Ammonia is more stable, less expensive, and less corrosive than other amines. However, ammonia boils at -33 o C and has a high vapor pressure, leading to rapid loss of absorbent and deterioration of absorption capacity. Ammonia loss can be mitigated by absorption of CO2 at low temperature, but the absorption efficiency is compromised and the energy requirements for cooling decrease energy efficiency. Washing with water or acids also improves ammonia retention, 48, 49 but generates large amounts of wastewater or chemical waste.