The objectives of this paper are to determine the effectiveness of bioadditive in the form of yeasts and zeolite in reducing odour and ammonia emissions during composting and to assess its effects on the process. Two series of experiments were conducted. The higher dosage treatments reached thermophilic temperatures sooner and the high temperatures stayed longer. The application of bioadditive at 10% (w/w) resulted in a greater degree of degradation and ammonia emission was reduced by 50%. Odour emission analysis generates mixed results, though lower odour concentrations and a 12% decrease in total odour emission were observed with higher dosages.