Combining fluoride with either phenolic compounds or plant extracts offers potential mitigation strategy for ammonia and methane emissions from livestock manure

Emissions of ammonia and methane from agriculture caused by microbes in manure are an increasing challenge to sustainable agriculture. We screened several commercially available polyphenols, phenolic compounds, and polyphenol-rich extracts for their ability to inhibit the production of ammonia and mitigate methane emissions in pig manure in the absence and presence of sodium fluoride (NaF) using a short-term high-throughput set-up. Tested compounds were chlorogenic acid, lignosulfonic acid, lignin, chitosan, green tea extract, and chestnut tannins. Green tea extract, at a concentration of 8.5 mg/ml with 1 mM NaF, reduced total ammonia nitrogen (TAN) in pig manure by 72%, while methane emissions were lowered by 95% at an extract concentration of 2.5 mg/ml. The ability of four extracts of plant waste (spent coffee grounds, noble fir needles, shea meal, and rapeseed press cakes) to mitigate ammonia production and methanogenesis in pig manure was also investigated. Adding 7.0 ± 0.7 mg/ml of extract from shea meal, noble fir, or rapeseed press cake, or 3.2 mg/ml of coffee ground extract reduced TAN production in manure by approximately 50%. Shea meal and noble fir had the largest effect on methane emissions, with reductions of approximately 60%. Gallocatechin- and epigallocatechin-rich extracts appeared to be especially potent for the inhibition of methane emissions, while ammonia production could be inhibited by a variety of tannins. Based on the current work, we conclude that extracts from certain plants have the potential for use in sustainable manure management to reduce ammonia and methane emissions.