| 초록 |
Anaerobic digestion (AD) of protein-rich wastes is limited by ammonia (NH3) inhibition, reducing CH4 production yield and necessitating feedstock dilution. Meanwhile, NH3 is increasingly valued as a carbon-free hydrogen carrier, prompting intensive research on its recovery from anaerobic digestate. However, due to the low concentration in digestate, a huge amount of energy is required for NH3 extraction. To solve these, in the present work, an NH3 fermentation-based two-stage AD (AF-TSAD) system was developed, in which both NH3 and CH4 were obtained with higher efficiency compared to the single-stage AD (SSAD). Gelatin was selected as a model substrate and fed to reactors with increased concentrations (14.3 -* 171.7 g COD/L, providing 2.0 -* 24.0 g TN/L). In SSAD, both biogas production rate (BPR) and NH3 concentration were gradually increased, reaching 3.7 L/L/d and 5.2 g TAN (total NH3 nitrogen)-N/L at 42.9 g COD/L, respectively, after which the drop of methanogenic performance was observed. On the other hand, in AF (the first-stage of AF-TSAD), targeting to produce highly-concentrated NH3 broth, 14.0 g TAN-N/L was attained at 143.1 g COD/L, which enabled the reduction of NH3 extraction thermal energy input by one-third compared to the SSAD. Then, the second-stage reaction of methanogenesis was conducted using the NH3-depleted effluent (1 g TAN-N/L), where a stable BPR of 5.0 L/L/d with a CH4 content of 90% was observed. Overall, AF-TSAD could reduce thermal energy input by more than 50% compared to SSAD, resulting in the net energy recovery of 10.9 kJ/g CODadded (42% enhancement).
|
