Volatile fatty acids as odor indicators in swine manure - A critical review

Determination of odor indicators in swine manure is critical for many aspects of developing effective odor control techniques. Past research has used volatile fatty acids (VFAs) as an odor indicator; however, using all VFAs can still be misleading. This article presents the available information regarding the mechanisms in microbiology and biochemistry of producing volatile fatty acids in swine manure and an extensive discussion on using VFAs as odor indicators. Long chain and branching VFAs (C₄-C₉) may represent the offensiveness of malodors in swine manure better than short and straight chain acids and thus should receive further research to correlate them with odor indicators. Two bacterial genera, Eubacterium and Clostridium, appear to be the most likely major contributors to the production of odorous compounds, such as volatile fatty acids, in swine manure. More research is needed to identify the species within these two genera to determine the types and quantities of odorous compounds produced by different species.