Department of Agricultural and Biological Engineering, Purdue University, 225 S. University Street, West Lafayette, IN 47907, USA.
Department of Agricultural and Biological Engineering, Purdue University, 225 S. University Street, West Lafayette, IN 47907, USA.
J Environ Manage. 2015 Apr 1;152:91-8. doi: 10.1016/j.jenvman.2015.01.024. Epub 2015 Jan 21.
Volatile fatty acids (VFA) play an important role in the biodegradation of organic wastes and production of bioenergy under anaerobic digestion, and are related to malodors. However, little is known about the dynamics of VFA during dairy manure storage. This study evaluated the characteristics of VFA in dairy manure before and after anaerobic co-digestion in a laboratory experiment using eight lab-scale reactors. The reactors were loaded with four different types of dairy manure: (1) liquid dairy manure from a freestall barn, (2) mixture of dairy manure and co-digestion food processing wastes at the inlet of an anaerobic digester, (3) effluent from the digester outlet, and (4) the liquid fraction of effluent from a solid separator. Four VFA (acetic, propionic, butyric, and 2-methylbutyric acids) were identified and quantified in weekly manure samples from all reactors. Results showed that the dominant VFA was acetic acid in all four manure sources. The off-farm co-digestion wastes significantly increased the total VFA concentrations and the proportions of individual VFA in the influent. The dairy manure under storage demonstrated high temporal and spatial variations in pH and VFA concentrations. Anaerobic digestion reduced the total VFA by 86%-96%; but solid-liquid separation did not demonstrate a significant reduction in total VFA in this study. Using VFA as an indicator, anaerobic digestion exhibited an effective reduction of dairy manure odor offensiveness.
挥发性脂肪酸（VFA）在厌氧消化过程中有机废物的生物降解和生物能源生产中起着重要作用，并且与恶臭有关。然而，人们对奶牛粪便储存过程中 VFA 的动态变化知之甚少。本研究通过 8 个实验室规模的反应器进行实验室实验，评估了奶牛粪便在厌氧共消化前后 VFA 的特征。反应器中装入了 4 种不同类型的奶牛粪便：（1）自由放养牛舍的液体奶牛粪便，（2）进入厌氧消化器入口的奶牛粪便和共消化食品加工废物的混合物，（3）来自消化器出口的流出物，以及（4）固体分离器流出物的液体部分。从所有反应器的每周粪便样本中鉴定并定量了四种 VFA（乙酸、丙酸、丁酸和 2-甲基丁酸）。结果表明，所有四种粪便来源中的优势 VFA 均为乙酸。场外共消化废物显著增加了进水的总 VFA 浓度和各 VFA 的比例。储存中的奶牛粪便在 pH 值和 VFA 浓度方面表现出很高的时间和空间变化。厌氧消化将总 VFA 降低了 86%-96%；但在本研究中，固液分离并没有显著降低总 VFA。使用 VFA 作为指标，厌氧消化显示出有效降低奶牛粪便气味的不良性。
