextraction (SPME) was used for field air sampling of odorous air near and downwind of a beef cattle feedyard and a swine finisher barn in Texas. Multidimensional gas chromatography-olfactometry (MDGC-O) was utilized in an attempt to define and prioritize the basic building blocks of odor character associated with these livestock operations. Although scores of potential odorant volatiles have been previously identified in high-density livestock operations, the odor profile results developed herein suggest that only a very few of these may constitute the preponderance of the odor complaints associated with these environments. This appeared to be especially true for the case of increasing distance from both cattle feedyard and swine barn facilities, with p-cresol consistently taking on the dominant odor impact role with ever increasing distance. In contrast, at- or near-site odor profiles were shown to be much more complex, with many of the well-known lower tier odorant compounds rising in relative significance. For the cattle feedyard at- or near-site odor profiles, trimethylamine was shown to represent a significantly greater individual odor impact relative to the more often cited livestock odorants such as hydrogen sulfide, the organic sulfides, and volatile fatty acids. This study demonstrates that SPME combined with a MDGC-O-mass spectrometry system can be used for the sampling, identification, and prioritization of odors associated with livestock.

Characterization of livestock odors using steel plates, solid-phase microextraction, and multidimensional gas chromatography-mass spectrometry-olfactometry.

Abstract Livestock operations are associated with emissions of odor, gases, and particulate matter (PM). Livestock odor characterization is one of the most challenging analytical tasks. This is because odor-causing gases are often present at very low concentrations in a complex matrix of less important or irrelevant gases. The objective of this project was to develop a set of characteristic reference odors from a swine barn in Iowa and, in the process, identify compounds causing characteristic swine odor. Odor samples were collected using a novel sampling methodology consisting of clean steel plates exposed inside and around the swine barn for ≤1 week. Steel plates were then transported to the laboratory and stored in clean jars. Head-space solid-phase microextraction was used to extract characteristic odorants collected on the plates. All of the analyses were conducted on a gas chromatography-mass spectrometry-olfactometry system where the human nose is used as a detector simultaneously with chemical analysis via mass spectrometry. Multidimensional chromatography was used to isolate and identify chemicals with high-characteristic swine odor. The effects of sampling time, distance from a source, and the presence of PM on the abundance of specific gases, odor intensity, and odor character were tested. Steel plates were effectively able to collect key volatile compounds and odorants. The abundance of specific gases and odor was amplified when plates collected PM. The results of this research indicate that PM is major carrier of odor and several key swine odorants. Three odor panelists were consistent in identifying p-cresol as closely resembling characteristic swine odor, as well as attributing to p-cresol the largest odor response out of the samples. Further research is warranted to determine how the control of PM emissions from swine housing could affect odor emissions.

Multidimensional Gas Chromatography-Olfactometry for Identification and Prioritization of Malodors from Confined Animal Feeding Operations

Odor profiling efforts were directed at applying to high-density livestock operations, some of the lessons learned in resolving past, highly diverse, odor-focused investigations in the consumer product industry. Multidimensional-GC-Olfactometry was utilized in an attempt to define and prioritize the basic building blocks of odor character associated with representative cattle feedyard and swine feeding operations. Although scores of potential odorant volatiles have been previously identified in high-density livestock operations, the odor profile results developed herein suggest that only a very few of these may constitute the preponderance of the odor complaints associated with these environments. This appeared to be especially true for the case of increasing distance from the cattle feedyard facilities; with para-cresol consistently taking on the preeminent odor impact role with ever increasing distance. In contrast, at or near-site odor profiles were shown to be much more complex; with many of the traditional lower tier odorant compounds rising in relative significance. Surprisingly, for the at or near-site odor profiles, trimethylamine was shown to represent a significantly greater individual odor impact relative to hydrogen sulfide, the organic sulfides and volatile fatty acids; the more often cited target odorants.

