Impact of Bacillus subtilis on manure solids, odor, and microbiome

• Published in: Journal of environmental management Vol. 333; p. 117390
• Main Authors: Hwang, Okhwa, Yun, Yeo-Myeong, Trabue, Steven
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.05.2023
• Subjects: Ammonia - analysis; Animals; Bacillus subtilis; Manure; Microbial additives; Microbial community; Microbiota; Odor; Odorants; Sulfur; Sulfur Compounds; Swine; Swine manure; Microbial additives; Bacillus subtilis; Swine manure; Odor; Microbial community
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2023.117390

A study was conducted to determine the effectiveness of supplementing swine manure with Bacillus subtilis (BS) to improve digestion of manure solids and lower odor emission. Large bioreactors (400 L) with manure (100 L) were treated with commercially available BS at a rate of 1% manure volume by either directly pouring or surface spraying the manure with inoculum. Manure physicochemical properties, gas emissions, and microbiome were monitored. Manures treated multiple times with BS or surface sprayed had significantly (P < 0.05) lower electrical conductivity, volatile solids, and chemical oxygen demand, by 3–5% compared to non-treated control manures. Volatile sulfur compound emissions (VSCs) were reduced by 20–30% in both experiments, while ammonia and volatile organic compounds were reduced by 40% and 15%, respectively, in surface spray experiment only. The manure indigenous microbiome remained relatively stable following treatment and BS were never detected in the raw or treated manure following multiple treatments. The reduction in manure organic carbon and VSCs emissions were a result of physical mixing during manure treatment and biological material in the microbial inoculum stimulating microbial activity and not growth of BS. •Bacillus subtilis inoculum did not survive in swine manure following multiple treatments.•Bacillus subtilis inoculum did not impact microbiome but increased aerobic microbes.•Spraying microbial inoculum on manure reduced surface crusting and organic carbon.•Microbial inoculum material added to manure significantly reduced organic carbon.•Volatile sulfur compound odor most impacted by microbial inoculum treatment.