At the mid-year meeting of the Association of Responsible Recyclers (NORA) in Chicago, Ill., U.S.A., members of the Antifreeze Working Group discussed the issue of antifreeze being contaminated with diesel exhaust fluid (DEF). The group discussed ways that urea from DEF ends up in antifreeze streams, creating ammonia, and ways to alert manufacturers of this.
DEF is a solution of 32.5% urea and distilled water, and is meant to lower the concentration of nitrogen oxides (NOx) in the exhaust of diesel vehicles. When heated, it releases carbon dioxide and ammonia. This happens in the exhaust system as well as in the cooling system. The recycling process can remove some of the ammonia from antifreeze, but not all of it, so it is essential that when the used antifreeze is collected, DEF is not collected with it.
There are other possible sources of DEF in used antifreeze, such as line washes in bottling facilities. The working group recommends that bottlers test their lines and segregate the two fluids. The group has also drafted laboratory and field procedures that manufacturers could use to test for urea. This is not yet a NORA Standard Operating Procedure, but the group hopes member-companies will try this recommendation and report on whether it is helpful.
NORA has also sent a letter to member-companies to distribute to their customers who generate used ammonia. The letter says that even a few parts per million of ammonia in antifreeze can cause corrosion of soft metals, such as the aluminum in radiators. Ammonia can also raise the pH, which has a similar corroding effect. Therefore, even though DEF is not toxic (urea is a common fertilizer), it must be kept away from antifreeze. The letter informs used antifreeze generators that antifreeze with any amount of DEF will not be accepted for recycling.
NORA has also sent a letter to DEF manufacturers, asking for assistance in educating customers about mixing these fluids destined for recycling.