AMMONIA INHIBITION OF METHANOGENESIS FROM CATTLE WASTES

Ammonia inhibition of methanogenesis from cattle wastes was studied using laboratory scale, mesophilic and thermophilic fermentors fed beef-cattle manure (40 kg Volatile Solids per cubic meter) and various levels of 5N ammonium chloride. Results showed that ammonia inhibition began at about 2. 5 kg Nm** minus **3 for both thermophilic and mesophilic fermentations that were not previously acclimated to high ammonia concentrations and about 4 kg Nm** minus **3 for thermophilic fermentors previously acclimated to ammonia concentrations between 1. 4 and 3. 3 kg Nm** minus **3. This study also showed that assuming 'steady state' after three to four volume turnovers may lead to erroneous conclusions when inhibitory substances are present in the substrate.