摘要：The development of new options to reduce ammonia (NH<sub>3</sub>) emissions during slurry manure storage is still required due to the shortcomings of the current technologies. This study aimed to identify to what extent untreated and acid-treated biochar (BC) and pure acids could reduce ammonia nitrogen (NH<sub>3</sub>-N) volatilization and increase nitrogen retention in slurry digestate. The NH<sub>3</sub>-N emissions were effectively reduced by H<sub>2</sub>SO<sub>4</sub> and H<sub>3</sub>PO<sub>4</sub> acids, untreated BC when applied mixed into the digestate and acidified BC treatments applied on the surface of the digestate. Acidification increased the specific surface area and number of O-containing surface functional groups of the BC and decreased the pH, alkalinity and the hydrophobic property. Compared to untreated BC, the ability of BC to reduce NH<sub>3</sub>-N emissions was greater when it was acidified with H<sub>2</sub>SO<sub>4</sub> and applied to the digestate surface. The effect on digestate pH of acidified BC when applied mixed into the digestate was not different, except for H<sub>2</sub>O<sub>2</sub>, from that of the addition of the respective pure acid to digestate. The total N concentration in digestate was not significantly correlated with NH<sub>3</sub>-N emissions. These findings indicate that acidified BC could be an effective conditioner to reduce NH<sub>3</sub>-N emissions from slurry digestate storage.
