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ODORS FROM EVAPORATION OF ACIDIFIED PIG URINE
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.orgCitation: Pp. 318-322 in Air Pollution from Agricultural Operations III, Proceedings of the 12-15 October 2003 Conference (Research Triangle Park, North Carolina USA), Publication Date 12 October 2003. 701P1403.(doi:10.13031/2013.15524)
Authors: H. C. Willers, P. J. Hobbs, N. W. M. Ogink
Keywords: odor, evaporation, pig waste, urine, ammonia emission
In the Dutch Hercules project feces and urine from pigs are collected separately underneath the slatted floor in a pig house and treated in two processes. Feces are composted and urine is concentrated by water evaporation in a packed bed. Exhaust air from the pig house is used for the evaporation in a packed bed scrubber. Before entering the scrubber, urine is acidified with nitric acid to retain ammonia in the liquid and to absorb ammonia from the air. In this way a concentrated nitrogen/potassium fertilizer is produced from pig urine and ammonia is removed from the pig house exhaust air. Odor in the air inlet and the exhaust of the pig urine scrubber was measured using gas chromatography mass spectrometry (GC-MS) and olfactometry. The measurements were made weekly during six weeks in a pig fattening round where operation of the Hercules system was tested under pilot conditions. The olfactometric odor concentration of the scrubber inlet air averaged 2,290±1,760 OUE /m3 and the outlet concentration averaged 3,860±3,270 OUE /m3. When one measurement with a very high outlet concentration (10,320 OUE /m3) was ignored, a paired one-sided t-test (p<0.10) showed no significant difference in odor perception between inlet and outlet air. The deviant result could be explained by a high ratio of fresh acidified urine and concentrated liquid in the scrubber. Odor release from the scrubber may be reduced when this ratio is kept low. A continuous supply of fresh urine should be preferred to batch replacement of the liquid. Further odor control can be achieved by stripping odor compounds from the fresh urine during or after acidification. GC-MS measurements showed that volatile fatty acids, phenols and indoles were the dominating odor compounds in both inlet and outlet air of the scrubber. 3-Methyl butanoic acid, Pentanoic acid, 4-Methyl phenol and Indole were detected at levels far exceeding their odor threshold, both in the inlet and the outlet air of the scrubber. Only acetic acid and phenol levels were significantly higher in the outlet air.
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