Effect of carvacrol and thymol on odor emissions from livestock wastes

A majority of the beef cattle and swine in the United States is produced in confined facilities. This generates significant environmental pollutants f rom the waste produced, including global warming gases, odor, and pathogens . The objectives of this study were to control the fermentation activity an d pathogens in cattle and swine wastes with antimicrobial plant essential o ils. Anaerobic one litre flasks with a working volume of 0.5 l 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 gl(-1) each of carvacrol and thymol completely inhibited the production of volatile fatty acids and lactate over 23 days. In swine waste, 2.5 gl(-1) carvacrol inhibited the production of all volatile fatty acids. We conclude that these essential oils are effective in controlling l ivestock waste odor emissions and field studies are warranted.