With U.S. EPA Tier 4 Final engines making their way into inland waterway vessels, there’s a lot of talk about those with selective catalytic reduction (SCR). They require the use of diesel exhaust fluid (DEF), also known as urea, and there are plenty of misconceptions about its supply and safety. To clear up the confusion, we went to one of the U.S.’s leading midstreamers responsible for delivering fuel, DEF and a host of other supplies on the water. Here’s what Tony Odak, COO of Stone Oil, has to say about urea:

Q: Is your company prepared to deliver DEF to vessels on the inland waterways?

A: Stone Oil planned for this when we built our newest refueling barges around eight years ago. Whether by bulk or by package, Stone has been delivering DEF for several years now. We have a distribution plan for our customers, and I believe other midstreamers now see that it’s in their financial best interests to get on this bus and get on it quickly. Delivering urea makes good business for midstreamers because it’s a complimentary product to what they’re delivering now. They’re going to get on board as volume builds.

Q: How difficult or expensive will it be for a vessel to get DEF in a year or two?

A: We have no problem getting DEF throughout the Gulf of Mexico, on the inland river system, on the intercoastal waterway or on either U.S. coast now, so there should be even less problem getting it a couple years from now. The cost of urea is higher today because of the infrastructure buildout (last mile), but as the market gets more saturated with Tier 4 Final engines, that price will inevitably come down.

Q: Some people say DEF is dangerous because it’s caustic. Do you have any concerns about safety?

A: The urea solution is either 67.5% or 60% water, depending on the concentration. It’s as simple as this: If you come in contact with it, then wash it off. We encourage people to wear gloves and eye protection just as they would when loading fuel, lubricants or other compounds. But don’t think that DEF is any more hazardous than diesel fuel, because it isn’t. Truck drivers have been using urea for years on the roads without issues.

Q: What should vessel owners and operators know about DEF storage?

A: It’s critical to start with a quality product and keep it free of contaminants. The methods and materials used to store and deliver DEF to the SCR solution are important. Proper materials include stainless steel (304, 304L, 316) and some polyethylene/polypropylene (which are free of additives), but definitely NOT carbon steel, zinc-coated metals, nonferrous metals, soldered joints or metals containing aluminum or magnesium.

Though DEF will degrade at extreme temperatures, naval architects have addressed this issue. The size of the tanks in conjunction with the consumption and location outside of extreme temperature zones should eliminate nearly any degradation effect on the product.

Q: How will you decide which type of Tier 4 Final engines to choose for your own vessels?

A: Total lifecycle cost is important, and even though we are a fuel supplier, we are keen to see the fuel consumption differences between various solutions, as well as the net energy gain/loss (keel cooler additions/lengthening). Another critical concern in our evaluation will be the introduction of a new type or series of engines to our fleet and what that would mean for the mechanics who service those engines in the way of training and inventory of spares.

Do you have more questions about Tier 4 Final engines for inland waterways, DEF supply and safety or the differences between SCR and EGR? You’ll find answers here, or you can always talk to your local Cat® dealer.