# VOC Removal from Manure Gaseous Emissions with UV Photolysis and UV-TiO\({}_{2}\) Photocatalysis
## 4 Conclusions  
The following conclusions were drawn:  
1. Experiments confirmed that it is feasible to substantially remove odorous VOCs with both photolysis and photocatalysis (synthetic VOCs air mixture) or photocatalysis (real manure atmosphere) during reaction times of only seconds. 2. For synthetic VOCs mixtures: (I) The treatment effectiveness of four treatment options followed an order of UV\({}_{185+254}\) + TiO\({}_{2}\) > UV\({}_{254}\) + TiO\({}_{2}\) > UV\({}_{185+254}\); no catalyst > UV\({}_{254}\); no catalyst. (II) Significant percent conversion (\(R\)) of VOCs (\(>\)80%) and linear dependence on UV dose was achieved when light energy was \(>\)60 J L\({}^{-1}\). Up to \(\sim\)80% of odor removal was also observed. (III) Deep UV (UV\({}_{185+254}\)) improved \(R\), particularly when photolysis was the primary treatment. (IV) The use of photocatalyst (TiO\({}_{2}\)), especially at deep UV, resulted in increased \(R\) for all VOCs and VFAs particularly, whose concentrations increased from reaction intermediates. Still, the effect of catalysts and deep UV should be considered independently. (V) Mass conversion rate (mass per energy) of \(p\)-cresol, a characteristic offensive barn odor compound (78.8-111 ng J\({}^{-1}\)) among all nine odorous VOCs. (VI) No apparent effects of RH on \(R\) were observed. However, a significant decrease in VOC mass removed was observed with high RH. (VII) No apparent effects of air temperature on \(R\) were observed for \(p\)-cresol and most of the VFAs. An apparent increase of both \(R\) and mass converted was observed for mercaptans with a temperature increase to 25 \({}^{\circ}\)C.
3. For real manure atmosphere: (I) between \(\sim\)80% and 100% removal of target VOCs at a treatment time of at least \(\sim\)6 s was observed. (II) Ammonia removal was not effective. (III) Odor removal of 77% was observed for emission from fresh odorous manure, but no odor removal was detected at low emission from aged manure. Ozone was generated with photocatalysis. The determination of ozone contributions to the overall treatment is warranted. **Supplementary Materials:** The following are available online at [[http://www.mdpi.com/2073-4344/10/6/607/s1](http://www.mdpi.com/2073-4344/10/6/607/s1)]([http://www.mdpi.com/2073-4344/10/6/607/s1](http://www.mdpi.com/2073-4344/10/6/607/s1)), Figure S1: Effect of RH (%) on Part A) percent conversion; Part B) mass removed (ng) of target odorous VOCs and treatment with UV\({}_{185+254}\) + TiO\({}_{2}\). _Experimental conditions_: light intensity at 254 nm, 312 nm and 365 nm was 1.5, 0.230 and 0.084 mW cm\({}^{-2}\), respectively; 25 mg TiO\({}_{2}\); 400 mL min\({}^{-1}\) airflow; treatment time = 28 s; CAR/PDMS 85 \(\mu\)m; 5 min sampling time; T = 25 \({}^{\circ}\)C. Figure S2: Effect of RH (%) on Part A) percent conversion; Part B) mass removed (ng) of target odorous VOCs treatment with UV\({}_{185+254}\), no catalyst. _Experimental conditions_: light intensity at 254 nm, 312 nm and 365 nm was 1.5, 0.230 and 0.084 mW cm\({}^{-2}\), respectively; 25 mg TiO\({}_{2}\); 400 mL min\({}^{-1}\) airflow; treatment time = 28 s; CAR/PDMS 85 \(\mu\)m; 5 min sampling time; T = 25 \({}^{\circ}\)C. Figure S3: Effect of RH (%) on Part A) percent conversion; Part B) mass removed (ng) of target odorous VOCs treatment with UV\({}_{185+254}\), no catalyst. _Experimental conditions_: light intensity at 254 nm, 312 nm and 365 nm was 1.5, 0.230 and 0.084 mW cm\({}^{-2}\), respectively; 25 mg TiO\({}_{2}\); 400 mL min\({}^{-1}\) airflow; treatment time = 28 s; CAR/PDMS 85 \(\mu\)m; 5 min sampling time; T = 25 \({}^{\circ}\)C. Figure S4: Effect of RH (%) on Part A) percent conversion; Part B) mass removed (ng) of target odorous VOCs treated with UV\({}_{254}\), no catalyst. _Experimental conditions_: light intensity at 254 nm, 312 nm and 365 nm was 1.5, 0.230 and 0.084 mW cm\({}^{-2}\), respectively; 25 mg TiO\({}_{2}\); 400 mL min\({}^{-1}\) airflow; treatment time = 28 s; CAR/PDMS 85 \(\mu\)m; 5 min sampling time; RH = 30%.