Agriculture, Ecosystems and Environment 78 2000 93–106
Review
A review of microbiology in swine manure odor control
Jun Zhu
∗
Biosystems Agricultural Engineering, University of Minnesota, Southern Experiment Station, 35838-120th Street, Waseca, MN 56093, USA Received 15 April 1999; received in revised form 16 July 1999; accepted 30 July 1999
Abstract
Generation of odors is a complex process that involves many bacterial species, producing an extensive array of volatile organic compounds under different manure storage systems currently used. A lack of understanding of the basic microbiology
in manure leads to a poor odor prevention and control from animal wastes. This review covers pertinent available information about the indigenous bacterial genera in swine manure and their potentials of producing odorous volatile compounds. It
addresses not only the odorous compounds in swine manure but also the inherent relations between the bacterial species and the related compounds. It also discusses several odor control techniques that have been developed based on microbial
activities and the limitations with these techniques. Two bacterial genera, Eubacterium and Clostridium, are most likely the major contributors to odorous volatile fatty acids. It appears that anaerobic lagoons may not be an appropriate choice for
treating swine manure for odor control due to the reduced methonogenic activities resulted from the low temperatures in lagoon liquid. Also, it seems questionable that the microbial-based manure additives will work, without aeration, in a real
storage system for the purpose of odor control. ©2000 Elsevier Science B.V. All rights reserved.
Keywords: Microbiology; Swine manure; Odor control
1. Introduction
The trend toward high-density, confinement rear- ing of hogs has increased tremendously in recent
years. Associated with this increase is the air pol- lution problem odors which has become a center
of public concern. This is reflected in the increased frequency of odor-related complaints in areas where
swine production facilities are more intensified. Odor management is currently impacting many aspects of
the swine industry and there appears a potential that the sustainability, productivity, and profitability of
swine producers will be dependent upon whether they
∗
Tel.: +1-507-835-3620; fax: +1-507-835-3622. E-mail address: zhuxx034tc.umn.edu J. Zhu.
can reduce the emission of offensive odorants from operating swine production units to a level which
surrounding communities could tolerate. Therefore, there exists an acute need for effective methods of
odor control, for if the swine industries are to coexist with their neighbors, such control measures will have
to be put into operation.
Microbial activities are normally considered to be responsible for the malodor generation from the stored
swine manure slurry. As a matter of fact, microbes play a major role in both production and reduction of
malodors. In odor generation, the odorous volatile or- ganic compounds are the normal end products or inter-
mediate products of fermentative degradation of fecal substances by anaerobic bacteria. In odor reduction,
many odor control techniques that are being developed
0167-880900 – see front matter ©2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 8 8 0 9 9 9 0 0 1 1 6 - 4
94 J. Zhu Agriculture, Ecosystems and Environment 78 2000 93–106
rely on the microbial properties in the swine manure. Since the malodor originates from microbial activi-
ties involving a variety of microbes, understanding the characteristics of the microflora present in swine ma-
nure is essential for developing effective odor control techniques.
This paper reviews the available information in the literature related to the types of bacteria in swine ma-
nure, the potential odorous compounds associated with different bacterial genera, and the corresponding tech-
niques used to control odor based on microbiological principles. Areas that need further research are also
recommended.
2. Microflora in swine manure and odor indicators
