Simple sugars alter the odorant composition of dairy cow manure

Authors: Loughrin, John; Agga, Getahun; Lovanh, Nanh

Submitted to: Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/4/2024
Publication Date: 7/9/2024
Citation: Loughrin, J.H., Agga, G.E., Lovanh, N.C. 2024. Simple sugars alter the odorant composition of dairy cow manure. Environments. https://doi.org/10.3390/environments11070145.
DOI: https://doi.org/10.3390/environments11070145

Interpretive Summary: Offensive odors from animal waste are a concern due to their potential to contribute to air pollution and cause complaints from neighbors. This study was conducted to determine if adding sugar to cow manure to determine if they could improve the odor of animal waste. Glucose, lactose, and sucrose were added to the cow manure in concentrations ranging from 0.63 to 12.5 percent by weight. The manure was then incubated for four weeks while measuring gas production, organic acids such as acetic and lactic acids, and the concentration of aroma compounds after four weeks. Waste not treated with sugar had high concentrations of typical manure malodors while waste treated with sugar produced less of the malodors. Waste treated with sugar also produced fruit-like aroma compounds. Sugar-amended manure therefore had a sweeter smell than did unamended manure. Addition of sugar also increased the acidity of the manure. The production of lactic acid was particularly enhanced at high concentrations of sugar suggesting lactic acid bacteria were responsible for the improvement of manure odor. Future research will investigate if the addition of lesser amounts of sugars or agricultural wastes rich in carbohydrates can reduce manure malodor.

Technical Abstract: A study was conducted to determine if the odor profile of Bos taurus manure could be altered by the addition of the simple saccharides glucose, lactose, and sucrose. Sucrose was added to manure slurry at 0, 12.5, 25, 50, or 125 g L-1, while glucose and lactose were added at 0, 6.45, 13.2, 26.4, or 65.8 g L-1. One hundred mL slurries were incubated in capped bottles at 30 °C for four weeks. Biogas production was measured throughout the incubations, and the pH and concentrations of short-chain fatty acids were measured at the end of the incubations. Odor compounds of the final manure slurries were isolated by stir bar sorptive extraction and identified by stir bar gas chromatography/mass spectroscopy. Unamended manure had high concentrations of the typical manure malodorants phenol, p-cresol, p-ethylphenol, indole, and skatole. The addition of the sugars decreased these malodors in a dose-dependent manner. The addition of sugars shifted odor production to aliphatic esters including ethyl butyrate and propyl propanoate. The sugar-amended manure therefore had a different odor profile than the unamended manure did. The addition of sugar also caused the accumulation of short-chain fatty acids and, thus, decreased the pH of the manure. The production of lactic acid was particularly enhanced at high concentrations of sugar, suggesting that lactic acid bacteria could be responsible for changes in the odor profile. Future research will investigate if the addition of lesser concentrations of sugars or agricultural and food wastes rich in carbohydrates can reduce manure malodor.