Effects of combined tannic acid/fluoride on sulfur transformations and methanogenic pathways in swine manure

Abstract

Livestock manure emits reduced sulfur compounds and methane, which affect nature and the climate. These gases are efficiently mitigated by addition of a tannic acid-sodium fluoride combination inhibitor (TA-NaF), and to some extent by acidification. In this paper, TA-NaF treatment was performed on swine manure to study the treatment influence on methanogenic pathways and sulfur transformation pathways in various laboratory experiments. Stable carbon isotope labeling revealed that both untreated and TA-NaF treated swine manures were dominated by hydrogenotrophic methanogenesis. However, in supplementary experiments in wastewater sludge, TA-NaF clearly inhibited acetoclastic methanogenesis, whereas acidification inhibited hydrogenotrophic methanogenesis. In swine manure, TA-NaF inhibited s-amino acid catabolism to a larger extent than sulfate reduction. Conversely, acidification reduced sulfate reduction activity more than s-amino acid degradation. TA-NaF treatment had no significant effect on methanogenic community structure, which was surprising considering clear effects on isotope ratios of methane and carbon dioxide. Halophile sulfate reducers adapted well to TA-NaF treatment, but the community change also depended on temperature. The combined experimental work resulted in a proposed inhibition scheme for sulfur transformations and methanogenic pathways as affected by TA-NaF and acidification in swine manure and in other inocula.

Low-Dose Acidification as a Methane Mitigation Strategy for Manure Management

“…Slurry storage is a well-known source of odorants, in particular S-containing compounds such as H 2 S and methanethiol, but also 4-methylphenol, indole, 3-methyl-1 H -indole, trimethylamine, and, in some cases, carboxylic acids. − Apart from being an odorant, H 2 S also contributes to the atmospheric burden of sulfur and contributes to the formation of secondary particles . In untreated slurry, H 2 S is produced mostly from sulfate reduction, but slurry acidification with H 2 SO 4 and hydrochloric acid has been found to inhibit sulfate reduction. Although laboratory studies indicate that H 2 SO 4 has only minor effects on total odor emissions, , the effects of slurry acidification on the odor profile should be documented to avoid pollution swapping.…”