Mitigation of NH3 emission from pig house using a rice husk biochar column and fertilizer potential of collected biochar

NH₃ emissions have significant implications for ecosystems and human health. Pig houses are important sources of NH₃ emissions. This study aimed to evaluate the NH₃ adsorption capacity of rice husk biochar (RHB), its effectiveness in mitigating NH₃ emission from pig house using a RHB column, and the fertilizer potential of the collected RHB for maize growth. In a laboratory assay, NH₃ adsorption by RHB was measured using a closed chamber where NH₃ was diffused from NH₄OH. NH₃ adsorption in RHB packed in column was the highest at a flow rate of 2.0 L min^-1 (6.52 mg g^-1). H₂SO₄-mixed RHB enhanced NH₃ adsorption by 41.7% compared to RHB alone. When compared the efficiency of RHB column in NH₃ emission, the emission reduced by 34.5% and 58.2%, respectively, after passing RHB and H₂SO₄-mixed RHB columns compared to that measured without column (0.59 g d^-1). In a pig house setting, NH₃ concentration after passing the columns of control, RHB, and H₂SO₄-mixed RHB was in average 14.8, 8.5, and 3.9 mg m^-3, respectively, during experiment period. Cumulative emissions were reduced by 42.6% and 73.3% using RHB and H₂SO₄-mixed RHB columns, respectively. The application of RHBs collected from the column significantly increased dry matter and crude protein production in maize, with notable enhancement by H₂SO₄-mixed RHB application. These results demonstrate the integrated effectiveness of RHB application in NH₃ management, in which NH₃ emissions from the pig house are adsorbed using RHB column, and the NH₃-adsorbed RHB collected from column is recycled through the soil to support plant growth.