International standards call for highly effective exhaust after-treatment systems in order to mitigate the environmental impact of diesel engine emissions. The after-treatment process relies on diesel exhaust fluid (DEF), also known by the brand name AdBlue, to break down harmful pollutants. Here, we take a look at what diesel exhaust fluid is, why it’s needed, and the requirements for using it.
Why is Diesel Fuel Harmful?
Diesel fuel was patented in 1892 and then used in high-speed diesel engines in the 1920s for commercial vehicles applications and in the 1930s for passenger cars. Diesel Fuel is refined from crude oil but thicker than gasoline, which causes it to evaporate more slowly. Due to its viscosity, diesel fuel requires higher temperatures and pressure to ignite and run an engine but in turn it gets better fuel efficiency.
Today, diesel fuel is used for most freight and delivery trucks, trains, buses, boats, and farm, construction, and military 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 classified it as a Category 1 or “definite” carcinogen as of 2012. Compare this with gasoline (petrol) emissions, classified as 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; they have also been linked to bladder cancer.
Diesel and the Environment
Besides threatening human health, NOx contributes to greenhouse gases 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 a source of acid rain. These gases are therefore not only sources of atmospheric pollution, but also contribute to the general acidification of soil and water.
How Does SCR Break Down Diesel Exhaust Fluid (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.
DEF then combines with the NOx gases, 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.
SCR equipped engines are cost-effective and fuel-efficient, providing return in both economic and environmental benefits. They have demonstrated a fuel efficiency increase of at least 5%.
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), that represents companies including Navistar and Daimler North America, is actively working with the government and industry to achieve its goals of cleaner, cost-effective technology and environmental benefits.
What is AdBlue?
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 Diesel Exhaust Fluid (DEF)?
In the U.S., 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, including 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 therefore should never be purchased.
The EPA regulates impurities and their acceptable amounts. High-quality DEF contains much lower levels of acceptable impurities such as zinc and aluminum. In addition, the EPA requires the DEF manufacturers to use far purer pharmaceutical urea instead of agricultural urea. The additional cost is worth the benefits.
Next, always keep DEF at the recommended level in your tank. If DEF is substantially reduced below a specific threshold, you will need to fill up your tank with DEF almost entirely 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, and engine OEMs to design and manufacture components for the SCR system in accordance with ISO 22241 and the rigorous American Petroleum Institute standards in order to meet emission laws and regulations.
KUS being one of the most capable designers and manufacturers of SCR system components in the world, and understands that it is necessary to provide quality parts that are reliable and durable enough to survive the extreme operating conditions typically seen on our customer’s equipment. KUS DEF tanks generally range in size from 10 to 120 liters, available with a variety of storage and dispensing methods. Sizes can be customized to consumers preferences. Visit the KUS website to shop exhaust aftertreatment products.