Effects of Cattle Manure and Swine Slurry Acidification on Ammonia Emission as Estimated by an Acid Trap System

This study was conducted to assess the efficacy of slurry acidification in reducing ammonia emission from manure storage and application. The non-fermented cattle manure (NFC) and swine slurry (SS) were acidified by sulfuric acid and stored in an acryl chamber for 168 and 96 hours, respectively. Ammonia emitted from the chamber was collected using an acid trap system. The amount of ammonia emission was significantly reduced when the livestock manures were treated with sulfuric acid. The absolute amount of ammonia in NFC increased rapidly starting from 48 h and 72 h in the control (pH 8.6) and acidified NFC (pH 6.5), respectively. The absolute amount of ammonia was the highest at 96 h ($3.65g\;kg^{-1}h^{-1}$) in the control and at 144 h ($2.34g\;kg^{-1}h^{-1}$) in pH 6.5 NFC. The cumulative ammonia content in the control continuously increased until 96 h and was maintained until 168 h, whereas the increase rate of emission gas accumulation in acidified NFC was much less throughout the experimental period. Acidification of SS mitigated ammonia emission as proven in NFC. The cumulative amount of ammonia emission was decreased by 49.4% and 92.3% in the acidified SS at pH 6.5 and pH 5.5, respectively, compared to the control at 96 h after treatment. These results indicate that ammonia emission can be significantly reduced by sulfuric acid treatment of livestock manure during processing and the subsequent land application.