Diesel Exhaust Fluid Storage Considerations for the Upcoming Summer Months

In today’s world, having a newer fleet of trucks means using Diesel Exhaust Fluid (DEF). DEF is a mixture of high purity synthetic urea and deionized water that is injected into a trucks active Selective Catalytic Reduction system (SCR).  As exhaust gases exit the engine, they enter the SCR where DEF is injected onto a catalyst setting off a chain of chemical reactions. These reactions cause the nitrogen oxides (NOx) to convert into nitrogen, water, and small quantities of carbon dioxide (CO2), reducing the overall tailpipe emissions and NOx levels to nearly zero. In addition to lowering emissions, this cost-effective SCR system gives the added benefit of reducing fuel consumption by 3-4%.

With spring in full bloom, it’s a good idea to brush up on proper storing techniques to maintain DEF integrity. According to the International Organization for Standardization (ISO 22241), DEF should be stored in a cool, dry location, and at a temperature between 12⁰F and 86⁰F. It is also recommended DEF be stored out of direct sunlight. The temperature at which DEF is stored will determine the recommended shelf life with higher storage temperatures resulting in a shorter shelf life. Among many truck drivers and equipment operators, there is a debate regarding just how closely these recommendations should be followed, with some using climate-controlled environments and others storing DEF outdoors.

What happens to Diesel Exhaust Fluid at higher temperatures? When the temperature of DEF, not the outside air but the liquid itself, exceeds 86⁰F it is possible for some of the synthetic urea and water to react. This can cause the formation of ammonia and CO2. DEF is injected onto the hot catalyst creating ammonia and small amounts of carbon dioxide. The CO2 is release and the ammonia converts the nitrogen oxides (NOx) into nitrogen gas (N2) and water. Knowing this, can lead to one side of the argument. However, degradation of stored DEF can result in losses of urea and ammonia.

In today’s fast-paced economy, most users find turning over DEF fluid not to be an issue, thus shelf life and degradation will not have the same effect on everyone. It is recommended that users follow the guidelines provided for proper DEF storage set forth by the ISO. Some additional considerations:

  • Keep out of direct sunlight, storing inside a garage or warehouse.
  • If needed, use canopies or shaded areas for outdoor storage.
  • Selecting the appropriate container size that allows you to turnover inventory regularly.
  • Always keep fluids tightly sealed.
  • Keep all storage containers and dispensing equipment clean and free of contaminates.
  • Use quality American Petroleum Institute Certified DEF.




How to Winterize Diesel Exhaust Fluid (DEF) (motortrend.com)

ISO – ISO 22241-1:2019 – Diesel engines — NOx reduction agent AUS 32 — Part 1: Quality requirements



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