In 2007, as many truck and engine makers started announcing they would use selective catalytic reduction to meet 2010 federal emissions regulations, a new term entered our trucking dictionary: diesel exhaust fluid.

As we soon learned, SCR is an aftertreatment technology that injects small amounts of DEF, a water-based solution containing urea, into an engine’s hot exhaust stream to reduce emissions of nitrogen oxides (NOx).

In the exhaust, DEF vaporizes and forms ammonia and carbon dioxide, explains Mark Ulrich, director of customer support for Cummins Emissions Solutions. When the exhaust gas and ammonia are then passed over a catalyst, NOx is converted into harmless nitrogen and water.

DEF is a necessity to make this happen. Kept in a separate reservoir tank from the diesel fuel, it’s a solution of 32.5% high-purity urea mixed with very high-purity water. Urea is an organic nitrogen-containing compound commonly used in agriculture as a fertilizer.

However, you can’t just buy fertilizer and make your own DEF. The urea used to make DEF is known as automotive grade or environmental grade, a higher grade than the kind used for fertilizer.

Although it meant a new technology and a new fluid to deal with, the good news was, SCR meant fuel savings. Because engineers no longer had to optimize the in-cylinder combustion process for NOx control, they instead were able to tune the engine for better fuel economy.

Manufacturers and suppliers were soon meeting to discuss developing an infrastructure to distribute DEF. There was controversy as Navistar International, which was attempting to develop an emissions solution that did not involve the add-on liquid, claimed DEF would be expensive, hard for drivers to deal with, even toxic.

With Navistar’s decision last year to go the SCR route after all, it’s clear that DEF is here to stay.

“The naysayers were those who originally wanted to go with a non-SCR technology,” says Frank Cook, senior vice president of new product development at Old World Industries, which sells Peak BlueDEF. “In reality the engines and systems are running better with SCR (and less EGR) and drivers have gotten used to DEF quickly.”

Brian Hoover, national sales director of DEF at Mansfield Oil, notes “any time there is a change or a new product to be monitored and managed by the driver community, there will be some resistance. However, we see a general acceptance that has been adopted over the past 24 months, and DEF is becoming more of a common practice of implementation.”

However, drivers and fleets new to SCR typically have questions about DEF relative to storage, safe handling and availability.

Availability and price

There are almost three quarters of a million Class 4-8 SCR-equipped vehicles on the road in North America today, according to Integer Research, the leading DEF market analyst.

DEF consumption in North America by Class 4-8 vehicles is expected to reach 204 million gallons by the end of the year, according to Ed Wells, director of sales, Air1, for DEF supplier Yara North America.

Integer predicts this will double to 402 million gallons by 2015.

Truckstops, truck dealers, aftermarket parts stores and other outlets carry DEF in 1-gallon and 2.5-gallon containers. A growing number of truckstops carry it at the fuel island. In fact, the number of truckstops offering DEF at the fuel island topped 1,000 earlier this year.

Pilot Flying J accounts for over a third of the DEF pump network, offering it at more than 3,000 lanes, followed by Love’s and TravelCenters of America.
In addition, many fleets have chosen to use 55-gallon drums, 275-gallon or 330-gallon totes, or other bulk supply options for their own facilities.

Jeff Lewis, vice president of sales for Airgas Specialty Products, which sells AiRx DEF, explains that there are only a handful of companies that actually make urea. It’s a very capital-intensive process, requiring billion-dollar facilities. Instead, many companies that sell DEF buy dry or concentrated urea and “solutionize” it with high-quality water to meet ISO standards.

The per-gallon price for DEF is highest in jug form, according to Integer’s DEF Tracker, running about $6.25 per gallon as of April. At the pump, the price was running an average of $2.79, while tote refills were 27% less at $2.04.

“Going beyond totes, getting into permanent storage units of 1,000 or more gallons, they can really get a better price at that point,” says ChrisGoodfellow, an analyst with Integer Research.

“North America has historically enjoyed a surplus in production of DEF,” notes

Cummins’s Ulrich. “It’s reasonable to expect DEF prices to remain steady, or potentially even decline, due to free market completion and abundant retail infrastructure.”

On the other hand, urea also is a publicly traded commodity subject to fluctuations, as crude oil is. The biggest driver in that marketplace is fertilizer, so there could be seasonal fluctuations in the price based on projections of what’s going to happen in the agriculture business.

Handling and storage

The biggest concern in handling and storage is contamination, followed by the slight corrosiveness of DEF. Equipment used for DEF needs to be dedicated, both to address contamination concerns and because DEF will corrode some metals, such as copper and brass. That’s why DEF tanks on trucks are plastic.

“While DEF does have a pungent aroma similar to that of ammonia, it is a non-toxic, non-polluting, and non-flammable substance that is safe to handle and store and poses no serious risk to humans, animals, equipment or the environment when handled properly,” Ulrich says.

You do need to keep DEF in a temperature-controlled location and out of direct sunlight.

High temperatures will shorten the life of the product, and DEF does freeze at about 12 degrees. However, freezing doesn’t harm the product or the engine, and SCR systems are designed to deal with DEF that may be frozen or slushy when the truck starts up, explains Thomas Kalagher, product development manager for Prestone Performance Chemicals, which earlier this year introduced its Command brand of DEF.

Airgas’s Lewis says DEF does have a tendency to crystalize when it get exposed to air. “It almost looks like frost, but it’s just crystallizing. It also has a tendency to creep a little bit, but regular care and maintenance will take care of a lot of that.”

Despite concerns that DEF can “go bad” quickly, Hoover says, “DEF will be just fine for years when stored properly.”

The importance of purity

When you do hear of problems with DEF, the culprit is often poor quality or contamination. Buy from a reputable source that is API registered and meets the ISO 22241 standard. Beyond that, different brands of DEF all basically work the same.

“Impurities can cause premature failure of the catalyst, and that can cost $8,000 to $15,000 to replace,” says Prestone’s Kalagher.

“There’s some risk if you’re not buying from a reputable source just to save a penny a gallon.”

“Based on what we’ve seen in Europe and the U.S., we know that 80% of contamination happens at fleet terminals,” says Yara’s Wells.

To safeguard against DEF contamination, he recommends a few simple tips:

1. Keep DEF away from materials such as fuel, oil, grease, water, dust, dirt, metal and detergent.

2. If the DEF fueling equipment at your terminal needs to be cleaned, rinse it with de-mineralized water - NOT tap water.

3. Only use dedicated DEF equipment for storing and dispensing DEF. Do not use funnels or bottles that have been used for other fluids.

4. While a DEF pump’s magnetic guard will prevent you from accidentally putting DEF into the wrong tank, be sure to insert the DEF nozzle into the truck’s DEF inlet to avoid contaminating the spout.

5. Do not refill previously used DEF containers, as they may be contaminated.