Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2001
Publication Date: 3/25/2001
Citation: Varel, V.H., Miller, D.N. 2001. Effect of carvacrol and thymol on odor emissions from livestock wastes. In: Proceedings of the 1st IWA International Conference on Odour and VOCs: Measurement, Regulation and Control Techniques, March 25-29, 2001, University of New South Wales, Sydney, Australia. p. 231-236.
Interpretive Summary: Stored manure from livestock production facilities contain pathogenic microorganisms and produce offensive odors as a result of microorganisms fermenting these wastes. In laboratory studies we have identified two chemicals, carvacrol and thymol, which can be added to cattle and swine wastes to stop the fermentation. These two chemicals are oils that can be extracted from plants; thus, they are natural products which we assume would not be harmful to the environment. These chemicals, 2000 ppm and 2500 ppm for cattle and swine wastes, respectively, inhibited the production of the primary source of odor, short-chain volatile fatty acids, for 23 days. We conclude that these chemicals may be useful as antimicrobial agents to control pathogens and odor in stored livestock waste. Field tests are needed to determine the economics and usefulness of these agents in production facilities.
Technical Abstract: A majority of the beef cattle and swine in the United States is produced in confined facilities. This generates significant environmental pollutants from the waste produced, including global warming gases, odor, and pathogens. Our objectives of this study were to control the fermentation activity and pathogens in cattle and swine wastes with antimicrobial plant essential oils. Anaerobic one-liter flasks with a working volume of 0.5 liter were used to evaluate the effect of carvacrol and thymol on production of fermentation gas, short-chain volatile fatty acids, lactate, and bacterial populations. In cattle waste, 1 g l**-1 each of carvacrol and thymol completely inhibited the production of volatile fatty acids and lactate over 23 days. In swine waste, 2.5 g l**-1 carvacrol inhibited the production of all volatile fatty acids. We conclude that these essential oils are effective in controlling livestock waste odor emissions and field studies are warranted.