Ammonia Inhibition in High-Solids Biogasification: An Overview and Practical Solutions

TLDR

Ammonia inhibition in biogasification arises from free ammonia disrupting biochemical pathways of nitrogenous compounds, thereby reducing digester performance. The study reviewed literature and UC Davis pilot data, evaluating two mitigation strategies—dilution with fresh water and adjusting feedstock C/N ratio—to counter ammonia inhibition. Pilot experiments showed inhibition at 1200 mg L⁻¹ ammonia, and both dilution and C/N adjustment proved practical and effective.

Abstract

A comprehensive literature search was conducted to evaluate ammonia inhibition in biogasification. An overview of ammonia inhibition including the fundamentals of biochemical pathways of nitrogenous compounds, ammonia inhibition mechanisms and impact of free ammonia inhibition was conducted. Past studies and the experience gained with the pilot project at the University of California, Davis (UC Davis) were reviewed and discussed. Long-term experimental studies at the pilot scale revealed that ammonia inhibition in a high-solids thermophilic anaerobic digestion occurs at ammonia concentration of 1200 mg l−1. Two methods: (1) dilution of digester content with fresh water and (2) adjustment of feedstock C/N ratio were evaluated to mitigate ammonia inhibition. Both methods were found to be practical and effective.