Why Peeing in Your DEF Tank is a Terrible Idea
Misinterpretations can be a source of entertainment, even when you’re talking about something as mundane as urine and DEF (diesel exhaust fluid). Somewhere along the line a rumor gets started, it spreads slowly, somehow sounds like a good idea, builds in momentum and then the next thing you know, it’s a “thing.” Like peeing in your DEF tank. Yep. Urine and DEF as an interchangeable match has somehow become an acceptable practice in some circles. But in case you’re wondering, it is not in fact an acceptable practice, ever. Here’s why:
Urine and DEF Are Not Created Equal
DEF is a non-hazardous, aqueous solution made up of 32.5% urea and 67.5% de-ionized water. Used in the selective catalytic reduction (SCR) systems of diesel engines years 2010 and later, diesel exhaust fluid reduces the amount of particulate matter in the form of noxious gas emissions, primarily nitrogen, from the atmosphere. Now for a biology lesson: Urine is defined as, “A watery, typically yellowish fluid stored in the bladder and discharged through the urethra. It is one of the body’s chief means of eliminating excess water and salt and also contains nitrogen compounds such as urea and other waste substances removed from the blood by the kidneys.” The chemical makeup of human urine contains the following:
- Urea: 9.3 grams/L (In contrast, DEF requires 32.5% urea)
- Chloride: 1.87 grams/L
- Sodium: 1.17 grams/L
- Potassium: 0.750 grams/L
- Creatinine: 0.670 grams/L
- Other dissolved ions, inorganic and organic compounds
Human urine (as well as urine from other animals) contains a much different urea content than is required for the making of DEF. It also contains additional compounds and dissolved ions that a diesel engine’s catalytic reduction system (SCR) cannot handle. On top of the differences in chemical makeup, human urine has a much higher concentration of water (95%, while DEF is 67.5% de-ionized water) and that water contains an abundance of ions and minerals that are also not appropriate for an SCR system. Diesel exhaust fluid requires de-ionized water, which is both de-ionized and de-mineralized. To de-ionize water, a highly specialized filtration device is necessary, with ample testing to ensure the quality and purity of filtration. Therefor, both DEF and urine contain urea and water, but that does not mean the two are interchangeable, or that urine is somehow an adequate substitute for DEF. In short, the combination of urine and DEF is a very bad idea.
Naturally Occurring versus Synthetic Urea
Urea is an organic compound that is also referred to as carbamide. The chemical formula of urea is CO(NH2)2, and it is across the board, whether in the human body or in a diesel engine, important for the metabolism and chemical reactivity of nitrogen-containing compounds. Urea is colorless, odorless, solid and highly soluble in water. It has a neutral pH, neither acidic or alkaline when dissolved in water, and the body uses it in many ways for the urea cycle – a series of biochemical reactions that produce urea as the end product from ammonia (NH3). In 1828, German organic chemist, Friedrich Wöhler discovered that urea can be created using inorganic elements. As a result of his discovery – considered a milestone in the field of modern chemistry – it was proven that a substance originally recognized as only being produced through natural processes could in fact be synthesized. Wöhler’s discovery paved the way not only for the development of synthetic, highly refined urea for commercial purposes such as the manufacture of DEF, but that many other chemical compounds for industrial and pharmaceutical use can be synthetically derived.
The Big Business of Urea
The human race as a whole relies heavily upon the development of urea as a critical element for agriculture and the production of food. Over 90% of the world’s urea is allocated for agriculture to be used as a nitrogen releasing fertilizer. Urea has the highest Nitrogen content of any of the nitrogen containing fertilizer options available and is readily absorbed by plants, which promotes significant foliar growth. It finds its way into many chemical and industrial applications, from medical to automotive, but nothing in comparison to urea’s prominent role in the agricultural sector. Commercial grade urea, such as what is used in the manufacture of DEF and AdBlue – the specific non-hazardous aqueous urea formulation (AUS32) designed by the European Union to meet their stringent emissions legislation – is made up of synthetic ammonia and carbon dioxide. When subjected to high heat, the solution can be produced into either a liquid or solid form. DEF is most commonly manufactured in a prill, or granular form. The higher grade, “environmental” urea used to make DEF has had all contaminants removed to maintain the cleanliness and integrity of a diesel engine’s SCR system, which is designed to be highly sensitive to any and all contamination. In contrast, urea designated for agricultural use as a fertilizer is solutionized with additional chemicals such as formaldehyde and is far less pure in its chemical composition. Urea is produced on a massive industrial scale, and in 2012 it was estimated that worldwide production capped out at 184 million tons. Besides fertilizer and DEF, some additional ways that urea is used include road de-icing rock salt, tooth whitening products, the flame proofing chemicals found in fire extinguishers, dish soap, as an additive for textile dye, and for hair removal products such as Nair.
Where It Comes From
The most common types of urine that people think go into the making of urea for DEF – urine from cows and bats, which is not correct. Contrary to popular myth, cow and bat urine and DEF are not a thing. The urea used in the manufacture of DEF is synthetically derived from ammonia and carbon dioxide, and urea production plants are often adjacent to other sites where ammonia is produced, such as coal and natural gas refineries. This allows for the capture of hydrocarbons from ammonia plant feedstocks to be used in the manufacture of urea, rather than allowing harmful emissions to enter the atmosphere, and eliminating the need to purchase ammonia as a separate commodity. In short, it is easier and more economical to manufacture urea on-site or nearby where ammonia is already being produced.
The Bottom Line on Urine and DEF
Diesel exhaust fluid is not made of urine, and if you are going to urinate in your SCR system, you’re looking at having to pay some pretty hefty repair costs to clean and replace engine components once they have been contaminated. Following the deductive reasoning that urine has urea in it, therefore, urine + water = DEF is 100% wrong, and will cause you a myriad of expensive mechanical problems. The urea found in urine is not in the proper concentration needed for DEF, nor is it of a sufficient level of purity, in either urea or water. The bottom line, to spell it out just one more time… urine and DEF = Never. DON’T PEE IN YOUR DEF TANK!
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