Diesel Exhaust Fluid (DEF)

Diesel Exhaust Fluid (DEF) is a non-hazardous solution, which is 32.5% urea and 67.5% de-ionized water. DEF is sprayed into the exhaust stream of diesel vehicles to break down dangerous NOx emissions into harmless nitrogen and water. In maritime context, DEF is used in vessels with diesel engines to reduce the amount of harmful pollutants released into the atmosphere. The use of DEF is part of a process called Selective Catalytic Reduction (SCR) which is one of the most effective ways to reduce nitrogen oxide emissions which are a major source of air pollution. The SCR system injects DEF into the exhaust gas stream, where it reacts with the NOx to form harmless nitrogen and water. This process significantly reduces the emissions of NOx, a key contributor to smog and acid rain. DEF is stored in a separate tank on the vessel and is automatically injected into the exhaust system. The amount of DEF used is proportional to the amount of fuel burned, so the consumption rate of DEF varies depending on the engine load.