Diesel engine emissions can be harmful to both humans and the environment. As a result, international standards call for highly effective exhaust after-treatment systems to mitigate adverse effects. The after-treatment process relies on diesel exhaust fluid (DEF), also known by the brand name AdBlue®, to break down dangerous pollutants. Here’s what you need to know about DEF, including what it is, why it’s needed, and the requirements for using it.
What Is Diesel Fuel and Why Is It Harmful?
Diesel fuel is a petroleum product refined from crude oil. Diesel is similar to gasoline but with a thicker viscosity, causing it to evaporate slower than gasoline. Due to its viscosity, diesel fuel requires higher temperature and pressure to ignite and power an engine. However, diesel engines are more efficient as a result.
Though originally patented in 1892, diesel fuel was first used in the 1920s for commercial vehicle applications. In the 1930s its use spread to passenger vehicles. Today, diesel fuel is used in a wide variety of applications, including freight and delivery vehicles, boats, and farm equipment. Diesel is also commonly used for trains, military equipment, and construction vehicles. Some passenger vehicles also use diesel, as do generators for electricity. In the U.S., it accounts for 15% of fuel consumption and 25% of total energy consumption by the transportation sector.
Diesel and Human Health
Despite its benefits, diesel fuel poses certain hazards. Diesel fuel exhaust contains nitric oxide and nitrogen dioxide (together known as NOx). NOx is toxic to humans when inhaled, even at relatively low concentrations. The International Agency for Research on Cancer classifies it as a Category 1 or “definite” carcinogen, making it notably more dangerous than gasoline (petrol) emissions, which are classified as a Category 2B or “possible” cause of cancer.
Chemicals in diesel exhaust called Polycyclic Aromatic Hydrocarbons (PAH) damage DNA, which raises the risk of cancer. Particulates can cause inflammation and cell mutations in the lungs, leading to lung cancer. These chemicals have also been linked to bladder cancer.
Diesel and the Environment
Besides threatening human health, NOx contributes to greenhouse gasses that cause climate change by trapping heat in the Earth’s atmosphere. The U.S. Energy Information Administration estimates that in 2019, diesel fuel consumption in the U.S. transportation sector resulted in the emission of 456 million metric tons of carbon dioxide (CO₂), the main contributor to the greenhouse effect. NO₂ forms ozone, another significant greenhouse gas contributing to climate change. Soot is another culprit, and is a much more efficient warming agent per unit mass than CO₂.
NOx emissions are also a source of acid rain, meaning these gasses contribute to the general acidification of soil and water in addition to atmospheric pollution.
How Does an SCR System Break Down DEF?
Fortunately, the industry has developed a product for mitigating the harmful effects of NOx from diesel fuel emissions. A Selective Catalytic Reduction (SCR) system is a technology designed for this purpose. An SCR system works by injecting DEF into the exhaust stream as it runs. DEF is 32.5% urea, or aqueous ammonia solution, and 67.5% deionized water.
After injection, DEF combines with the NOx gasses, setting off a chemical reaction that converts nitrogen oxides into nitrogen, water, and small amounts of CO₂. NOx emissions are reduced by an average of 80% through this process. It also reduces CO₂ emissions and particulate matter. An SCR system uses two to four ounces of DEF per gallon of fuel.
In addition to protecting health and the environment, SCR–equipped engines are cost-effective and fuel-efficient, providing a return in both economic and environmental benefits. They have demonstrated a fuel efficiency increase of at least 5%. This leads to less emissions and less fuel waste.
The EPA is setting out to create stricter standards on NOx emissions from heavy-duty truck engines that are close to zero, through the Cleaner Trucks Initiative. The Truck and Engine Manufacturers Association (EMA), which represents companies including Navistar and Daimler North America, is actively working with government and industry regulators to achieve its goals of cleaner, cost-effective technology and environmental benefits.
Is AdBlue® Different From DEF?
If you work with diesel engines, you may be familiar with the name AdBlue®. AdBlue is a German brand name for DEF trademarked by the German Association of the Automotive Industry. Other DEFs available on the American market include BlueTec by German automotive corporation Daimler AG and the Canadian H2Blu.
What Are the Requirements for Using DEF?
In the United States, all heavy– and medium–duty diesel truck engines produced after January 1, 2010, must meet the latest EPA emissions standards. Off-road equipment, including construction and agricultural equipment, must meet EPA’s Tier 4 emissions standards requiring similar reductions in NOx, PM, and other pollutants. In addition, marine vessels worldwide have been equipped with SCR technology. This includes cargo vessels, ferries, and tugboats. DEF is an integral part of the emissions control system and must be present in the tank at all times to assure continued operation of the vehicle or equipment.
How to Use DEF Effectively
Your SCR system will work most effectively if you follow some basic guidelines for using and handling DEF. First, only purchase and use DEF that meets the ISO 22241 standard. Often, you may see liquids that may appear or claim to be DEF that are substantially cheaper. If they aren’t ISO 22241 certified, they cannot be considered DEF and should not be used.
The EPA regulates impurities and their acceptable amounts. High-quality DEF contains much lower levels of impurities like zinc and aluminum. In addition, the EPA requires DEF manufacturers to use pharmaceutical urea instead of agricultural urea. While pharmaceutical urea is more expensive than agricultural urea, the product is much purer and provides greater benefits.
Next, always keep DEF at the recommended level in your tank. If DEF levels fall below a specific threshold, you will need to fill up your tank almost entirely with DEF to restart your engine. Your user manual will provide specific instructions.
Keep good inventory records and watch the age of any DEF that you store. DEF typically has a two-year shelf life. An abundance of factors will influence this shelf life, such as storage temperature or exposure to direct sunlight. Using DEF past the two-year mark or specified expiration date can cause performance and maintenance problems.
Depend on KUS for DEF Level Senders and Tanks
Since 2003, KUS has been working with global exhaust after-treatment system integrators, vehicle manufacturers, and engine OEMs to design and manufacture components for the SCR system. All products are built in accordance with ISO 22241 and the rigorous American Petroleum Institute standards in order to meet emission laws and regulations.
As a leading designer and manufacturer of SCR system components like level senders with quality sensors and DEF tanks, we understand the importance of quality parts built to be durable and reliable. That’s why our standard DEF tanks are among the best in the industry. Ranging in size from 10 to 120 liters, our premium tanks feature a variety of options for storage and dispensing methods. We also have custom DEF tank options available for projects that require special dimensions or performance.
Visit the KUS store to shop all of our exhaust aftertreatment products.