Evaluation of Sample Recovery of Malodorous Gases from Air Sampling Bags, SPME, and Sampling Canisters

Odorous gases associated with livestock operations are complex mixtures of hundreds if not thousands of compounds. Research is needed to know how best to sample and analyze these compounds. The main objective of this research was to compare recoveries of a standard gas mixture of 11 odorous compounds from the Carboxen/PDMS 75 µm SPME fibers, PVF (Tedlar), FEP (Teflon), foil, and PET (Melinex) air sampling bags, and standard 6 L Stabilizer™ sampling canisters after sample storage at room temperature. A standard mixture consisted of 7 VFAs from acetic to hexanoic, and 4 semi-VOCs including p-cresol, indole, 4-ethylphenol, and 2’-aminoacetopheone with concentrations ranging from 5.1 ppb for indole to 1,270 ppb for acetic acid. On average, SPME had the highest mean recovery for all 11 gases of 106.2%, and 98.3% for 0.5 and 24 hrs sample storage time, respectively. This was followed by the PET bags (71.7% and 47.2%), FEP bags (75.4% and 39.4%), in-house-made Tedlar bags (47.3% and 37.4%), commercial Tedlar bags (67.6% and 22.7%), foil bags (16.4% and 4.3%), and canisters (4.2% and 0.5%), for 0.5 and 24 hrs, respectively. VFAs had higher recoveries than semi-VOCs for all bags and canisters. New FEP bags and new foil bags had the lowest and the highest amounts of chemical impurities, respectively. New commercial Tedlar bags had measurable concentrations of DMAC and phenol. Foil bags had measurable concentrations of acetic, propionic, butyric, valeric and hexanoic acids. Further research is warranted to determine how recoveries from bags affect odor concentrations as measured by olfactometry.

Evaluation of Sample Recovery of Odorous VOCs and Semi‐VOCs From Odor Bags, Sampling Canisters, Tenax TA Sorbent Tubes, and SPME

Odor samples collected in field research are complex mixtures of hundreds if not thousands of compounds. Research is needed to know how best to sample and analyze these compounds. The main objective of this research was to compare recoveries of a standard gas mixture of 11 odorous compounds from the Carboxen/PDMS 75 μm SPME fibers, PVF (Tedlar), FEP (Teflon), foil, and PET (Melinex) air sampling bags, sorbent Tenax TA tubes and standard 6 L Stabilizer™ sampling canisters after sample storage for 0.5, 24, and 120 (for sorbent tubes only) hrs at room temperature. The standard gas mixture consisted of 7 volatile fatty acids (VFAs) from acetic to hexanoic, and 4 semi‐VOCs including p‐cresol, indole, 4‐ethylphenol, and 2’‐aminoacetophenone with concentrations ranging from 5.1 ppb for indole to 1, 270 ppb for acetic acid. On average, SPME had the highest mean recovery for all 11 gases of 106.2%, and 98.3% for 0.5 and 24 hrs sample storage time, respectively. This was followed by the Tenax TA sorbent tubes (94.8...

Carthage Bottoms Area Odor Study: A Missouri Test Case for Odorant Prioritization as a Prelude to Instrument Based Downwind Odor Monitoring Protocol Development

Past experience with crisis-driven odor investigations has shown that there is an odor impact priority ranking which is definable for virtually every malodor issue; whether from natural or synthetic source. An accurate definition of such odorant priority ranking is, in turn, critical to the development of accurate and objective instrument-based methods for odor assessment and monitoring relative to that source. This paper reports on the results-to-date relative to the Carthage Bottoms Area Odor Study; a test case undertaken by the Missouri DNR to evaluate the concept of odorant prioritization by MDGC-MS-Olfactometry. The ultimate goal of this study was to explore the utility of odorant prioritization as a first step toward the translation of sensory-only odor monitoring protocols to sensory-directed but instrument based alternatives. The Carthage Bottoms Area was selected by the Missouri DNR for this exploratory effort based upon a number of factors: including; (1) an intermittent but long-standing unresolved odor issue with respect to downwind citizenry; (2) a uniquely complex, diverse and densely co-located source industry mix within the combined Bottoms Area; (3) limited past success in point-source differentiation utilizing sensory-only protocols and (4) a past history of cooperation between citizenry, community officials, industry leaders and regulatory agencies in the exploration and implementation of technologies targeting enhanced mutually beneficial co-existance. MDGC-MS-O odorant profile and prioritization results are presented for SPME collections taken near and at-distance downwind as well as reference upwind with respect to the combined Bottoms Area.

