Going Green: How to Dispose of DEF Fluid


The EPA (Environmental Protection Agency) conducted a study in the 1990s and found that diesel engines were among the worst polluters in the U.S. As a result, they required manufacturers to begin a 4 phase emission reduction program from 1996 to 2014. They focused on two types of pollution, particulate matter (smoke) and nitrogen oxide or NOx gas. 

Today’s diesel engines emit 100 times less pollution than in 1996. In other words, one 1996 model diesel engine put out as much pollution as 100 modern diesel engines. Most of this reduction is due to a fluid injected into the exhaust system. It’s called Diesel Exhaust Fluid or DEF. Every diesel engine on the road and off, between 174 and 750 hp, uses DEF. But what happens when you no longer need DEF, it becomes contaminated, or it reaches its expiration date? 

This article explores how to dispose of def fluid, the dangers of improper disposal, and how to clean up any spills safely. 

What is DEF, And What Are Its Benefits for Diesel Engines

Diesel Exhaust Fluid (DEF) is a colorless and odorless solution with 32.5% urea and 67.5% deionized water. DEF is an essential component of the  Selective Catalytic Reduction (SCR) system. It reduces polluting diesel engine emissions by 70% to 95%. Besides combating air pollution, DEF improves fuel efficiency and engine performance by optimizing combustion. 

The purpose of the Selective Catalytic Reduction (SCR) system is to reduce pollution from diesel exhaust. As the hot exhaust gases flow from the engine, DEF sprays onto a catalyst creating a chemical reaction with the exhaust. The catalyst converts the NOx gases into nitrogen, water, and carbon dioxide, which are natural components in the air. 

What are DEF’s characteristics? It is a non-toxic, stable, and colorless liquid. DEF is Non-polluting, non-flammable, and non-hazardous. 

DEF can freeze at 12°F (-11°C), and degrade at high temperatures, so proper storage is critical. Although non-toxic, the urea is corrosive to most metals and coatings. Proper disposal is necessary, which we will cover in a moment. For more information, visit our DEF reference guide.

How to Store DEF and How Long It Lasts

Proper storage of DEF is crucial to maintain its effectiveness and quality. Store DEF in a dedicated tote or tank specifically for this purpose. DEF tanks are typically made of non-reactive materials such as high-density polyethylene (HDPE) or stainless steel to prevent contamination. All handling equipment must be non-reactive to DEF, including the pumps, hoses, fittings, and thread seals.

When storing DEF, be aware of the ambient temperature if you live in very cold or hot regions. To protect it from freezing, use DEF tank storage heaters to maintain the ideal temperature. 

The shelf life of DEF depends on the storage conditions. Adequately sealed and stored between 50°F and 75°F (10°C to 23.8°C), DEF can retain its quality and effectiveness for 12 to 24 months. If it’s cloudy or has a color, the product is old or contaminated, and you should not use it.

ISO 22241 is the guideline for handling DEF. It’s so sensitive to impurities that even 0.1 teaspoon of metals like copper, zinc, chromium, nickel, or 0.3 teaspoon of iron can contaminate an entire 5,000-gallon tank, causing it to become out of spec. Using contaminated DEF will ruin the SCR system, and you have no choice but to dispose of it.

Do’s and Don’ts of How to Dispose of DEF Fluid

Contaminated DEF cannot be purified; no known filtration process can restore it, so proper disposal is the only option. Depending on the contaminant, you can clean a contaminated DEF tank with deionized water or clean DEF. However, it may be less expensive to dispose of the tank to avoid compromising the engine’s SCR system. Check with the DEF supplier or engine manufacturer.

The question remains, how do you dispose of old DEF fluid? Follow the appropriate guidelines to minimize environmental impact:


  1. Dispose of DEF in accordance with local regulations and guidelines. 
  2. Check with your local waste management authority or hazardous waste materials recycling center for specific instructions.
  3. If possible, recycle empty DEF containers. Many recycling facilities accept empty containers made of HDPE or stainless steel.


  1. Do not dispose of DEF in regular trash or landfills to prevent contamination of the environment.
  2. Avoid pouring DEF onto the ground or into storm drains, as it can enter waterways and harm aquatic ecosystems.
  3. Do not mix DEF with other substances or chemicals, which may cause adverse reactions.

There is some ambiguity regarding DEF Disposal Regulations. Many forums suggest using it as fertilizer on your lawn because the urea is 46% nitrogen. We can’t recommend doing that because it can contaminate groundwater.

The Dangers of Improperly Disposing of DEF

DEF is a non-hazardous substance used as intended but can contaminate ground or surface water if dumped in heavy concentrations.

DEF’s active ingredient is urea, an ingredient in lotions, skin creams, explosives, hair removers, plastics, dish soaps, and power fuel cells. DEF is not overly toxic to humans but can irritate the eyes, skin, and respiratory tract, so it’s best to use proper PPE, such as gloves and goggles, when handling it.

If dumped into ponds or lakes, urea can cause unwanted algae blooms that will disrupt the ecosystem. If urea mixes with certain oxidants, chlorides, and nitrites, it can cause fire or even explosions.

How to Safely Clean Up A Spill Or Leak

In the event of a spill, use a spill containment kit as you would for diesel. The kit will have absorbent pads or granules to soak up the fluid and a sealable container for disposing of the used materials. For small spills, use the absorbing materials to soak up the liquid. Contact a professional environmental cleanup service for proper handling and disposal of large spills. 


Here are four of the most common questions people have about handling diesel exhaust fluid.

1. Can I Dump DEF On the Ground? 

We do not recommend dumping DEF on the ground. Although it can act as a fertilizer, high concentrations can kill plants and affect the water quality of streams, ponds, and groundwater. 

2. Can I Dump DEF Down the Drain?

No, never dump DEF down the drain. The nitrogen content in DEF can disrupt aquatic ecosystems and harm aquatic organisms. 

3. Is DEF a Hazardous Waste? 

DEF is not hazardous waste unless contaminated with substances the EPA considers hazardous. It is considered a non-hazardous substance. However, properly handling and disposing of DEF is important to prevent any negative impact. 

4. Is DEF Fluid Harmful To The Environment?

DEF is not harmful to the environment when used as intended and properly disposed of. DEF plays a crucial role in reducing harmful emissions from diesel engines and promoting cleaner air quality. 

For more answers, see our article, Frequently asked questions about DEF.

Safe DEF Disposal

Properly disposing of diesel exhaust fluid is essential to protect the environment. Search for treatment, storage, and disposal facilities (TSDFs) in your state to get started. By understanding what DEF is, how to store it, and the proper disposal methods, you can contribute to a cleaner and greener world. If your DEF is contaminated, follow the disposal rules for the substance causing the contamination. Always check with your local regulations and guidelines when handling and disposing of DEF to minimize the environmental impact. 

Explore DEF Storage Heaters by Powerblanket. They make custom DEF tank heaters that are the most efficient method to heat and maintain diesel exhaust fluid. Its advanced heating technology ensures that DEF remains at the ideal temperature for optimal performance. Investing in a DEF storage heater can ensure a reliable and efficient supply, reducing the risk of freezing or degradation.

The Powerblanket DEF tank heater is the most efficient and effective way to heat and store diesel exhaust fluid.


Jen Reyes

Jen Reyes is the Business Development Director for Custom Solutions at Powerblanket. In this role, she works with custom products in all industries to deliver the best possible solution for her clients. With an extensive background in construction and electricity, Jen has a focused knowledge that makes her an invaluable asset to the Powerbanket team. When she's not working, Jen enjoys spending her free time golfing, working out, and spending time camping, fishing, and playing card games with her family.

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