The Best DEF Storage: Diesel Exhaust Fluid Storage Guide

Diesel engines, with their higher heat and pressure, are more efficient than gasoline engines, but they also produce more nitrogen oxides (NOx), a harmful air pollutant. Exposure can lead to respiratory problems and cardiovascular issues, formation of acid rain, smog formation, eutrophication, and other cumulative effects. This is where DEF fluid for diesel engines comes in.

While regular catalysts struggle to remove NOx, Diesel Exhaust Fluid (DEF) offers a solution. However, effectively using DEF requires proper storage. Improper DEF storage can lead to contamination, degradation, and ultimately, failure of the emissions reduction system. This guide explores the best DEF storage solutions to ensure your diesel engines run clean and comply with environmental regulations.

What Is DEF Fluid and How Does It Solve Emission Concerns?

Diesel Exhaust Fluid (DEF), also known as AdBlue®, is a colorless, odorless, and non-flammable fluid used in diesel engines. DEF is a combination of high-purity urea (specifically carbamide) and deionized water. This combination aligns with ISO 22241 standard. When heated up, the mixture breaks into a highly reactive ammonia gas.

When injected into the hot exhaust stream, DEF fluid undergoes hydrolysis, breaking down the urea into ammonia (NH₃) and carbon dioxide (CO₂). This ammonia then reacts with nitrogen oxides (NOx) in the Selective Catalytic Reduction (SCR) converter, transforming them into harmless nitrogen (N₂) and water (H₂O).

The SCR system's effectiveness in reducing NOx emissions is directly linked to the quality and concentration of the DEF used, making proper storage paramount. Contamination or degradation of the DEF solution can significantly impair the SCR system's ability to meet stringent emissions standards. It cuts the amount of NOx from the exhaust system, helping these engines meet EU6 emissions standards.

The SCR system relies on a catalyst, typically a zeolite-based material, to facilitate the chemical reaction between ammonia and NOx. However, this catalytic process is highly sensitive to contaminants. Impurities in the DEF, often introduced through improper storage, can "poison" the catalyst, reducing its efficiency and leading to increased NOx emissions. 

How to Handle DEF Fluid

DEF is a non-hazardous, user-friendly working fluid comprised of 32.5% high-purity urea and 67.5% deionized water.. It is not fuel or a fuel additive, but rather a highly concentrated urea solution that must be stored in a dedicated DEF tank (separate from the diesel tank) and replaced as needed. DEF consumption is typically 2-3% of fuel consumption, resulting in significantly smaller DEF tank sizes compared to fuel tanks.

While modern vehicles have sensors that warn when DEF levels are low, we recommend keeping an eye on the DEF levels through a visual inspection of the tank, or by utilizing a dipstick if the tank is equipped with one.

Notably, you don't need special equipment to use, handle, or transfer DEF from its storage container to your diesel vehicle. However, it's important to remember that Diesel Exhaust Fluid (DEF) is considered corrosive, primarily towards metals like copper, brass, zinc, and aluminum, meaning it can damage these materials when directly exposed, especially at high temperatures. While it is not considered corrosive to human skin and is generally considered non-toxic when handled properly, be sure to wash your hands after use and wipe off any surfaces that may have also come in contact with the fluid.

To ensure that the emissions control system runs well, the DEF solution must contain 32.5% urea. A lower concentration produces less ammonia. This will impact its ability to assist your engine to fulfill emission regulations. Luckily, most injection control systems can manage modest concentration changes. Closed loop control systems continuously monitor the entrance and outlet of NOx emissions to detect any changes.

DEF Fluid Consumption: Calculating Your Needs

Understanding your Diesel Exhaust Fluid (DEF) consumption rate is crucial for ensuring your diesel engine operates smoothly and complies with emissions regulations. While the exact amount of DEF your vehicle uses will vary, there are some general guidelines and factors to consider.

A typical DEF consumption rate is approximately 2-3% of your diesel fuel consumption. For example, if you use 100 gallons of diesel fuel, you can expect to use roughly 2 to 3 gallons of DEF. This is a good starting point for estimation, but several factors can influence the actual rate:

• Driving Conditions: Frequent stop-and-go city driving often leads to higher DEF consumption compared to steady highway driving.
• Engine Load: Towing heavy loads or operating under demanding conditions will increase DEF usage, as the engine works harder and produces more NOx.
• Ambient Temperature: Extreme temperatures, both hot and cold, can impact the efficiency of the SCR system, potentially altering DEF consumption. Very cold temperatures can cause DEF to freeze (though the system is designed to handle this – more on that later). Extreme heat can, over time, degrade DEF if it's not stored properly.
• Engine Size and Type: Larger, more powerful diesel engines generally consume more DEF than smaller engines. The specific engine design and calibration also play a role.

