Effective ammonia recovery from swine excreta through dry anaerobic digestion followed by ammonia stripping at high total solids content

• Thermophilic condition favors ammonia production during dry anaerobic digestion.
• Ammonia production has strongly negative linear relationship with manure's TS.
• First-order kinetic models well fit the dry ammonia fermentation process.
• 65% of organic-N conversion was achieved under optimal 8 days' dry AD conditions.
• > 90% of TAN in swine manure was recovered by dry AD and stripping at 20% TS.

This study investigated ammonia recovery from swine excreta through dry anaerobic digestion (AD) and ammonia stripping. The effects of different operation conditions including temperature (25–55 °C), total solids (TS, 20%–35%) and initial pH (7.0–12.0) were assessed on ammonia production in terms of organic nitrogen (organic-N) conversion and process kinetics through 8 days' trials. All experimental data fitted well to the pseudo first-order kinetic models during dry AD and the maximum organic-N mass conversion ratio was estimated to be 65.1% when dry AD was conducted at 55 °C, 20% TS, and initial pH 10.0. Changes in biogas production and its composition signaled the bioactivity of the bacteria involving in ammonia production from swine excreta during dry AD. Finally, greater than 90% of the total ammonia nitrogen (TAN) in swine excreta was efficiently recovered by air stripping at TS about 20%. Restated, the combination of short-term dry AD with ammonia stripping achieved about 60% of total nitrogen recovery efficiency.