Tier 4 And The Inland Waterways

Q&A With Gary Sarrat, Inland Waterways Segment Manager For Caterpillar Marine

WJ: Can you briefly describe the regulatory implementation timeline for Tier 4 marine engines?

GS: The EPA began to implement emissions regulations on marine diesel engines back in 1996 with Tier 1, and the journey to T4 began at that time. The EPA originally began to implement T4 emissions levels in stages starting in 2014 and continuing through 2017. It was at that time the EPA offered some relief based on availability of T4 certified engines from the engine manufacturers and the shipyards’ ability to get the equipment designed.

WJ: What aspects of the EPA rule effectively allowed for a delay in Tier 4 implementation on the inland waterways? Unpack for me the requirements for continuing to build Tier 3-powered towboats after the Tier 4 implementation date.

GS: As I mentioned, in 2017, OEMs were still finalizing their line-up of production T4 engines, so some revisions to the CFR had to be made. Owners and operators were requesting more time to allow the industry to catch up to the regulations: for engine manufacturers to fully test and certify their engines, for vessel designers to make the necessary engineering changes to their designs, and for the shipyards to actually build in the new equipment. Part of those revisions allowed for vessels under construction (i.e. keel laying date prior to regulation) and engines previously delivered to be paired for that specific. Owners and shipyards saw this uncertainty and decided to build in advance of the regulatory date instead of just after.

WJ: What is it about Tier 3 engines that would make operators want to take advantage of available “Tier 3 keels” rather than build Tier 4 boats? Are there any of these keels/engine packages still up for grabs?

GS: Operators chose to order vessels with T3 engines to avoid some of the uncertainty of SCR systems on board. Although these SCR systems are not overly complex, they do impact the vessel design and operations. There is an additional space claim that has to be considered and a cost impact in having DEF on board. 

WJ: How many Tier 4 engine packages has Caterpillar supplied for towing vessels thus far? How many are currently under construction?

GS: Caterpillar has provided T4 engine packages for several dozen inland, coastal and tug packages. There are currently quite a few T4 vessels under construction that will soon join the mv. Gretchen V Cooper, Caterpillar’s first pair of T4 3512s powering a U.S. inland vessel, in the coming year or two.

WJ: Practically speaking and regulation-wise, is it feasible to repower a Tier 3 boat with Tier 4 engines?

GS: Practically speaking, repowering any previous tier vessel is absolutely feasible. We are lucky in our inland waterways segment that our towing vessels generally have space to accommodate the engine’s SCR system and corresponding DEF tanks. Now that’s not to say it won’t require some engineering and shipyard work to get the job done, but in general inland towboats have more space than, say, harbor tugs, and installation of the SCR systems and DEF tanks can be accomplished without changing the vessel’s dimensions or affecting the operations. The engine envelope itself doesn’t change, so really, we are only talking about placing the SCR system and shifting some ballast capacity to store DEF.

WJ: For anyone unfamiliar, can you explain the difference between a Tier 3 engine and a Tier 4 engine with SCR? From a design and tankage standpoint, what’s different? What about fuel consumption, DEF consumption and maintenance requirements?

GS: The engine itself shows very little difference in the previous T3 model when compared to its T4 version. By using SCR technology to meet Tier 4, you minimize the impacts to the engine. The envelope of the engine has not changed between T3 and T4, other than the addition of the SCR, which is remote mounted, similar to a muffler. Fuel consumption on most of our Tier 4 engines with SCR is better than Tier 3. We are able to optimize fuel in the engine and reduce emissions with the SCR. DEF consumption was originally thought to be significant for SCR systems, but testing and practical applications have proven that DEF consumption is at about 3 percent to 4 percent of fuel, so tankage can usually be accomplished by shifting some ballast capacity from water to DEF. As far as maintenance goes, Caterpillar has designed its  SCR systems to minimize maintenance, so in general you would service your SCR when you would perform your engine overhaul.

WJ: What kind of performance impacts will I see using an SCR system compared to my previous T2 or T3 engines?

GS: Our T4 solution is designed to perform as well, or better, than our T3 engines. In most cases, we have seen between a 4 and 9 percent decrease in fuel consumption from T2 to T4 engines. From a safety standpoint, even in the event of a fault with the SCR system, the engine is still capable of operating at full power so that you can safely complete your maneuver or get your vessel to dock.

WJ: At one point, there was a concern with availability of DEF for Tier 4 engines. What’s the current state of availability for the urea solution throughout the inland waterways? What percentage urea content are Caterpillar engines optimized for?

GS: DEF has been readily available for more than a couple of decades now for on and off-highway applications, and mid-streamers and fuel suppliers have been ready to put DEF anywhere it is needed for some time now. As I have been told by several suppliers, if you need DEF on the river, we will put it there. Cat Marine SCR systems are optimized to use both 32.5 percent (highway grade) and 40 percent (marine grade) DEF, but most operators choose to use 40 percent DEF as it requires less tankage, and the lower freezing point of 32.5 percent is not typically required in a marine application.

WJ: What are the other Tier 4 options out there (EGR, for example)? Why did Caterpillar opt for SCR?

GS: For engines over 600 kW, T4 is the regulatory requirement, and that requires an emissions reduction technology. SCR and EGR are the two technologies available to meet T4 emissions standards. Cat has used both EGR and SCR to meet different market and customer needs, but the decision to go to SCR for marine was simple. Fuel consumption is lower with SCR, and reliability is better. Our customers need to have an engine they can depend on, and that helps them make money.

WJ: Over the next two to five years, what could lead to an increase in Tier 4 engines/Tier 4 vessels on the U.S. inland waterways?

GS: Over the next two to five years, I think we will see a dramatic increase in the utilization of T4 engines on the U.S. inland waterways. Vessel operators have embraced ESG and sustainability initiatives. There is a real interest in upgrading vessels to the highest emissions tier, whether that be for new construction or repowers, and we see a strong need for engine upgrades that would bring older vessels up to current standards to improve a vessel’s emissions footprint. With some advance planning and engineering, upgrading to a T4 engine package can be done in coordination with a haul-out inspection at shipyard to make planning and scheduling a repower less impactful on a vessel’s revenue producing timeline.

WJ: If a company suspects one of its vessels may have certification issues arise during its five-year haul out, what can company leaders be doing now to prepare for potentially replacing that vessel with a new Tier 4 towboat?

GS: If an operator is concerned about compliance at a five-year haul out or really anytime, the best thing to do is have a plan. A simple call to your engine provider can kick start the process of reviewing your needs and provide an engineered solution that fits an individual vessel. Although the prospect of widespread adoption of T4 emissions engines for a customer fleet seems daunting, we as engine manufacturers have been developing solutions that will make your sustainability journey much easier.