Characterizing reduced sulfur compounds and non-methane volatile organic compounds emissions from a swine concentrated animal feeding operation

Abstract

ABSTRACT

RUMSEY, IAN COOPER. Characterizing reduced sulfur compounds and non-methane volatile organic compounds emissions from a swine concentrated animal feeding operation. (Under the direction of Viney P. Aneja.)

Reduced sulfur compounds (RSCs) and non-methane volatile organic compounds (NMVOCs) emissions from concentrated animal feeding operations (CAFOs) have become a potential environmental and human health concern. Both RSCs and NMVOCs contribute to odor. In addition, RSCs also have the potential to form fine particulate matter (PMfine) and NMVOCs the potential to form ozone. Measurements of RSCs and NMVOCs emissions were made from both an anaerobic lagoon and barn at a swine CAFO in North Carolina. Emission measurements were made over all four seasonal periods. In each seasonal period, measurements were made from both the anaerobic lagoon and barn for ~1 week. RSC and NMVOCs samples were collected using passivated canisters. Nine to eleven canister samples were taken from both the lagoon and barn over each sampling period. The canisters were analyzed ex-situ using gas chromatography flame ionization detection (GC-FID). Hydrogen sulfide (H2S) measurements were made in-situ using a pulsed fluorescence H2S/SO2 analyzer. During sampling, measurements of meteorological and physiochemical parameters were made. H2S had the largest RSC flux, with an overall average lagoon flux of 1.33 ï ­g m-2 min-1. The two main RSCs identified by the GC-FID, dimethyl sulfide (DMS) and dimethyl disulfide (DMDS), had overall average lagoon fluxes an order of magnitude lower, 0.12 and 0.09 ï ­g m-2 min-1, respectively. Twelve significant NMVOCs were identified in lagoon samples (ethanol, 2-ethyl-1-hexanol, methanol, acetaldehyde, decanal, heptanal, hexanal, nonanal, octanal , acetone, methyl ethyl ketone, and 4-methylphenol). The overall average fluxes for these NMVOCs, ranged from 0.08 ï ­g m-2 min-1 (4-methylphenol) to 2.11 ï ­g m-2 min-1 (acetone). Seasonal H2S barn concentrations ranged from 72-631 ppb. DMS and DMDS seasonal concentrations were 2-3 orders of magnitude lower. There were six significant NMVOCs identified in barn samples (methanol, ethanol, acetone 2-3 butanedione, acetaldehyde and 4-methylphenol). Their overall average NMVOCs concentrations ranged from 2.87 ppb (4-methylphenol) to 16.21 ppb (ethanol). The overall average barn normalized emissions were 3.3 g day-1 AU-1 (AU (animal unit) = 500 kg) for H2S, 0.018 g day-1 AU-1 for DMS and 0.037 g day-1 AU-1 for DMDS. Normalized overall average NMVOC emissions ranged from 0.45 g day-1 AU-1 for ethanol to 0.16 g day-1 AU-1 for acetaldehyde. Barn H2S concentrations were generally one to two orders of magnitude above their odor thresholds. DMDS concentrations also regularly exceeded the lower limit of an odor threshold. Four NMVOCs (2-3 butanedione, decanal, 4-methylphenol and nonanal) had barn concentrations exceeding an odor threshold. Using overall average lagoon and barn emissions, the emissions from swine CAFOs in North Carolina were estimated. H2S had the largest RSC emission with an estimated North Carolina emission of 1.46 million kg yr-1, which was ~21% of total North Carolina H2S emissions. Ethanol was the NMVOC with the largest North Carolina emission with an emission of 206,367 kg yr-1. H2S manure emissions were modeled using a process based air-manure interface (A-MI) mass transfer model. Different approaches were used to calculate the three main components of the A-MI mass transfer model: the dissociation constant, the Henry’s law constant and the overall mass transfer coefficient. The A-MI mass transfer model performed fairly well in comparison to 15 minute average lagoon fluxes (r2 = 0.57, p<0.0001) and seasonal lagoon fluxes. It is hypothesized that with appropriate information on the overall mass transport coefficient, that the model could be applied to predict CAFO trace gas emissions from different manure surfaces, therefore providing a method for quantifying emissions in different production, management and environmental conditions.