High levels of ammonia nitrogen for biological biogas upgrading

Abstract This study aimed to propose a novel method for ex-situ biogas upgrading by adding ammonium chloride to increase the concentration of ammonia nitrogen. The results showed that ammonia nitrogen had a significant effect on biogas upgrading. The maximum content of CH4 reached 94.1% when the concentration of ammonia nitrogen was 5500 mg/L. At the same time, CH4 yield of increased by 57.5%. High throughput sequencing results showed that the relative abundance of hydrogenotrophic methanogens reached 73.1%, while that of acetotrophic methanogens was only 1.3%, which greatly increased the content and yield of CH4. For the bacterial community, Clostridium was the dominant bacteria and the ammonia nitrogen concentration had little effect on it. These results demonstrate that upgrading biogas by increasing the concentration of ammonia nitrogen is feasible.