## 5 Conclusions  
This study evaluated the photocatalytic UV-A and UV-C treatment of gaseous emissions of odor, odorous VOCs, NH\({}_{3}\), and other gases (GHGs, O\({}_{3}\)) from stored swine manure on a pilot-scale. To our knowledge, this is the first study of this scope that was needed for scaling up technologies treating gaseous emissions of odor, odorous VOCs, NH\({}_{3}\), H\({}_{2}\)S, \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **UV Wavelength,** \\ **nm** \\ **(UV dose, \(\mu\)/cm\({}^{2}\))** \\ \end{tabular} } & \multirow{2}{*}{**Targeted Gas**} & \multicolumn{2}{c}{**Target Gas Concentration**} & \multirow{2}{*}{**\% Reduction**} \\ \cline{3-3} \cline{5-5}  & & & **(ppm; O\({}_{3}\) = ppb)** & \\ \cline{3-3} \cline{5-5}  & & **b** & **UV Treatment** & \\ \hline \multirow{3}{*}{\begin{tabular}{c} 185 + 254 \\ (0.03) \\ \end{tabular} } & VOCs & N/A & N/A & \begin{tabular}{c} _p-Cresol (47);_ \\ **Indole (54)** \\ \end{tabular} \\ \cline{1-1}  & CH\({}_{4}\) & 3.7 \(\pm\) 0.9 & 1.1 \(\pm\) 0.0 & **71** \\ \cline{1-1}  & N\({}_{2}\)O & 0.2 \(\pm\) 0.0 & 0.2 \(\pm\) 0.0 & **25** \\ \hline \multirow{3}{*}{\
\begin{tabular}{c} 222 \\ (2.80) \\ \end{tabular} } & N\({}_{2}\)O & 0.2 \(\pm\) 0.0 & 0.2 \(\pm\) 0.0 & **8** \\ \cline{1-1}  & O\({}_{3}\) & 18.6 \(\pm\) 2.2 & 0.0 \(\pm\) 0.0 & **100** \\ \hline \multirow{3}{*}{
\begin{tabular}{c} 254 \\ (1.76) \\ \end{tabular} } & N\({}_{2}\)O & 0.2 \(\pm\) 0.0 & 0.2 \(\pm\) 0.0 & **14** \\ \cline{1-1}  & O\({}_{3}\) & 16.8 \(\pm\) 2.9 & 0.0 \(\pm\) 0.0 & **100** \\ \hline \hline \end{tabular} Note: N/A = not available.  
\end{table} 
Table 14: Summary of the % reduction of targeted gases with UV-C photocatalysis. Bold signifies statistical significance. ozone, and GHGs. The study bridged the knowledge gap between lab-scales and simplified treatment of model gases to the treatment of complex gaseous mixtures emitted from swine manure in fast-moving air. The results showed that the proposed UV technology is ready for the next stage of testing and mitigation of emissions from swine farms. The treatment effectiveness depended on the UV dose and wavelength. Specific findings are summarized below. Under UV-A (367 nm) photocatalysis, the percent reduction of targeted gases was up to:  
* 63% of odor,
* 51%, 51%, 53%, 67%, and 32% of acetic acid, propanoic acid, butanoic acid, \(p\)-cresol, and indole, respectively,
* 14% of nitrous oxide (N\({}_{2}\)O),
* 100% of O\({}_{3}\), 6% of NH\({}_{3}\), and
* 26% generation of CO\({}_{2}\). Under UV-C (185 + 254 nm) photocatalysis, the percent reduction of target gases was up to:  
* 54% and 47% for \(p\)-cresol and indole, respectively,
* 25% of N\({}_{2}\)O,
* 71% of CH\({}_{4}\), and
* 46% and 139% generation of CO\({}_{2}\) and O\({}_{3}\), respectively. UV-C (222 nm) photocatalysis showed a reduction of 8% for N\({}_{2}\)O, 100% for O\({}_{3}\). Lastly, UV-C (254 nm) photocatalysis showed a reduction of 14% for N\({}_{2}\)O, 100% for O\({}_{3}\). The UV-A photocatalysis (367 nm) was not economical to reduce NH\({}_{3}\); while it appeared to be economical and effective in mitigating odor and VOC. The 2.5 mJ/cm\({}^{2}\) dose is required to significantly reduce odor. UV-C photocatalysis (185 + 254 nm) was shown to be more efficient than UV-A photocatalysis by significantly reducing several target gases with a low dose, but additional research is needed because there was a limit to the dose control of UV-C in this study. The results proved that the UV technology was sufficiently effective in treating odorous gases in a simulated swine emissions environment, and the mobile lab was ready for farm-scale trials. The UV technology can be considered for the scaled-up treatment of emissions and air quality improvement inside livestock barns.