Estimating Your DEF Needs:

While the 2-3% rule is a helpful guideline, monitoring your DEF gauge (if your vehicle has one) and tracking your consumption over time is the most accurate way to determine your specific needs. Some vehicles provide DEF level information on the dashboard, similar to a fuel gauge.

How to Store DEF Fluid

Now that we know the dos and don’ts of DEF handling, how do we store it? Since DEF is not a fuel; it cannot be treated like diesel. The main focus when storing it should be maintaining its purity.

DEF is less regulated than fuel because it is non-toxic, however, there are still some criteria to adhere to. ISO 2224 is the standard for handling, transporting, and manufacturing DEF, specifying the guidelines for safe storage.

Some basic rules include:

• Store DEF separate from other fuels and chemicals to prevent contamination.
• Keep DEF in a secluded location with few surface water drains.
• Keep it out of direct sunshine to avoid losing urea potency.
• Clean dispensing nozzles, equipment, and gear regularly to reduce the possibility of crystallization
• Only utilize specific DEF pumping systems and do not mix with other fuels

Additionally. DEF fluid should always be stored in its original, sealed container or in a dedicated DEF storage tank made of compatible materials.  Metals like aluminum, copper, and zinc can react with DEF, leading to corrosion and contamination. 

Using incompatible containers can introduce impurities that degrade the DEF and harm the SCR system.  Furthermore, it's essential to prevent contamination of DEF with dust, dirt, or other fluids. Even small amounts of these contaminants can negatively impact the SCR system's performance.

DEF Fluid and Diesel Trucks - A Cost-Benefit Analysis

The SCR system, and therefore DEF fluid, is particularly crucial for heavy-duty diesel trucks. These vehicles, due to their size and engine power, traditionally produced significantly higher levels of NOx emissions. The implementation of EPA 2010 standards in the United States mandated substantial reductions in NOx emissions from heavy-duty trucks. DEF, in conjunction with SCR technology, became a primary means of achieving these stricter standards.

Beyond compliance, using DEF in trucks offers several key benefits:

• Improved Fuel Efficiency: A common misconception is that DEF reduces fuel economy. In reality, a properly functioning SCR system can optimize engine performance, often leading to better fuel efficiency compared to older, less-regulated diesel engines. This is because the engine can be tuned for optimal performance, with the SCR system handling the NOx reduction.
• Reduced Environmental Impact: As discussed, DEF dramatically reduces NOx emissions, contributing to cleaner air and a healthier environment.
• Maintained Engine Performance: By preventing the buildup of harmful deposits associated with NOx, DEF helps maintain engine performance and longevity, particularly under the demanding conditions often faced by trucks.

The Rise of DEF: A Regulatory Timeline

The adoption of DEF fluid in diesel vehicles wasn't an overnight change; it was a gradual process driven by increasingly stringent emissions regulations. Understanding this regulatory timeline provides context for the widespread use of DEF today.

• Early 2000s: The Environmental Protection Agency (EPA) in the United States and similar agencies in Europe began to introduce stricter emission standards for diesel engines, targeting NOx in particular.
• Mid-2000s: SCR technology, using DEF, emerged as a leading solution for meeting these new standards. Manufacturers began developing and testing SCR systems.
• 2010: The EPA 2010 standards took full effect in the US, significantly tightening NOx emission limits for heavy-duty on-road diesel vehicles. This marked a major turning point, making DEF and SCR systems effectively mandatory for most new heavy-duty diesel trucks.
• CARB The California Air Resources Board has compliances and mandates in addition to the EPA.
• Post-2010: DEF requirements expanded to include many other diesel vehicles, including some passenger cars and off-road equipment, although specific timelines vary by application and region.

Current Mandates:

Today, DEF is mandatory for most new on-road diesel engines sold in the United States and Europe after 2010. It's crucial to consult your vehicle's owner's manual to confirm the specific requirements for your engine. While most on-road vehicles are now subject to these regulations, some off-road equipment, such as agricultural machinery, may have different timelines or be subject to tiered emission standards, meaning DEF requirements may vary.

Factors to Consider During DEF Fluid Storage

Maintaining a high-quality DEF supply is crucial for optimal performance and longevity of your diesel engine's emissions control system. DEF, while stable under normal conditions, is susceptible to degradation from several factors, making proper storage essential.

Temperature Sensitivity: Exposure to high temperatures, especially for prolonged periods, can cause the urea in DEF to decompose, leading to a reduction in its concentration and the formation of byproducts like biuret, triuret, and cyanuric acid. These byproducts can clog the SCR system's injector nozzles and catalyst, hindering its effectiveness and potentially causing costly repairs.

