What is selective catalytic reduction (SCR)?
Selective catalytic reduction is the process whereby a reductant such as ammonia or urea is mixed with NOx emissions then passed through a special flow-through catalyst to create a reduction process. During the process, the ammonia-NOx mixture is converted into harmless nitrogen and water. SCR catalysts can be made of either vanadium-based or iron zeolite-based. Vanadium is classified as toxic. Iron zeolite catalysts are non-toxic and considered a safer alternative for SCR systems.
