Making Sense of Smells A Guide for Understanding Farmstead Odors Douglas W. Hamilton Waste Management Specialist Biosystems and Agricultural Engineering Making Sense of Smells A Guide for Understanding Farmstead Odors Between 2003 and 2010, seven classes of BAE 1012, Data Analysis in Biosystems Engineering, at Oklahoma State University have taken the sniff test lab described in an earlier section of this series. In all, 187 freshmen engineering students have sampled odors. Part 7: The OSU Experience with the Simulated Olfactometry Exercise

Mystery Liquids Tested A number of liquids have been used in the experiment over the years.

Mystery Liquids Tested Tap Water Water taken from the tap, dyed with food coloring, provides a negative control for intensity and offensive.

Mystery Liquids Tested Tap Water Cologne A few drops of cologne in colored water is an effective positive control for intensity and negative control for offensiveness.

Mystery Liquids Tested Tap Water Cologne Raw Swine Wastewater The students have sampled liquids associated with animal agriculture. Including liquid swine manure taken directly from in-house pits.

Mystery Liquids Tested Tap Water Cologne Raw Swine Wastewater Facultative Lagoon Wastewater Swine manure treated in a purple non-sulfur bacteria containing, facultative lagoon.

Mystery Liquids Tested Tap Water Cologne Raw Swine Wastewater Facultative Lagoon Wastewater Covered Anaerobic Lagoon Wastewater Effluent taken from under the cover of a covered, anaerobic lagoon.

Mystery Liquids Tested Tap Water Cologne Raw Swine Wastewater Facultative Lagoon Wastewater Covered Anaerobic Lagoon Wastewater Aerobic Lagoon Wastewater Effluent from an algae filled, aerobic lagoon.

Results from Spring 2010 Class Cologne Here are histograms taken from results gathered in 2010. The class of 29 students gave the cologne tainted water an average intensity of 3.45 (distinct to strong odor) and average offensiveness of 0.90 (very faintly offensive). But, there was a fairly wide range of opinions … It is always interesting to see that at least a few students find the cologne strongly to very strongly offensive. After all, it is pretty cheap stuff. Results from Spring 2010 Class

Results from Spring 2010 Class Cologne This is the same data from 2010 plotted on Cartesian coordinates, averages plus and minus one standard deviation. Because of the skewed data, the error bars go into the negative range. It is not technically possible to have a negative offensiveness. This is perhaps a entry to introduce a logarithmic transformation. As a visual representation, though, the message gets across. Even though the odor is intense, it is fairly inoffensive; some might even consider it pleasant. Results from Spring 2010 Class

Cologne The cologne stimulus has been presented to students in every exercise since 2003. You can see the histograms using all 187 responses are amazing similar to the single class data. Results from 2003-2010

Cologne Plots from all seven classes fall within the same cloud of variability. Results from 2003-2010

In the years between 2006 and 2010, liquids collected from various points in the OSU Swine Research and Education Center waste handling system have been presented to the students.

Raw Manure Results from 2006-2010 Responses to raw manure taken from the buildings is almost consistent as the cologne data, with one year in four falling a little out of range. Results from 2006-2010

Raw Manure Results from 2006-2010 This plot is the combined statistics of 4 classes and 99 students. On average, the students considered raw swine manure to be strong and strongly to very strongly offensive. Results from 2006-2010

Results from 2006-2010 Raw Manure Another representation technique is to draw an ellipse around the average plus and minus one standard deviation All the opinions contained within the ellipse can be considered valid within a certain cloud of uncertainty. Results from 2006-2010

The next liquid was taken after the raw manure had been treated in a covered anaerobic lagoon.

Results from 2006-2010 Raw Manure Covered Lagoon Results of the 99 stimuli showed that the student considered anaerobically treated manure to be an improvement in both odor intensity and offensiveness over raw manure. The cloud of uncertainty of the two samples barely touch. Results from 2006-2010

Another sample was taken from an aerobic lagoon that treats effluent flowing from the covered lagoon.

Results from 2006-2010 Raw Manure Covered Lagoon Students found this to be further improvement in both intensity and offensiveness. Before you get too excited and start advocating aerobic treatment of swine manure. Aerobic Lagoon Results from 2006-2010

Consider the results of liquids taken from a facultative lagoon treating manure from a similar farm.

Results from 2003-2010 Raw Manure Covered Lagoon The results of 88 students sampled between 2003 and 2006 showed similar results to the aerobic samples taken between 2006 and 2020. In fact the students decided, on average, that facultative effluent was slightly less offensive than aerobic lagoon effluent. A single-stage facultative lagoon may be just as effective in reducing odors as a two-stage anaerobic-aerobic lagoon. Release of ammonia and green house gases, well, that’s another story. Aerobic Lagoon Results from 2003-2010