Abstract
<b><sc>Abstract.</sc></b> UV-A photocatalysis has been investigated to comprehensively mitigate odor and selected air pollutants in the livestock environment. This study was conducted to confirm the performance of UV-A photocatalysis on the swine farm. The objectives of this research were to (1) scale-up of the UV-A photocatalysis treatment, (2) evaluate the mitigation of odorous gases from swine slurry pit, and (3) evaluate the effect of suspended particulate matter (PM). We tested UV-A photocatalysis at a mobile laboratory-scale capable of treating ~0.2 - 0.8 m<sup>3</sup>·s<sup>-1</sup> of barn exhaust air. The targeted gaseous emissions of barn exhaust air were significantly mitigated (p < 0.05) up to 40% reduction of measured odor; 63%, 44%, 32%, 40%, 66%, and 49% reduction of dimethyl disulfide, isobutyric acid, butanoic acid, p-cresol, indole, and skatole, respectively; 40% reduction of H<sub>2</sub>S; 100% reduction of O<sub>3</sub>; and 13% reduction of N<sub>2</sub>O. The PM mitigation effect was not significant. Formaldehyde levels did not change, and a 21% generation of CO<sub>2</sub> was observed. The smell of benzoic acid generated in UV-A treatment was likely one of the compounds responsible for the less-offensive overall odor character of the UV-treated emissions. Results are needed to inform the design of a farm-scale trial, where the interior barn walls can be treated with the photocatalyst, and foul air will be passively treated as it moves through the barn.
Highlights
Ultraviolet (UV) light ranges between 200 to 400 nm in the electromagnetic spectrum adjacent to the purple band, invisible to the human eye
We aimed to evaluate the on-farm-scale efficacy of UV photocatalysis performance in mitigating odorous gaseous emissions using swine barn exhaust air
We investigated UV-A photocatalysis treatment to mitigate gaseous emissions at the farm-scale
Summary
Ultraviolet (UV) light ranges between 200 to 400 nm in the electromagnetic spectrum adjacent to the purple band, invisible to the human eye. UV-A (~315–400 nm) is considered the least toxic and is used in consumer product applications such as commercial indoor tanning. UV treatment can be considered for both 'end-of-pipe' (treating a point-source exhaust air from mechanically-ventilated barns) and source-based (e.g., improving the indoor air quality inside the barn) applications. UV treatment can be classified as either direct photolysis (i.e., mitigation primarily via direct absorption UV light by the ambient gases) and photocatalysis (i.e., mainly via surface-based reactivity based on catalyst activation by the UV light). With its relatively long wavelength, fewer pollutants directly absorb UV-A, and it is generally less effective than using the same wavelengths with a photocatalyst designed to operate by UV-A absorption (Lee et al, 2020a; Lee et al, 2020b;). Photocatalysis is commonly facilitated on surfaces coated with nanosized titanium dioxide (TiO2), which is considered reasonably durable and costefficient (Hashimoto et al, 2005; Zaleska, 2008; Schneider et al, 2014)
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