Mitigation of nitrogen in the poultry litter to enhance biomethane production

The objective of the study is to lower the nitrogen content in the substrate to mitigate the ammonia nitrogen generated in the anaerobic digestion of poultry litter using air stripping technique. The effect of nitrogen mitigation on the biomethane yield from poultry litter was studied in batch experiments with an organic load of 8 kg for a hydraulic retention time of 21 days in mesophilic ambiance. Air stripping results indicate that the free ammonia stripping is greatly influenced by the pH of the substrate and the aeration time. It is observed that the total Kjeldahl nitrogen content in the poultry litter substrate is reduced from 6.9% to 3.69% that is about a reduction of 53%. A significant improvement in the biomethane yield was noticed for poultry litter of which nitrogen content is lowered at a pH 11. The cumulative yield for air stripped substrate increased from 8.77 L/kg to 10.66 L/kg volatile solids. The biomethane production from air stripped poultry litter shows improvement of 18% compared to the control test. From this results, it is evident that the reduction in the nitrogen content of the substrate using air stripping at high pH value is a possible option for enhancing the biomethanisation of poultry litter.