Exploring Natural Models for the ‘Rolling Unmasking Effect’ of Downwind Odor Dispersion; Prairie Verbena, Prehensile-Tailed Porcupine and Virginia Pepperweed

As natural scale-models for community environmental odor issues, these odorant prioritization results illustrate an important consideration: ... ‘with respect to focusing an environmental odor issue, it is possible to look too closely at the source’... Although simple odor dilution, as measured by odor concentration and intensity, certainly occurs during downwind dispersive migration from the source, these authors propose that the term dynamic dilution is limiting with respect to environmental odor impact. The results presented herein suggest that the odor character from an environmental source can vary dramatically, depending upon the distance of the human receptors from that source. It is further suggested that the process of downwind environmental odorant prioritization can best be characterized as a rolling unmasking effect or RUE. The RUE is exhibited by the masking odors nearest the source sequentially ‘falling away’ with distance from the source, revealing a succession of increasingly simplified odor characteristic and composition. Because of scaling factors and meteorological unpredictability, the logistics involved in carrying-out odorant prioritization studies can be very challenging when targeting large-scale odor sources. However, for these authors’ illustrative purposes, these challenges were reduced significantly by selecting natural, ‘scale-model’ odor-sources which represented significant reductions in the primary scaling factors; especially, reductions in the size of the odor sources and the distance of their downwind reach. Driven by odorant prioritization and the RUE, extremes of odor simplification-upon-dilution were demonstrated for two Central Texas plant varieties, prairie verbena and virginia pepperweed. Their ‘odor frontal boundaries’ were shown to be dominated by single, character-defining odorants; prairie verbena presenting with a p-cresol dominated ‘barnyard’ odor and virginia pepperweed with a benzyl mercaptan dominated ‘burnt match’ odor. Similar odor simplification was also shown for the South American prehensile-tailed porcupine (i.e., pt porcupine); its downwind ‘odor frontal boundary’ dominated by two potent, character-defining odorants (i.e. as yet unidentified): (1) ‘onion’/‘body odor’ odorant #1 and (2) ‘onion’/‘grilled’ odorant #2. In contrast to their outer-boundary simplicities, each of these sources also presented, at the source, with odor compositions reflecting considerable complexity and corrresponding composite odor characters that were distinctly different from those reflected at their respective ‘odor frontal boundaries’.

Field Air Sampling with SPME for Ranking and Prioritization of Downwind Livestock Odors with MDGC‐MS‐Olfactometry

Air sampling and characterization of odorous livestock gases is one of the most challenging analytical tasks. This is due to low concentrations, physicochemical properties, and problems with sample recoveries for typical odorants. Livestock operations emit a very complex mixture of volatile organic compounds and other gases. Many of these gases are odorous. Relatively little is known about the link between specific VOCs/gases and specifically, about the impact of specific odorants downwind from sources. In this research, solid phase microextraction (SPME) was used for field air sampling of odors downwind from swine and beef cattle operations. Sampling time ranged from 20 min to 1 hr. Samples were analyzed using a commercial GC‐MS‐Olfactometry system. Odor profiling efforts were directed at odorant prioritization with respect to distance from the source. The results indicated the odor downwind was increasingly defined by a smaller number of high priority odorants. These ‘character defining’ odorants appear...

A Novel Approach to CAFO Odor Assessment: Odorant Field Collection by Sorbent Tube / Thermal Reconstitution in the Laboratory

Historically, odor emission monitoring of high density livestock operations has been limited to direct, whole-air assessment utilizing remote site sampling by plastic bags, human sensory panelists and dynamic dilution olfactometry. On-going efforts by these authors are directed at enabling the translation of these sensory ‘only’ monitoring protocols to instrument ‘primarily, with sensory oversight’ alternatives. This current work attempts to address the latter requirement for sensory oversight and the associated need for improved methods of remote site whole-air sample collection. Published works by these authors as well as others places in serious question the appropriateness of the use of plastic bags for the challenge of CAFO odor assessment; especially relative to sample points at increasing downwind distance from the source. Concerns increase due to the associated natural dilution effects relative to priority semi-volatile odorants. This current submission reports on the progress to date in the development and evaluation of alternative whole-air sampling strategies which attempt to address the primary limitation of plastic sampling bags; the adsorption loss-to-wall of high impact semi-volatile odorants such as p-cresol. In this approach the actual field air sampling is carried out utilizing sorbent tubes for on-site collection of the volatiles/odorants from a measured volume of air. These sorbent tube collections are then transported to the laboratory for reconstitution within a heat traced, passivated and piston-displaced vessel prior to composite odor assessment. The sample reconstitution process is accomplished simply by thermally desorbing the collected odorants into a flowing diluent gas stream and making up to final volume to yield a match of the originally sampled environment.