Emission rates of odorous compounds from pig slurries

Techniques to identify odorous compounds and to determine their emission rates from liquid wastes are described. Odorous compounds, or odorants, were analysed by GC‐MS and odour concentration was measured by olfactometry after being emitted from slurry under controlled environmental conditions using a specially designed odour emission chamber. The slurries were obtained from pigs fed commercial and reduced crude protein diets and stored for 6 weeks, the effects of age and sex upon the odours produced in the headspace of the chamber were evaluated. The major odorous compounds were identified as belonging to the sulphide, volatile fatty acid, phenolic and indolic chemical groups. The mean emission rates from 200 litres of stirred slurry samples with a surface area of 1 m2 using a wind speed of 4 m s−1 were 1·35 million Odour Units min−1 for odour and 214, 2·15, 0·21, 0·44, 0·068 and 0·02 mg min−1 for hydrogen sulphide, ammonia, phenol, 4‐methyl phenol, 4‐ethyl phenol and indole respectively. Sex and sex/diet interaction effects were demonstrated for emission rates. © 1998 SCI.