Sodium Persulfate and Potassium Permanganate Inhibit Methanogens and Methanogenesis in Stored Liquid Dairy Manure

Stored liquid dairy manure is a hotspot for methane (CH4) emission, thus effective mitigation strategies are required. We assessed sodium persulfate (Na2S2O8), potassium permanganate (KMnO4), and sodium hypochlorite (NaOCl) for impacts on the abundance of microbial communities and CH4production in liquid dairy manure. Liquid dairy manure treated with different rates (1, 3, 6, and 9 g or mL L−1slurry) of these chemicals or their combinations were incubated under anoxic conditions at 22.5 ± 1.3°C for 120 d. Untreated and sodium 2‐bromoethanesulfonate (BES)‐treated manures were included as negative and positive controls, respectively, whereas sulfuric acid (H2SO4)‐treated manure was used as a reference. Quantitative real‐time polymerase chain reaction was used to quantify the abundances of bacteria and methanogens on Days 0, 60, and 120. Headspace CH4/CO2ratios were used as a proxy to determine CH4production. Unlike bacterial abundance, methanogen abundance and CH4/CO2ratios varied with treatments. Addition of 1 to 9 g L−1slurry of Na2S2O8and KMnO4reduced methanogen abundance (up to ∼28%) and peak CH4/CO2ratios (up to 92‐fold). Except at the lowest rate, chemical combinations also reduced the abundance of methanogens (up to ∼17%) and CH4/CO2ratios (up to ninefold), although no impacts were observed when 3% NaOCl was used alone. With slurry acidification, the ratios reduced up to twofold, whereas methanogen abundance was unaffected. Results suggest that Na2S2O8and KMnO4may offer alternative options to reduce CH4emission from stored liquid dairy manure, but this warrants further assessment at larger scales for environmental impacts and characteristics of the treated manure. Chemical oxidants were assessed for potential effects on methanogens and methane production.The abundance of methanogens and CH4production were affected by Na2S2O8and KMnO4.Na2S2O8and KMnO4had similar effects on CH4production compared with acidification.Na2S2O8and KMnO4may provide options to mitigate CH4emissions from stored liquid dairy manure.