The control of odor, odorous volatile organic compounds (VOCs), hydrogen sulfide (H2S), ammonia (NH3), and greenhouse gases (GHGs) emissions associated with commercial swine production is a critical need. Manure storage is the major source of gaseous emissions. This study aimed for the most comprehensive, to date, assessment of a manure additive for mitigation of gaseous emissions of all major compounds of interest from swine manure. This study assessed topical application of manure additive treatment in controlled pilot and farm scales (soybean peroxidase (SBP); product code 516-IND; Bio-Research Products, Inc.). This research builds on the previous published study where SBP product was mixed into manure and resulted in significant mitigation of odorous VOCs in lab scale. In this research both pilot and farm scale testing of topical SBP treatment (and ~23.5:1 weight/weight mix of SBP:CaO2 catalyst) was conducted over ~5 month and ~1.5 month, respectively. Effects of SBP dose and time were tested on pilot scale. The effects of time were tested on farm scale using the lowest SBP dose selected from the pilot study. This work aimed at providing a comprehensive assessment of SBP treatment efficacy to mitigate emissions of odorous VOCs, odor, H2S, NH3, and GHGs, i.e., a set of target gases of concern to swine industry. Results of farm scale testing were, in general consistent with the results of pilot scale controlled tests.
Specifically, farm scale testing of SBP resulted in mitigation of many important gases:
1. Ammonia emissions were reduced by 21.7% and were statistically significant.
2. Hydrogen sulfide emissions were reduced by 79.7% and were statistically significant.
3. Greenhouse gas emissions were reduced for nitrous oxide (N2O) at 9.8% and were not statistically significant. Both methane (CH4) and carbon dioxide (CO2) emissions were reduced by 6.2% and 3.0%, respectively, and were not statistically significant.
4. Sulfur VOCs emissions were significantly increased by 30.6% for dimethyl disulfide. Effects on dimethyl trisulfide could not be assessed.
5. Volatile fatty acids emissions were significantly reduced by 37.2% (butyric acid), 47.7% (valeric acid) and 39.3% (isovaleric acid).
6. Phenolics emissions were reduced by 14.4% (p-cresol), 31.2% (indole) and 43.5% (skatole) and were statistically significant for indole and skatole.
The estimated cost of treatment (additives only) was estimated at $1.45 per marketed pig and $2.62 per marketed pig when the cost of labor was added. Similarly, the estimated cost was $2.19/pig space/year of the (additives only) and $3.95 when the cost of labor was included (2014 price benchmarking). The cost estimate was at the lower range of comparable products tested for air quality mitigation ($0.01 to $18.2 per marketed pig). The SBP treatment also resulted in a more comprehensive mitigation of a greater number of gases of concern for swine industry.
