Mixing ground swine carcasses with the manure waste stream is a new concept that is currently being researched as an alternative carcass disposal method. This method recycles nutrients back into the food chain through the cropping system when the manure is land-applied. A concern associated with this process is the possible additional odor emissions that could arise during storage of the manure-carcass blend. A research project was initiated to study the additional odor emissions of adding ground carcass material to manure.
Eight 200-gallon polyethylene tanks were located at the Rosemount Experiment Station and filled with swine waste and ground swine carcass material. Ground carcass material was added at the rate of 1%, 2% and 4% (dry-matter basis) of the existing swine waste in the tanks using a randomized block design of two blocks. Two additional tanks, to which no ground carcass material was added, served as the controls. The 1% rate is considered normal loading for a typical farrowing operation. Total solids of the waste was 2.06% (dry basis, db). Total solids content of the ground carcass material was 10.5% and 11.0% (db) for the two prepared batches.
Carcass material was added to tanks on May 16 (Day 0), June 18 (Day 33), and August 5 (Day 81). Gas samples were collected over the tanks for odor analysis on May 21, June 4, June 18, July 2, July 16, July 30, August 6, and August 8. Odor analysis was determined using a dynamic olfactometer and hydrogen sulfide gas concentration was determined using a Jerome meter.
The accompanying figures illustrate the collected data, including odor units and hydrogen sulfide concentration. Odor units are a measure of the dilutions-to-threshold or the maximum amount of dilution of filtered air with the collected air sample that will still allow a panelist to detect or be aware of the presence of an odor. Hydrogen sulfide concentration is reported in parts per billion (ppb) of the air sample. The same data is presented twice in Figs. 1 and 2 and Figs. 3 and 4, with the x-axis representing cumulative days since the start of the experiment and days since the addition of carcass material. Each point on each graph of Figs. 1 to 4 represents an average of two data points. For Fig. 5, each point is an individual observation.
Analysis of Variance (ANOVA) was performed using treatment (control, 1%, 2%, and 4%), blocking, and time as main effects. Treatment-by-block and treatment-by-time interactions were also included in the ANOVA analysis to help account for part of the variation in data. The error term for testing significance of treatments was the treatment-by-block interaction. The data was transformed to a logarithmic scale to adjust for unequal variation within collection days. Statistical analysis was done on the whole data set and parts of the set.
When pooled over the complete data set (n=56), there was no significant difference in odor units and hydrogen sulfide concentration across the four treatments.
Using the data (n=24) from the first three collection periods (cumulative days 5, 19, and 33), there was no significant difference in odor units and hydrogen sulfide concentration across the four treatments.
Using the data (n=40) from the first five collection periods after carcass addition (cumulative days 5, 19, 47, 82, and 84; carcass addition days 1, 3, 5, 14, and 19), there was no significant difference in odor units and hydrogen sulfide concentration across the four treatments.
Using the data (n=24) from the first three collection periods (cumulative days 5, 82, and 84; carcass addition days 1, 3, and 5), there was no significant difference in odor units and hydrogen sulfide concentration across the four treatments.
Using the data (n=8) from the first collection day (cumulative day 5; carcass addition day 5), there was no significant difference in odor units and hydrogen sulfide concentration across the four treatments. Even though there was no significant differences, there is a general increase in emissions with increased carcass material (Fig. 5) on the first collection day. This trend was not observed in any other gas collection period. On that day only, the odor units and hydrogen sulfide concentration emissions from the 4% treatment was 2.8 and 2.1 times the emissions from the control tanks, respectively. Based only on this single collection period, our results may indicate that adding carcass material at the 4% level may be too high.
The following is a summary of probability levels:
|
|
|||
|
|
|
|
|
|
Full Data Set |
|
|
|
|
First three collection periods |
|
|
|
|
First five collection periods |
|
|
|
|
First three collection periods |
|
|
|
|
First collection period |
|
|
|
In conclusion, based on the data collected in this study, ground
carcasses can be mixed into the manure stream at a rate up to 4%
(dry-matter basis) without significantly increasing odor emissions
above existing swine manure emissions as indicated by odor units and
hydrogen sulfide concentration. However, a more reasonable upper
limit might be 2% carcass material (dry-matter basis), with this
recommendation based solely on the first air samples collected
(Day 5).
Contribution of the Minnesota Agricultural Experiment Station based on research conducted under Project No. 062. Research funded by the Minnesota Pork Producers Association and Minnesota Department of Agriculture.
Last updated July 1, 1998 by David R. Schmidt
For questions and further information, send email to David Schmidt
at: schmi071@maroon.tc.umn.edu
© 1998 Regents of the University of Minnesota. All Rights
Reserved.
The University of Minnesota is an equal opportunity educator and employer.
This page is part of the Biosystems and Agricultural Engineering Department web at http://www.bbe.umn.edu/