Effect of low-dose liquid ozonation on gaseous emissions from pig slurry

The effect of low-dose liquid ozonation on gaseous emissions from pig slurry was investigated in a laboratory-scale ozonation chamber. The slurry samples were ozonated and/or mixed for 8 to 80 min in order to achieve ozone doses of 20–200 mg [O3] l−1 of slurry. The hydrogen sulphide (H2S) emission rate from ozonated slurry samples was lower than from non-ozonated controls and had lower H2S emissions than the controls for at least 5 h after treatment. The highest H2S reduction in emission rate (98%) was reached when applying 80 mg [O3] l−1. This implies that ozonation of slurry could be used as a means of reducing H2S emissions during soil application and thereby the immediate odour nuisance, although there were no change to emissions of other odour compounds such as volatile fatty acids (VFA), phenols and indoles. The concentration of total ammoniacal nitrogen (TAN) was not affected by ozonation. However, the ammonia (NH3) emission rate increased in proportion to mixing time, and slurry ozonation tended to increase the NH3 emission rate even further, though the concentration of total ammoniacal nitrogen (TAN) was unchanged. Hence the risk of higher NH3 emissions limits the application potential of slurry ozonation.