Influencing mechanisms of different additives on ammonia–nitrogen emission during aerobic composting

Abstract This study investigated the effects of biochar, fly ash, and biomass power plant ash on ammonia–nitrogen (NH 3 ) emission reduction and nitrogen retention during aerobic composting (AC) of chicken manure and corn straw. In detail, 9 groups treated with different proportions (4, 8, and 12%) of additives (biochar, fly ash, and biomass power plant ash) were designed through 21-day AC experiments. Further, the impacts of different temperatures (20, 40, and 60 °C) on nitrogen emission were explored and analyzed. Results showed that 8% biochar (T 1-2 ) reduced total NH 3 emission by 54.83% and peak emission by 70.26%, while increasing final total nitrogen by 22.40% versus the control. At the same time, it significantly increases the content of nitrate nitrogen and optimizes the nitrogen-transformation efficiency. Fly ash (T 2-2 ) and biomass power plant ash (T₃-₁) achieved 35.61 and 42.34% inhibition rates, respectively. Temperature experiments revealed optimal NH 3 suppression at 20 °C (T20), while 60 °C (T60) enhanced total nitrogen by 39.8% and organic matter degradation by 30.91%. Excessive additive proportions (12%) prolonged high-temperature phases, diminishing efficacy. The optimal strategy combines 8% biochar addition at 20 °C (initial stage) to mitigate NH 3 volatilization, followed by maintaining 60 °C to ensure composting efficiency and nitrogen retention. This approach balances emission reduction and nutrient conservation in AC processes.