Submitted to: Bioresource Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/9/2012
Publication Date: 9/17/2012
Citation: Parker, D.B., Cai, L., Kim, K., Hales, K.E., Spiehs, M.J., Woodbury, B.L., Atkin, A.L., Nickerson, K.W., Patefield, K.D. 2012. Reducing odorous VOC emissions from swine manure using soybean peroxidase and peroxides. Bioresource Technology. 124:95-104. Interpretive Summary: Air emissions from swine facilities can cause odor nuisance issues. Soybean peroxidase (SBP) is a naturally occurring enzyme found in soybean hulls. The enzyme has been shown to decrease concentrations of odorous phenolic compounds in industrial wastewaters, but little is known about its effectiveness in swine manure . A commercially available SBP product was applied to swine manure with either hydrogen peroxide or calcium peroxide as an oxidizing agent. The emission rates of the chemical compounds were measured in a wind tunnel using a gas chromatograph. The optimum SBP application rate was 50 grams per liter. At this application rate, the chemical most responsible for swine odor was reduced by up to 98 percent. These results confirm that plant-based peroxidase enzymes might be a promising odor treatment option for swine manure.
Technical Abstract: Air emissions from swine production facilities can cause odor nuisance issues. Peroxidase enzymes have been used to treat phenolic compounds in industrial wastewaters, but little is known about their efficacy for treating swine manure. The objective of the research was to determine the optimum application rates of soybean peroxidase (SBP) and peroxide (SBPP: SBP plus peroxide) for reducing odorous VOC emissions from swine manure. In our study of the SBPP method, industrial-grade SBP (0.88 U mg-1, 0 to 100 g L 1) was applied in combination with either liquid hydrogen peroxide (H2O2, 30%, 0 to 38.0 mM) or powdered calcium peroxide (CaO2, 20%, 0 to 76.0 mM) to standard phenolic solutions and swine manure. Emission rates of phenol, 4 methylphenol, indole, skatole, dimethyl disulfide, dimethyl trisulfide, and eight volatile fatty acids from swine manure slurry were measured in a small wind tunnel. The compound 4 methylphenol was the primary odorant, accounting for 68 to 77% of the odor activity value in the untreated manure. At the optimum application rate of SBPP (50 g L 1), 4 methylphenol emission rates were reduced by 62% (H2O2) and 98% (CaO2) after 24 h (P < 0.0001). Comparison of reduction patterns indicated that the latter remained effective for 48 h with 92% reduction in emission rates (P < 0.0001), while the former was not different from the control at 48 h (P = 0.28). Both peroxides were effective enough to treat the two sulfide compounds for 48 h, with reductions in emission rates of 88 to 96% (P < 0.0001). CaO2 did not affect volatile fatty acid (VFA) emissions (P = 0.90), but H2O2 increased total VFA emissions by ten-fold (P < 0.0001) after 48 h, accompanied by pH drop (0.73 units) in the manure. The overall results of our SBPP approach strongly suggest that plant-based peroxidase enzymes should be a promising treatment option for odor reduction from swine manure.