According to the European Union (EU) Green Deal, the greenhouse gas (GHG) emissions from water resources should be reduced by 30% until 2030. Dam lake treatment is one of the main important GHG resources according to the European Union (EU) Green Deal. Due to the natural texture of dam lakes, they emit nitrous oxide (N₂O) emissions at higher amounts. The main aim of this study was the reduction of the N₂O emissions resulting from dam lake treatment using malt dust-derived biochar. The biochar was derived from malt dust using a slow pyrolysis process under three various temperatures:250 (M1), 300 (M2) and 500 °C (M3). A biochar adsorption process was applied as not only as a water treatment technique but also a nitrous oxide emission reduction method. Before and after the biochar adsorption process, N₂O was sampled and measured seasonally using gas chromatography equipped with an electron capture detector (GC-ECD). The water samples were taken seasonally from Ataturk Dam Lake inTurkey. Also, the GHGs originating from water treatment was collected and adsorbed using the same biochar to determine the experimental nitrous oxide capture ability of biochar in a gas adsorption column. On average, a 21.1% reduction in N₂O emissions from dam lake treatment was reported using malt dust-derived biochar. The maximum nitrous oxide capture capacity corresponded to the malt dust-derived biochar produced at the minimum temperature (M1). This study verified that malt dust-derived biochar was an efficient N₂O adsorbent and air pollutant disposer. The Box–Behnken experimental design method was performed using MATLAB to determine the optimum operating parameters for the minimum N₂O emission. The statistical analysis results revealed that the optimum parameters were 4 mg/L of dissolved oxygen (DO) and 11 mg/L of nitrate (NO₃^-) concentration for the minimum N₂O emission.