Abstract
Swine farming facilities have increased the production of malodorous gases, which negatively affects people. Hence, we developed a new feasible bio-foam technology wherein long-lasting surfactant foam, including bacteria, were sprayed on swine manure. The surfactant foam acted as a physical barrier, suppressing NH3 release, and the aqueous-phase bacteria formed after foam breaking infiltrated in manure and degraded NH3. In this study, we first isolated NH3-degrading bacteria from swine manure. A bacterial consortium was prepared using the effective NH3-degrading strains Saccharomyces cerevisiae NRRL Y-12632 (99.88%) (TP1), Lactococcus lactis subsp. hordniae NBRC100931T (99.93%) (TP3), and Lactobacillus argentoratensis DSM 16365T (100%) (TP5). The surfactant foam used in this study was a dry foam (foam quality 98.5–99.0% and foam density 0.025–0.026 g/cm3), with a foam expansion of 110–112 and high foamability. Large bubbles were generated with a bubble density of 1 bubble/cm2 and a foam lamella thickness of 0.12 mm. In a lab-scale study, foam was sprayed onto NH3-contaminated soil or real swine manure, which reduced the NH3 emission from the source (soil/manure) almost completely (97–100%), but NH3 was re-emitted after foam breaking (5 h: open reactor, 7 h: closed reactor). After loading the bacteria on the foam, the initial NH3 odor suppression was similar to that of the foam alone. However, NH3 was effectively reduced by microbial degradation even after foam breaking. Complete odor degradation was observed after 3 days (72 h; 90–100% reduction) for the NH3-contaminated soil, and 97.7% NH3 in the swine manure was reduced in 24 h. Furthermore, the reagent cost for preparing stable foam was reasonable, indicating its possible field extension.
Highlights
Pig farming is increasing annually; pigs are majorly used for human consumption, in addition to supplying skin, fat, and other materials for use as clothing, ingredients for processed foods, cosmetics, and medicine [1,2,3]
This study selected three strains among the 16 strains for further odor reduction study: Saccharomyces cerevisiae (TP1), Lactococcus lactis (TP3), and Lactobacillus argentoratensis (TP5). These three bacterial strains were selected based on their ability to remove NH3 and the influence of surfactant foam on their growth
Phylogenetic analysis based on 16S rRNA and 18S rRNA gene sequence showed high sequence similarities with Saccharomyces cerevisiae NRRL Y-12632—TP1 (99.88%), Lactococcus lactis subsp. hordniae NBRC100931T—TP3 (99.93%), and Lactobacillus argentoratensis DSM 16365T—TP5 (100%)
Summary
Pig farming is increasing annually; pigs are majorly used for human consumption, in addition to supplying skin, fat, and other materials for use as clothing, ingredients for processed foods, cosmetics, and medicine [1,2,3]. The odorous gases from manure generally contain sulfur (e.g., H2S and mercaptans), nitrogen (e.g., amines and ammonia (NH3)), alcohols, phenols, and volatile organic acids These malodorous gases in swine manure adversely affect human beings, such as causing irritation to the eyes and nose, asphyxiation at high levels, nausea, headache, dizziness, unconsciousness, and even death [6,7,8,9]. The former technology, adsorption and masking, is expensive, and the latter involves the process of diluting air, wherein malodorous gases from manure are diluted by adding other gases such as camphor and indole-coumarin These physical-based technologies are extremely useful for treating low concentrations of gases produced from manure, but appear to be ineffective for high concentrations [11,12]
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