Conversely, freezing temperatures can also damage DEF. While DEF will thaw, repeated freeze-thaw cycles can cause the urea and water to separate, affecting the solution's uniformity and potentially impacting the SCR system's performance. The ideal storage temperature range for DEF is between 10°F and 86°F (-12°C and 30°C).

Light Sensitivity: Direct sunlight and UV exposure can accelerate the degradation of DEF, similar to the effects of high temperatures. Therefore, storing DEF in opaque containers and in a shaded area is recommended.

Contamination: DEF purity is paramount. Contamination with even small amounts of dust, dirt, metals (especially copper, zinc, and aluminum), or other fluids can negatively impact the SCR system. These contaminants can "poison" the catalyst, reducing its efficiency and leading to increased NOx emissions. Using dedicated DEF storage containers made of compatible materials is essential to prevent contamination.

Moisture and Humidity: While DEF is a water-based solution, excessive humidity promotes deposit formation, especially when DEF is exposed to air. These deposits can clog filters and injectors, disrupting proper DEF dosing into the exhaust stream. Proper sealing of DEF containers and storage tanks is crucial to minimize moisture exposure. The "sticky" consistency of aged DEF is a result of these deposits forming through air exposure and partial evaporation.

Impact on Engine Performance: A degraded or contaminated DEF supply can have a cascading effect on engine performance. An inefficient SCR system leads to increased NOx emissions, which can trigger the engine's diagnostic system and potentially limit engine power. While the connection to "unburned hydrocarbons entering the combustion chambers" is less direct, a malfunctioning SCR system can indeed impact overall engine efficiency and fuel economy due to the engine management system's response to the emissions issue.

By adhering to proper DEF storage guidelines, you can ensure the longevity and effectiveness of your diesel engine's emissions control system, prevent costly repairs, and maintain optimal engine performance.

Best DEF Fluid Storage Practices

Only two major factors are considered for efficient DEF storage:

Shelf Life

The shelf life of DEF determines how effectively it neutralizes harmful emissions. DEF expiration dates are typically set between one and two years from the date of manufacture. DEF's shelf life can vary depending on storage conditions.

It becomes less effective after it expires, which can cause problems with the engine. Any oil or fuel contamination directly impacts the DEF shelf life. Safe storage is critical to avoiding premature DEF expiration.

Temperature Ranges

The most suitable temperature range for DEF storage is 12°F (-11°C) to 86°F (30°C). If the temperature goes outside this range, it can impact DEF quality and performance. Furthermore, temperatures above 86°F can degrade the quality of DEF because it evaporates or decomposes faster at higher temperatures.

As a result, it is critical to store and handle DEF appropriately within the ideal temperature range to guarantee maximum efficiency and avoid possible damage or problems in your diesel engine's SCR system.

Recommended DEF Storage Tanks

Tank Depot offers a number of vertical storage tanks. For DEF storage, opt for units with  specific gravity of 1.5 or higher. The top picks include:

Portable DEF Tanks
Portable DEF tanks offer a convenient solution for DEF storage and dispensing, particularly for smaller operations or on-site refueling. Polyethylene is a commonly used material due to its chemical resistance and durability. When selecting a portable tank, consider material compatibility, ensuring it's specifically designed for DEF storage and adheres to industry standards. Capacity should match your DEF consumption needs, while the pumping system is crucial for efficient dispensing. Look for high-quality, DEF-compatible pumps, ideally stainless steel, with features like auto shut-off nozzles. Portability features like handles and a lightweight design are also important for ease of movement.

Beyond the tank itself, the pumping system is critical. A quality, DEF-compatible pump, preferably stainless steel, with an auto shut-off nozzle prevents spills and ensures efficient transfer. Consider pump flow rate and features like lockable compartments for security. For portable tanks, look for molded handles, forklift pockets, or wheels for easy handling. Additional features like level indicators, integrated spill containment, and a long-reach hose enhance usability.

The 55 Gallon Enduraplas DEF Fuel Boss®, for example, incorporates many of these features, including a durable polyethylene tank, a stainless steel pump with auto shut-off, and a lockable compartment. Choosing the right portable DEF tank ensures safe and efficient DEF storage and dispensing, protecting your emissions system.

Tank Depot’s Solution to DEF Fluid Storage

Tank Depot is a leading brand offering storage solutions across various needs. We vet all our partners to guarantee our clients quality products that meet industry standards. We offer DEF tanks to ensure you properly store your DEF fluids and, by extension, adhere to emission standards. Our units are also portable, so you can always refill your DEF fluid when you refuel your gas tank.

Contact Tank Depot today to inquire about DEF storage tanks and get a quick consultation and quotation.

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