Low-energy ammonia production from organic solid wastes through continuous ammonia fermentation

초록

To extract ammonia (NH3) efficiently from anaerobic digestate, a novel approach is to generate high-concentrated NH3 broth through ammonia fermentation (AF). However, studies on AF are limited, and in particular, the continuous operation using actual wastes has not been investigated. Here, four fermenters fed with sludge cake (SC) at 100 g COD/L and chicken manure (CM) at 100/200/300 g COD/L were operated under reduced hydraulic retention time (HRT). SC maintained the NH3 conversion efficiency of 51–57 % until HRT 3 d, with a drop to 33 % at HRT 2 d, while in CM, it was maintained at 67–76 % until HRT 1 d. The different performance was linked to their amino acid composition, revealed by two additional fermenter operation fed with the mixture of amino acid mimicking SC and CM. For SC, amino acid degradation dropped to 38 % at HRT 2 d, while in CM, stable performance was maintained down to an HRT 8 h, with conversion efficiencies of 84–90 %. NH3 concentration was also increased in CM broth at the higher concentrated substrate (from 4.0 → 11.6 g TAN-N/L), reducing the specific energy consumption in the air-stripping process by three-fold. Finally, bacterial analysis revealed significant community differences between the microorganisms responsible for SC and CM degradation, with a complete shift from the initial inoculum. © 2025 Elsevier B.V.

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