Pilot-scale testing of renewable biocatalyst for swine manure treatment and mitigation of odorous VOCs, ammonia and hydrogen sulfide emissions

Abstract

<p>Comprehensive control of odors, hydrogen sulfide (H₂S), ammonia (NH₃), and greenhouse gas (GHG) emissions associated with swine production is a critical need. A pilot-scale experiment was conducted to evaluate surface-applied soybean peroxidase (SBP) and calcium peroxide (CaO₂) as a manure additive to mitigate emissions of odorous volatile organic compounds (VOC) including dimethyl disulfide/methanethiol (DMDS/MT), dimethyl trisulfide, <em>n</em>-butyric acid, valeric acid, isovaleric acid, <em>p</em>-cresol, indole, and skatole. The secondary impact on emissions of NH₃, H₂S, and GHG was also measured. The SBP was tested at four treatments (2.28–45.7 kg/m² manure) with CaO₂(4.2% by weight of SBP) over 137 days. Significant reductions in VOC emissions were observed: DMDS/MT (36.2%–84.7%), <em>p</em>-cresol (53.1%–89.5%), and skatole (63.2%–92.5%). There was a corresponding significant reduction in NH₃ (14.6%–67.6%), and significant increases in the greenhouse gases CH₄ (32.7%–232%) and CO₂ (20.8%–124%). The remaining emissions (including N₂O) were not statistically different. At a cost relative to 0.8% of a marketed hog it appears that SBP/CaO₂ treatment could be a promising option at the lowest (2.28 kg/m²) treatment rate for reducing odorous gas and NH₃ emissions at swine operations, and field-scale testing is warranted.</p>